The problem is hardware acceleration. Turn it OFF for the particular View that you are painting with CLEAR. If you’re using a custom view, do this in the constructors: if (android.os.Build.VERSION.SDK_INT >= 11) { setLayerType(View.LAYER_TYPE_SOFTWARE, null); } You can also call setLayerType on a view reference.
AFAIK, a View’s onDraw() is called when: The view is initially drawn Whenever invalidate() is called on the view Invalidate can be called by you or the system whenever needed. For example, a lot of Views change how they look onTouch, like an EditText getting an outline and cursor, or a button being in the … Read more
None of the answers here actually answer the question: From a Bitmap of any size displayed by an ImageView, find the actual dimensions of the displayed image as opposed to the dimensions of the supplied Bitmap. Namely: Using ImageView.getDrawable().getInstrinsicWidth() and getIntrinsicHeight() will both return the original dimensions. Getting the Drawable through ImageView.getDrawable() and casting it … Read more
Finally I got the solution from this code: float radius = 20; final RectF oval = new RectF(); oval.set(point1.x – radius, point1.y – radius, point1.x + radius, point1.y+ radius); Path myPath = new Path(); myPath.arcTo(oval, startAngle, -(float) sweepAngle, true); To calculate startAngle, use this code: int startAngle = (int) (180 / Math.PI * Math.atan2(point.y – … Read more
You need to call setWillNotDraw(false) in your constructor. Because by default a layout does not need to draw, so an optimization is to not call is draw method. By calling setWillNotDraw(false) you tell the UI toolkit that you want to draw.