Android广播接收器+静态变量

Question

I am working with a broadcast receiver and wondering how it works. I have the following code to catch the state of a phone call:

private static String mLastState="Unknown last state";
private String phoneState="Unknown phone state";
private static boolean incomingCall=false;


@Override
public void onReceive(Context context, Intent intent) {
   phoneState = intent.getStringExtra(TelephonyManager.EXTRA_STATE);
    if (intent.getAction().equals("android.intent.action.NEW_OUTGOING_CALL")) {
        LOG.debug("Outgoing call");
    } else {
        LOG.debug("Incoming call" + " " + String.valueOf(incomingCall));
    if (!mLastState.equals(phoneState)) {
     switch (phoneState) {
        case("RINGING"):
            incomingCall=true;
            mLastState="RINGING";
            LOG.debug("RINGING");
            break;
        case("OFFHOOK"):
            if (incomingCall) {
                mLastState = "OFFHOOK";
                LOG.debug("OFFHOOK");
            }
            break;
        case("IDLE"):
            if (incomingCall) {
                 mLastState="IDLE";                   
                 incomingCall=false;
                 LOG.debug("IDLE");
            }
            break;
        }
     }
    }
}

Incoming call logs:

main: [Incoming call false]

main: [RINGING]  
main: [Incoming call true]

main: [OFFHOOK]  
main: [Incoming call true]

main: [IDLE]  
main: [Incoming call false]

The logs confused me (specifically, the state of the incoming call static variable). When we have [RINGING] , Broadcast initializes all variables ( incomingCall = false ), and then executes the onReceive method (we get incomingCall = true ). The second operation is triggered ( [OFFHOOK] ), but does not initialize static field ( incomingCall would be false ), and the receiver takes the old value of the variable; although between these events may take more time and the same thing happens with the third operation ( [IDLE] ).

How does the receiver initialize variables? What happens with static variables? Does the receiver initialize variables every time or not? How do I save the incoming call variable correctly -- maybe Shared Preferences?

Answer 1

You can use PhoneStateListener as given below:

public class BroadCastReceiver extends BroadcastReceiver {

TelephonyManager telManager;
Context context;
PhoneListener pl;


@Override
public void onReceive(Context context, Intent intent) {

    telManager = (TelephonyManager) context.getSystemService(Context.TELEPHONY_SERVICE);

    this.context = context;

    String action = intent.getStringExtra(TelephonyManager.EXTRA_STATE);
    Log.d("Actions--------->", action);

        pl=PhoneListener.getInstance();
        telManager.listen(pl, PhoneStateListener.LISTEN_CALL_STATE);
}
}


public class PhoneListener extends PhoneStateListener {
private static PhoneListener phoneListenerInstance;


private PhoneListener()
{

}

public static PhoneListener getInstance()
{
    if(phoneListenerInstance==null)
    {
        phoneListenerInstance=new PhoneListener();
    }
    return phoneListenerInstance;
}


@Override
public void onCallStateChanged(int state, String incomingNumber) {
    super.onCallStateChanged(state, incomingNumber);

                  switch (state) {
                      case TelephonyManager.CALL_STATE_RINGING: {
                          Log.d("State", "ringing");
                          break;
                      }
                      case TelephonyManager.CALL_STATE_OFFHOOK: {
                          Log.d("State", "offhook");
                          break;
                      }
                      case TelephonyManager.CALL_STATE_IDLE: {
                         Log.d("State", "idle");
                         break;
                      }
                      default: {
                      }
                  }
    }
 }