ViewGroupUtilsHoneycomb.java

package org.lntu.online.ui.widget.design;

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 ViewGroupUtilsHoneycomb {

    private static final ThreadLocal<Matrix> sMatrix = new ThreadLocal<>();
    private static final ThreadLocal<RectF> sRectF = new ThreadLocal<>();
    private static final Matrix IDENTITY = new Matrix();

    public 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 = (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));
    }

    public static void offsetDescendantMatrix(ViewParent target, View view, Matrix m) {
        ViewParent parent = view.getParent();
        if (parent instanceof View && parent != target) {
            View vp = (View) parent;
            offsetDescendantMatrix(target, vp, m);
            m.preTranslate((float) (-vp.getScrollX()), (float) (-vp.getScrollY()));
        }

        m.preTranslate((float) view.getLeft(), (float) view.getTop());
        if (!view.getMatrix().isIdentity()) {
            m.preConcat(view.getMatrix());
        }
    }

}