Android Custom View move back to original position when refreshing

Question

I'm implementing a time picker which looks like this:

That yellow block is MyCustomView. When moving MyCustomView, I should calculate new date and set tvDate.

partial layout file:

<LinearLayout 
    android:orientation="vertical">

    <TextView android:id="@+id/tv_date">

    <RelativeLayout 
        android:id="@+id/rl">

        <MyCustomView
         android:layout_centerInParent="true"/>

        <OtherViews/>
    </RelativeLayout>
</LinearLayout>

code:

class MyCustomView extends View{

    // move listener
    public interface IMoveCallback{
        void update(int index);
    }

    private IMoveCallback listener = null; 

    // set listener
    public void setMoveCallback(IMoveCallback callback){
        this.listener = callback;
    }

    @Override
    protected void onDraw(Canvas c){
        super.onDraw(c);
        // draw yellow block and four arrows here.
    }

    @Override
    public boolean onTouch(View v, MotionEvent event) {
        processDrag(v, event);
        invalidate();
        return false;
    }

    private void processDrag(View v, MotionEvent event){
        // calculate new position(left, top, right, bottom)
        v.layout(newLeft, newTop, newRight, newBottom); 
        if(listener != null){
            // calculate index by new position
            listener.update(index);
        }
    }
}

class MainActivity extends Activity implements MyCustomView.IMoveCallback{

    MyCustomView view; // view.setMoveCallback(MainActivity.this)

    @Override
    public void update(int index){
        tvDate.setText(String.valueOf(System.currentTimeMillis()))//update tvDate
    }
}

If tvDate.setText() is removed, MyCustomView follows the finger, like this:

If I update tvDate, MyCustomView moves back to the center of rl:

I don't think it an activity-lifecycle issue. Someone mentioned ((MarginLayoutParams)rl.getLayoutParams()).topMargin but did not explain why.
Anybody can help me?

Answer 1

You need to save the location of your view and render it at the same spot when the activity resumes(coming back from home) or starts(coming back after pressing back). This Picture shows methods you can override to achieve that such as onPause when losing focus etc.

EDIT

From the looks of it, it is resetting back to its original state. Post more about how you are setting the location etc. If that is a view you are moving. Then implement a on drag listener instead of that update. And let me know how that works out.