返回上一个活动，（返回和主页按钮onPause错误）

时间：2012-02-13 01:21:01

标签： android back-button onpause

我有2个活动让我们说A和B.在第一个（A）我选择我的列表视图，在第二个我列出这个列表视图（电台）并使用我从这个列表视图播放的媒体播放器。 我想要做的是，在第二个活动（B）中收听广播电台时，我想回到之前的活动并选择其他列表视图并更新活动B的列表视图。 我只是想从活动B回到A.但我不能。当我按下模拟器的后退按钮时，它给了我错误。我也试图让自己的后退按钮。相同的目的，但在应用程序中只有一个。

你能帮帮我吗，我做错了什么？因为在我之前的应用程序中，后退按钮和主页按钮功能正常而无需执在这一个中它们都不起作用。我使用的是2.2 SDK

logcat的：

02-13 02:42:52.106: E/AndroidRuntime(874): FATAL EXCEPTION: main
02-13 02:42:52.106: E/AndroidRuntime(874): java.lang.RuntimeException: Unable to pause activity {com.beanie.samples.streaming/com.beanie.samples.streaming.HomeActivity}: java.lang.NullPointerException
02-13 02:42:52.106: E/AndroidRuntime(874):  at android.app.ActivityThread.performPauseActivity(ActivityThread.java:3348)
02-13 02:42:52.106: E/AndroidRuntime(874):  at android.app.ActivityThread.performPauseActivity(ActivityThread.java:3305)
02-13 02:42:52.106: E/AndroidRuntime(874):  at android.app.ActivityThread.handlePauseActivity(ActivityThread.java:3288)
02-13 02:42:52.106: E/AndroidRuntime(874):  at android.app.ActivityThread.access$2500(ActivityThread.java:125)
02-13 02:42:52.106: E/AndroidRuntime(874):  at android.app.ActivityThread$H.handleMessage(ActivityThread.java:2044)
02-13 02:42:52.106: E/AndroidRuntime(874):  at android.os.Handler.dispatchMessage(Handler.java:99)
02-13 02:42:52.106: E/AndroidRuntime(874):  at android.os.Looper.loop(Looper.java:123)
02-13 02:42:52.106: E/AndroidRuntime(874):  at android.app.ActivityThread.main(ActivityThread.java:4627)
02-13 02:42:52.106: E/AndroidRuntime(874):  at java.lang.reflect.Method.invokeNative(Native Method)
02-13 02:42:52.106: E/AndroidRuntime(874):  at java.lang.reflect.Method.invoke(Method.java:521)
02-13 02:42:52.106: E/AndroidRuntime(874):  at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:868)
02-13 02:42:52.106: E/AndroidRuntime(874):  at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:626)
02-13 02:42:52.106: E/AndroidRuntime(874):  at dalvik.system.NativeStart.main(Native Method)
02-13 02:42:52.106: E/AndroidRuntime(874): Caused by: java.lang.NullPointerException
02-13 02:42:52.106: E/AndroidRuntime(874):  at com.beanie.samples.streaming.HomeActivity.onPause(HomeActivity.java:439)
02-13 02:42:52.106: E/AndroidRuntime(874):  at android.app.Activity.performPause(Activity.java:3842)
02-13 02:42:52.106: E/AndroidRuntime(874):  at android.app.Instrumentation.callActivityOnPause(Instrumentation.java:1190)
02-13 02:42:52.106: E/AndroidRuntime(874):  at android.app.ActivityThread.performPauseActivity(ActivityThread.java:3335)

我也试图实现onBackPressed，但它没有用。

@Override
    public void onBackPressed() {
        // TODO Auto-generated method stub
        super.onBackPressed();
        Intent info = new Intent(B_Activity.this,A_Activity.class);
            moveTaskToBack(true);
        info.setFlags(Intent.FLAG_ACTIVITY_REORDER_TO_FRONT);
        startActivity(info);
    }

这是我的活动A 

import android.app.Activity;
import android.content.Intent;
import android.os.Bundle;
import android.util.Log;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.Toast;

public class index extends Activity implements OnClickListener{
Button btnYerli,btnYabanci,btnFvrKanal,btnFvrSarki,btnRecs;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        // TODO Auto-generated method stub
        super.onCreate(savedInstanceState);

        setContentView(R.layout.index);

        initializeUI();

        if (AppStatus.getInstance(this).isOnline(this)) {

            Toast t = Toast.makeText(this,"You are online!!!!",8000);
            t.show();       
            } else{  
                  Toast t = Toast.makeText(this,"You are not online!!!!",8000);
                  t.show();
                  Log.v("Home", "You are not online!!!!");    
             }      
    }
    public void initializeUI(){
        btnYerli = (Button) findViewById(R.id.btnYerli);
        btnYerli.setOnClickListener(this);

        btnYabanci = (Button) findViewById(R.id.btnYabanci);
        btnYabanci.setOnClickListener(this);

        btnFvrKanal = (Button) findViewById(R.id.btnKanalFvr);
        btnFvrKanal.setOnClickListener(this);

        btnFvrSarki = (Button) findViewById(R.id.btnSarkiFvr);
        btnFvrSarki.setOnClickListener(this);

        btnRecs = (Button) findViewById(R.id.btnRecs);
        btnRecs.setOnClickListener(this);

    }

    public void onClick(View arg0) {
        // TODO Auto-generated method stub
        //String kanalList="yerli";
        switch(arg0.getId()){
        case R.id.btnYerli:
            Intent openHomeActivityYerli = new Intent("com.beanie.samples.streaming.HOMEACTIVITY");     
            openHomeActivityYerli.putExtra("kanalList","yerli");
            startActivity(openHomeActivityYerli);
        break;
        case R.id.btnYabanci:
            Intent openHomeActivityYabanci = new Intent(index.this,HomeActivity.class);
            openHomeActivityYabanci.putExtra("kanalList","yabanci");
            startActivityForResult(openHomeActivityYabanci,0);
        break;
        case R.id.btnKanalFvr:
            Intent openHomeActivityFavoriKanal = new Intent("com.beanie.samples.streaming.HOMEACTIVITY");
            openHomeActivityFavoriKanal.putExtra("kanalList","favori");
            startActivity(openHomeActivityFavoriKanal);
        break;
        }
    }
}

这是我的Activiy B 

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.net.MalformedURLException;
import java.net.URL;
import java.net.URLConnection;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import java.util.Timer;
import java.util.TimerTask;
import java.util.regex.Matcher;
import java.util.regex.Pattern;

import org.apache.http.HttpEntity;
import org.apache.http.HttpResponse;
import org.apache.http.client.HttpClient;
import org.apache.http.client.methods.HttpPost;
import org.apache.http.impl.client.DefaultHttpClient;
import org.json.JSONArray;
import org.json.JSONException;
import org.json.JSONObject;

import com.spoledge.aacdecoder.AACPlayer;

import android.app.ListActivity;
import android.content.Intent;
import android.content.SharedPreferences;
import android.gesture.Gesture;
import android.gesture.GestureLibraries;
import android.gesture.GestureLibrary;
import android.gesture.GestureOverlayView;
import android.gesture.Prediction;
import android.gesture.GestureOverlayView.OnGesturePerformedListener;
import android.graphics.Color;
import android.media.AudioManager;
import android.media.MediaPlayer;
import android.media.MediaPlayer.OnBufferingUpdateListener;
import android.media.MediaPlayer.OnPreparedListener;
import android.os.Bundle;
import android.os.Handler;
import android.os.Message;
import android.util.Log;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.AdapterView;
import android.widget.AdapterView.OnItemLongClickListener;
import android.widget.ArrayAdapter;
import android.widget.Button;
import android.widget.ListView;
import android.widget.ProgressBar;
import android.widget.TextView;
import android.widget.Toast;

public class HomeActivity extends ListActivity implements OnClickListener, OnGesturePerformedListener{

    private String[] radioNames;
    private String[] radioUrls; 
    private String[] favoriteRadioNames;
    private String[] favoriteRadioUrls;
    private String selectedRadioUrl="http://46.20.4.58:8040/";
    private String selectedRadioName="Select a radio station";
    private String artist;
    private String song;
    private String stopMsg;
    private String welcomeMsg;
    private String noServerConnectionMsg;
    private boolean favoriteButton=true;
    private boolean metaDataThreadStop=false;
    private int mediaType=1;
    private int channelList=1;

    private String JSONUrl; 
    private JSONObject JSONStations;

    private ProgressBar playSeekBar;
    private Button buttonChannelList;
    private Button buttonStopPlay; 
    private Button buttonBack; 
    private TextView stationView,artistView,songView;

    //private Button buttonRecord;
    //private Button buttonStopRecord;

    private MediaPlayer player;
    private AACPlayer aacPlayer;

    private Map<String, ?> favoriteChannelsMap;
    private GestureLibrary mLibrary;

    private Thread getMetaData;

    //private InputStream recordingStream;
    //private RecorderThread recorderThread;
    //private boolean isRecording = false;

    /** Called when the activity is first created. */
    @Override
    public void onCreate(Bundle savedInstanceState) {

        SharedPreferences favoriteChannels = getSharedPreferences("favorite_channels_list", 0);

        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);  

        initializeUIElements();
        setChannelChoice();

        JSONStations = getJSONfromURL(JSONUrl);
        if(JSONStations == null){
            Toast t = Toast.makeText(this,noServerConnectionMsg,8000);
            t.show();
            radioNames = getResources().getStringArray(R.array.radioName);    
            radioUrls = getResources().getStringArray(R.array.radioURL);  
        }else{
            parseJSONtoArray(JSONStations);
        }

        mLibrary = GestureLibraries.fromRawResource(this, R.raw.radiogestures);
        if (!mLibrary.load()) {
            finish();
        }

        GestureOverlayView gestures = (GestureOverlayView) findViewById(R.id.gestures);
        gestures.addOnGesturePerformedListener(this);
        gestures.setGestureColor(Color.TRANSPARENT);

        initializeMediaPlayer();        
        stationView.setText(welcomeMsg);

        chooseChannelList();     
    }

    private void initializeUIElements() {

        stopMsg = getResources().getString(R.string.stopMsg);
        welcomeMsg=getResources().getString(R.string.welcomeMsg);
        noServerConnectionMsg=getResources().getString(R.string.noServerConnection);

        stationView = (TextView) findViewById(R.id.stationView);
        artistView = (TextView) findViewById(R.id.artistView);
        songView = (TextView) findViewById(R.id.songView);

        //channelList = (TextView) findViewById(R.id.channelList);
        //channelList.setOnClickListener(this);

        //likeCheckBox =(CheckBox) findViewById(R.id.likeCheckBox);
        //likeCheckBox.setOnClickListener(this);

        playSeekBar = (ProgressBar) findViewById(R.id.progressBar1);
        playSeekBar.setMax(100);
        playSeekBar.setVisibility(View.INVISIBLE);

        buttonChannelList = (Button) findViewById(R.id.buttonChannelList);
        buttonChannelList.setOnClickListener(this);

        buttonBack =(Button) findViewById(R.id.buttonBack); 
        buttonBack.setOnClickListener(this);

        getFavoritChannels();
        if (favoriteChannelsMap.isEmpty()){
            buttonChannelList.setEnabled(false);
        }else{
            buttonChannelList.setEnabled(true);
        }

        buttonStopPlay = (Button) findViewById(R.id.buttonStopPlay);
        buttonStopPlay.setEnabled(false);
        buttonStopPlay.setOnClickListener(this);

        /*buttonRecord = (Button) findViewById(R.id.buttonRecord);
        buttonRecord.setOnClickListener(this);

        buttonStopRecord = (Button) findViewById(R.id.buttonStopRecord);
        buttonStopRecord.setOnClickListener(this);*/
    }

    @Override
    public void onBackPressed() {
        // TODO Auto-generated method stub
        super.onBackPressed();
        Toast t = Toast.makeText(this,"Back Button",8000);
        t.show();
    }

    private void setChannelChoice(){
        Bundle extras = getIntent().getExtras();
        if(extras !=null) {
            String channels = extras.getString("kanalList");  
            if(channels.compareTo("yerli")==0){
                JSONUrl = getResources().getString(R.string.JSONUrlYerli);
                channelList = 1;
            }
            else if (channels.compareTo("yabanci")==0){
                JSONUrl = getResources().getString(R.string.JSONUrlYabanci);
                channelList = 1;
            }
            else if(channels.compareTo("favori")==0){
                channelList = 2;    
            }

        }else{

        }
    }

    private void chooseChannelList(){
        switch(channelList){
        case 1:
            showChannelsList();
        break;
        case 2:
            showFavoriteChannelList();      
        break;
        }   
    }

    private void parseJSONtoArray(JSONObject JSONText){
        List<String> radioNamesArrayList = new ArrayList<String>();
        List<String> radioURLsArrayList = new ArrayList<String>();      
        try {
            JSONObject KanallarObject = JSONText.getJSONObject("Kanallar");
            //String versionString = KanallarObject.getString("Version");
            JSONArray kanalArray = KanallarObject.getJSONArray("Kanal");
            for(int i=0;i < kanalArray.length();i++){  
                radioNamesArrayList.add(kanalArray.getJSONObject(i).getString("Isim").toString());
                radioURLsArrayList.add(kanalArray.getJSONObject(i).getString("Adres").toString());
            }

        } catch (JSONException e) {
            // TODO Auto-generated catch block
            Log.e("log_tag", "Error parsing data "+e.toString());       
        }
        radioNames = radioNamesArrayList.toArray(new String[radioNamesArrayList.size()]);
        radioUrls = radioURLsArrayList.toArray(new String[radioURLsArrayList.size()]);
    }

    public void onClick(View v) {
        switch (v.getId()){
        case R.id.buttonBack:    
            Intent info = new Intent(HomeActivity.this,index.class);
            Log.d("1","1");
            moveTaskToBack(true);
            Log.d("2","2");
            info.setFlags(Intent.FLAG_ACTIVITY_REORDER_TO_FRONT);
            Log.d("3","3");

            startActivityForResult(info,0);
        break;
        case R.id.buttonChannelList:
            if (favoriteButton){
                showFavoriteChannelList();
            }else{
                showChannelsList();
            }
        break;
        case R.id.buttonStopPlay:
            stopPlaying();
        break; 
        }
        /*else if (v == buttonRecord) {
            recorderThread = new RecorderThread();
            recorderThread.start();

            buttonRecord.setEnabled(false);
            buttonStopRecord.setEnabled(true);
        } else if (v == buttonStopRecord) {
            stopRecording();
        }*/
    }

    @Override
    protected void onRestart() {
        // TODO Auto-generated method stub
        super.onRestart();
        Log.d("onReStart","^^^^^^^^^RESTART^^^^^^");

    }

    @Override
    protected void onResume() {
        // TODO Auto-generated method stub
        super.onResume();
        Log.d("onResume","^^^^^^^^^RESUME^^^^^^");

    }

    @Override
    protected void onStart() {
        // TODO Auto-generated method stub
        super.onStart();
        Log.d("onStart","^^^^^^^^^START^^^^^^");
    }

    @Override
    protected void onStop() {
        // TODO Auto-generated method stub
        super.onStop();
        Log.d("onStop","^^^^^^^^^STOP^^^^^^");
    }


    private void startPlaying() {

        stationView.setText(selectedRadioName);
        buttonStopPlay.setEnabled(true);
        playSeekBar.setVisibility(View.VISIBLE);
        initializeMediaPlayer();

        switch(mediaType){
        case 1:
            aacPlayer.playAsync(selectedRadioUrl);
            metaDataThreadStop=false;
            getMetaData = new Thread(){
                    public void run(){                  
                        getMeta();                                  
                    }   
            };
            getMetaData.start();
            break;
        case 2:
            player.setAudioStreamType(AudioManager.STREAM_RING);     
            player.prepareAsync();                
            player.setOnPreparedListener(new OnPreparedListener() {
                public void onPrepared(MediaPlayer mp) {  
                    player.start();     
                    //buttonRecord.setEnabled(true);
                }
            });
            break;
        }

    }

    private void stopPlaying() {
        int i=0;
        stationView.setText(stopMsg);
        switch(mediaType){
        case 1:
            aacPlayer.stop();
            //aacPlayer.
            metaDataThreadStop=true;
            /*if (getMetaData!=null){
                Log.d("Stop","threadNULL");
                getMetaData.interrupt();
                Log.d("threadInterrupted",String.valueOf(getMetaData.isInterrupted()));             
                try{
                    Log.d("Stop","threadJoin");
                    getMetaData.join();
                }catch(InterruptedException e){
                    Thread.currentThread().interrupt();
                }
            }*/
            break;
        case 2:
            if (player.isPlaying()){
            player.stop();
             //aacPlayer.stop();
             player.release();
            }
            break;
        }
        buttonChannelList.setEnabled(true);
        buttonStopPlay.setEnabled(false);
        playSeekBar.setVisibility(View.INVISIBLE);
        //buttonRecord.setEnabled(false);
        //buttonStopRecord.setEnabled(false);
        /*stopRecording();*/
    }

    private void initializeMediaPlayer() {
        switch(mediaType){
        case 1:
            aacPlayer = new AACPlayer();
            break;
        case 2:
            player = new MediaPlayer();       
            try {
                player.setDataSource(selectedRadioUrl);      
            } catch (IllegalArgumentException e) {
                e.printStackTrace();
            } catch (IllegalStateException e) {
                e.printStackTrace();
            } catch (IOException e) {
                e.printStackTrace();
            }
            player.setOnBufferingUpdateListener(new OnBufferingUpdateListener() {
                public void onBufferingUpdate(MediaPlayer mp, int percent) {
                    playSeekBar.setSecondaryProgress(percent);
                    Log.i("Buffering", "" + percent);
                }
            });
            break;
        }
    }

    @Override
    protected void onListItemClick(ListView l, View v, int position, long id) {
        // TODO Auto-generated method stub
        //super.onListItemClick(l, v, position, id);
        String selection = l.getItemAtPosition(position).toString();
        Toast.makeText(this, selection, Toast.LENGTH_LONG).show();
        artistView.setText("looking for artist info");
        songView.setText("looking for song info");
        if (favoriteButton){
            selectedRadioUrl = radioUrls[position];
            selectedRadioName = radioNames[position];
        }else{
            selectedRadioUrl = favoriteRadioUrls[position];
            selectedRadioName = favoriteRadioNames[position];
        }
        switch(mediaType){
        case 1:
            stopPlaying();
            startPlaying();
            break;
        case 2:
            if (player.isPlaying()) {
            stopPlaying();
            startPlaying();
            }
            else{      
                startPlaying();    
                }
            break;
        }
    }

    @Override
    protected void onPause() {
        super.onPause();
        if (player.isPlaying()) {
            player.stop();
        }
    }

    public static JSONObject getJSONfromURL(String url){

        //initialize
        InputStream is = null;
        String result = "";
        JSONObject jArray = null;

        //http post
        try{
            HttpClient httpclient = new DefaultHttpClient();
            HttpPost httppost = new HttpPost(url);
            HttpResponse response = httpclient.execute(httppost);
            HttpEntity entity = response.getEntity();
            is = entity.getContent();

        }catch(Exception e){
            Log.e("log_tag", "Error in http connection "+e.toString());
        }

        //convert response to string
        try{
            BufferedReader reader = new BufferedReader(new InputStreamReader(is,"UTF-8"),8000);
            StringBuilder sb = new StringBuilder();
            String line = null;
            while ((line = reader.readLine()) != null) {
                sb.append(line + "\n");
            }
            is.close();
            result=sb.toString();
        }catch(Exception e){
            Log.e("log_tag", "Error converting result "+e.toString());
        }

        //try parse the string to a JSON object
        try{
                jArray = new JSONObject(result);
        }catch(JSONException e){
            Log.e("log_tag", "Error parsing data "+e.toString());
        }

        return jArray;
    }

    private void runLongClick(int clickId){
        SharedPreferences favoriteChannels = getSharedPreferences("favorite_channels_list", 0);
        SharedPreferences.Editor favoriteChannelsEditor = favoriteChannels.edit();
        if (favoriteButton){        
            favoriteChannelsEditor.putString(radioNames[clickId], radioUrls[clickId]);
            Toast.makeText(this, radioNames[clickId]+" added to favorites", Toast.LENGTH_LONG).show();
            buttonChannelList.setEnabled(true);
            favoriteChannelsEditor.commit();
        }else{
            Toast.makeText(this, favoriteRadioNames[clickId]+" removed From favorites", Toast.LENGTH_LONG).show();
            favoriteChannelsEditor.remove(favoriteRadioNames[clickId]);     
            favoriteChannelsEditor.commit();
            showFavoriteChannelList();          
        }       
    }
    private void getFavoritChannels(){
        SharedPreferences favoriteChannels = getSharedPreferences("favorite_channels_list", 0);
        favoriteChannelsMap=favoriteChannels.getAll();
        int i=0;
        favoriteRadioNames = new String[favoriteChannelsMap.size()];
        favoriteRadioUrls = new String[favoriteChannelsMap.size()];
        Log.d("String Arrays",String.valueOf(favoriteRadioNames.length));
        for(String s : favoriteChannelsMap.keySet()){
            favoriteRadioNames[i]=s;
            favoriteRadioUrls[i]=favoriteChannelsMap.get(s).toString();
            i++;
            }
    }

    private void showChannelsList(){
        buttonChannelList.setText("Favorite Channels");
        ArrayAdapter<String> adapter;
        adapter = new ArrayAdapter<String>(this,R.layout.channels,R.id.channelList,radioNames);
        setListAdapter(adapter);
        ListView lv = getListView();
        lv.setOnItemLongClickListener(new OnItemLongClickListener(){
        public boolean onItemLongClick(AdapterView<?> arg0, View arg1,int row, long arg3) {
            runLongClick(row);
            return true;
           }});
        favoriteButton=!favoriteButton;
    }
    private void showFavoriteChannelList(){
        buttonChannelList.setText("Channel List");
        getFavoritChannels();
        ArrayAdapter<String> adapterFavorits;
        adapterFavorits = new ArrayAdapter<String>(this,R.layout.channels,R.id.channelList,favoriteRadioNames);
        setListAdapter(adapterFavorits);
        ListView lv = getListView();
        lv.setOnItemLongClickListener(new OnItemLongClickListener(){
        public boolean onItemLongClick(AdapterView<?> arg0, View arg1,int row, long arg3) {
            runLongClick(row);
            return true;
           }});
        favoriteButton=!favoriteButton;

    }
    public void onGesturePerformed(GestureOverlayView overlay, Gesture gesture) {
        Log.d("Gesture","Gesture Aldi");
        // TODO Auto-generated method stub
        ArrayList<Prediction> predictions = mLibrary.recognize(gesture);
        // We want at least one prediction
        if (predictions.size() > 0) {
            Prediction prediction = predictions.get(0);
            // We want at least some confidence in the result
            if (prediction.score > 1.0) {
                // Show the spell
                Toast.makeText(this, String.valueOf(prediction.score), Toast.LENGTH_SHORT).show();
                stopPlaying();
            }
        }

    }

    public void getMeta(){
        Timer timer;
        timer = new Timer();
        while(!metaDataThreadStop){
        timer.schedule(new TimerTask() {
            public void run() {
                URL url;
                //Message msg = handler.obtainMessage();
                try {
                    Log.d("Metadatos","Dentro del try para obtener los metadatos");
                    url = new URL(selectedRadioUrl);
                    IcyStreamMeta icy = new IcyStreamMeta(url);

                    artist=icy.getArtist();
                    Log.d("artist",artist);
                    song=icy.getTitle();
                    Log.d("song",song);
                    handler.sendEmptyMessage(0);


                } catch (MalformedURLException e) {
                    // TODO Auto-generated catch block
                    e.printStackTrace();
                }catch (IOException e) {
                    // TODO Auto-generated catch block
                    e.printStackTrace();
                }

            }
        }, 0, 30000);}
        timer.cancel();
    } 

    private Handler handler = new Handler() {
         @Override
         public void handleMessage(Message msg) {
             if(artist.compareTo("")==0 || artist.compareTo("-")==0)
                artistView.setText("no artist info");
             else{
                artistView.setText(artist);
                Log.d("handler_artist",artist);
             }

             if(song.compareTo("")==0 || song.compareTo("-")==0)
                songView.setText("no song info");
             else{
                 Log.d("handler_song",song);
                songView.setText(song);
                }

         }
    };
     @Override
    public void onSaveInstanceState(Bundle savedInstanceState) {
         super.onSaveInstanceState(savedInstanceState);
         // your stuff or nothing
     }

     @Override
    public void onRestoreInstanceState(Bundle savedInstanceState) {

1 个答案:

答案 0 :(得分：1)

堆栈跟踪表明player为空。 

02-13 02:42:52.106: E/AndroidRuntime(874): Caused by: java.lang.NullPointerException
02-13 02:42:52.106: E/AndroidRuntime(874):  at com.beanie.samples.streaming.HomeActivity.onPause(HomeActivity.java:439)

@Override
protected void onPause() {
    super.onPause();
    if (player.isPlaying()) {
        player.stop();
    }
}

您显然仅针对player为2的情况初始化mediaType。否则，您正在初始化aacPlayer。 

private void initializeMediaPlayer() {
    switch(mediaType){
    case 1:
        aacPlayer = new AACPlayer();
        break;
    case 2:
        player = new MediaPlayer();       
        ...

因此，您需要对player进行空检查。或者，重构您的代码以封装两个不同媒体播放器的存在。

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