下一个按钮强制意外关闭app？

时间：2014-10-18 15:43:09

标签： android audio android-mediaplayer

该程序是一个简单的音乐播放器，但只要按下该按钮，下一个按钮就会关闭该应用程序。

         public void next(View view) {
          Toast.makeText(getApplicationContext(), "Next song", 
          Toast.LENGTH_SHORT).show();
          mp.reset();
            if(SONG_NUMBER < (SONG_NUMBER - 1)){
                mp.selectTrack(SONG_NUMBER + 1);
                SONG_NUMBER = SONG_NUMBER + 1;
            }
            else {
                mp.start();
                SONG_NUMBER = 0;
             }
            mp.start();
}

这是代码的其余部分

package com.android.SimplePlayer;

import java.io.File;
import java.io.FilenameFilter;
import java.io.IOException;
import java.util.ArrayList;
import java.util.List;

import com.example.SimplePlayer.R;
import com.example.SimplePlayer.R.id;
import com.example.SimplePlayer.R.layout;
import com.example.SimplePlayer.R.string;

import android.app.ListActivity;
import android.content.Intent;
import android.media.MediaPlayer;
import android.media.MediaPlayer.OnCompletionListener;
import android.os.Bundle;
import android.os.Environment;
import android.util.Log;
import android.view.View;
import android.widget.ArrayAdapter;
import android.widget.ImageButton;
import android.widget.ListView;
import android.widget.Toast;


class Mp3Filter implements FilenameFilter {
public boolean accept(File dir, String name) {
    return (name.endsWith(".mp3"));
}
}
public class MainActivity extends ListActivity implements OnCompletionListener {
private static final String SD_PATH = new String(Environment.getExternalStorageDirectory().getPath() + "/");
private List<String> songs = new ArrayList<String>();
private MediaPlayer mp = new MediaPlayer();
private View play;
private View pause;
private View stop;
private View next;
public static int SONG_NUMBER=0;



  @Override
  protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    updatePlaylist();
    play = (ImageButton)findViewById(R.id.imageButton1);
    pause = (ImageButton)findViewById(R.id.imageButton2);
    stop = (ImageButton)findViewById(R.id.imageButton3);
    next = (ImageButton)findViewById(R.id.imageButton4);
    mp.setOnCompletionListener(this);
    play.setEnabled(false);
    pause.setEnabled(false);
    stop.setEnabled(false);
    next.setEnabled(true);
  }

@Override
  protected void onListItemClick(ListView list, View view, int position, long id) {
    try { 
        SONG_NUMBER=position;
        mp.reset();
        mp.setDataSource(SD_PATH + songs.get(position));
        mp.prepare();
        mp.start();
        play.setEnabled(false);
        pause.setEnabled(true);
        stop.setEnabled(true);
        next.setEnabled(true);
    } catch(IOException e) {
        Log.v(getString(R.string.app_name), e.getMessage());
    }
}
private void updatePlaylist() {
    File home = new File(SD_PATH);
    if (home.listFiles(new Mp3Filter()).length > 0) {
        for (File file : home.listFiles( new Mp3Filter())) {
            songs.add(file.getName());
        }
    ArrayAdapter<String> songList = new ArrayAdapter<String>(this,R.layout.song_item,songs);
    setListAdapter(songList);
}
}
  public void play(View view){
       Toast.makeText(getApplicationContext(), "Playing song", 
       Toast.LENGTH_SHORT).show();
       mp.start();
       play.setEnabled(false);
       pause.setEnabled(true);
       stop.setEnabled(true);
       next.setEnabled(true);
       }



  public void pause(View view){
      Toast.makeText(getApplicationContext(), "Pausing song", 
      Toast.LENGTH_SHORT).show();
      mp.pause();
      play.setEnabled(true);
      pause.setEnabled(false);
      stop.setEnabled(true);
      next.setEnabled(true);
   }    


  public void stop(View view){
       Toast.makeText(getApplicationContext(), "Stopping song", 
       Toast.LENGTH_SHORT).show();
          mp.stop();
          play.setEnabled(false);
          pause.setEnabled(false);
          stop.setEnabled(false);
  }


      public void next(View view) {
          Toast.makeText(getApplicationContext(), "Next song", 
          Toast.LENGTH_SHORT).show();
          mp.reset();
            if(SONG_NUMBER < (SONG_NUMBER - 1)){
                mp.selectTrack(SONG_NUMBER + 1);
                SONG_NUMBER = SONG_NUMBER + 1;
            }
            else {
                mp.start();
                SONG_NUMBER = 0;
             }
            mp.start();
}

 @Override
        public void onCompletion(MediaPlayer mp1) {
        try { 
            mp.reset();
            mp.setDataSource(SD_PATH + songs.get(SONG_NUMBER + 1));
            if(SONG_NUMBER < (SONG_NUMBER - 1)){
                SONG_NUMBER = SONG_NUMBER + 1;
            } 
            else {
                mp.start();
                SONG_NUMBER = 0;
             }
            mp.prepare();
            mp.start();
            play.setEnabled(false);
            pause.setEnabled(true);
            stop.setEnabled(true);
            next.setEnabled(true);
        } 
        catch(IOException e) {
            Log.v(getString(R.string.app_name), e.getMessage());
        }
 }
}

任何人都知道如何解决这个问题？我会非常感激。

以下是我的logcat错误

10-19 01:32:16.428: E/MediaPlayer(7511): start called in state 1
10-19 01:32:16.428: E/MediaPlayer(7511): error (-38, 0)
10-19 01:32:16.428: E/MediaPlayer(7511): start called in state 0
10-19 01:32:16.461: E/MediaPlayer(7511): Error (-38,0)
10-19 01:32:16.473: E/MediaPlayer(7511): start called in state 2
10-19 01:32:16.473: E/MediaPlayer(7511): error (-38, 0)
10-19 01:32:16.474: E/MediaPlayer(7511): prepareAsync called in state 0
10-19 01:32:16.491: D/AndroidRuntime(7511): Shutting down VM
10-19 01:32:16.491: W/dalvikvm(7511): threadid=1: thread exiting with uncaught exception (group=0x41ff39a8)
10-19 01:32:16.534: E/AndroidRuntime(7511): FATAL EXCEPTION: main
10-19 01:32:16.534: E/AndroidRuntime(7511): java.lang.IllegalStateException
10-19 01:32:16.534: E/AndroidRuntime(7511):     at android.media.MediaPlayer.prepare(Native Method)
10-19 01:32:16.534: E/AndroidRuntime(7511):     at com.android.SimplePlayer.MainActivity.onCompletion(MainActivity.java:148)
10-19 01:32:16.534: E/AndroidRuntime(7511):     at android.media.MediaPlayer$EventHandler.handleMessage(MediaPlayer.java:2044)
10-19 01:32:16.534: E/AndroidRuntime(7511):     at android.os.Handler.dispatchMessage(Handler.java:107)
10-19 01:32:16.534: E/AndroidRuntime(7511):     at android.os.Looper.loop(Looper.java:194)
10-19 01:32:16.534: E/AndroidRuntime(7511):     at android.app.ActivityThread.main(ActivityThread.java:5400)
10-19 01:32:16.534: E/AndroidRuntime(7511):     at java.lang.reflect.Method.invokeNative(Native Method)
10-19 01:32:16.534: E/AndroidRuntime(7511):     at java.lang.reflect.Method.invoke(Method.java:525)
10-19 01:32:16.534: E/AndroidRuntime(7511):     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:837)
10-19 01:32:16.534: E/AndroidRuntime(7511):     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:604)
10-19 01:32:16.534: E/AndroidRuntime(7511):     at dalvik.system.NativeStart.main(Native Method)

3 个答案:

答案 0 :(得分：0)

if(SONG_NUMBER < (SONG_NUMBER - 1)){
    mp.selectTrack(SONG_NUMBER + 1);
    SONG_NUMBER = SONG_NUMBER + 1;
} else {
    mp.start();
    SONG_NUMBER = 0;
}

嘿，在下一次点击时，它总是进入其他部分，因为该条件永远不会满足。并且你已经添加了mp.reset（）以及稍后你正在尝试mp.start（）你必须在启动音乐之前将数据源添加到mp。

答案 1 :(得分：0)

Yout逻辑是错误的。 (SONG_NUMBER < (SONG_NUMBER - 1))永远不会是true。

所以会发生两次调用mp.start()，一个在else子句中，一个在它之后。这就是异常说明start called in state...

的原因

您可能想要做的是：

if(SONG_NUMBER < songs.size()-1){
    SONG_NUMBER += 1;
    mp.selectTrack(SONG_NUMBER);
} else {
    SONG_NUMBER = 0;
}
mp.start();

答案 2 :(得分：0)

 public void prev(View view) {
      Toast.makeText(getApplicationContext(), "Previous song", 
      Toast.LENGTH_SHORT).show();
      try {
        if(SONG_NUMBER < songs.size()+1){
            SONG_NUMBER -= 1;
            mp.reset();
            mp.setDataSource(SD_PATH + songs.get(SONG_NUMBER));
        }
        else {
              Toast.makeText(getApplicationContext(), "Cannot play previous song", 
                      Toast.LENGTH_SHORT).show();
        prev.setEnabled(false);
        }
        mp.start();
         } catch(IOException e) {
                Log.v(getString(R.string.app_name), e.getMessage());
         }
  }

根据下一个按钮，我尝试制作上一个按钮。除非你正在播放第一首歌，否则它会有效。我想要它，这样如果按下上一个按钮，prev.setEnabled()会变为false，音乐会继续播放。我也想要它，以便说它在尝试时无法播放以前的歌曲。

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