Java 准备音频播放器时出现空指针异常
我正在准备一个小型音频播放器,并显示设备中的音频歌曲列表,但每当我点击任何要播放的歌曲时,每次都会出错 完整Logcat:Java 准备音频播放器时出现空指针异常,java,android,android-contentprovider,Java,Android,Android Contentprovider,我正在准备一个小型音频播放器,并显示设备中的音频歌曲列表,但每当我点击任何要播放的歌曲时,每次都会出错 完整Logcat: 06-10 15:52:28.440: W/dalvikvm(3732): threadid=1: thread exiting with uncaught exception (group=0x41e0d2a0) 06-10 15:52:28.450: E/AndroidRuntime(3732): FATAL EXCEPTION: main 06-10 15:52:28
06-10 15:52:28.440: W/dalvikvm(3732): threadid=1: thread exiting with uncaught exception (group=0x41e0d2a0)
06-10 15:52:28.450: E/AndroidRuntime(3732): FATAL EXCEPTION: main
06-10 15:52:28.450: E/AndroidRuntime(3732): java.lang.IllegalStateException: Could not execute method of the activity
06-10 15:52:28.450: E/AndroidRuntime(3732): at android.view.View$1.onClick(View.java:3699)
06-10 15:52:28.450: E/AndroidRuntime(3732): at android.view.View.performClick(View.java:4223)
06-10 15:52:28.450: E/AndroidRuntime(3732): at android.view.View$PerformClick.run(View.java:17275)
06-10 15:52:28.450: E/AndroidRuntime(3732): at android.os.Handler.handleCallback(Handler.java:615)
06-10 15:52:28.450: E/AndroidRuntime(3732): at android.os.Handler.dispatchMessage(Handler.java:92)
06-10 15:52:28.450: E/AndroidRuntime(3732): at android.os.Looper.loop(Looper.java:137)
06-10 15:52:28.450: E/AndroidRuntime(3732): at android.app.ActivityThread.main(ActivityThread.java:4921)
06-10 15:52:28.450: E/AndroidRuntime(3732): at java.lang.reflect.Method.invokeNative(Native Method)
06-10 15:52:28.450: E/AndroidRuntime(3732): at java.lang.reflect.Method.invoke(Method.java:511)
06-10 15:52:28.450: E/AndroidRuntime(3732): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1036)
06-10 15:52:28.450: E/AndroidRuntime(3732): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:803)
06-10 15:52:28.450: E/AndroidRuntime(3732): at dalvik.system.NativeStart.main(Native Method)
06-10 15:52:28.450: E/AndroidRuntime(3732): Caused by: java.lang.reflect.InvocationTargetException
06-10 15:52:28.450: E/AndroidRuntime(3732): at java.lang.reflect.Method.invokeNative(Native Method)
06-10 15:52:28.450: E/AndroidRuntime(3732): at java.lang.reflect.Method.invoke(Method.java:511)
06-10 15:52:28.450: E/AndroidRuntime(3732): at android.view.View$1.onClick(View.java:3694)
06-10 15:52:28.450: E/AndroidRuntime(3732): ... 11 more
06-10 15:52:28.450: E/AndroidRuntime(3732): Caused by: java.lang.NullPointerException
06-10 15:52:28.450: E/AndroidRuntime(3732): at com.example.syncing.MainActivity.songPicked(MainActivity.java:98)
06-10 15:52:28.450: E/AndroidRuntime(3732): ... 14 more
06-10 15:52:38.065: I/Process(3732): Sending signal. PID: 3732 SIG: 9
检查我的完整源代码MainActivity.java:-
public class MainActivity extends Activity implements MediaPlayerControl {
//song list variables
private ArrayList<Song> songList;
private ListView songView;
//service
private MusicService musicSrv;
private Intent playIntent;
//binding
private boolean musicBound=false;
//controller
private MusicController controller;
//activity and playback pause flags
private boolean paused=false, playbackPaused=false;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
//retrieve list view
songView = (ListView)findViewById(R.id.song_list);
//instantiate list
songList = new ArrayList<Song>();
//get songs from device
getSongList();
//sort alphabetically by title
Collections.sort(songList, new Comparator<Song>(){
public int compare(Song a, Song b){
return a.getTitle().compareTo(b.getTitle());
}
});
//create and set adapter
SongAdapter songAdt = new SongAdapter(this, songList);
songView.setAdapter(songAdt);
//setup controller
setController();
}
//connect to the service
private ServiceConnection musicConnection = new ServiceConnection(){
@Override
public void onServiceConnected(ComponentName name, IBinder service) {
MusicBinder binder = (MusicBinder)service;
//get service
musicSrv = binder.getService();
//pass list
musicSrv.setList(songList);
musicBound = true;
}
@Override
public void onServiceDisconnected(ComponentName name) {
musicBound = false;
}
};
//start and bind the service when the activity starts
@Override
protected void onStart() {
super.onStart();
if(playIntent==null){
playIntent = new Intent(this, MusicService.class);
bindService(playIntent, musicConnection, Context.BIND_AUTO_CREATE);
startService(playIntent);
}
}
//user song select
public void songPicked(View view){
musicSrv.setSong(Integer.parseInt(view.getTag().toString()));
musicSrv.playSong();
if(playbackPaused){
setController();
playbackPaused=false;
}
controller.show(0);
}
//method to retrieve song info from device
public void getSongList(){
//query external audio
ContentResolver musicResolver = getContentResolver();
Uri musicUri = android.provider.MediaStore.Audio.Media.EXTERNAL_CONTENT_URI;
Cursor musicCursor = musicResolver.query(musicUri, null, null, null, null);
//iterate over results if valid
if(musicCursor!=null && musicCursor.moveToFirst()){
//get columns
int titleColumn = musicCursor.getColumnIndex
(android.provider.MediaStore.Audio.Media.TITLE);
int idColumn = musicCursor.getColumnIndex
(android.provider.MediaStore.Audio.Media._ID);
int artistColumn = musicCursor.getColumnIndex
(android.provider.MediaStore.Audio.Media.ARTIST);
//add songs to list
do {
long thisId = musicCursor.getLong(idColumn);
String thisTitle = musicCursor.getString(titleColumn);
String thisArtist = musicCursor.getString(artistColumn);
songList.add(new Song(thisId, thisTitle, thisArtist));
}
while (musicCursor.moveToNext());
}
}
@Override
public boolean canPause() {
return true;
}
@Override
public boolean canSeekBackward() {
return true;
}
@Override
public boolean canSeekForward() {
return true;
}
@Override
public int getAudioSessionId() {
return 0;
}
@Override
public int getBufferPercentage() {
return 0;
}
@Override
public int getCurrentPosition() {
if(musicSrv!=null && musicBound && musicSrv.isPng())
return musicSrv.getPosn();
else return 0;
}
@Override
public int getDuration() {
if(musicSrv!=null && musicBound && musicSrv.isPng())
return musicSrv.getDur();
else return 0;
}
@Override
public boolean isPlaying() {
if(musicSrv!=null && musicBound)
return musicSrv.isPng();
return false;
}
@Override
public void pause() {
playbackPaused=true;
musicSrv.pausePlayer();
}
@Override
public void seekTo(int pos) {
musicSrv.seek(pos);
}
@Override
public void start() {
musicSrv.go();
}
//set the controller up
private void setController(){
controller = new MusicController(this);
//set previous and next button listeners
controller.setPrevNextListeners(new View.OnClickListener() {
@Override
public void onClick(View v) {
playNext();
}
}, new View.OnClickListener() {
@Override
public void onClick(View v) {
playPrev();
}
});
//set and show
controller.setMediaPlayer(this);
controller.setAnchorView(findViewById(R.id.song_list));
controller.setEnabled(true);
}
private void playNext(){
musicSrv.playNext();
if(playbackPaused){
setController();
playbackPaused=false;
}
controller.show(0);
}
private void playPrev(){
musicSrv.playPrev();
if(playbackPaused){
setController();
playbackPaused=false;
}
controller.show(0);
}
@Override
protected void onPause(){
super.onPause();
paused=true;
}
@Override
protected void onResume(){
super.onResume();
if(paused){
setController();
paused=false;
}
}
@Override
protected void onStop() {
controller.hide();
super.onStop();
}
@Override
protected void onDestroy() {
stopService(playIntent);
musicSrv=null;
super.onDestroy();
}
}
公共类MainActivity扩展活动实现MediaPlayerControl{
//歌曲列表变量
私人ArrayList歌曲列表;
私有列表视图;
//服务
私人音乐服务;
私人意图;
//装订
私有布尔值musicBound=false;
//控制器
专用音乐控制器;
//活动和播放暂停标志
private boolean paused=false,playbackPaused=false;
@凌驾
创建时受保护的void(Bundle savedInstanceState){
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
//检索列表视图
songView=(ListView)findViewById(R.id.song_列表);
//实例化列表
songList=newarraylist();
//从设备获取歌曲
getSongList();
//按标题按字母顺序排序
Collections.sort(songList,newcomparator(){
公共整数比较(歌曲a、歌曲b){
返回a.getTitle().compareTo(b.getTitle());
}
});
//创建并设置适配器
SongAdapter songAdt=新的SongAdapter(此,歌曲列表);
songView.setAdapter(songAdt);
//设置控制器
setController();
}
//连接到服务
专用ServiceConnection musicConnection=新ServiceConnection(){
@凌驾
服务连接上的公共无效(组件名称,IBinder服务){
MusicBinder=(MusicBinder)服务;
//得到服务
musicSrv=binder.getService();
//通行证
音乐集列表(歌曲列表);
musicBound=正确;
}
@凌驾
ServiceDisconnected上的公共无效(组件名称){
musicBound=假;
}
};
//在活动启动时启动并绑定服务
@凌驾
受保护的void onStart(){
super.onStart();
如果(playIntent==null){
playIntent=新的意图(这是MusicService.class);
bindService(playIntent、musicConnection、Context.BIND\u AUTO\u CREATE);
startService(playIntent);
}
}
//用户歌曲选择
已拾取公共空视图(视图){
musicSrv.setSong(Integer.parseInt(view.getTag().toString());
musicSrv.playSong();
如果(播放暂停){
setController();
playbackPaused=false;
}
控制器显示(0);
}
//从设备检索歌曲信息的方法
public void getSongList(){
//查询外部音频
ContentResolver musicResolver=getContentResolver();
Uri musicUri=android.provider.MediaStore.Audio.Media.EXTERNAL\u CONTENT\u Uri;
游标musicCursor=musicSolver.query(musicUri,null,null,null);
//迭代结果(如果有效)
if(musicCursor!=null&&musicCursor.moveToFirst()){
//获取列
int titleColumn=musicCursor.getColumnIndex
(android.provider.MediaStore.Audio.Media.TITLE);
int idColumn=musicCursor.getColumnIndex
(android.provider.MediaStore.Audio.Media.\u ID);
int artistColumn=musicCursor.getColumnIndex
(android.provider.MediaStore.Audio.Media.ARTIST);
//将歌曲添加到列表中
做{
long thisId=musicCursor.getLong(idColumn);
String thisttitle=musicCursor.getString(titleColumn);
String thisArtist=musicCursor.getString(artistColumn);
歌曲列表。添加(新歌(thisId,thisTitle,thisArtist));
}
while(musicCursor.moveToNext());
}
}
@凌驾
公共布尔canPause(){
返回true;
}
@凌驾
公共布尔值canSeekBackward(){
返回true;
}
@凌驾
公共布尔值canSeekForward(){
返回true;
}
@凌驾
public int getAudioSessionId(){
返回0;
}
@凌驾
public int getBufferPercentage(){
返回0;
}
@凌驾
public int getCurrentPosition(){
if(musicSrv!=null&&musicBound&&musicSrv.isPng())
返回musicSrv.getPosn();
否则返回0;
}
@凌驾
public int getDuration(){
if(musicSrv!=null&&musicBound&&musicSrv.isPng())
返回musicSrv.getDur();
否则返回0;
}
@凌驾
公共布尔值显示(){
if(musicSrv!=null&&musicBound)
返回musicSrv.isPng();
返回false;
}
@凌驾
公共空间暂停(){
playbackPaused=true;
musicSrv.pausePlayer();
}
@凌驾
公共无效seekTo(内部位置){
音乐搜索(pos);
}
@凌驾
公开作废开始(){
musicSrv.go();
}
//设置控制器
私有void setController(){
控制器=新的音乐控制器(此);
//设置上一个和下一个按钮侦听器
controller.setPrevNextListeners(新视图.OnClickListener(){
@凌驾
公共void onClick(视图v){
playNext();
}
},新视图。OnClickListener(){
@凌驾
公共void onClick(视图v){
playprov();
}
});
//布展
控制器.setMediaPlayer(此);
控制器setAnchorView(findViewById(R.id.song_列表));
控制器.setEnabled(真);
}
下一个()的私有空间{
musicSrv.playNext();
如果(播放暂停){
setController();
playbackPaused=false;
}
骗局
if(view.getTag() != null) {
...
}