Question

 public class MainActivity extends Activity implements SurfaceHolder.Callback 
{
private Intent intent;

protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);


       if (activityReceiver != null)
{ 
       IntentFilter intentFilter = new IntentFilter();
      registerReceiver(activityReceiver, intentFilter);
}

    intent = new Intent(this, Service.class);
    startService(intent);

    }

 private BroadcastReceiver activityReceiver = new BroadcastReceiver(){
    public void onReceive(Context context, Intent intent) {
    int value=intent.getIntExtra("VALUE", 0);
    txtData.setText(""+value);
    }}

}

SERVICE

public class Service extends IOIOService {
//Intent intent=new Intent(this, MainActivity.class);
private final int BUTTON_PIN = 34;
@Override
protected IOIOLooper createIOIOLooper() {
    return new BaseIOIOLooper() {
        private DigitalOutput led_;
        private DigitalInput mButton;
        int  oneTime = 0;



        @Override
        protected void setup() throws ConnectionLostException,
                InterruptedException {
            led_ = ioio_.openDigitalOutput(IOIO.LED_PIN);
            mButton = ioio_.openDigitalInput(BUTTON_PIN, DigitalInput.Spec.Mode.PULL_UP);
        }

        @Override
        public void loop() throws ConnectionLostException,
                InterruptedException {

             final boolean reading1 = mButton.read();
             if (reading1) 
             {
                 led_.write(false);
                 if(oneTime == 0)
                 {
                                             Intent intent = new Intent();
                     intent.putExtra("VALUE", 100);
                     sendBroadcast(intent);
                     oneTime = 1;
                 }

                          } 
             else 

             {
                               led_.write(true);
                             }
            Thread.sleep(100);
              }

    };
}
}
  @Override
public void onStart(Intent intent, int startId) {
    super.onStart(intent, startId);
    NotificationManager nm = (NotificationManager) getSystemService(NOTIFICATION_SERVICE);
    if (intent != null && intent.getAction() != null
            && intent.getAction().equals("stop")) {
        // User clicked the notification. Need to stop the service.
        nm.cancel(0);
        stopSelf();
    } else 
    {
        // Service starting. Create a notification.
        Notification notification = new Notification(
                R.drawable.ic_launcher, "IOIO service running",
                System.currentTimeMillis());
        notification
                .setLatestEventInfo(this, "IOIO Service", "Click to stop",
                        PendingIntent.getService(this, 0, new Intent(
                                "stop", null, this, this.getClass()), 0));
        notification.flags |= Notification.FLAG_ONGOING_EVENT;
        nm.notify(0, notification);
    }
}

@Override
public IBinder onBind(Intent arg0) {
    return(null);

}

} 我试图使用广播将一个整数值从服务发送到活动，并将该整数显示在活动的文本框中。这很简单，但我的程序仍在崩溃。这是我的代码的一部分，我已经添加了广播代码。任何人都可以告诉我这有什么不对吗？还有什么可以添加的吗？

Answer 1

在onCreate()更改以下行：

   intent = new Intent(this, Service.class);
    startService(new Intent(this, Service.class));

到此：

intent = new Intent(this, Service.class);
startService(intent);

<强>编辑：

//send broadcast from activity to all receivers listening to the action 
        Intent intent = new Intent();
        intent.putExtra("VALUE", 100);
        sendBroadcast(intent);

并获取活动的onRecieve()方法中的值。

在活动中注册广播：

public class MainActivity extends Activity implements SurfaceHolder.Callback 
{
private Intent intent;

protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    intent = new Intent(this, Service.class);
    startService(intent);
if (activityReceiver != null)
  {
           IntentFilter intentFilter = new IntentFilter();
        //Map the intent filter to the receiver
         registerReceiver(activityReceiver, intentFilter);
  }

}

 private BroadcastReceiver activityReceiver = new BroadcastReceiver() {

    @Override
    public void onReceive(Context context, Intent intent) {
        Toast.makeText(getApplicationContext(), "received message in activity..!", Toast.LENGTH_SHORT).show();
           int value=intent.getIntExtra("VALUE", 0);
           txtData.setText(value);
    }
};


 }

Answer 2

在清单中声明服务。

<service
                android:name=".Service">
 </service>

Answer 3

             // cuase for null pointer exception, intent is getting set as null first
then ur using putExtra method on it.  
              Intent intent = null;
                 intent.putExtra("VALUE", 100);
                 sendBroadcast(intent);
                 oneTime = 1;

通过广播发送数据

3 个答案: