Zelter Ady Zelter Ady - 1 month ago 24
Android Question

android: move a view on touch move (ACTION_MOVE)

I'd like to do a simple control: a container with a view inside. If I touch the container and I move the finger, I want to move the view to follow my finger.

What kind of container (layout) should I use? How to do this?

I don't need to use a surface, but a simple layout.

Answer

Something like this:

public class MyActivity extends Activity implements View.OnTouchListener {

TextView _view;
ViewGroup _root;
private int _xDelta;
private int _yDelta;

@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.main);

    _root = (ViewGroup)findViewById(R.id.root);

    _view = new TextView(this);
    _view.setText("TextView!!!!!!!!");

    RelativeLayout.LayoutParams layoutParams = new RelativeLayout.LayoutParams(150, 50);
    layoutParams.leftMargin = 50;
    layoutParams.topMargin = 50;
    layoutParams.bottomMargin = -250;
    layoutParams.rightMargin = -250;
    _view.setLayoutParams(layoutParams);

    _view.setOnTouchListener(this);
    _root.addView(_view);
}

public boolean onTouch(View view, MotionEvent event) {
    final int X = (int) event.getRawX();
    final int Y = (int) event.getRawY();
    switch (event.getAction() & MotionEvent.ACTION_MASK) {
        case MotionEvent.ACTION_DOWN:
            RelativeLayout.LayoutParams lParams = (RelativeLayout.LayoutParams) view.getLayoutParams();
            _xDelta = X - lParams.leftMargin;
            _yDelta = Y - lParams.topMargin;
            break;
        case MotionEvent.ACTION_UP:
            break;
        case MotionEvent.ACTION_POINTER_DOWN:
            break;
        case MotionEvent.ACTION_POINTER_UP:
            break;
        case MotionEvent.ACTION_MOVE:
            RelativeLayout.LayoutParams layoutParams = (RelativeLayout.LayoutParams) view.getLayoutParams();
            layoutParams.leftMargin = X - _xDelta;
            layoutParams.topMargin = Y - _yDelta;
            layoutParams.rightMargin = -250;
            layoutParams.bottomMargin = -250;
            view.setLayoutParams(layoutParams);
            break;
    }
    _root.invalidate();
    return true;
}}

In main.xml just RelativeLayout with @+id/root

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