啓動時線程崩潰的代碼（android初學者）

Question

我正在嘗試製作一個應用程序，它將通過麥克風獲取的音頻樣本傳遞給揚聲器。這是源代碼：

public class MainActivity extends Activity { 
    AudioManager am = null; 
    AudioRecord record =null; 
    AudioTrack track =null; 
    final int SAMPLE_FREQUENCY = 44100; 
    final int SIZE_OF_RECORD_ARRAY = 1024; 
    boolean isPlaying = false; 
    class MyThread extends Thread{ 
     @Override 
     public void run(){ 
      recordAndPlay(); 
     } 
    } 

    MyThread newThread; 

    private void init() { 
     int min = AudioRecord.getMinBufferSize(SAMPLE_FREQUENCY, AudioFormat.CHANNEL_IN_MONO, AudioFormat.ENCODING_PCM_16BIT); 
     record = new AudioRecord(MediaRecorder.AudioSource.VOICE_COMMUNICATION, SAMPLE_FREQUENCY, AudioFormat.CHANNEL_IN_MONO, 
           AudioFormat.ENCODING_PCM_16BIT, min); 
     int maxJitter = AudioTrack.getMinBufferSize(SAMPLE_FREQUENCY, AudioFormat.CHANNEL_OUT_MONO, AudioFormat.ENCODING_PCM_16BIT); 
     track = new AudioTrack(AudioManager.MODE_IN_COMMUNICATION, SAMPLE_FREQUENCY, AudioFormat.CHANNEL_OUT_MONO, 
           AudioFormat.ENCODING_PCM_16BIT, maxJitter, AudioTrack.MODE_STREAM); 
    } 

    @Override 
    protected void onCreate(Bundle savedInstanceState) { 
     super.onCreate(savedInstanceState); 
     setContentView(R.layout.activity_main); 
     setVolumeControlStream(AudioManager.STREAM_MUSIC); 
     init(); 
     newThread.start(); 
    } 

    @Override 
    public boolean onCreateOptionsMenu(Menu menu) { 
     // Inflate the menu; this adds items to the action bar if it is present. 
     getMenuInflater().inflate(R.menu.main, menu); 
     return true; 
    } 

    private void recordAndPlay() { 
     short[] lin = new short[SIZE_OF_RECORD_ARRAY]; 
     int num = 0; 
     am = (AudioManager) this.getSystemService(Context.AUDIO_SERVICE); 
     am.setMode(AudioManager.MODE_IN_COMMUNICATION); 
     record.startRecording(); 
     track.play(); 
     while (true) { 
      num = record.read(lin, 0, SIZE_OF_RECORD_ARRAY); 
      track.write(lin, 0, num); 
     } 
    } 

    public void passStop(View view){ 
     Button playBtn = (Button) findViewById(R.id.playBtn); 
     // /* 
     if(!isPlaying){ 
      record.startRecording(); 
      track.play(); 
      isPlaying = true; 
      playBtn.setText("Pause"); 
     } 
     if(isPlaying){ 
      record.stop(); 
      track.pause(); 
      isPlaying=false; 
      playBtn.setText("Pass through"); 
     } 
     // */ 
    } 

    @SuppressWarnings("deprecation") 
    @Override 
    public void onDestroy(){ 
     newThread.stop(); 
    } 
} 

不幸的是，一旦我嘗試通過eclipse運行它，程序就會停止。這是西隧我在logcat中獲取，但我不知道這一切意味着什麼：

08-19 18:58:43.365: D/AndroidRuntime(27915): Shutting down VM 
08-19 18:58:43.365: W/dalvikvm(27915): threadid=1: thread exiting with uncaught exception (group=0x4161f700) 
08-19 18:58:43.365: E/AndroidRuntime(27915): FATAL EXCEPTION: main 
08-19 18:58:43.365: E/AndroidRuntime(27915): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.mypassthrough/com.example.mypassthrough.MainActivity}: java.lang.NullPointerException 
08-19 18:58:43.365: E/AndroidRuntime(27915): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2211) 
08-19 18:58:43.365: E/AndroidRuntime(27915): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2261) 
08-19 18:58:43.365: E/AndroidRuntime(27915): at android.app.ActivityThread.access$600(ActivityThread.java:141) 
08-19 18:58:43.365: E/AndroidRuntime(27915): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1256) 
08-19 18:58:43.365: E/AndroidRuntime(27915): at android.os.Handler.dispatchMessage(Handler.java:99) 
08-19 18:58:43.365: E/AndroidRuntime(27915): at android.os.Looper.loop(Looper.java:137) 
08-19 18:58:43.365: E/AndroidRuntime(27915): at android.app.ActivityThread.main(ActivityThread.java:5103) 
08-19 18:58:43.365: E/AndroidRuntime(27915): at java.lang.reflect.Method.invokeNative(Native Method) 
08-19 18:58:43.365: E/AndroidRuntime(27915): at java.lang.reflect.Method.invoke(Method.java:525) 
08-19 18:58:43.365: E/AndroidRuntime(27915): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:737) 
08-19 18:58:43.365: E/AndroidRuntime(27915): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:553) 
08-19 18:58:43.365: E/AndroidRuntime(27915): at dalvik.system.NativeStart.main(Native Method) 
08-19 18:58:43.365: E/AndroidRuntime(27915): Caused by: java.lang.NullPointerException 
08-19 18:58:43.365: E/AndroidRuntime(27915): at com.example.mypassthrough.MainActivity.onCreate(MainActivity.java:46) 
08-19 18:58:43.365: E/AndroidRuntime(27915): at android.app.Activity.performCreate(Activity.java:5133) 
08-19 18:58:43.365: E/AndroidRuntime(27915): at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1087) 
08-19 18:58:43.365: E/AndroidRuntime(27915): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2175) 
08-19 18:58:43.365: E/AndroidRuntime(27915): ... 11 more 

可能是什麼這個代碼崩潰的原因，以及它如何進行調試？我很確定它與Thread有關，因爲我沒有包含Thread的這段代碼的其他版本在啓動時不會崩潰。

Answer 1

變量newThread不oncreate()method初始化，這就是爲什麼它給nullpointerexception

在init（）方法添加此它將工作

newThread=new Thread(); 

Answer 2

你得到一個空指針異常，因爲newThread尚未初始化，當您嘗試啓動時它爲空。線程也沒有任何事情要做。你應該考慮在你的活動中實現一個可運行的，處理程序和定時器，而不是一個線程。

Answer 3

使用子類延伸的AsyncTask類

class TestActivity extends AsyncTask <String, Void, String > { 
    protected String doInBackground(String... urls) { 
    // execution 
    } 
    protected void onPostExecute(String result) { 
    // post execution 
    } 
    protected void onPreExecute() { 
    super.onPreExecute(); 
    // initial activities 
    } 
}