一个 XML 文件的多项活动

Question

我正在 android 中制作音乐播放器应用程序。该应用程序有

MainActivity.java（对应XMLFile:activity_main）：这个Activity有一个列表视图，显示所有可用歌曲的列表。
PlayerScreen.java（对应XMLFile:activity_player_screen）：当一首歌曲点击第一个activity，这个activity启动并播放该特定歌曲。这个 activity 有 3 个按钮（Play/Pause、NextSong、PreviousSong）和一个搜索栏。

这就是我面临的问题

我创建了一个单独的 class (SeekBarThread.java) 用于使用线程实现 activity_player_screen 的搜索栏。

问题是，当我从 PlayerScreen.java 调用我的线程 class 的启动方法时，没有任何反应。不会抛出异常。歌曲继续播放，但 activity_player_screen 的小部件停止工作，即我无法暂停歌曲或播放下一首歌曲。搜索栏也不起作用。

我想我无法 link 包含 PlayerScreen.java 和 SeekBarThread.java 的 activity_player_screen 文件。

这是 PlayerScreen.java

对线程 class 的调用

mySeekBarThread = new SeekBarThread(this, mySeekBar, mediaPlayer);
myThread = new Thread(mySeekBarThread);
myThread.start();

我真的没有摆脱异常的想法，所以我将 seekbar 对象和 mediaplayer 对象引用以及当前上下文引用传递给了 SeekBarThread class。但是没用。

这里是 SeekBarThread.java class 代码：

public class SeekBarThread implements Runnable{

private PlayerScreen myPlayerScreen;
private SeekBar seekBar;
private MediaPlayer mp;
private Context context;

public SeekBarThread(Context context, SeekBar seekBar, MediaPlayer mp) {
    this.context = context;
    this.seekBar = seekBar;
    this.mp = mp;
}

public void run() {

    ((Activity)context).setContentView(R.layout.activity_player_screen);
    seekBar.setMax(mp.getDuration());

    seekBar.setOnSeekBarChangeListener(new SeekBar.OnSeekBarChangeListener() {
        @Override
        public void onProgressChanged(SeekBar seekBar, int progress, boolean fromUser) {

        }

        @Override
        public void onStartTrackingTouch(SeekBar seekBar) {

        }

        @Override
        public void onStopTrackingTouch(SeekBar seekBar) {
            mp.seekTo(seekBar.getProgress());
        }
    });

    int totalduration = mp.getDuration();
    int currentposition = 0;
    while(currentposition < totalduration) {
        try {
            sleep(500);
            currentposition = mp.getCurrentPosition();
            seekBar.setProgress(currentposition);
        }
        catch(InterruptedException ex) {
            ex.printStackTrace();
        }
    }
}
}

activity_player_screen XML 文件：

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:id="@+id/activity_player_screen"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:paddingBottom="@dimen/activity_vertical_margin"
android:paddingLeft="@dimen/activity_horizontal_margin"
android:paddingRight="@dimen/activity_horizontal_margin"
android:paddingTop="@dimen/activity_vertical_margin"
tools:context="prakhar.simplemusicplayer20.PlayerScreen">

<Button
    android:id="@+id/play_pause"
    android:layout_width="42dp"
    android:layout_height="42dp"
    android:layout_alignParentBottom="true"
    android:layout_centerInParent="true"
    android:background="@drawable/pause" />

<Button
    android:id="@+id/next_song"
    android:layout_height="42dp"
    android:layout_width="42dp"
    android:background="@drawable/next"
    android:layout_marginEnd="25dp"
    android:layout_alignParentBottom="true"
    android:layout_alignParentEnd="true" />

<Button
    android:id="@+id/prev_song"
    android:layout_height="42dp"
    android:layout_width="42dp"
    android:background="@drawable/previous"
    android:layout_marginStart="25dp"
    android:layout_alignParentBottom="true"
    android:layout_alignParentStart="true" />

<Button
    android:text="F"
    android:layout_width="42dp"
    android:layout_height="42dp"
    android:id="@+id/forward_song"
    android:layout_alignParentBottom="true"
    android:layout_toStartOf="@+id/next_song"
    android:layout_marginEnd="22dp" />

<Button
    android:text="R"
    android:layout_width="42dp"
    android:layout_height="42dp"
    android:id="@+id/rewind_song"
    android:layout_marginEnd="23dp"
    android:layout_alignParentBottom="true"
    android:layout_toStartOf="@+id/play_pause" />

<SeekBar
    android:id="@+id/seek_bar"
    android:layout_height="wrap_content"
    android:layout_width="match_parent"
    android:layout_marginBottom="26dp"
    android:layout_above="@+id/play_pause"
    android:layout_alignParentStart="true" />

<TextView
    android:text="TextView"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:layout_alignParentTop="true"
    android:layout_centerHorizontal="true"
    android:layout_marginTop="146dp"
    android:id="@+id/details_text_view" />


</RelativeLayout>

这里是 PlayerScreen.java class:

public class PlayerScreen extends AppCompatActivity implements     View.OnClickListener{

private Button playPause, nextSong, prevSong;
public SeekBar mySeekBar;
private int count = 0;
public MediaPlayer mediaPlayer;
private Bundle newBundle = new Bundle();
private Intent newIntent;
private int pos;
private ArrayList<String> name;
private ArrayList<String> path;
private SeekBarThread mySeekBarThread;
private Thread myThread;
private TextView detailsTextView;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_player_screen);

    playPause = (Button)findViewById(R.id.play_pause);
    nextSong = (Button)findViewById(R.id.next_song);
    prevSong = (Button)findViewById(R.id.prev_song);
    mySeekBar = (SeekBar)findViewById(R.id.seek_bar);
    detailsTextView = (TextView)findViewById(R.id.details_text_view);

    playPause.setOnClickListener(this);
    nextSong.setOnClickListener(this);
    prevSong.setOnClickListener(this);

    newIntent = this.getIntent();
    newBundle = newIntent.getExtras();

    name = newBundle.getStringArrayList("title");
    path = newBundle.getStringArrayList("songpath");
    pos = newBundle.getInt("post");

    detailsTextView.setText(name.get(pos));

    mediaPlayer = new MediaPlayer();
    setMediaPlayer(pos);
}

public void setMediaPlayer(int position) {
    mySeekBarThread = new SeekBarThread(this, mySeekBar, mediaPlayer);
    myThread = new Thread(mySeekBarThread);
    myThread.start();

    File mySong = new File(path.get(pos));
    mediaPlayer = new MediaPlayer();
    FileInputStream is = null;
    try {
        is = new FileInputStream(mySong);
    }
    catch(FileNotFoundException ex) {
        ex.printStackTrace();
    }

    try {
        mediaPlayer.setDataSource(is.getFD());
    }
    catch(IOException ex) {
        ex.printStackTrace();
    }

    try {
        mediaPlayer.prepare();
    }
    catch(IOException ex) {
        ex.printStackTrace();
    }
    finally {
        if(is != null) {
            try {
                is.close();
            }
            catch(IOException ex) {
                ex.printStackTrace();
            }
        }
    }
    mediaPlayer.start();
}

@Override
protected void onPause() {
    super.onPause();
    mediaPlayer.pause();
}

@Override
protected void onDestroy() {
    super.onDestroy();
    mediaPlayer.stop();
}

@Override
public void onClick(View v) {
    switch(v.getId()) {
        case R.id.play_pause:
            count++;
            if(count%2 == 0) {
                v.setBackgroundResource(R.drawable.pause);
                mediaPlayer.seekTo(mediaPlayer.getCurrentPosition());
                mediaPlayer.start();
            }
            else {
                v.setBackgroundResource(R.drawable.play);
                mediaPlayer.pause();
            }
            break;

        case R.id.next_song:
            mediaPlayer.stop();
            pos = pos + 1;
            setMediaPlayer(pos);
            break;

        case R.id.prev_song:
            mediaPlayer.stop();
            pos = pos - 1;
            setMediaPlayer(pos);
            break;
    }
}
}

大部分的 onCreate() 代码是 class 处理根据用户在之前 activity 中的选择播放哪首歌。由于正在播放这首歌，我认为那部分代码没有问题。

Answer 1

@prakhar，通过代码，我发现了以下问题：

1) 在 SeekBarThread class 中运行() 方法 setContentView() 不应该设置，因为它已经在 activity class 中设置，因为你不会重新初始化点击侦听器。

2) 此外，seekbarchangeListener 不应在运行() 方法中设置，而应在主 activity 本身中设置，因为它不需要一直重新初始化。

3) 这里的重点是你在初始化 MediaPlayer 之前初始化了 SeekBarThread class，因此即使在搜索 seekbar 之后也没有任何动作。

修正了上述修改的详细代码。

public class PlayerScreen extends AppCompatActivity implements View.OnClickListener {

    private Button playPause, nextSong, prevSong;
    public SeekBar mySeekBar;
    private int count = 0;
    public MediaPlayer mediaPlayer;
    private Bundle newBundle = new Bundle();
    private Intent newIntent;
    private int pos;
    private ArrayList<String> name;
    private ArrayList<String> path;
    private SeekBarThread mySeekBarThread;
    private Thread myThread;
    private TextView detailsTextView;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        playPause = (Button) findViewById(R.id.play_pause);
        nextSong = (Button) findViewById(R.id.next_song);
        prevSong = (Button) findViewById(R.id.prev_song);
        mySeekBar = (SeekBar) findViewById(R.id.seek_bar);
        detailsTextView = (TextView) findViewById(R.id.details_text_view);

        playPause.setOnClickListener(this);
        nextSong.setOnClickListener(this);
        prevSong.setOnClickListener(this);

        mySeekBar.setOnSeekBarChangeListener(new SeekBar.OnSeekBarChangeListener() {
            @Override
            public void onProgressChanged(SeekBar seekBar, int progress, boolean fromUser) {

            }

            @Override
            public void onStartTrackingTouch(SeekBar seekBar) {

            }

            @Override
            public void onStopTrackingTouch(SeekBar seekBar) {
                mediaPlayer.seekTo(seekBar.getProgress());
            }
        });

        newIntent = this.getIntent();
        newBundle = newIntent.getExtras();

        name = newBundle.getStringArrayList("title");
        pos = newBundle.getInt("post");

        detailsTextView.setText(name.get(pos));

        mediaPlayer = new MediaPlayer();
        setMediaPlayer(pos);
    }

    public void setMediaPlayer(int position) {

        File mySong = new File(path.get(pos));
        mediaPlayer = new MediaPlayer();
        FileInputStream is = null;
        try {
            is = new FileInputStream(mySong);
        } catch (FileNotFoundException ex) {
            ex.printStackTrace();
        }

        try {
            mediaPlayer.setDataSource(is.getFD());
        } catch (IOException ex) {
            ex.printStackTrace();
        }

        try {
            mediaPlayer.setAudioStreamType(AudioManager.STREAM_MUSIC);
            mediaPlayer.prepare();
        } catch (IOException ex) {
            ex.printStackTrace();
        } finally {
            try {
                is.close();
            } catch (IOException ex) {
                ex.printStackTrace();
            }
        }
        mediaPlayer.start();

        mySeekBarThread = new SeekBarThread(this, mySeekBar, mediaPlayer);
        myThread = new Thread(mySeekBarThread);
        myThread.start();
    }

    @Override
    protected void onPause() {
        super.onPause();
        mediaPlayer.pause();
    }

    @Override
    protected void onDestroy() {
        super.onDestroy();
        mediaPlayer.stop();
    }

    @Override
    public void onClick(View v) {
        switch (v.getId()) {
            case R.id.play_pause:
                count++;
                if (count % 2 == 0) {
                    v.setBackgroundResource(R.drawable.pause);
                    mediaPlayer.seekTo(mediaPlayer.getCurrentPosition());
                    mediaPlayer.start();
                } else {
                    v.setBackgroundResource(R.drawable.play);
                    mediaPlayer.pause();
                }
                break;

            case R.id.next_song:
                mediaPlayer.stop();
                pos = pos + 1;
                setMediaPlayer(pos);
                break;

            case R.id.prev_song:
                mediaPlayer.stop();
                pos = pos - 1;
                setMediaPlayer(pos);
                break;
        }
    }
}

public class SeekBarThread 实现 Runnable{

private SeekBar seekBar;
private MediaPlayer mp;
private Context context;

public SeekBarThread(Context context, SeekBar seekBar, MediaPlayer mp) {
    this.context = context;
    this.seekBar = seekBar;
    this.mp = mp;
}

public void run() {

    seekBar.setMax(mp.getDuration());



    int totalduration = mp.getDuration();
    int currentposition = 0;
    while(currentposition < totalduration) {
        try {
            sleep(500);
            currentposition = mp.getCurrentPosition();
            seekBar.setProgress(currentposition);
        }
        catch(InterruptedException ex) {
            ex.printStackTrace();
        }
    }
}

}

一个 XML 文件的多项活动

Multiple Activities with one XML File

multithreading

android

mediastore

android-mediaplayer

android-seekbar