如何确定我的一个活动是否在前台，然后注册广播接收器接收短信

Question

我想注册广播接收器接收短信只有当我的应用程序在前台，否则注销广播接收器。

<receiver android:name="smsreader.com.messagereciver.IncomingSms">
        <intent-filter>
            <action android:name="android.provider.Telephony.SMS_RECEIVED"/>
        </intent-filter>
    </receiver>

//接收短信代码

public class IncomingSms extends BroadcastReceiver {
    // Get the object of SmsManager
    final SmsManager sms = SmsManager.getDefault();
    public void onReceive(Context context, Intent intent) {
        // Retrieves a map of extended data from the intent.
        final Bundle bundle = intent.getExtras();
        try {
        // receive SMS code
        } catch (Exception e) {
            Log.e("SmsReceiver", "Exception smsReceiver" +e);
        }
    }
}

Answer 1

这将帮助你知道你的应用程序是否在前台

 private boolean isFG;
@Override
protected void onPause() {
    super.onPause();
    isFG = false;
}
@Override
protected void onResume() {
    super.onResume();
    isFG = true;
}
// Some function.
public boolean isInForeground() {
    return isFG;
}

然后用下面的方式编写一个函数以编程方式注册您的Broadcast receiver。

在代码(MyBroadcastReceiver)中创建BroadcastReceiver。在你的活动范围内声明MyBroadcastReceiver:

MyBroadcastReceiver mMyBroadcastReceiver;

注册BroadcastReceiver在您的活动:

if(isFG == true){
IntentFilter filter = new IntentFilter(android.provider.Telephony.SMS_RECEIVED);
this.registerReceiver(mMyBroadcastReceiver, filter);
}else{
//dont register
}

希望这对你有帮助。谢谢。

Answer 2

你可以在Application的onCreate()方法中注册一个ActivityLifecycleCallbacks，当一个活动开始时回调计数，当一个活动停止时回调计数。如果count大于1，这意味着至少有一个活动已经启动，你可以注册广播接收器，如果它是零，那么没有启动(用户可见)的活动，你可以取消注册广播接收器。

此解决方案是独立于活动的，并且将在您的任何活动启动时工作。

Answer 3

我建议你在onResume()中注册广播接收器，并在onPause()中取消注册。

:

@Override
protected void onResume() {
     super.onResume();
     registerReceiver(receiver, intentFilter);
}
@Override
protected void onPause() {
    unregisterReceiver(receiver);
    super.onPause();
} 

Answer 4

我按语法创建了Broadcastreceiver，并在活动的onResume()中注册，也在onPause()中未注册，在我的情况下工作得很好。

 IncomingSms smsReceiver;
 private IntentFilter myFilter;    

        @Override
        protected void onPause() {
            unregisterReceiver(smsReceiver); // UnRegister BroadCastReceiver as you no longer have your activity at Foreground -- Saving CPU & Battery Drainage
            super.onPause();
        }
        @Override
        protected void onResume()
        {
            smsReceiver = new IncomingSms();
            myFilter = new IntentFilter();
            myFilter.addAction("android.provider.Telephony.SMS_RECEIVED");
            registerReceiver(smsReceiver, myFilter); // Register BroadCastReceiver Once again as your activity comes from pause to forground state again.
            super.onResume();
        }