getGraphics() 正在返回空值
getGraphics() Is returning null value
我的 JPanel 预览在 drawToScreen 方法中调用 getGraphics() 时返回 null。测试 class 确实扩展了 JPanel，因为它被保存在 TabbedPane 中。 class 还实现了 Runnable、KeyListener 和 MouseListener
System.out.println的log是
javax.swing.JPanel[,172,149,1280x720,layout=java.awt.FlowLayout,alignmentX=0.0,alignmentY=0.0,border=,flags=9,maximumSize=,minimumSize=,preferredSize=null]
下面是现有代码的示例。 运行 它不会工作，因为它使用外部方法来完成自身，但希望能找到答案。
public Test() {
setBackground(Color.DARK_GRAY);
setLayout(null);
preview = new JPanel();
preview.setBounds(172, 149, 1280, 720);
add(preview);
}
public void addNotify() {
preview.addNotify();
if(thread == null) {
thread = new Thread(this);
preview.addKeyListener(this);
preview.addMouseListener(this);
thread.start();
}
}
private void init() {
image = new BufferedImage(WIDTH, HEIGHT,
BufferedImage.TYPE_INT_ARGB);
g = (Graphics2D) image.getGraphics();
running = true;
}
private long redraw() {
long t = System.currentTimeMillis();
if(onTab) {
if(!FileManager.isSleeping())
update();
if(!pause) {
draw();
drawToScreen();
}
}
return System.currentTimeMillis() - t;
}
public void run() {
init();
while(running) {
long durationMs = redraw();
try {
Thread.sleep(Math.max(0, FPS - durationMs));
} catch (InterruptedException e) {
e.printStackTrace();
}
}
}
private void update () {
reupdateImages();
}
private void draw() {
g.setColor(Color.black);
g.fillRect(0, 0, WIDTH, HEIGHT);
for(int i = 0; i < layers.length; i++) {
if(layers[i] != null) {
g.drawImage(
layers[i].getImage(),
layers[i].getX(),
layers[i].getY(),
layers[i].getWidth(),
layers[i].getHeight(),
null
);
g.setColor(Color.red);
for(int j = 0; j < layers.length; j++) {
if(layers[j].isSelected())
g.drawRect(
layers[j].getX(),
layers[j].getY(),
layers[j].getWidth(),
layers[j].getHeight()
);
}
}
}
}
private void drawToScreen() {
System.out.println(preview);
System.out.println(preview.getGraphics());
Graphics g2 = preview.getGraphics();
g2.drawImage(image, 0, 0,
WIDTH, HEIGHT,
null);
panelImage = image;
g2.dispose();
}
至于代码的其余部分，应 markspace 的要求，我添加了其余代码，只是为了揭穿所提供示例之外的内容。
@SuppressWarnings("serial")
public class ThumbnailEditor extends JPanel implements Runnable, KeyListener, MouseListener {
private JComboBox layerBox;
private int pos = 0;
private JFileChooser jfc;
// automated gui, I'm lazy and its dynamic
private int numberOfLayers = 24; // even numbers only guys and keep above 8
private JPanel preview;
private JSpinner localWidth;
private JSpinner localHeight;
private JSpinner posx;
private JSpinner posy;
private boolean ignore = false;
private JTextField width;
private JTextField height;
private JButton remove;
private JButton add;
private JButton select;
private JButton edit;
// drawing stoof
public int WIDTH = 1280;
public int HEIGHT = 720;
private Thread thread;
private boolean running;
private int FPS = 60;
private File location;
private BufferedImage panelImage;
private BufferedImage image;
private Graphics2D g;
private boolean pause = false;
private boolean onTab = false;
// when it gets too big, annoying issues start to happen with the text. This automatically fixes it
private static int[] overrideSizes = {
8,
9,
10,
11,
12,
14,
16,
18,
20,
22,
24,
26,
28,
36,
48,
72
};
// adjust this, low the more sensitive the changing of the font is.
private static int sensitivity = 4;
// layer stoof
// layer 0 --> at 0. layer 1 --> at 1
private static ThumbnailObject[] layers;
public static TextEditor[] te;
public ThumbnailEditor() {
setBackground(Color.DARK_GRAY);
setLayout(null);
preview = new JPanel();
preview.setBounds(172, 149, 1280, 720);
add(preview);
layerBox = new JComboBox();
layerBox.setBackground(Color.DARK_GRAY);
layerBox.setFont(new Font("Arial Black", Font.BOLD, 14));
layerBox.setBounds(10, 11, 100, 40);
add(layerBox);
add = new JButton("Add");
add.setBackground(Color.DARK_GRAY);
add.setFont(new Font("Arial Black", Font.BOLD, 14));
add.setBounds(120, 11, 100, 40);
add(add);
select = new JButton("Select");
select.setBackground(Color.DARK_GRAY);
select.setFont(new Font("Arial Black", Font.BOLD, 14));
select.setBounds(230, 11, 100, 40);
add(select);
edit = new JButton("Edit");
edit.setBackground(Color.DARK_GRAY);
edit.setFont(new Font("Arial Black", Font.BOLD, 14));
edit.setBounds(340, 11, 100, 40);
add(edit);
remove = new JButton("Remove");
remove.setBackground(Color.DARK_GRAY);
remove.setFont(new Font("Arial Black", Font.BOLD, 14));
remove.setBounds(450, 11, 100, 40);
add(remove);
JButton generate = new JButton("Generate Test Image");
generate.setBackground(Color.DARK_GRAY);
generate.setFont(new Font("Arial Black", Font.BOLD, 14));
generate.setBounds(1376, 11, 239, 40);
add(generate);
JButton deselect = new JButton("Deselect All Layers");
deselect.setBackground(Color.DARK_GRAY);
deselect.setFont(new Font("Arial Black", Font.BOLD, 14));
deselect.setBounds(120, 62, 210, 40);
add(deselect);
JLabel widthLabel = new JLabel("Width");
widthLabel.setHorizontalAlignment(SwingConstants.CENTER);
widthLabel.setForeground(Color.WHITE);
widthLabel.setFont(new Font("Arial Black", Font.BOLD, 14));
widthLabel.setBounds(10, 149, 70, 40);
add(widthLabel);
JLabel heightLabel = new JLabel("Height");
heightLabel.setHorizontalAlignment(SwingConstants.CENTER);
heightLabel.setFont(new Font("Arial Black", Font.BOLD, 14));
heightLabel.setForeground(Color.WHITE);
heightLabel.setBounds(90, 149, 70, 40);
add(heightLabel);
localWidth = new JSpinner();
localWidth.setFont(new Font("Arial Black", Font.BOLD, 14));
localWidth.setBounds(10, 184, 70, 20);
add(localWidth);
localHeight = new JSpinner();
localHeight.setFont(new Font("Arial Black", Font.BOLD, 14));
localHeight.setBounds(90, 184, 70, 20);
add(localHeight);
JLabel xSizeLabel = new JLabel("X");
xSizeLabel.setHorizontalAlignment(SwingConstants.CENTER);
xSizeLabel.setForeground(Color.WHITE);
xSizeLabel.setFont(new Font("Arial Black", Font.BOLD, 14));
xSizeLabel.setBounds(10, 215, 70, 40);
add(xSizeLabel);
JLabel ySizeLabel = new JLabel("Y");
ySizeLabel.setHorizontalAlignment(SwingConstants.CENTER);
ySizeLabel.setForeground(Color.WHITE);
ySizeLabel.setFont(new Font("Arial Black", Font.BOLD, 14));
ySizeLabel.setBounds(90, 215, 70, 40);
add(ySizeLabel);
posx = new JSpinner();
posx.setFont(new Font("Arial Black", Font.BOLD, 14));
posx.setBounds(10, 248, 70, 20);
add(posx);
posy = new JSpinner();
posy.setFont(new Font("Arial Black", Font.BOLD, 14));
posy.setBounds(92, 248, 70, 20);
add(posy);
pause = true;
layers = new ThumbnailObject[numberOfLayers];
te = new TextEditor[numberOfLayers];
for(int i = 0; i < layers.length; i++) {
layers[i] = new ThumbnailObject();
}
for(int i = 0; i < numberOfLayers; i++) {
layerBox.addItem("Layer [" + i + "]");
}
remove.addActionListener(new ActionListener() {
@Override
public void actionPerformed(ActionEvent arg0) {
pos = layerBox.getSelectedIndex();
layers[pos].reset();
add.setToolTipText("");
if(te[pos] != null) {
te[pos].getFrame().dispose();
te[pos] = null;
}
}
});
select.addActionListener(new ActionListener() {
@Override
public void actionPerformed(ActionEvent e) {
pos = layerBox.getSelectedIndex();
if(layers[pos].getImage() != null) {
for(int i = 0; i < layers.length; i++) {
layers[i].setSelected(false);
}
layers[pos].setSelected(true);
localWidth.setValue(layers[pos].getWidth());
localHeight.setValue(layers[pos].getHeight());
posx.setValue(layers[pos].getX());
posy.setValue(layers[pos].getY());
}
}
});
edit.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent e) {
pos = layerBox.getSelectedIndex();
if(layers[pos].getImage() != null) {
if(te[pos] != null) {
te[pos].getFrame().setVisible(true);
}
}
}
});
add.addActionListener(new ActionListener() {
@Override
public void actionPerformed(ActionEvent arg0) {
pos = layerBox.getSelectedIndex();
jfc = new JFileChooser();
jfc.setCurrentDirectory(new java.io.File("user.home"));
jfc.setDialogTitle("Select Layer 0 Image File");
jfc.setFileSelectionMode(JFileChooser.FILES_ONLY);
if (jfc.showOpenDialog(add) == JFileChooser.APPROVE_OPTION) {
try {
layers[pos].setFile(jfc.getSelectedFile());
if(!layers[pos].isReversed())
if(layers[pos].getFile().getName().contains(".txt")) {
if(te[pos] == null)
te[pos] = new TextEditor(pos);
else
te[pos].getFrame().setVisible(true);
// load defaults, this will be overriden when saved
layers[pos].setFont(te[pos].getFont());
layers[pos].setAlignment(te[pos].getAlignment());
layers[pos].setSize(te[pos].getSize());
layers[pos].setColor(te[pos].getColor()[0], te[pos].getColor()[1], te[pos].getColor()[2]);
layers[pos].setBold(te[pos].isBold());
layers[pos].setItalic(te[pos].isItalic());
layers[pos].setAdjusted(te[pos].isAdjusted());
layers[pos].setWidth(te[pos].getWidth());
layers[pos].setHeight(te[pos].getHeight());
layers[pos].setImage(convertTextToImage(layers[pos].getFile(), pos));
} else
if(layers[pos].getFile().getName().contains("png") ||
layers[pos].getFile().getName().contains("jpg") ||
layers[pos].getFile().getName().contains("jpeg") ||
layers[pos].getFile().getName().contains("bmp")){
layers[pos].setImage(ImageIO.read(layers[pos].getFile()));
layers[pos].setX(0);
layers[pos].setY(0);
layers[pos].setWidth((int) (layers[pos].getImage().getWidth()));
layers[pos].setHeight((int) (layers[pos].getImage().getHeight()));
} else {
JOptionPane.showMessageDialog(null, "txt, png, jpg, and bmp files only!");
layers[pos].reset();
add.setToolTipText("");
if(te[pos] != null) {
te[pos].getFrame().dispose();
te[pos] = null;
}
return;
}
else {
reverseImage(pos);
}
edit.setEnabled(true);
add.setToolTipText(jfc.getSelectedFile().getAbsolutePath());
} catch (IOException e) {
e.printStackTrace();
}
}
}
});
pause = false;
deselect.addActionListener(new ActionListener() {
@Override
public void actionPerformed(ActionEvent arg0) {
for(int i = 0; i < numberOfLayers; i++) {
layers[i].setSelected(false);
}
}
});
generate.addActionListener(new ActionListener() {
@Override
public void actionPerformed(ActionEvent arg0) {
try {
generatePanel(null);
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
});
posx.addChangeListener(new ChangeListener() {
@Override
public void stateChanged(ChangeEvent arg0) {
for(int i = 0; i < layers.length; i++) {
if(layers[i].isSelected()) {
layers[i].setX((int) posx.getValue());
}
}
}
});
posy.addChangeListener(new ChangeListener() {
@Override
public void stateChanged(ChangeEvent e) {
for(int i = 0; i < layers.length; i++) {
if(layers[i].isSelected()) {
layers[i].setY((int) posy.getValue());
}
}
}
});
localWidth.addChangeListener(new ChangeListener() {
public void stateChanged(ChangeEvent e) {
for(int i = 0; i < layers.length; i++) {
if(layers[i].isSelected())
layers[i].setWidth((int) localWidth.getValue());
}
}
});
localHeight.addChangeListener(new ChangeListener() {
public void stateChanged(ChangeEvent e) {
if(!ignore) {
for(int i = 0; i < layers.length; i++) {
if(layers[i].isSelected())
layers[i].setHeight((int) localHeight.getValue());
}
} else {
ignore = false;
}
}
});
}
public void addNotify() {
preview.addNotify();
preview.requestFocus();
preview.setFocusable(true);
preview.setVisible(true);
if(thread == null) {
thread = new Thread(this);
preview.addKeyListener(this);
preview.addMouseListener(this);
thread.start();
}
}
private void init() {
image = new BufferedImage(WIDTH, HEIGHT,
BufferedImage.TYPE_INT_ARGB);
g = (Graphics2D) image.getGraphics();
running = true;
}
private long redraw() {
long t = System.currentTimeMillis();
if(onTab) {
if(!FileManager.isSleeping())
update();
if(!pause) {
draw();
//drawToScreen();
}
}
return System.currentTimeMillis() - t;
}
public void run() {
init();
while(running) {
long durationMs = redraw();
try {
Thread.sleep(Math.max(0, FPS - durationMs));
} catch (InterruptedException e) {
e.printStackTrace();
}
}
}
private void update () {
reupdateImages();
}
private void draw() {
g.setColor(Color.black);
g.fillRect(0, 0, WIDTH, HEIGHT);
for(int i = 0; i < layers.length; i++) {
if(layers[i] != null) {
g.drawImage(
layers[i].getImage(),
layers[i].getX(),
layers[i].getY(),
layers[i].getWidth(),
layers[i].getHeight(),
null
);
g.setColor(Color.red);
for(int j = 0; j < layers.length; j++) {
if(layers[j].isSelected())
g.drawRect(
layers[j].getX(),
layers[j].getY(),
layers[j].getWidth(),
layers[j].getHeight()
);
}
}
}
}
private void drawToScreen() {
System.out.println(preview);
System.out.println(preview.getGraphics());
Graphics g2 = preview.getGraphics();
g2.drawImage(image, 0, 0,
WIDTH, HEIGHT,
null);
panelImage = image;
g2.dispose();
}
public BufferedImage generateThumbnail() {
// so draw doesnt interfere
if(!pause) pause = true;
for(int i = 0; i < numberOfLayers; i++) {
layers[i].setSelected(false);
}
draw();
drawToScreen();
int genwidth = Integer.parseInt(width.getText());
int genheight = Integer.parseInt(height.getText());
// manipulate the width and height to specs
BufferedImage resized = new BufferedImage(genwidth, genheight, BufferedImage.TYPE_INT_ARGB);
Graphics g = resized.createGraphics();
g.drawImage(panelImage, 0, 0, genwidth, genheight, null);
g.dispose();
pause = false;
return resized;
}
public void deselect() {
for(int i = 0; i < numberOfLayers; i++) {
layers[i].setSelected(false);
}
}
private void generatePanel(String n) throws IOException {
if(!pause) pause = true;
for(int i = 0; i < numberOfLayers; i++) {
layers[i].setSelected(false);
}
draw();
drawToScreen();
String user = System.getProperty("user.name");
String location = FileManager.getMediaDirectory().replaceAll("/", "\\") + "\";
int genwidth = WIDTH;
int genheight = HEIGHT;
// manipulate the width and height to specs
BufferedImage resized = new BufferedImage(genwidth, genheight, BufferedImage.TYPE_INT_ARGB);
Graphics g = resized.createGraphics();
g.drawImage(panelImage, 0, 0, genwidth, genheight, null);
g.dispose();
//print
File outputfile = null;
if(n == null || n == "")
outputfile = new File(location + "\test.png");
else
outputfile = new File(n);
pause = false;
ImageIO.write(resized, "png", outputfile);
}
public static void reupdateImagesOverride() {
/* basically, this will update any changes thus
* if a char change happened, it will change ONLY if you are
* using root as your media center
*/
for(int i = 0; i < layers.length; i++) {
if(layers[i] != null && layers[i].getFile() != null && layers[i].getImage() != null) {
try {
if(!layers[i].isReversed()) {
if(layers[i].getFile().getName().contains(".txt")) {
layers[i].setImage(convertTextToImage(layers[i].getFile(), i));
layers[i].setWidth(layers[i].getImage().getWidth());
layers[i].setHeight(layers[i].getImage().getHeight());
} else
layers[i].setImage(ImageIO.read(layers[i].getFile()));
} else {
reverseImage(i);
}
try{
layers[i].collectTimeStamp();
} catch (Exception e2) {
}
} catch (Exception e) {
e.printStackTrace();
}
}
}
}
private void reupdateImages() {
/* basically, this will update any changes thus
* if a char change happened, it will change ONLY if you are
* using root as your media center
*/
for(int i = 0; i < layers.length; i++) {
if(layers[i] != null && layers[i].getFile() != null && layers[i].getImage() != null) {
if(layers[i].getFile().lastModified() != layers[i].getTimeStamp()) {
try {
if(!layers[i].isReversed()) {
if(layers[i].getFile().getName().contains(".txt")) {
layers[i].setImage(convertTextToImage(layers[i].getFile(), i));
layers[i].setWidth(layers[i].getImage().getWidth());
layers[i].setHeight(layers[i].getImage().getHeight());
} else
layers[i].setImage(ImageIO.read(layers[i].getFile()));
} else {
reverseImage(i);
}
try{
layers[i].collectTimeStamp();
} catch (Exception e2) {
}
} catch (Exception e) {
e.printStackTrace();
}
}
}
}
}
// really simple
public static BufferedImage convertTextToImage(File f, int i) {
try {
int tmpy = 0;
int type = Font.PLAIN;
if(layers[i].isBold()) type = Font.BOLD;
if(layers[i].isItalic()) type = type | Font.ITALIC;
layers[i].setFont(te[i].getFont());
layers[i].setAlignment(te[i].getAlignment());
layers[i].setSize(te[i].getSize());
layers[i].setColor(te[i].getColor()[0], te[i].getColor()[1], te[i].getColor()[2]);
layers[i].setBold(te[i].isBold());
layers[i].setItalic(te[i].isItalic());
layers[i].setAdjusted(te[i].isAdjusted());
layers[i].setWidth(te[i].getWidth());
layers[i].setHeight(te[i].getHeight());
// grab width of longest line, if it's multi-line
BufferedImage tmp = new BufferedImage(layers[i].getWidth(), layers[i].getHeight(), BufferedImage.TYPE_INT_ARGB);
BufferedImage actual;
BufferedImage ghetto;
Graphics2D gx = tmp.createGraphics();
gx.setColor(new Color(layers[i].getColor()[0], layers[i].getColor()[1], layers[i].getColor()[2]));
gx.setFont(new Font(layers[i].getFont(), type, layers[i].getSize()));
String line = null;
BufferedReader reader = new BufferedReader(new FileReader(f));
int longest = 0;
while((line = reader.readLine()) != null) {
if(gx.getFontMetrics().stringWidth(line) > longest) {
longest = gx.getFontMetrics().stringWidth(line);
}
}
// check if the image/text is longer then designated width
if(longest > layers[i].getWidth()) {
if(layers[i].isAdjusted()) {
int tmpnum = longest - layers[i].getWidth();
int reduce = 0;
while(tmpnum > sensitivity) {
tmpnum %= sensitivity;
reduce++;
}
for(int z = 0; z < overrideSizes.length; z++) {
if(overrideSizes[z] > layers[i].getSize()) {
if(z - reduce >= 0) {
layers[i].setSize(overrideSizes[z - reduce]);
if(layers[i].getAlignment().equals("right") || layers[i].getAlignment().equals("center")) {
if(z - (reduce + 1) >= 0) layers[i].setSize(overrideSizes[z - (reduce + 1)]);
}
} else {
layers[i].setSize(overrideSizes[0]);
}
break;
}
}
}
// draw to image, ignore controllers wish of width, we will do that later
actual = new BufferedImage(longest, layers[i].getHeight(), BufferedImage.TYPE_INT_ARGB);
gx.dispose();
tmp = null;
gx = actual.createGraphics();
gx.setColor(new Color(te[i].getColor()[0], te[i].getColor()[1], te[i].getColor()[2]));
gx.setFont(new Font(layers[i].getFont(), type, layers[i].getSize()));
reader.close();
reader = new BufferedReader(new FileReader(f));
while((line = reader.readLine()) != null) {
gx.drawString(line,0, (tmpy += gx.getFontMetrics().getHeight()));
}
reader.close();
// now lets resize this
ghetto = new BufferedImage(layers[i].getWidth(), layers[i].getHeight(), BufferedImage.TYPE_INT_ARGB);
Graphics2D g2x = ghetto.createGraphics();
g2x.drawImage(actual, 0, 0, layers[i].getWidth(), layers[i].getHeight(), null);
g2x.dispose();
return ghetto;
} else {
actual = new BufferedImage(layers[i].getWidth(), layers[i].getHeight(), BufferedImage.TYPE_INT_ARGB);
gx.dispose();
tmp = null;
gx = actual.createGraphics();
gx.setColor(new Color(te[i].getColor()[0], te[i].getColor()[1], te[i].getColor()[2]));
gx.setFont(new Font(layers[i].getFont(), type, layers[i].getSize()));
reader.close();
reader = new BufferedReader(new FileReader(f));
while((line = reader.readLine()) != null) {
if(layers[i].getAlignment().equals("left"))
gx.drawString(line,0, (tmpy += gx.getFontMetrics().getHeight()));
else
if(layers[i].getAlignment().equals("right"))
gx.drawString(line, layers[i].getWidth() - gx.getFontMetrics().stringWidth(line), (tmpy += gx.getFontMetrics().getHeight()));
else
if(layers[i].getAlignment().equals("center"))
gx.drawString(line, (layers[i].getWidth() / 2) - (gx.getFontMetrics().stringWidth(line) / 2), (tmpy += gx.getFontMetrics().getHeight()));
}
reader.close();
return actual;
}
} catch (Exception e) {
e.printStackTrace();
}
return null;
}
private static void reverseImage(int i) {
BufferedImage tmp = new BufferedImage(
layers[i].getImage().getWidth(),
layers[i].getImage().getHeight(),
BufferedImage.TYPE_INT_ARGB);
Graphics gx = tmp.createGraphics();
try {
if(layers[i].getFile().getName().contains(".txt")) {
layers[i].setImage(convertTextToImage(layers[i].getFile(), i));
} else
layers[i].setImage(ImageIO.read(layers[i].getFile()));
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
gx.drawImage(
layers[i].getImage(),
layers[i].getImage().getWidth(),
0,
-layers[i].getImage().getWidth(),
layers[i].getImage().getHeight(),
null);
gx.dispose();
layers[i].setImage(tmp);
}
public void mouseClicked(MouseEvent arg0) {
}
public void mouseEntered(MouseEvent arg0) {
}
public void mouseExited(MouseEvent arg0) {
}
public void mousePressed(MouseEvent arg0) {
// button is being held, scanning layers that match
if(arg0.getButton() == MouseEvent.BUTTON3) {
for(int i = 0; i < layers.length; i++) {
if(layers[i].getFile() != null && layers[i].getImage() != null && layers[i].isSelected()) {
if(layers[i].isReversed()) {
layers[i].setReversed(false);
reupdateImagesOverride();
return;
} else {
layers[i].setReversed(true);
reupdateImagesOverride();
return;
}
}
}
}
if(arg0.getButton() == MouseEvent.BUTTON1) {
for(int i = 0; i < layers.length; i++) {
if(layers[i].isSelected()) {
layers[i].setX(arg0.getX());
layers[i].setY(arg0.getY());
posx.setValue(arg0.getX());
posy.setValue(arg0.getY());
}
}
}
}
public void mouseReleased(MouseEvent arg0) {
}
public void keyPressed(KeyEvent arg0) {
}
public void keyReleased(KeyEvent arg0) {
}
public void keyTyped(KeyEvent arg0) {
}
public void setOnTab(boolean b) {
onTab = b;
}
}
不要覆盖 addNotify！
A JPanel 只有一个 Graphics 实例 ，并且仅当 它被添加到父容器时。
Graphics 实例是在 Component.addNotify() 期间构建的，但您覆盖了它，阻止了它的创建。
也许尝试调用 super.addNotify() 作为快速解决方法。
我的 JPanel 预览在 drawToScreen 方法中调用 getGraphics() 时返回 null。测试 class 确实扩展了 JPanel，因为它被保存在 TabbedPane 中。 class 还实现了 Runnable、KeyListener 和 MouseListener
System.out.println的log是
javax.swing.JPanel[,172,149,1280x720,layout=java.awt.FlowLayout,alignmentX=0.0,alignmentY=0.0,border=,flags=9,maximumSize=,minimumSize=,preferredSize=null]
下面是现有代码的示例。 运行 它不会工作，因为它使用外部方法来完成自身，但希望能找到答案。
public Test() {
setBackground(Color.DARK_GRAY);
setLayout(null);
preview = new JPanel();
preview.setBounds(172, 149, 1280, 720);
add(preview);
}
public void addNotify() {
preview.addNotify();
if(thread == null) {
thread = new Thread(this);
preview.addKeyListener(this);
preview.addMouseListener(this);
thread.start();
}
}
private void init() {
image = new BufferedImage(WIDTH, HEIGHT,
BufferedImage.TYPE_INT_ARGB);
g = (Graphics2D) image.getGraphics();
running = true;
}
private long redraw() {
long t = System.currentTimeMillis();
if(onTab) {
if(!FileManager.isSleeping())
update();
if(!pause) {
draw();
drawToScreen();
}
}
return System.currentTimeMillis() - t;
}
public void run() {
init();
while(running) {
long durationMs = redraw();
try {
Thread.sleep(Math.max(0, FPS - durationMs));
} catch (InterruptedException e) {
e.printStackTrace();
}
}
}
private void update () {
reupdateImages();
}
private void draw() {
g.setColor(Color.black);
g.fillRect(0, 0, WIDTH, HEIGHT);
for(int i = 0; i < layers.length; i++) {
if(layers[i] != null) {
g.drawImage(
layers[i].getImage(),
layers[i].getX(),
layers[i].getY(),
layers[i].getWidth(),
layers[i].getHeight(),
null
);
g.setColor(Color.red);
for(int j = 0; j < layers.length; j++) {
if(layers[j].isSelected())
g.drawRect(
layers[j].getX(),
layers[j].getY(),
layers[j].getWidth(),
layers[j].getHeight()
);
}
}
}
}
private void drawToScreen() {
System.out.println(preview);
System.out.println(preview.getGraphics());
Graphics g2 = preview.getGraphics();
g2.drawImage(image, 0, 0,
WIDTH, HEIGHT,
null);
panelImage = image;
g2.dispose();
}
至于代码的其余部分，应 markspace 的要求，我添加了其余代码，只是为了揭穿所提供示例之外的内容。
@SuppressWarnings("serial")
public class ThumbnailEditor extends JPanel implements Runnable, KeyListener, MouseListener {
private JComboBox layerBox;
private int pos = 0;
private JFileChooser jfc;
// automated gui, I'm lazy and its dynamic
private int numberOfLayers = 24; // even numbers only guys and keep above 8
private JPanel preview;
private JSpinner localWidth;
private JSpinner localHeight;
private JSpinner posx;
private JSpinner posy;
private boolean ignore = false;
private JTextField width;
private JTextField height;
private JButton remove;
private JButton add;
private JButton select;
private JButton edit;
// drawing stoof
public int WIDTH = 1280;
public int HEIGHT = 720;
private Thread thread;
private boolean running;
private int FPS = 60;
private File location;
private BufferedImage panelImage;
private BufferedImage image;
private Graphics2D g;
private boolean pause = false;
private boolean onTab = false;
// when it gets too big, annoying issues start to happen with the text. This automatically fixes it
private static int[] overrideSizes = {
8,
9,
10,
11,
12,
14,
16,
18,
20,
22,
24,
26,
28,
36,
48,
72
};
// adjust this, low the more sensitive the changing of the font is.
private static int sensitivity = 4;
// layer stoof
// layer 0 --> at 0. layer 1 --> at 1
private static ThumbnailObject[] layers;
public static TextEditor[] te;
public ThumbnailEditor() {
setBackground(Color.DARK_GRAY);
setLayout(null);
preview = new JPanel();
preview.setBounds(172, 149, 1280, 720);
add(preview);
layerBox = new JComboBox();
layerBox.setBackground(Color.DARK_GRAY);
layerBox.setFont(new Font("Arial Black", Font.BOLD, 14));
layerBox.setBounds(10, 11, 100, 40);
add(layerBox);
add = new JButton("Add");
add.setBackground(Color.DARK_GRAY);
add.setFont(new Font("Arial Black", Font.BOLD, 14));
add.setBounds(120, 11, 100, 40);
add(add);
select = new JButton("Select");
select.setBackground(Color.DARK_GRAY);
select.setFont(new Font("Arial Black", Font.BOLD, 14));
select.setBounds(230, 11, 100, 40);
add(select);
edit = new JButton("Edit");
edit.setBackground(Color.DARK_GRAY);
edit.setFont(new Font("Arial Black", Font.BOLD, 14));
edit.setBounds(340, 11, 100, 40);
add(edit);
remove = new JButton("Remove");
remove.setBackground(Color.DARK_GRAY);
remove.setFont(new Font("Arial Black", Font.BOLD, 14));
remove.setBounds(450, 11, 100, 40);
add(remove);
JButton generate = new JButton("Generate Test Image");
generate.setBackground(Color.DARK_GRAY);
generate.setFont(new Font("Arial Black", Font.BOLD, 14));
generate.setBounds(1376, 11, 239, 40);
add(generate);
JButton deselect = new JButton("Deselect All Layers");
deselect.setBackground(Color.DARK_GRAY);
deselect.setFont(new Font("Arial Black", Font.BOLD, 14));
deselect.setBounds(120, 62, 210, 40);
add(deselect);
JLabel widthLabel = new JLabel("Width");
widthLabel.setHorizontalAlignment(SwingConstants.CENTER);
widthLabel.setForeground(Color.WHITE);
widthLabel.setFont(new Font("Arial Black", Font.BOLD, 14));
widthLabel.setBounds(10, 149, 70, 40);
add(widthLabel);
JLabel heightLabel = new JLabel("Height");
heightLabel.setHorizontalAlignment(SwingConstants.CENTER);
heightLabel.setFont(new Font("Arial Black", Font.BOLD, 14));
heightLabel.setForeground(Color.WHITE);
heightLabel.setBounds(90, 149, 70, 40);
add(heightLabel);
localWidth = new JSpinner();
localWidth.setFont(new Font("Arial Black", Font.BOLD, 14));
localWidth.setBounds(10, 184, 70, 20);
add(localWidth);
localHeight = new JSpinner();
localHeight.setFont(new Font("Arial Black", Font.BOLD, 14));
localHeight.setBounds(90, 184, 70, 20);
add(localHeight);
JLabel xSizeLabel = new JLabel("X");
xSizeLabel.setHorizontalAlignment(SwingConstants.CENTER);
xSizeLabel.setForeground(Color.WHITE);
xSizeLabel.setFont(new Font("Arial Black", Font.BOLD, 14));
xSizeLabel.setBounds(10, 215, 70, 40);
add(xSizeLabel);
JLabel ySizeLabel = new JLabel("Y");
ySizeLabel.setHorizontalAlignment(SwingConstants.CENTER);
ySizeLabel.setForeground(Color.WHITE);
ySizeLabel.setFont(new Font("Arial Black", Font.BOLD, 14));
ySizeLabel.setBounds(90, 215, 70, 40);
add(ySizeLabel);
posx = new JSpinner();
posx.setFont(new Font("Arial Black", Font.BOLD, 14));
posx.setBounds(10, 248, 70, 20);
add(posx);
posy = new JSpinner();
posy.setFont(new Font("Arial Black", Font.BOLD, 14));
posy.setBounds(92, 248, 70, 20);
add(posy);
pause = true;
layers = new ThumbnailObject[numberOfLayers];
te = new TextEditor[numberOfLayers];
for(int i = 0; i < layers.length; i++) {
layers[i] = new ThumbnailObject();
}
for(int i = 0; i < numberOfLayers; i++) {
layerBox.addItem("Layer [" + i + "]");
}
remove.addActionListener(new ActionListener() {
@Override
public void actionPerformed(ActionEvent arg0) {
pos = layerBox.getSelectedIndex();
layers[pos].reset();
add.setToolTipText("");
if(te[pos] != null) {
te[pos].getFrame().dispose();
te[pos] = null;
}
}
});
select.addActionListener(new ActionListener() {
@Override
public void actionPerformed(ActionEvent e) {
pos = layerBox.getSelectedIndex();
if(layers[pos].getImage() != null) {
for(int i = 0; i < layers.length; i++) {
layers[i].setSelected(false);
}
layers[pos].setSelected(true);
localWidth.setValue(layers[pos].getWidth());
localHeight.setValue(layers[pos].getHeight());
posx.setValue(layers[pos].getX());
posy.setValue(layers[pos].getY());
}
}
});
edit.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent e) {
pos = layerBox.getSelectedIndex();
if(layers[pos].getImage() != null) {
if(te[pos] != null) {
te[pos].getFrame().setVisible(true);
}
}
}
});
add.addActionListener(new ActionListener() {
@Override
public void actionPerformed(ActionEvent arg0) {
pos = layerBox.getSelectedIndex();
jfc = new JFileChooser();
jfc.setCurrentDirectory(new java.io.File("user.home"));
jfc.setDialogTitle("Select Layer 0 Image File");
jfc.setFileSelectionMode(JFileChooser.FILES_ONLY);
if (jfc.showOpenDialog(add) == JFileChooser.APPROVE_OPTION) {
try {
layers[pos].setFile(jfc.getSelectedFile());
if(!layers[pos].isReversed())
if(layers[pos].getFile().getName().contains(".txt")) {
if(te[pos] == null)
te[pos] = new TextEditor(pos);
else
te[pos].getFrame().setVisible(true);
// load defaults, this will be overriden when saved
layers[pos].setFont(te[pos].getFont());
layers[pos].setAlignment(te[pos].getAlignment());
layers[pos].setSize(te[pos].getSize());
layers[pos].setColor(te[pos].getColor()[0], te[pos].getColor()[1], te[pos].getColor()[2]);
layers[pos].setBold(te[pos].isBold());
layers[pos].setItalic(te[pos].isItalic());
layers[pos].setAdjusted(te[pos].isAdjusted());
layers[pos].setWidth(te[pos].getWidth());
layers[pos].setHeight(te[pos].getHeight());
layers[pos].setImage(convertTextToImage(layers[pos].getFile(), pos));
} else
if(layers[pos].getFile().getName().contains("png") ||
layers[pos].getFile().getName().contains("jpg") ||
layers[pos].getFile().getName().contains("jpeg") ||
layers[pos].getFile().getName().contains("bmp")){
layers[pos].setImage(ImageIO.read(layers[pos].getFile()));
layers[pos].setX(0);
layers[pos].setY(0);
layers[pos].setWidth((int) (layers[pos].getImage().getWidth()));
layers[pos].setHeight((int) (layers[pos].getImage().getHeight()));
} else {
JOptionPane.showMessageDialog(null, "txt, png, jpg, and bmp files only!");
layers[pos].reset();
add.setToolTipText("");
if(te[pos] != null) {
te[pos].getFrame().dispose();
te[pos] = null;
}
return;
}
else {
reverseImage(pos);
}
edit.setEnabled(true);
add.setToolTipText(jfc.getSelectedFile().getAbsolutePath());
} catch (IOException e) {
e.printStackTrace();
}
}
}
});
pause = false;
deselect.addActionListener(new ActionListener() {
@Override
public void actionPerformed(ActionEvent arg0) {
for(int i = 0; i < numberOfLayers; i++) {
layers[i].setSelected(false);
}
}
});
generate.addActionListener(new ActionListener() {
@Override
public void actionPerformed(ActionEvent arg0) {
try {
generatePanel(null);
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
});
posx.addChangeListener(new ChangeListener() {
@Override
public void stateChanged(ChangeEvent arg0) {
for(int i = 0; i < layers.length; i++) {
if(layers[i].isSelected()) {
layers[i].setX((int) posx.getValue());
}
}
}
});
posy.addChangeListener(new ChangeListener() {
@Override
public void stateChanged(ChangeEvent e) {
for(int i = 0; i < layers.length; i++) {
if(layers[i].isSelected()) {
layers[i].setY((int) posy.getValue());
}
}
}
});
localWidth.addChangeListener(new ChangeListener() {
public void stateChanged(ChangeEvent e) {
for(int i = 0; i < layers.length; i++) {
if(layers[i].isSelected())
layers[i].setWidth((int) localWidth.getValue());
}
}
});
localHeight.addChangeListener(new ChangeListener() {
public void stateChanged(ChangeEvent e) {
if(!ignore) {
for(int i = 0; i < layers.length; i++) {
if(layers[i].isSelected())
layers[i].setHeight((int) localHeight.getValue());
}
} else {
ignore = false;
}
}
});
}
public void addNotify() {
preview.addNotify();
preview.requestFocus();
preview.setFocusable(true);
preview.setVisible(true);
if(thread == null) {
thread = new Thread(this);
preview.addKeyListener(this);
preview.addMouseListener(this);
thread.start();
}
}
private void init() {
image = new BufferedImage(WIDTH, HEIGHT,
BufferedImage.TYPE_INT_ARGB);
g = (Graphics2D) image.getGraphics();
running = true;
}
private long redraw() {
long t = System.currentTimeMillis();
if(onTab) {
if(!FileManager.isSleeping())
update();
if(!pause) {
draw();
//drawToScreen();
}
}
return System.currentTimeMillis() - t;
}
public void run() {
init();
while(running) {
long durationMs = redraw();
try {
Thread.sleep(Math.max(0, FPS - durationMs));
} catch (InterruptedException e) {
e.printStackTrace();
}
}
}
private void update () {
reupdateImages();
}
private void draw() {
g.setColor(Color.black);
g.fillRect(0, 0, WIDTH, HEIGHT);
for(int i = 0; i < layers.length; i++) {
if(layers[i] != null) {
g.drawImage(
layers[i].getImage(),
layers[i].getX(),
layers[i].getY(),
layers[i].getWidth(),
layers[i].getHeight(),
null
);
g.setColor(Color.red);
for(int j = 0; j < layers.length; j++) {
if(layers[j].isSelected())
g.drawRect(
layers[j].getX(),
layers[j].getY(),
layers[j].getWidth(),
layers[j].getHeight()
);
}
}
}
}
private void drawToScreen() {
System.out.println(preview);
System.out.println(preview.getGraphics());
Graphics g2 = preview.getGraphics();
g2.drawImage(image, 0, 0,
WIDTH, HEIGHT,
null);
panelImage = image;
g2.dispose();
}
public BufferedImage generateThumbnail() {
// so draw doesnt interfere
if(!pause) pause = true;
for(int i = 0; i < numberOfLayers; i++) {
layers[i].setSelected(false);
}
draw();
drawToScreen();
int genwidth = Integer.parseInt(width.getText());
int genheight = Integer.parseInt(height.getText());
// manipulate the width and height to specs
BufferedImage resized = new BufferedImage(genwidth, genheight, BufferedImage.TYPE_INT_ARGB);
Graphics g = resized.createGraphics();
g.drawImage(panelImage, 0, 0, genwidth, genheight, null);
g.dispose();
pause = false;
return resized;
}
public void deselect() {
for(int i = 0; i < numberOfLayers; i++) {
layers[i].setSelected(false);
}
}
private void generatePanel(String n) throws IOException {
if(!pause) pause = true;
for(int i = 0; i < numberOfLayers; i++) {
layers[i].setSelected(false);
}
draw();
drawToScreen();
String user = System.getProperty("user.name");
String location = FileManager.getMediaDirectory().replaceAll("/", "\\") + "\";
int genwidth = WIDTH;
int genheight = HEIGHT;
// manipulate the width and height to specs
BufferedImage resized = new BufferedImage(genwidth, genheight, BufferedImage.TYPE_INT_ARGB);
Graphics g = resized.createGraphics();
g.drawImage(panelImage, 0, 0, genwidth, genheight, null);
g.dispose();
//print
File outputfile = null;
if(n == null || n == "")
outputfile = new File(location + "\test.png");
else
outputfile = new File(n);
pause = false;
ImageIO.write(resized, "png", outputfile);
}
public static void reupdateImagesOverride() {
/* basically, this will update any changes thus
* if a char change happened, it will change ONLY if you are
* using root as your media center
*/
for(int i = 0; i < layers.length; i++) {
if(layers[i] != null && layers[i].getFile() != null && layers[i].getImage() != null) {
try {
if(!layers[i].isReversed()) {
if(layers[i].getFile().getName().contains(".txt")) {
layers[i].setImage(convertTextToImage(layers[i].getFile(), i));
layers[i].setWidth(layers[i].getImage().getWidth());
layers[i].setHeight(layers[i].getImage().getHeight());
} else
layers[i].setImage(ImageIO.read(layers[i].getFile()));
} else {
reverseImage(i);
}
try{
layers[i].collectTimeStamp();
} catch (Exception e2) {
}
} catch (Exception e) {
e.printStackTrace();
}
}
}
}
private void reupdateImages() {
/* basically, this will update any changes thus
* if a char change happened, it will change ONLY if you are
* using root as your media center
*/
for(int i = 0; i < layers.length; i++) {
if(layers[i] != null && layers[i].getFile() != null && layers[i].getImage() != null) {
if(layers[i].getFile().lastModified() != layers[i].getTimeStamp()) {
try {
if(!layers[i].isReversed()) {
if(layers[i].getFile().getName().contains(".txt")) {
layers[i].setImage(convertTextToImage(layers[i].getFile(), i));
layers[i].setWidth(layers[i].getImage().getWidth());
layers[i].setHeight(layers[i].getImage().getHeight());
} else
layers[i].setImage(ImageIO.read(layers[i].getFile()));
} else {
reverseImage(i);
}
try{
layers[i].collectTimeStamp();
} catch (Exception e2) {
}
} catch (Exception e) {
e.printStackTrace();
}
}
}
}
}
// really simple
public static BufferedImage convertTextToImage(File f, int i) {
try {
int tmpy = 0;
int type = Font.PLAIN;
if(layers[i].isBold()) type = Font.BOLD;
if(layers[i].isItalic()) type = type | Font.ITALIC;
layers[i].setFont(te[i].getFont());
layers[i].setAlignment(te[i].getAlignment());
layers[i].setSize(te[i].getSize());
layers[i].setColor(te[i].getColor()[0], te[i].getColor()[1], te[i].getColor()[2]);
layers[i].setBold(te[i].isBold());
layers[i].setItalic(te[i].isItalic());
layers[i].setAdjusted(te[i].isAdjusted());
layers[i].setWidth(te[i].getWidth());
layers[i].setHeight(te[i].getHeight());
// grab width of longest line, if it's multi-line
BufferedImage tmp = new BufferedImage(layers[i].getWidth(), layers[i].getHeight(), BufferedImage.TYPE_INT_ARGB);
BufferedImage actual;
BufferedImage ghetto;
Graphics2D gx = tmp.createGraphics();
gx.setColor(new Color(layers[i].getColor()[0], layers[i].getColor()[1], layers[i].getColor()[2]));
gx.setFont(new Font(layers[i].getFont(), type, layers[i].getSize()));
String line = null;
BufferedReader reader = new BufferedReader(new FileReader(f));
int longest = 0;
while((line = reader.readLine()) != null) {
if(gx.getFontMetrics().stringWidth(line) > longest) {
longest = gx.getFontMetrics().stringWidth(line);
}
}
// check if the image/text is longer then designated width
if(longest > layers[i].getWidth()) {
if(layers[i].isAdjusted()) {
int tmpnum = longest - layers[i].getWidth();
int reduce = 0;
while(tmpnum > sensitivity) {
tmpnum %= sensitivity;
reduce++;
}
for(int z = 0; z < overrideSizes.length; z++) {
if(overrideSizes[z] > layers[i].getSize()) {
if(z - reduce >= 0) {
layers[i].setSize(overrideSizes[z - reduce]);
if(layers[i].getAlignment().equals("right") || layers[i].getAlignment().equals("center")) {
if(z - (reduce + 1) >= 0) layers[i].setSize(overrideSizes[z - (reduce + 1)]);
}
} else {
layers[i].setSize(overrideSizes[0]);
}
break;
}
}
}
// draw to image, ignore controllers wish of width, we will do that later
actual = new BufferedImage(longest, layers[i].getHeight(), BufferedImage.TYPE_INT_ARGB);
gx.dispose();
tmp = null;
gx = actual.createGraphics();
gx.setColor(new Color(te[i].getColor()[0], te[i].getColor()[1], te[i].getColor()[2]));
gx.setFont(new Font(layers[i].getFont(), type, layers[i].getSize()));
reader.close();
reader = new BufferedReader(new FileReader(f));
while((line = reader.readLine()) != null) {
gx.drawString(line,0, (tmpy += gx.getFontMetrics().getHeight()));
}
reader.close();
// now lets resize this
ghetto = new BufferedImage(layers[i].getWidth(), layers[i].getHeight(), BufferedImage.TYPE_INT_ARGB);
Graphics2D g2x = ghetto.createGraphics();
g2x.drawImage(actual, 0, 0, layers[i].getWidth(), layers[i].getHeight(), null);
g2x.dispose();
return ghetto;
} else {
actual = new BufferedImage(layers[i].getWidth(), layers[i].getHeight(), BufferedImage.TYPE_INT_ARGB);
gx.dispose();
tmp = null;
gx = actual.createGraphics();
gx.setColor(new Color(te[i].getColor()[0], te[i].getColor()[1], te[i].getColor()[2]));
gx.setFont(new Font(layers[i].getFont(), type, layers[i].getSize()));
reader.close();
reader = new BufferedReader(new FileReader(f));
while((line = reader.readLine()) != null) {
if(layers[i].getAlignment().equals("left"))
gx.drawString(line,0, (tmpy += gx.getFontMetrics().getHeight()));
else
if(layers[i].getAlignment().equals("right"))
gx.drawString(line, layers[i].getWidth() - gx.getFontMetrics().stringWidth(line), (tmpy += gx.getFontMetrics().getHeight()));
else
if(layers[i].getAlignment().equals("center"))
gx.drawString(line, (layers[i].getWidth() / 2) - (gx.getFontMetrics().stringWidth(line) / 2), (tmpy += gx.getFontMetrics().getHeight()));
}
reader.close();
return actual;
}
} catch (Exception e) {
e.printStackTrace();
}
return null;
}
private static void reverseImage(int i) {
BufferedImage tmp = new BufferedImage(
layers[i].getImage().getWidth(),
layers[i].getImage().getHeight(),
BufferedImage.TYPE_INT_ARGB);
Graphics gx = tmp.createGraphics();
try {
if(layers[i].getFile().getName().contains(".txt")) {
layers[i].setImage(convertTextToImage(layers[i].getFile(), i));
} else
layers[i].setImage(ImageIO.read(layers[i].getFile()));
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
gx.drawImage(
layers[i].getImage(),
layers[i].getImage().getWidth(),
0,
-layers[i].getImage().getWidth(),
layers[i].getImage().getHeight(),
null);
gx.dispose();
layers[i].setImage(tmp);
}
public void mouseClicked(MouseEvent arg0) {
}
public void mouseEntered(MouseEvent arg0) {
}
public void mouseExited(MouseEvent arg0) {
}
public void mousePressed(MouseEvent arg0) {
// button is being held, scanning layers that match
if(arg0.getButton() == MouseEvent.BUTTON3) {
for(int i = 0; i < layers.length; i++) {
if(layers[i].getFile() != null && layers[i].getImage() != null && layers[i].isSelected()) {
if(layers[i].isReversed()) {
layers[i].setReversed(false);
reupdateImagesOverride();
return;
} else {
layers[i].setReversed(true);
reupdateImagesOverride();
return;
}
}
}
}
if(arg0.getButton() == MouseEvent.BUTTON1) {
for(int i = 0; i < layers.length; i++) {
if(layers[i].isSelected()) {
layers[i].setX(arg0.getX());
layers[i].setY(arg0.getY());
posx.setValue(arg0.getX());
posy.setValue(arg0.getY());
}
}
}
}
public void mouseReleased(MouseEvent arg0) {
}
public void keyPressed(KeyEvent arg0) {
}
public void keyReleased(KeyEvent arg0) {
}
public void keyTyped(KeyEvent arg0) {
}
public void setOnTab(boolean b) {
onTab = b;
}
}
不要覆盖 addNotify！
A JPanel 只有一个 Graphics 实例 ，并且仅当 它被添加到父容器时。
Graphics 实例是在 Component.addNotify() 期间构建的，但您覆盖了它，阻止了它的创建。
也许尝试调用 super.addNotify() 作为快速解决方法。