Zoomable TextView in ScrollView

Issue

I would like to make a TextView that can change the size of it’s text based on pinch zooming. The TextView is inside a ScrollView. I’ve got the TextView to zoom when pinching BUT only when you move your fingers almost perfectly horizontally. If there is a vertical component to the pinch-zoom it defaults to scrolling instead of zooming

Is there a way to disable the scrolling of the ScrollView when there is more than 1 pointer on it then re-enable scrolling when the pointer count returns to 1 or 0? Is the best way to create a CustomScrollView widget or is there an easier way?

Solution

Inspired by this answer https://stackoverflow.com/a/14577399/2014236

scaleGD = new ScaleGestureDetector(this, new simpleOnScaleGestureListener());
mTextView.setOnTouchListener(new OnTouchListener() {

    @Override
    public boolean onTouch(View v, MotionEvent event) {
        if(event.getPointerCount() == 1){
            //stuff for 1 pointer
        }else{ //when 2 pointers are present
            switch (event.getAction()) {
            case MotionEvent.ACTION_DOWN:
                // Disallow ScrollView to intercept touch events.
                v.getParent().requestDisallowInterceptTouchEvent(true);
                scaleGD.onTouchEvent(event);
                break;

            case MotionEvent.ACTION_MOVE:
                // Disallow ScrollView to intercept touch events.
                v.getParent().requestDisallowInterceptTouchEvent(true);
                scaleGD.onTouchEvent(event);
                break;

            case MotionEvent.ACTION_UP:
                // Allow ScrollView to intercept touch events.
                v.getParent().requestDisallowInterceptTouchEvent(false);
                break;
            }
        }
        return true;
    }
});

EDIT:

//later in the code
public class simpleOnScaleGestureListener extends SimpleOnScaleGestureListener {

    @Override
    public boolean onScale(ScaleGestureDetector detector) {
        float size = codedText.getTextSize();
        float factor = detector.getScaleFactor();
        int increase = 0;
        if(factor > 1.0f)
            increase = 2;
        else if(factor < 1.0f)
            increase = -2;

        size += increase;

        codedText.setTextSize(TypedValue.COMPLEX_UNIT_PX, size);
        plainText.setTextSize(TypedValue.COMPLEX_UNIT_PX, size);            
        try {
            Thread.sleep(200);
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
        //remembering the favourable text size
        Editor edit = sp.edit();
        edit.putFloat("TXTSIZE", size);
        edit.commit();
        return true;
    }
}

By no means perfect but does a good enough job for me – feel free to make improvements.

Answered By – Uwais A

Answer Checked By – Robin (FlutterFixes Admin)