android studio隐式intent实现音乐播放

首先，需要在AndroidManifest.xml文件中声明以下权限和服务：

<uses-permission android:name="android.permission.READ_EXTERNAL_STORAGE" />
<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />

<service android:name=".MusicService" />

然后，创建一个MusicService类来处理音乐播放：

public class MusicService extends Service implements MediaPlayer.OnPreparedListener {

    private MediaPlayer mediaPlayer = null;

    @Override
    public void onCreate() {
        super.onCreate();
        mediaPlayer = new MediaPlayer();
        mediaPlayer.setOnPreparedListener(this);
    }

    @Override
    public int onStartCommand(Intent intent, int flags, int startId) {
        String action = intent.getAction();
        if (action.equals("play")) {
            String path = intent.getStringExtra("path");
            playMusic(path);
        } else if (action.equals("stop")) {
            stopMusic();
        }
        return super.onStartCommand(intent, flags, startId);
    }

    private void playMusic(String path) {
        try {
            mediaPlayer.reset();
            mediaPlayer.setDataSource(path);
            mediaPlayer.prepareAsync();
        } catch (IOException e) {
            e.printStackTrace();
        }
    }

    private void stopMusic() {
        mediaPlayer.stop();
    }

    @Override
    public void onPrepared(MediaPlayer mp) {
        mediaPlayer.start();
    }

    @Nullable
    @Override
    public IBinder onBind(Intent intent) {
        return null;
    }
}

在主Activity中，可以使用以下代码来启动和停止MusicService：

private void playMusic(String path) {
    Intent intent = new Intent(this, MusicService.class);
    intent.setAction("play");
    intent.putExtra("path", path);
    startService(intent);
}

private void stopMusic() {
    Intent intent = new Intent(this, MusicService.class);
    intent.setAction("stop");
    startService(intent);
}

要播放音乐，只需使用以下代码：

Intent intent = new Intent(Intent.ACTION_GET_CONTENT);
intent.setType("audio/*");
startActivityForResult(intent, 1);

在onActivityResult方法中，可以获取选定音乐文件的URI，并将其传递给MusicService：

@Override
protected void onActivityResult(int requestCode, int resultCode, @Nullable Intent data) {
    super.onActivityResult(requestCode, resultCode, data);

    if (resultCode == RESULT_OK && requestCode == 1) {
        Uri uri = data.getData();
        String path = getRealPathFromURI(uri);
        playMusic(path);
    }
}

private String getRealPathFromURI(Uri uri) {
    String[] projection = {MediaStore.Audio.Media.DATA};
    Cursor cursor = getContentResolver().query(uri, projection, null, null, null);
    int column_index = cursor.getColumnIndexOrThrow(MediaStore.Audio.Media.DATA);
    cursor.moveToFirst();
    String path = cursor.getString(column_index);
    cursor.close();
    return path;
}

完整的MainActivity代码如下：

public class MainActivity extends AppCompatActivity {

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

        Button btnPlay = findViewById(R.id.btn_play);
        btnPlay.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                Intent intent = new Intent(Intent.ACTION_GET_CONTENT);
                intent.setType("audio/*");
                startActivityForResult(intent, 1);
            }
        });

        Button btnStop = findViewById(R.id.btn_stop);
        btnStop.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                stopMusic();
            }
        });
    }

    private void playMusic(String path) {
        Intent intent = new Intent(this, MusicService.class);
        intent.setAction("play");
        intent.putExtra("path", path);
        startService(intent);
    }

    private void stopMusic() {
        Intent intent = new Intent(this, MusicService.class);
        intent.setAction("stop");
        startService(intent);
    }

    @Override
    protected void onActivityResult(int requestCode, int resultCode, @Nullable Intent data) {
        super.onActivityResult(requestCode, resultCode, data);

        if (resultCode == RESULT_OK && requestCode == 1) {
            Uri uri = data.getData();
            String path = getRealPathFromURI(uri);
            playMusic(path);
        }
    }

    private String getRealPathFromURI(Uri uri) {
        String[] projection = {MediaStore.Audio.Media.DATA};
        Cursor cursor = getContentResolver().query(uri, projection, null, null, null);
        int column_index = cursor.getColumnIndexOrThrow(MediaStore.Audio.Media.DATA);
        cursor.moveToFirst();
        String path = cursor.getString(column_index);
        cursor.close();
        return path;
    }
}