绘制多个矩形 android canvas

Question

我正在尝试在 canvas 上绘制 4 个矩形，以便将 canvas 分成 4 个相等的矩形。使用我现在拥有的代码，只绘制了代码中的最后一个矩形。

这是我的代码 Activity:

 protected void onCreate(Bundle savedInstanceState) {
     ...
setContentView(new MyView(this));
 }

public class MyView extends View {

    public MyView(Context context) {
        super(context);
        // TODO Auto-generated constructor stub
        setFocusableInTouchMode(true);
    }

    @Override
    protected void onDraw(Canvas canvas) {

        super.onDraw(canvas);
        int x = getWidth();
        int y = getHeight();


        Paint paintTopLeft = new Paint();
        paintTopLeft.setStyle(Paint.Style.FILL);
        paintTopLeft.setColor(Color.WHITE);
        canvas.drawPaint(paintTopLeft);
        // Use Color.parseColor to define HTML colors
        paintTopLeft.setColor(Color.parseColor("#F44336"));
        canvas.drawRect(0,0,x / 2,y / 2,paintTopLeft);

        Paint paintTopRight = new Paint();
        paintTopRight.setStyle(Paint.Style.FILL);
        paintTopRight.setColor(Color.WHITE);
        canvas.drawPaint(paintTopRight);
        // Use Color.parseColor to define HTML colors
        paintTopRight.setColor(Color.parseColor("#2196F3"));
        canvas.drawRect(x / 2, 0, x, y / 2, paintTopRight);

    }
}

我做错了什么？

Answer 1

实际上我只看到两个用您的代码绘制的矩形。但无论如何，问题是您正在调用 canvas.drawPaint 其中 clears/fills 具有该颜色的完整 canvas。因此，您正在擦除在绘制最后一个矩形之前已经绘制的所有矩形。

此代码应该有效：

protected void onCreate(Bundle savedInstanceState) {
     ...
setContentView(new MyView(this));
 }

public class MyView extends View {

    public MyView(Context context) {
        super(context);
        // TODO Auto-generated constructor stub
        setFocusableInTouchMode(true);
    }

    @Override
    protected void onDraw(Canvas canvas) {

        super.onDraw(canvas);
        int x = getWidth();
        int y = getHeight();    

        Paint paintTopLeft = new Paint();
        paintTopLeft.setStyle(Paint.Style.FILL);
        paintTopLeft.setColor(Color.WHITE);
        //canvas.drawPaint(paintTopLeft);  // don't do that
        // Use Color.parseColor to define HTML colors
        paintTopLeft.setColor(Color.parseColor("#F44336"));
        canvas.drawRect(0,0,x / 2,y / 2,paintTopLeft);

        Paint paintTopRight = new Paint();
        paintTopRight.setStyle(Paint.Style.FILL);
        paintTopRight.setColor(Color.WHITE);
        // canvas.drawPaint(paintTopRight);  // don't do that
        // Use Color.parseColor to define HTML colors
        paintTopRight.setColor(Color.parseColor("#2196F3"));
        canvas.drawRect(x / 2, 0, x, y / 2, paintTopRight);    
    }
}

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