Question

In Stackview, it seems that OnItemSelectedListener (from superclass
“AdapterView”) is never called…
How can I trigger some event when the view on top of the stack is
changed by the user ?

I want to display some text to show the position of the current item
inside the stack, so I need to find a way to update the textview when the user browses through the stack.

Thanks,

Answer 1

What i have done is writing a new class extending StackView and writing some code to get the OnItemSelected logics works. When the onTouchEvent gives me a MotionEvent.getAction() == ACTION_UP, i start a Thread that calls himself ’till the StackView.getDisplayedChild() changes. When it changes, i start the OnItemSelected logic, so i can always get the first displayed child.

public boolean onTouchEvent(MotionEvent motionEvent) {
    if (motionEvent.getAction() == MotionEvent.ACTION_UP && this.getAdapter() != null) {
        mPreviousSelection = this.getDisplayedChild();
        post(mSelectingThread);
    }
    return super.onTouchEvent(motionEvent);
}

This thread cycles himself untill he gets the new displayedChild:

private class SelectingThread implements Runnable {
    CustomStackView mStackView;

    public SelectingThread(CustomStackView stackView) {
        this.mStackView = stackView;
    }

    @Override
    public void run() {
        if(mStackView.getAdapter() != null) {
            if (mPreviousSelection == CustomStackView.this.getDisplayedChild()) {
                mThisOnItemSelectedListener.onItemSelected(mStackView, mStackView.getAdapter().getView(mPreviousSelection, null, mStackView),
                    mStackView.mPreviousSelection, mStackView.getAdapter().getItemId(mPreviousSelection));
                return;
            } else {
                mPreviousSelection = mStackView.getDisplayedChild();
                mStackView.post(this);
            }
        }
    }
}

This Listener instead sets the Selected flag to true after deselecting them all.

private class StackViewOnItemSelectedListener implements OnItemSelectedListener {

    CustomStackView mStackView;

    public StackViewOnItemSelectedListener(CustomStackView stackView) {
        this.mStackView = stackView;
    }

    @Override
    public void onItemSelected(AdapterView<?> parent, View selectedView, int position, long id) {
        deselectAll();
        if (mStackView.getAdapter() != null) {
            if (mOnItemSelectedListener != null) {
                mStackView.mOnItemSelectedListener.onItemSelected(parent, selectedView, position, id);
            }
            mStackView.getAdapter().getView(position, null, mStackView).setSelected(true);
        }
    }

    private void deselectAll() {
        if (mStackView.getAdapter() != null) {
            int adapterSize = mStackView.getAdapter().getCount();
            for (int i = 0; i < adapterSize; i++) {
                mStackView.getAdapter().getView(i, null, mStackView).setSelected(false);
            }
        }
    }

    @Override
    public void onNothingSelected(AdapterView<?> parent) {
        if (mStackView.getAdapter() != null) {
            if (mOnItemSelectedListener != null) {
                mStackView.mOnItemSelectedListener.onNothingSelected(parent);
            }
            deselectAll();
        }
    }
}

I’ve tested it a little and it works..