Android: Update current activity UI in Handler

Question

I have trouble to update the UI in activity when handler has called in other class. Below is the code that I created.

Activity A

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_A);

    Handler handler = new Handler(); //Here is where the handler is start, other class will update the Handler message.
    ......
}

Activity B

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_B);

    ......
}

//Just a dummy function called when handler is triggered
private void onChange(){
    TextView tv_status = findViewById(R.id.status);
    tv_status.setText("Complete");
}

Class Handler

public Handler {

    public Handler(){
         Handler handler = new Handler(){
               public void HandleMessage(Message msg){
                    switch (msg.what) {
                        case 1:
                             break;
                        case 2:
                             //should trigger to update the TextView in Activity B here
                             break;
                   }
              }
        };

        .......

    }
}

Activity A as main where the Handler is called to start the Handler, Activity B is just update the UI triggered by Handler.

How does your Activity know the Handler exists at all? Where are you creating the Handler there? — OneCricketeer, Jun 07 '18 at 03:27
For updating any view from handler you need to update the view in Main Thread. — Faysal Ahmed, Jun 07 '18 at 03:28
cricket_007. My bad cause did not show the full step. I will update my question. — Siti Aishah Ismail, Jun 07 '18 at 03:30
sorry bro ,misunderstand, as up ,you need sure you are in UI thread first — Lonie, Jun 07 '18 at 03:30
Hope this link helps you- https://stackoverflow.com/questions/15685752/how-to-use-an-android-handler-to-update-a-textview-in-the-ui-thread — LuminiousAndroid, Jun 07 '18 at 03:35
One Activity can't update the UI of another Activity as there is only one Activity loaded at once. Maybe you can use Fragments ? https://stackoverflow.com/a/13701071/2308683 — OneCricketeer, Jun 07 '18 at 18:40

score 0 · Answer 1 · answered Jun 07 '18 at 03:31

Hope this will help.

public Handler {

    public Handler(){
         Handler handler = new Handler(){
               public void HandleMessage(Message msg){
                    switch (msg.what) {
                        case 1:
                             break;
                        case 2:
                             //should trigger to update the TextView in Activity A here 
                            runOnUiThread(new Runnable() {
                             @Override
                               public void run() {
                                 // Update your view
                               }
                              });
                             break;
                   }
              }
        };

        .......

    }
}

Android: Update current activity UI in Handler

1 Answers1