如何在android中显示电源连接持续时间？

Question

我想显示电源连接和我的应用程序断开连接之间的持续时间....我试图做类似下面......

@Override 
    protected void onCreate(Bundle savedInstanceState) { 
     // TODO Auto-generated method stub 
     super.onCreate(savedInstanceState); 
     setContentView(R.layout.batterystat); 
batteryStatInfo = (TextView) findViewById(R.id.batteryStatusInfo); 
    this.registerReceiver(this.batteryStatRec, new IntentFilter(Intent.ACTION_BATTERY_CHANGED)); 
    } 

    private BroadcastReceiver batteryStatRec = new BroadcastReceiver() 
    { 
     public void onReceive(Context context, Intent intent) 
     { 
      int health = intent.getIntExtra(BatteryManager.EXTRA_HEALTH,0); 
      int icon = intent.getIntExtra(BatteryManager.EXTRA_ICON_SMALL, 0); 
      int level = intent.getIntExtra(BatteryManager.EXTRA_LEVEL, 0); 
      int plugged = intent.getIntExtra(BatteryManager.EXTRA_PLUGGED, 0); 
int chargingBy = intent.getIntExtra(BatteryManager.EXTRA_PLUGGED, 0); 
      boolean isChargingByUsb = chargingBy == BatteryManager.BATTERY_PLUGGED_USB; 
      boolean isChargingByAc = chargingBy == BatteryManager.BATTERY_PLUGGED_AC; 
if(intent.getAction().equals(Intent.ACTION_POWER_CONNECTED)) 
      { 
       time = new Time(); 
       time.setToNow(); 
       shour = time.hour; 
       sminutee = time.minute; 

       prefs.edit().putInt("shour", shour).commit(); 
       prefs.edit().putInt("sminute", sminutee).commit(); 
       statusBat += "Power Connected \n"; 
      } 

      else if(intent.getAction().equals(Intent.ACTION_POWER_DISCONNECTED)) 
      { 
       time = new Time(); 
       time.setToNow(); 
       ehour = time.hour; 
       eminutee = time.minute; 

       prefs.edit().putInt("ehour", ehour).commit(); 
       prefs.edit().putInt("eminute", eminutee).commit(); 
       statusBat += "Power Disconnected \n"; 
      } 

      int eHour = prefs.getInt("ehour", 0); 
      int sHour = prefs.getInt("shour", 0); 
      int eMinute = prefs.getInt("eminutee", 0); 
      int sMinute = prefs.getInt("sminutee", 0); 
      int fHour = eHour - sHour; 
      int fMinute = eMinute - sMinute; 

      //statusBat += "Total ChargingTime : "+fHour+":"+fMinute+"\n"; 

      batteryStatInfo.setText(statusBat); 
      //batteryStatImage.setImageResource(icon); 

     }; 
    }; 

，但我没有得到的结果....和我的应用程序一直崩溃......有没有其他方式来做到这一点？

错误：

03-03 13:04:32.910: E/AndroidRuntime(28227): FATAL EXCEPTION: main 
03-03 13:04:32.910: E/AndroidRuntime(28227): java.lang.RuntimeException: Error receiving broadcast Intent { act=android.intent.action.BATTERY_CHANGED flg=0x60000010 (has extras) } in com.rhs.systmenetworkstat.BatteryStatus$1@419261e0 
03-03 13:04:32.910: E/AndroidRuntime(28227): at android.app.LoadedApk$ReceiverDispatcher$Args.run(LoadedApk.java:798) 
03-03 13:04:32.910: E/AndroidRuntime(28227): at android.os.Handler.handleCallback(Handler.java:800) 
03-03 13:04:32.910: E/AndroidRuntime(28227): at android.os.Handler.dispatchMessage(Handler.java:100) 
03-03 13:04:32.910: E/AndroidRuntime(28227): at android.os.Looper.loop(Looper.java:194) 
03-03 13:04:32.910: E/AndroidRuntime(28227): at android.app.ActivityThread.main(ActivityThread.java:5410) 
03-03 13:04:32.910: E/AndroidRuntime(28227): at java.lang.reflect.Method.invokeNative(Native Method) 
03-03 13:04:32.910: E/AndroidRuntime(28227): at java.lang.reflect.Method.invoke(Method.java:525) 
03-03 13:04:32.910: E/AndroidRuntime(28227): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:833) 
03-03 13:04:32.910: E/AndroidRuntime(28227): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:600) 
03-03 13:04:32.910: E/AndroidRuntime(28227): at dalvik.system.NativeStart.main(Native Method) 
03-03 13:04:32.910: E/AndroidRuntime(28227): Caused by: java.lang.NullPointerException 
03-03 13:04:32.910: E/AndroidRuntime(28227): at com.rhs.systmenetworkstat.BatteryStatus$1.onReceive(BatteryStatus.java:139) 
03-03 13:04:32.910: E/AndroidRuntime(28227): at android.app.LoadedApk$ReceiverDispatcher$Args.run(LoadedApk.java:788) 
03-03 13:04:32.910: E/AndroidRuntime(28227): ... 9 more 

Answer 1

private final BroadcastReceiver receiver = new BroadcastReceiver() { 
     @SuppressWarnings("deprecation") 
    @Override 
     public void onReceive(final Context context, Intent intent) { 

      String action = intent.getAction(); 
      if(action.equals(Intent.ACTION_POWER_CONNECTED)) { 
        // Do something when power connected 
      //save time in proper format in preference or anywhere 
       } 
       else if(action.equals(Intent.ACTION_POWER_DISCONNECTED)) { 
        // Do something when power disconnected 
        //take the time differene between connted time that 
        // was saved and current time and dispay it 

         tv.setText(time_differenece); 
       } 

      } 

    }; 
IntentFilter filter = new IntentFilter(); 
    filter.addAction("android.intent.action.ACTION_POWER_CONNECTED"); 
    filter.addAction("android.intent.action.ACTION_POWER_DISCONNECTED"); 
    registerReceiver(receiver, filter);