Question

已更新

我有一个音乐播放器应用程序，最近，我试图实现一个SeekBar。但是在启动应用程序时，我遇到了运行时异常为什么？

我的代码：

super.onCreate(SavedInstanceState);
    setContentView(R.layout.media_player_layout);
    Intent intent = getIntent();
    String track = intent.getDataString();
    TextView txt = (TextView)findViewById(R.id.txt);
    txt.setGravity(Gravity.CENTER);
    txt.setText(track);
    ImageView img = (ImageView)findViewById(R.id.img);
    img.setLayerType(View.LAYER_TYPE_SOFTWARE, null);
    final Uri uri = getIntent() != null ? getIntent().getData() : null;
    final SharedPreferences premiumSettings = getSharedPreferences("PREMIUM", Context.MODE_PRIVATE);
    final boolean isPremium = premiumSettings.getBoolean("isPremium", false);
    SeekBar seekBar = (SeekBar) findViewById(R.id.seekBar);
    seekBar.setOnSeekBarChangeListener(this);
    if (isPremium) {
        musicPlayer = MediaPlayer.create(MusicPlayer.this, uri);
        seekBar.setMax(musicPlayer.getDuration());
        try {
            musicPlayer.prepare();
        } catch (IOException e) {
            e.printStackTrace();
        }
        musicPlayer.start();
        final ImageButton play = (ImageButton) findViewById(R.id.play);
        if(!musicPlayer.isPlaying()){

            play.setImageResource(android.R.drawable.ic_media_play);
        }
        else{
            play.setImageResource(android.R.drawable.ic_media_pause);

        }
        play.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                int position = musicPlayer.getCurrentPosition();
                if(musicPlayer.isPlaying()){
                    musicPlayer.pause();
                    play.setImageResource(android.R.drawable.ic_media_play);

                }
                else {
                    musicPlayer.seekTo(position);
                    musicPlayer.start();
                    play.setImageResource(android.R.drawable.ic_media_pause);

            }}
        });

        ImageButton exit = (ImageButton) findViewById(R.id.exit);
        exit.setImageResource(android.R.drawable.btn_dialog);
        exit.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                if (musicPlayer.isPlaying()) {
                    musicPlayer.stop();
                }
                    musicPlayer.release();
                    musicPlayer = null;
                    finish();

            }
        });


    }
    else {
        AlertDialog.Builder builder = new AlertDialog.Builder(MusicPlayer.this);
        builder.setTitle("Error");
        builder.setMessage("You are not premium user. Please enter the promocode or buy the full version");
        builder.setIcon(R.drawable.holo_dark_action_info);
        builder.setPositiveButton("OK", new DialogInterface.OnClickListener() {
            public void onClick(DialogInterface dialog, int whichButton) {
                finish();
            }
        });
        AlertDialog dialog = builder.create();
        dialog.show();
    }}
public void onBackPressed () {
        if(musicPlayer.isPlaying()) {
            musicPlayer.stop();
        }
            musicPlayer = null;
        finish();
}

@Override
public void onProgressChanged(SeekBar seekBar, int i, boolean b) {
    if(b){
        musicPlayer.seekTo(i);
    }
}

@Override
public void onStartTrackingTouch(SeekBar seekBar) {

}

@Override
public void onStopTrackingTouch(SeekBar seekBar) {

}

和我的logcat：

 Process: com.tproductions.Openit, PID: 13440
java.lang.RuntimeException: Unable to start activity ComponentInfo{com.tproductions.Openit/com.tproductions.Openit.MusicPlayer}: java.lang.IllegalStateException
        at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2237)
        at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2286)
        at android.app.ActivityThread.access$800(ActivityThread.java:144)
        at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1246)
        at android.os.Handler.dispatchMessage(Handler.java:102)
        at android.os.Looper.loop(Looper.java:212)
        at android.app.ActivityThread.main(ActivityThread.java:5135)
        at java.lang.reflect.Method.invokeNative(Native Method)
        at java.lang.reflect.Method.invoke(Method.java:515)
        at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:877)
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:693)
        at dalvik.system.NativeStart.main(Native Method)
 Caused by: java.lang.IllegalStateException
        at android.media.MediaPlayer.prepare(Native Method)
        at com.tproductions.Openit.MusicPlayer.onCreate(MusicPlayer.java:46)
        at android.app.Activity.performCreate(Activity.java:5231)
        at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1087)
        at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2201)

非常感谢您的回答。我在互联网上看了一眼，但找不到合适的答案。所以请不要低估这个问题。非常感谢你的时间

Answer 1

看起来好像是在实例化之前访问musicPlayer成员

seekBar.setMax(musicPlayer.getDuration());

if (isPremium) {
    musicPlayer = MediaPlayer.create(MusicPlayer.this, uri);

应该是

if (isPremium) {
    musicPlayer = MediaPlayer.create(MusicPlayer.this, uri);
    seekBar.setMax(musicPlayer.getDuration());

定义SeekBar时的运行时异常

1 个答案: