Add event when back arrow(getSupportActionBar().setDisplayHomeAsUpEnabled(true)) is clicked

Question

My problem is almost the same as this Stop AsyncTask in Fragments when Back Button is pressed

But I want to stop my AsyncTask when the back arrow is clicked. I have a code in stoping asynctask and it works when I implemented it in another way. I tried what I researched so far but I still got errors. Please help me with this.

I tried this code

    @Override
    public boolean onOptionsItemSelected(MenuItem item) {
    int id=item.getItemId();

    if(id==android.R.id.home)
    {
        Intent returnIntent = new Intent();
        returnIntent.putExtra("flag",userid);
        setResult(Activity.RESULT_OK,returnIntent);
        finish();
        return true;
    }}

UPDATED: I am using this code to go to another fragment.

Fragment2 fragmentChild = new Fragment2 ();

FragmentTransaction transaction = getFragmentManager().beginTransaction();
transaction.add(R.id.content, fragmentChild);
transaction.addToBackStack(null);
transaction.commit();

I have no problem in my backtrack when I go to another fragment. Then I'm using this code (getSupportActionBar().setDisplayHomeAsUpEnabled(true)) in my (Drawer.java) to show the back arrow. Now I want to add event when I clicked back arrow.

EDIT: (Drawer.java)

getSupportActionBar().setDisplayHomeAsUpEnabled(true);

    DrawerLayout drawer = (DrawerLayout) findViewById(R.id.drawer_layout);
    final ActionBarDrawerToggle toggle = new ActionBarDrawerToggle(
            this, drawer, toolbar, R.string.navigation_drawer_open, R.string.navigation_drawer_close);
    drawer.setDrawerListener(toggle);
    toggle.syncState();

    final View.OnClickListener originalToolbarListener = toggle.getToolbarNavigationClickListener();

    getSupportFragmentManager().addOnBackStackChangedListener(new FragmentManager.OnBackStackChangedListener() {
        @Override
        public void onBackStackChanged() {
            if (getSupportFragmentManager().getBackStackEntryCount() > 0) {
                toggle.setDrawerIndicatorEnabled(false);
                toggle.setToolbarNavigationClickListener(new View.OnClickListener() {
                    @Override
                    public void onClick(View v) {
                        getSupportFragmentManager().popBackStack();
                    }
                });
            } else {
                toggle.setDrawerIndicatorEnabled(true);
                toggle.setToolbarNavigationClickListener(originalToolbarListener);
            }
        }
    });

Answer 1

If you properly setup the action bar, then you should be able to achive that with the following:

@Override
public boolean onOptionsItemSelected(MenuItem item) {
    switch (item.getItemId()) {
    case android.R.id.home:
        // Add the code to stop the task
        break;
    }
    return super.onOptionsItemSelected(item);
}

EDIT: After you are able to handle the back button event, you can add the code to close the tasks in fragments. First of all, I created an interface that is implement by all fragments that should be able to close this tasks.

public interface TaskCancelFragment {
    void cancelTask();
}

The implementation in fragments should look something like this:

@Override
public void cancelTask() {
    //Add the code to cancel the task
    Toast.makeText(getContext(), "The task is canceled", Toast.LENGTH_SHORT).show();
}

The final step is to send the event from activity to fragment. Here I will assume some things since I don't have access to your code to see how you add/find the fragments, but fortunately this doesn't matter so much and is easy to change. In addition to the initial answer, I created a new method in activity to find the current fragment and close the task.

private void cancelTasks() {
    Fragment fragment = getSupportFragmentManager().findFragmentById(R.id.placeholder);
    if (fragment instanceof TaskCancelFragment) {
        ((TaskCancelFragment) fragment).cancelTask();
    }
}

And in the end, the case android.R.id.home looks like this:

case android.R.id.home:
    cancelTasks();
    onBackPressed(); // I think that you want to close the activity too
    break;