Android-从活动外部调用函数（通过AlarmManager和Notification）

Question

Ok, so I have a main activity called 'Main.java'. This main activity starts an AlarmManager which fires an intent leading to 'AlarmReceiver.java'. This 'AlarmReceiver.java' then creates a notification which has two buttons on it. One of the buttons is a deletion button, and so when the user clicks on that button, another intent is fired, leading it to 'DelPair.java'.

In DelPair.java, I modify a table in a Database, but then I need the UI of Main.java to reflect this change. I have created two functions in Main.java called updateArrayFromDB() and updateUIFromArray() to do this for me:

• updateArrayFromDB() will sync an ArrayList created in Main.java to a certain table in the DB.
• updateUIFromArray() will change the UI of Main.java to represent the ArrayList that has just been changed.

The problem is that I cannot call these two functions from DelPair.java (they don't exist in that space). I have come across Serializables in trying to find an answer but I don't know enough to know if they apply here or exactly how to implement them across the AlarmManager and the NotificationManager.

How can I access these methods from DelPair.java?

In Main.java:

public void updateArrayFromDB(){
    //... The code for this is long and irrelevant
}
public void updateUIFromArray(){
    //... The code for this is long and irrelevant
}

private void SendNotification() {
    Intent intent = new Intent(this, AlarmReceiver.class);
//... 
    PendingIntent sender = PendingIntent.getBroadcast(this, 2 , intent, PendingIntent.FLAG_UPDATE_CURRENT);
    AlarmManager am = (AlarmManager) getSystemService(ALARM_SERVICE);
    am.setRepeating(AlarmManager.RTC_WAKEUP, 5000, notif_freq, sender);
}

In AlarmReceiver.java:

Intent delPairI = new Intent(context, DelPair.class);
PendingIntent delPairPI = PendingIntent.getService(context, 0, delPairI, PendingIntent.FLAG_UPDATE_CURRENT);

Notification noti;
noti = new Notification.Builder(context)
        //...
        .addAction(R.drawable.ic_delete_icon, "Delete the thing", delPairPI)
        .build();

NotificationManager notificationManager = (NotificationManager) context.getSystemService(Context.NOTIFICATION_SERVICE);
notificationManager.notify(0, noti);

and then in DelPair.java:

public class DelPair extends IntentService {
//...
    @Override
    protected void onHandleIntent(final Intent intent) {
//...
        Intent it = new Intent(Intent.ACTION_CLOSE_SYSTEM_DIALOGS);
        getApplicationContext().sendBroadcast(it);

        handler.post(new Runnable() {
            @Override
            public void run() {
    //... here is where I update the database, which works perfectly
                //now need to update the UI and array in Main.java
                updateArrayFromDB();    //these lines
                updateUIFromArray();    //obviously don't work 
            }
        });
    }
}

Answer 1

Why not use broadcasts ? in onHandleIntent just send a broadcast

Intent i = new Intent();
i.setAction(CUSTOM_INTENT);
//put relevant data in intent
getApplicationContext().sendBroadcast(i);

The broadcast receiver:

public class IncomingReceiver extends BroadcastReceiver {
    private MainActivity act;
    public IncomingReceiver(MainActivity main){
        this.act = act;
    }
    @Override
    public void onReceive(Context context, Intent intent) {
        if (intent.getAction().equals(CUSTOM_INTENT)) {
            System.out.println("GOT THE INTENT");
            // call the method on act
        }
    }
}

In your activity onResume - register new IncomingReceiver, onPause unregister

    private IncomingReceiver receiver;
    public void onCreate(Bundle bOs){
        //other codes
        receiver = new IncomingReceiver(this);
    }
    @Override
    protected void onResume() {
        IntentFilter filter = new IntentFilter();
        filter.addAction(CUSTOM_INTENT);

        registerReceiver(receiver, filter);
        super.onResume();
    }

    @Override
    protected void onPause() {
        unregisterReceiver(receiver);
        super.onPause();
    }

Answer 2

由于需要基于数据库的更改来更新UI，因此可以在活动的onResume()方法中调用updateArrayFromDB()和updateUIFromArray() ，以便每次用户进入活动时UI都会更新。