1 /*
2  * Copyright (C) 2014 The Android Open Source Project
3  *
4  * Licensed under the Apache License, Version 2.0 (the "License");
5  * you may not use this file except in compliance with the License.
6  * You may obtain a copy of the License at
7  *
8  *      http://www.apache.org/licenses/LICENSE-2.0
9  *
10  * Unless required by applicable law or agreed to in writing, software
11  * distributed under the License is distributed on an "AS IS" BASIS,
12  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13  * See the License for the specific language governing permissions and
14  * limitations under the License.
15  */
16 
17 
18 package com.android.internal.widget;
19 
20 import android.graphics.Canvas;
21 import android.graphics.PixelFormat;
22 import android.graphics.drawable.Drawable;
23 import android.view.View;
24 import android.view.ViewGroup;
25 
26 /**
27  * Helper class for drawing a fallback background in framework decor layouts.
28  * Useful for when an app has not set a window background but we're asked to draw
29  * an uncovered area.
30  */
31 public class BackgroundFallback {
32     private Drawable mBackgroundFallback;
33 
setDrawable(Drawable d)34     public void setDrawable(Drawable d) {
35         mBackgroundFallback = d;
36     }
37 
hasFallback()38     public boolean hasFallback() {
39         return mBackgroundFallback != null;
40     }
41 
42     /**
43      * Draws the fallback background.
44      *
45      * @param boundsView The view determining with which bounds the background should be drawn.
46      * @param root The view group containing the content.
47      * @param c The canvas to draw the background onto.
48      * @param content The view where the actual app content is contained in.
49      */
draw(ViewGroup boundsView, ViewGroup root, Canvas c, View content)50     public void draw(ViewGroup boundsView, ViewGroup root, Canvas c, View content) {
51         if (!hasFallback()) {
52             return;
53         }
54 
55         // Draw the fallback in the padding.
56         final int width = boundsView.getWidth();
57         final int height = boundsView.getHeight();
58         int left = width;
59         int top = height;
60         int right = 0;
61         int bottom = 0;
62 
63         final int childCount = root.getChildCount();
64         for (int i = 0; i < childCount; i++) {
65             final View child = root.getChildAt(i);
66             final Drawable childBg = child.getBackground();
67             if (child == content) {
68                 // We always count the content view container unless it has no background
69                 // and no children.
70                 if (childBg == null && child instanceof ViewGroup &&
71                         ((ViewGroup) child).getChildCount() == 0) {
72                     continue;
73                 }
74             } else if (child.getVisibility() != View.VISIBLE || childBg == null ||
75                     childBg.getOpacity() != PixelFormat.OPAQUE) {
76                 // Potentially translucent or invisible children don't count, and we assume
77                 // the content view will cover the whole area if we're in a background
78                 // fallback situation.
79                 continue;
80             }
81             left = Math.min(left, child.getLeft());
82             top = Math.min(top, child.getTop());
83             right = Math.max(right, child.getRight());
84             bottom = Math.max(bottom, child.getBottom());
85         }
86 
87         if (left >= right || top >= bottom) {
88             // No valid area to draw in.
89             return;
90         }
91 
92         if (top > 0) {
93             mBackgroundFallback.setBounds(0, 0, width, top);
94             mBackgroundFallback.draw(c);
95         }
96         if (left > 0) {
97             mBackgroundFallback.setBounds(0, top, left, height);
98             mBackgroundFallback.draw(c);
99         }
100         if (right < width) {
101             mBackgroundFallback.setBounds(right, top, width, height);
102             mBackgroundFallback.draw(c);
103         }
104         if (bottom < height) {
105             mBackgroundFallback.setBounds(left, bottom, right, height);
106             mBackgroundFallback.draw(c);
107         }
108     }
109 }
110