progressbar活動力量關閉

我是新來的android和嘗試一些教程。我遇到了處理進度條的簡單教程。我最小的SDK是11progressbar活動力量關閉

以下是我已經嘗試並獲得活動，部隊密切當我運行它

public class HandlerDemo extends Activity { 

ProgressBar bar; 
Handler handler = new Handler() { 
    @Override 
    public void handleMessage(){  
     bar.incrementProgressBy(5); 
    } 

    @Override 
    public void close() { 
    } 

    @Override 
    public void flush() { 
    } 

    @Override 
    public void publish(LogRecord arg0) { 
    } 
}; 

AtomicBoolean isRunning = new AtomicBoolean(false); 

@Override 
public void onCreate(Bundle savedInstanceState) { 
    super.onCreate(savedInstanceState); 
    setContentView(R.layout.activity_handler_demo); 
    bar = (ProgressBar)findViewById(android.R.id.progress); 
} 


@Override 
public boolean onCreateOptionsMenu(Menu menu) { 
    getMenuInflater().inflate(R.menu.activity_handler_demo, menu); 
    return true; 
} 

public void onStart() { 
    super.onStart(); 
    bar.setProgress(0); 

    Thread background = new Thread(new Runnable() { 

     @Override 
     public void run() { 
      try{ 
       for(int i=0;i<20 && isRunning.get();i++){ 
         Thread.sleep(1000); 
         handler.sendMessage(handler.obtainMessage()); 
       } 
      } 
      catch(Throwable t){ 
      } 
     } 
    }); 
    isRunning.set(true); 
    background.start(); 
} 

public void onStop(){ 
    super.onStop(); 
    isRunning.set(false); 
} 
}

logcat的

03-14 23:18:51.408: E/AndroidRuntime(717): FATAL EXCEPTION: main 
03-14 23:18:51.408: E/AndroidRuntime(717): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.progrss/com.example.progrss.HandlerDemo}: java.lang.NullPointerException 
03-14 23:18:51.408: E/AndroidRuntime(717): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1736) 
03-14 23:18:51.408: E/AndroidRuntime(717): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:1752) 
03-14 23:18:51.408: E/AndroidRuntime(717): at android.app.ActivityThread.access$1500(ActivityThread.java:123) 
03-14 23:18:51.408: E/AndroidRuntime(717): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:993) 
03-14 23:18:51.408: E/AndroidRuntime(717): at android.os.Handler.dispatchMessage(Handler.java:99) 
03-14 23:18:51.408: E/AndroidRuntime(717): at android.os.Looper.loop(Looper.java:126) 
03-14 23:18:51.408: E/AndroidRuntime(717): at android.app.ActivityThread.main(ActivityThread.java:3997) 
03-14 23:18:51.408: E/AndroidRuntime(717): at java.lang.reflect.Method.invokeNative(Native Method) 
03-14 23:18:51.408: E/AndroidRuntime(717): at java.lang.reflect.Method.invoke(Method.java:491) 
03-14 23:18:51.408: E/AndroidRuntime(717): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:841) 
03-14 23:18:51.408: E/AndroidRuntime(717): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:599) 
03-14 23:18:51.408: E/AndroidRuntime(717): at dalvik.system.NativeStart.main(Native Method) 
03-14 23:18:51.408: E/AndroidRuntime(717): Caused by: java.lang.NullPointerException 
03-14 23:18:51.408: E/AndroidRuntime(717): at com.example.progrss.HandlerDemo.onStart(HandlerDemo.java:41) 
03-14 23:18:51.408: E/AndroidRuntime(717): at android.app.Instrumentation.callActivityOnStart(Instrumentation.java:1132) 
03-14 23:18:51.408: E/AndroidRuntime(717): at android.app.Activity.performStart(Activity.java:4320) 
03-14 23:18:51.408: E/AndroidRuntime(717): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1709) 
03-14 23:18:51.408: E/AndroidRuntime(717): ... 11 more

來源

2013-03-14 Karan Mer

的logcat的是那麼清楚，'com.example.progrss.HandlerDemo.onStart（HandlerDemo.java:41）'。行號41有一個空指針異常。同樣，當你提出這樣的問題時，你應該放在哪一行是41. – Siddharth 2013-04-22 10:58:36

@Siddharth：我一定會記住 – 2013-04-22 11:00:44

請在第41行編輯問題。請保持乾淨。 – Siddharth 2013-04-22 11:02:11

變化

bar = (ProgressBar)findViewById(android.R.id.progress);

到

bar = (ProgressBar)findViewById(R.id.progress);

您正在試圖訪問android.R.id.progress

來源

2013-03-14 17:58:53

@sir thnx很多先生...它的工作 – 2013-03-14 18:02:38

progressbar活動力量關閉

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