Java tutorial
//package com.java2s; //License from project: Apache License import android.graphics.Matrix; import android.graphics.Rect; import android.graphics.RectF; import android.view.View; import android.view.ViewGroup; import android.view.ViewParent; public class Main { private static final ThreadLocal<Matrix> sMatrix = new ThreadLocal<>(); private static final ThreadLocal<RectF> sRectF = new ThreadLocal<>(); private static final Matrix IDENTITY = new Matrix(); /** * Honeycomb IMPL borrowed from android.support.design.widget.ViewGroupUtils and * android.support.design.widget.ViewGroupUtilsHoneycomb */ public static void getDescendantRect(ViewGroup parent, View descendant, Rect out) { out.set(0, 0, descendant.getWidth(), descendant.getHeight()); offsetDescendantRect(parent, descendant, out); } static void offsetDescendantRect(ViewGroup group, View child, Rect rect) { Matrix m = sMatrix.get(); if (m == null) { m = new Matrix(); sMatrix.set(m); } else { m.set(IDENTITY); } offsetDescendantMatrix(group, child, m); RectF rectF = sRectF.get(); if (rectF == null) { rectF = new RectF(); } rectF.set(rect); m.mapRect(rectF); rect.set((int) (rectF.left + 0.5f), (int) (rectF.top + 0.5f), (int) (rectF.right + 0.5f), (int) (rectF.bottom + 0.5f)); } static void offsetDescendantMatrix(ViewParent target, View view, Matrix m) { final ViewParent parent = view.getParent(); if (parent instanceof View && parent != target) { final View vp = (View) parent; offsetDescendantMatrix(target, vp, m); m.preTranslate(-vp.getScrollX(), -vp.getScrollY()); } m.preTranslate(view.getLeft(), view.getTop()); if (!view.getMatrix().isIdentity()) { m.preConcat(view.getMatrix()); } } }