求救android程序问题

Question

先是错误信息

Answer 1

接着是代码 
 package hh.qq;import java.io.IOException;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.Random;import android.app.Activity;
import android.content.Intent;
import android.media.MediaPlayer;
import android.media.MediaPlayer.OnCompletionListener;
import android.os.Bundle;
import android.os.Handler;
import android.util.Log;
import android.view.View;
import android.widget.ImageButton;
import android.widget.SeekBar;
import android.widget.TextView;
import android.widget.Toast;
 public class AndroidBuildingMusicPlayerActivity extends Activity implements OnCompletionListener, SeekBar.OnSeekBarChangeListener {
     private ImageButton btnPlay;
     private ImageButton btnNext;
     private ImageButton btnPrevious;
     private ImageButton btnPlaylist;
     private ImageButton btnRepeat;
     private ImageButton btnShuffle;
     private SeekBar songProgressBar;
     private TextView songTitleLabel;
     private TextView songCurrentDurationLabel;
     private TextView songTotalDurationLabel;
     // Media Player
     private MediaPlayer mp;
     // Handler to update UI timer, progress bar etc,.
     private Handler mHandler = new Handler();;
     private SongsManager songManager;
     private Utilities utils;
     private int seekForwardTime =5000;// 5000 milliseconds
     private int seekBackwardTime =5000;// 5000 milliseconds
     private int currentSongIndex =0;
     private boolean isShuffle =false;
     private boolean isRepeat =false;
     private static final String TAG = "aa";
     private ArrayList<HashMap<String, String>> songsList = new ArrayList<HashMap<String, String>>();
     @Override
     public void onCreate(Bundle savedInstanceState) {
         super.onCreate(savedInstanceState);
         Log.v(TAG, "===== My log message");
         setContentView(R.layout.player);
         // All player buttons
         btnPlay = (ImageButton) findViewById(R.id.btnPlay);
         btnNext = (ImageButton) findViewById(R.id.btnNext);
         btnPrevious = (ImageButton) findViewById(R.id.btnPrevious);
         btnPlaylist = (ImageButton) findViewById(R.id.btnPlaylist);
         btnRepeat = (ImageButton) findViewById(R.id.btnRepeat);
         btnShuffle = (ImageButton) findViewById(R.id.btnShuffle);
         songProgressBar = (SeekBar) findViewById(R.id.songProgressBar);
         songTitleLabel = (TextView) findViewById(R.id.songTitle);
         songCurrentDurationLabel = (TextView) findViewById(R.id.songCurrentDurationLabel);
         songTotalDurationLabel = (TextView) findViewById(R.id.songTotalDurationLabel);
         // Mediaplayer
         mp =new MediaPlayer();
         songManager =new SongsManager();
         utils =new Utilities();
         // Listeners
         songProgressBar.setOnSeekBarChangeListener(this);// Important
         mp.setOnCompletionListener(this);// Important
         // Getting all songs list
         songsList = songManager.getPlayList();
         // By default play first song
         playSong(0);
         /**
          * Play button click event
          * plays a song and changes button to pause image
          * pauses a song and changes button to play image
          * */
         btnPlay.setOnClickListener(new View.OnClickListener() {
             @Override
             public void onClick(View arg0) {
                 // check for already playing
                 if(mp.isPlaying()){
                     if(mp!=null){
                         mp.pause();
                         // Changing button image to play button
                         btnPlay.setImageResource(R.drawable.playdefault);
                     }
                 }else{
                     // Resume song
                     if(mp!=null){
                         mp.start();
                         // Changing button image to pause button
                         btnPlay.setImageResource(R.drawable.pausedefault);
                     }
                 }
             }
         });
         /**
          * Next button click event
          * Plays next song by taking currentSongIndex + 1
          * */
         btnNext.setOnClickListener(new View.OnClickListener() {
             @Override
             public void onClick(View arg0) {
                 // check if next song is there or not
                 if(currentSongIndex < (songsList.size() - 1)){
                     playSong(currentSongIndex +1);
                     currentSongIndex = currentSongIndex +1;
                 }else{
                     // play first song
                     playSong(0);
                     currentSongIndex =0;
                 }
             }
         });
         /**
          * Back button click event
          * Plays previous song by currentSongIndex - 1
          * */
         btnPrevious.setOnClickListener(new View.OnClickListener() {
             @Override
             public void onClick(View arg0) {
                 if(currentSongIndex > 0){
                     playSong(currentSongIndex -1);
                     currentSongIndex = currentSongIndex -1;
                 }else{
                     // play last song
                     playSong(songsList.size() -1);
                     currentSongIndex = songsList.size() -1;
                 }
             }
         });
         /**
          * Button Click event for Repeat button
          * Enables repeat flag to true
          * */
         btnRepeat.setOnClickListener(new View.OnClickListener() {
             @Override
             public void onClick(View arg0) {
                 if(isRepeat){
                     isRepeat =false;
                     Toast.makeText(getApplicationContext(),"Repeat is OFF", Toast.LENGTH_SHORT).show();
                     btnRepeat.setImageResource(R.drawable.repeatdefault);
                 }else{
                     // make repeat to true
                     isRepeat =true;
                     Toast.makeText(getApplicationContext(),"Repeat is ON", Toast.LENGTH_SHORT).show();
                     // make shuffle to false
                     isShuffle =false;
                     btnRepeat.setImageResource(R.drawable.repeatfocus);
                     btnShuffle.setImageResource(R.drawable.shuffledefault);
                 }
             }
         });
         /**
          * Button Click event for Shuffle button
          * Enables shuffle flag to true
          * */
         btnShuffle.setOnClickListener(new View.OnClickListener() {
             @Override
             public void onClick(View arg0) {
                 if(isShuffle){
                     isShuffle =false;
                     Toast.makeText(getApplicationContext(),"Shuffle is OFF", Toast.LENGTH_SHORT).show();
                     btnShuffle.setImageResource(R.drawable.shuffledefault);
                 }else{
                     // make repeat to true
                     isShuffle=true;
                     Toast.makeText(getApplicationContext(),"Shuffle is ON", Toast.LENGTH_SHORT).show();
                     // make shuffle to false
                     isRepeat =false;
                     btnShuffle.setImageResource(R.drawable.shufflefocus);
                     btnRepeat.setImageResource(R.drawable.repeatdefault);
                 }
             }
         });
         /**
          * Button Click event for Play list click event
          * Launches list activity which displays list of songs
          * */
         btnPlaylist.setOnClickListener(new View.OnClickListener() {
             @Override
             public void onClick(View arg0) {
                 Intent i =new Intent(getApplicationContext(), PlayListActivity.class);
                 startActivityForResult(i,100);
             }
         });
     }

Answer 2

     /**
      * Receiving song index from playlist view
      * and play the song
      * */
     @Override
     protected void onActivityResult(int requestCode,int resultCode,Intent data) {
         super.onActivityResult(requestCode, resultCode, data);
         if(resultCode == 100){
              currentSongIndex = data.getExtras().getInt("songIndex");
              // play selected song
              playSong(currentSongIndex);
         }
     }
     /**
      * Function to play a song
      * @param songIndex - index of song
      * */
     public void playSong(int songIndex){
         // Play song
         try{
             mp.reset();
             mp.setDataSource(songsList.get(songIndex).get("songPath"));
             mp.prepare();
             mp.start();
             // Displaying Song title
             String songTitle = songsList.get(songIndex).get("songTitle");
             songTitleLabel.setText(songTitle);
             // Changing Button Image to pause image
             btnPlay.setImageResource(R.drawable.pausedefault);
             // set Progress bar values
             songProgressBar.setProgress(0);
             songProgressBar.setMax(100);
             // Updating progress bar
             updateProgressBar();
         }catch(IllegalArgumentException e) {
             e.printStackTrace();
         }catch(IllegalStateException e) {
             e.printStackTrace();
         }catch(IOException e) {
             e.printStackTrace();
         }
     }
     /**
      * Update timer on seekbar
      * */
     public void updateProgressBar() {
         mHandler.postDelayed(mUpdateTimeTask,100);
     } 
     /**
      * Background Runnable thread
      * */
     private Runnable mUpdateTimeTask = new Runnable() {
            public void run() {
                long totalDuration = mp.getDuration();
                long currentDuration = mp.getCurrentPosition();
                // Displaying Total Duration time
                songTotalDurationLabel.setText(""+utils.milliSecondsToTimer(totalDuration));
                // Displaying time completed playing
                songCurrentDurationLabel.setText(""+utils.milliSecondsToTimer(currentDuration));
                // Updating progress bar
                int progress = (int)(utils.getProgressPercentage(currentDuration, totalDuration));
                //Log.d("Progress", ""+progress);
                songProgressBar.setProgress(progress);
                // Running this thread after 100 milliseconds
                mHandler.postDelayed(this,100);
            }
         };
     /**
      *
      * */
     @Override
     public void onProgressChanged(SeekBar seekBar,int progress,boolean fromTouch) 
     {
      
     }
     /**
      * When user starts moving the progress handler
      * */
     @Override
     public void onStartTrackingTouch(SeekBar seekBar) {
         // remove message Handler from updating progress bar
         mHandler.removeCallbacks(mUpdateTimeTask);
     }
     /**
      * When user stops moving the progress hanlder
      * */
     @Override
     public void onStopTrackingTouch(SeekBar seekBar) {
         mHandler.removeCallbacks(mUpdateTimeTask);
         int totalDuration = mp.getDuration();
         int currentPosition = utils.progressToTimer(seekBar.getProgress(), totalDuration);
         // forward or backward to certain seconds
         mp.seekTo(currentPosition);
         // update timer progress again
         updateProgressBar();
     }
     /**
      * On Song Playing completed
      * if repeat is ON play same song again
      * if shuffle is ON play random song
      * */
     @Override
     public void onCompletion(MediaPlayer arg0) {
         // check for repeat is ON or OFF
         if(isRepeat){
             // repeat is on play same song again
             playSong(currentSongIndex);
         }else if(isShuffle){
             // shuffle is on - play a random song
             Random rand =new Random();
             currentSongIndex = rand.nextInt((songsList.size() -1) -0+1) +0;
             playSong(currentSongIndex);
         }else{
             // no repeat or shuffle ON - play next song
             if(currentSongIndex < (songsList.size() - 1)){
                 playSong(currentSongIndex +1);
                 currentSongIndex = currentSongIndex +1;
             }else{
                 // play first song
                 playSong(0);
                 currentSongIndex =0;
             }
         }
     }
     @Override
      public void onDestroy(){
      super.onDestroy();
         mp.release();
      }
 }

Answer 3

据错误信息描述是说你的playSong方法中有个集合（看着应该是songsList）长度是0，可是你还是去获取数据，所以抛出了IndexOutOfBounds Exception

Answer 4

看图中的倒数第2到6行，说明了错误原因，没行后面都带一个行号，你可以根据这个来确定错误位置，
这个错误的原因如楼上所说，songList是空列表，可以在trycatch后面加一个catch (Exception e){},来处理其他的异常

Answer 5

songsList在调用get()之前需要判断一下是否为空songsList.size()==0
在调用，否则会出异常。