CODEWITHSUNDEEP
javaandroidmultithreadingandroid-activity
Gaurav Deshpande
Gaurav Deshpande

Reputation: 454

Android - switching back from UI thread?

I have MainActivity and my separate class, name is MyClass. I want to run some code in MyClass. And I have methods for that in MyClass. In the constructor of MyClass I am passing Context of MainActivity class and converting that Context in Activity.

MyClass.java

    private Context context;
    private Activity activity;

    public MyClass(Context context) {
      this.context = context;
      this.activity = (Activity) context;
    }

    public void MyFunction() {
     activity.runOnUiThread(new Runnable() {
        public void run() {

          // Code
        }
    });
   }

Everything is going fine still here. In the runOnUiThread, I have written some code. There is a situation, After executing runOnUiThread() body, I want to go back to MyClass context. I want this to be done in runOnUiThread() only. Is there any way to switching back to current thread again?

Thanks

Upvotes: 0

Views: 4427

Answers (4)

Gagan
Gagan

Reputation: 1497

You can use one of the answers posted by ρяσѕρєя K or Kushal. Here are my 2 cents to make things a tad clear.

All the code inside runOnUiThread will be executed on UI thread and it can not be split into two parts; one running on UI thread and another in a different thread/context. Now, if you want to execute a code-block after runOnUiThread completes then you can modify your runOnUiThread function as below (as suggested in some of the answers here):

public void MyFunction() {
    activity.runOnUiThread(new Runnable() {
        @Override
        public void run() {
            // Add code to run on UI-Thread here
        }
    });
    // Add code to run on non UI-Thread here (i.e. on the calling Thread)
}

Upvotes: 4

Jim
Jim

Reputation: 10288

If you define and implement a custom class in the activity class, unless you create a new thread, all of your code will run in the UI thread.

The runOnUiThread method passes the information necessary to have a different thread reference the UI thread for updating views or other UI components.

To run code in your original class you should do a few things. First, you should define it as a separate class (in another file, not as a private class).

Second, you should pass it the Activity (maybe as a WeakReference) and then use the Activity method "runOnUiThread" when necessary.

Another option is to create a Handler or Thread to run off the UI when you want it to run.

You are not entirely clear about your use-case...

Upvotes: 1

Ammar
Ammar

Reputation: 1821

What I got from question is that you need to run some code in UI thread and some in background thread. I yes, you may modify MyClass to use Handler as following.

private Context context;
private Handler backgroundHandler;
private Handler uiHandler;

public MyClass(Context context, Handler handler) {
  this.context = context;
  // this.activity = (Activity) context;
  this.uiHandler = handler;

  HandlerThread handlerThread = new HandlerThread("MyClass.Handler");
  handlerThread.start();
  backgroundHandler = new Handler(handlerThread.getLooper());
}

public void MyFunction() {
    uiHandler.post(new Runnable() {
        public void run() {

          // Code to execute on ui thread

            backgroundHandler.post(new Runnable() {
                public void run() {
                  // Code to execute on bg thread
                }
            });           
        }
    });
}

Pass the Handler as:

MyClass myClass = new MyClass(context, new Handler());

Upvotes: 1

Kushal
Kushal

Reputation: 8508

Once you access APIs for PubNub from runOnUiThread(), android system will switch the processing to your current thread automatically and executes outer statements :

    public void MyFunction() {
     activity.runOnUiThread(new Runnable() {
        public void run() {

          // Code which runs on MAIN UI thread
        }
    });
    // once upper part is done, switching to current thread
    // these statements will be execute on current thread
    // statement 1;
    // ...
   }

Upvotes: 1

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