Android Drawable Resource学习（十二）、ShapeDrawable还是GradientDrawable？



一、发现奇怪的问题？

在研究Android Drawable资源的时候，发现了一个奇怪的问题。在官方API介绍中：

ShapeDrawable 介绍：This object can be defined in an XML file with the<shape> element（这个对象可以用<shape>元素在xml文件中定义）

GradientDrawable 介绍：This object can be defined in an XML file with the<shape> element（这个对象可以用<shape>元素在xml文件中定义）

两者的介绍一模一样，都说可以使用<shape>标签在xml文件中定义。

那么，到底用<shape>标签定义的是什么的呢？经过下面的实验：

在shape.xml中定义：

[java] view plaincopyprint?

1. <?xml version="1.0" encoding="utf-8"?>  
2. <shape xmlns:android="http://schemas.android.com/apk/res/android"  
3.     android:shape="rectangle">  
4.     <gradient  
5.         android:startColor="#FFFF0000"  
6.         android:endColor="#80FF00FF"  
7.         android:angle="45"/>  
8.     <padding android:left="7dp"  
9.         android:top="7dp"  
10.         android:right="7dp"  
11.         android:bottom="7dp" />  
12.     <corners android:radius="8dp" />  
13. </shape>  

<?xml version="1.0" encoding="utf-8"?><shape xmlns:android="http://schemas.android.com/apk/res/android"    android:shape="rectangle">    <gradient        android:startColor="#FFFF0000"        android:endColor="#80FF00FF"        android:angle="45"/>    <padding android:left="7dp"        android:top="7dp"        android:right="7dp"        android:bottom="7dp" />    <corners android:radius="8dp" /></shape>

在layout文件中使用：

[java] view plaincopyprint?

1. <TextView  
2.         android:id="@+id/textView"  
3.         android:layout_width="wrap_content"  
4.         android:layout_height="wrap_content"  
5.         android:background="@drawable/gradient_box"  
6.         android:text="测试" />  

<TextView        android:id="@+id/textView"        android:layout_width="wrap_content"        android:layout_height="wrap_content"        android:background="@drawable/gradient_box"        android:text="测试" />

在java代码中控制：

[java] view plaincopyprint?

1. TextView textView=(TextView)findViewById(R.id.textView);  
2.    ShapeDrawable gradientDrawable=(ShapeDrawable)textView.getBackground();  

 TextView textView=(TextView)findViewById(R.id.textView);    ShapeDrawable gradientDrawable=(ShapeDrawable)textView.getBackground();

结果发现，报错了：

[java] view plaincopyprint?

1. :java.lang.ClassCastException: android.graphics.drawable.GradientDrawable  

:java.lang.ClassCastException: android.graphics.drawable.GradientDrawable

不能将GradientDrawable转换为ShapeDrawable。

可见，使用<shape>标签定义的是GradientDrawable。

并且，在官方API Drawable Resource中ShapeDrawable介绍到：

[java] view plaincopyprint?

1. compiled resource datatype:  
2.     Resource pointer to a GradientDrawable.  

compiled resource datatype:    Resource pointer to a GradientDrawable.

编译资源类型

指向GradientDrawable的指针。

可见，编译的类型是GradientDrawable。

那么，ShapeDrawable是怎么定义的，找了网上的资料，结果硬是没找到如何在XML文件中定义它，只能通过代码的方式实现。如何使用它在后面再介绍。

二、使用GradientDrawable

GradientDrawable的作用在于定于各种样式的渐变。在XML文件中使用<shape>元素定义。

文件位置：

res/drawable/filename.xml
文件名即资源ID

编译资源类型：

指向 GradientDrawable.

资源引用

In Java: R.drawable.filename
In XML: @[package:]drawable/filename

语法

<span class="pun"><?</span><span class="pln">xml version</span><span class="pun">=</span><span class="str">"1.0"</span><span class="pln"> encoding</span><span class="pun">=</span><span class="str">"utf-8"</span><span class="pun">?></span><span class="pln"></span><span class="tag"><</span><a><span class="tag">shape</span></a><span class="pln">    </span><span class="atn">xmlns:android</span><span class="pun">=</span><span class="atv">"http://schemas.android.com/apk/res/android"</span><span class="pln">    </span><span class="atn">android:shape</span><span class="pun">=</span><span class="atv">["rectangle"</span><span class="pln"> | </span><span class="atv">"oval"</span><span class="pln"> | </span><span class="atv">"line"</span><span class="pln"> | </span><span class="atv">"ring"</span><span class="pln">] </span><span class="tag">></span><span class="pln">    </span><span class="tag"><</span><a><span class="tag">corners</span></a><span class="pln">        </span><span class="atn">android:radius</span><span class="pun">=</span><span class="atv">"</span><em><span class="atv">integer</span></em><span class="atv">"</span><span class="pln">        </span><span class="atn">android:topLeftRadius</span><span class="pun">=</span><span class="atv">"</span><em><span class="atv">integer</span></em><span class="atv">"</span><span class="pln">        </span><span class="atn">android:topRightRadius</span><span class="pun">=</span><span class="atv">"</span><em><span class="atv">integer</span></em><span class="atv">"</span><span class="pln">        </span><span class="atn">android:bottomLeftRadius</span><span class="pun">=</span><span class="atv">"</span><em><span class="atv">integer</span></em><span class="atv">"</span><span class="pln">        </span><span class="atn">android:bottomRightRadius</span><span class="pun">=</span><span class="atv">"</span><em><span class="atv">integer</span></em><span class="atv">"</span><span class="pln"> </span><span class="tag">/></span><span class="pln">    </span><span class="tag"><</span><a><span class="tag">gradient</span></a><span class="pln">        </span><span class="atn">android:angle</span><span class="pun">=</span><span class="atv">"</span><em><span class="atv">integer</span></em><span class="atv">"</span><span class="pln">        </span><span class="atn">android:centerX</span><span class="pun">=</span><span class="atv">"</span><em><span class="atv">integer</span></em><span class="atv">"</span><span class="pln">        </span><span class="atn">android:centerY</span><span class="pun">=</span><span class="atv">"</span><em><span class="atv">integer</span></em><span class="atv">"</span><span class="pln">        </span><span class="atn">android:centerColor</span><span class="pun">=</span><span class="atv">"</span><em><span class="atv">integer</span></em><span class="atv">"</span><span class="pln">        </span><span class="atn">android:endColor</span><span class="pun">=</span><span class="atv">"</span><em><span class="atv">color</span></em><span class="atv">"</span><span class="pln">        </span><span class="atn">android:gradientRadius</span><span class="pun">=</span><span class="atv">"</span><em><span class="atv">integer</span></em><span class="atv">"</span><span class="pln">        </span><span class="atn">android:startColor</span><span class="pun">=</span><span class="atv">"</span><em><span class="atv">color</span></em><span class="atv">"</span><span class="pln">        </span><span class="atn">android:type</span><span class="pun">=</span><span class="atv">["linear"</span><span class="pln"> | </span><span class="atv">"radial"</span><span class="pln"> | </span><span class="atv">"sweep"</span><span class="pln">]        </span><span class="atn">android:useLevel</span><span class="pun">=</span><span class="atv">["true"</span><span class="pln"> | </span><span class="atv">"false"</span><span class="pln">] </span><span class="tag">/></span><span class="pln">    </span><span class="tag"><</span><a><span class="tag">padding</span></a><span class="pln">        </span><span class="atn">android:left</span><span class="pun">=</span><span class="atv">"</span><em><span class="atv">integer</span></em><span class="atv">"</span><span class="pln">        </span><span class="atn">android:top</span><span class="pun">=</span><span class="atv">"</span><em><span class="atv">integer</span></em><span class="atv">"</span><span class="pln">        </span><span class="atn">android:right</span><span class="pun">=</span><span class="atv">"</span><em><span class="atv">integer</span></em><span class="atv">"</span><span class="pln">        </span><span class="atn">android:bottom</span><span class="pun">=</span><span class="atv">"</span><em><span class="atv">integer</span></em><span class="atv">"</span><span class="pln"> </span><span class="tag">/></span><span class="pln">    </span><span class="tag"><</span><a><span class="tag">size</span></a><span class="pln">        </span><span class="atn">android:width</span><span class="pun">=</span><span class="atv">"</span><em><span class="atv">integer</span></em><span class="atv">"</span><span class="pln">        </span><span class="atn">android:height</span><span class="pun">=</span><span class="atv">"</span><em><span class="atv">integer</span></em><span class="atv">"</span><span class="pln"> </span><span class="tag">/></span><span class="pln">    </span><span class="tag"><</span><a><span class="tag">solid</span></a><span class="pln">        </span><span class="atn">android:color</span><span class="pun">=</span><span class="atv">"</span><em><span class="atv">color</span></em><span class="atv">"</span><span class="pln"> </span><span class="tag">/></span><span class="pln">    </span><span class="tag"><</span><a><span class="tag">stroke</span></a><span class="pln">        </span><span class="atn">android:width</span><span class="pun">=</span><span class="atv">"</span><em><span class="atv">integer</span></em><span class="atv">"</span><span class="pln">        </span><span class="atn">android:color</span><span class="pun">=</span><span class="atv">"</span><em><span class="atv">color</span></em><span class="atv">"</span><span class="pln">        </span><span class="atn">android:dashWidth</span><span class="pun">=</span><span class="atv">"</span><em><span class="atv">integer</span></em><span class="atv">"</span><span class="pln">        </span><span class="atn">android:dashGap</span><span class="pun">=</span><span class="atv">"</span><em><span class="atv">integer</span></em><span class="atv">"</span><span class="pln"> </span><span class="tag">/></span><span class="pln"></span><span class="tag"></shape></span>

元素：

<shape>

定义这是一个GradientDrawable，必须作为根元素。

属性：

xmlns:android

String类型。必须的，定义xml文件的命名空间，必须是"http://schemas.android.com/apk/res/android".

android:shape

关键字。定义shape的值，必须是下面的之一：值描述"rectangle"矩阵，这也是默认的shape"oval"椭圆"line"一条水平的直线。这种shape必须使用 <stroke> 元素来定义这条线的宽度"ring"圆环

下面的属性只有当 android:shape="ring"才使用：

android:innerRadius

尺寸。 内环的半径。一个尺寸值（dip等等）或者一个尺寸资源。

android:innerRadiusRatio

Float类型。这个值表示内部环的比例，例如,如果android:innerRadiusRatio = " 5 ",那么内部的半径等于环的宽度除以5。这个值会被android:innerRadius重写。 默认值是9。

android:thickness

尺寸。环的厚度，是一个尺寸值或尺寸的资源。

android:thicknessRatio

Float类型。厚度的比例。例如,如果android:thicknessRatio= " 2 ",然后厚度等于环的宽度除以2。这个值是被android:innerRadius重写， 默认值是3。

android:useLevel

Boolean类型。如果用在 LevelListDrawable里，那么就是true。如果通常不出现则为false。

<corners>

为Shape创建一个圆角，只有shape是rectangle时候才使用。

属性：

android:radius

Dimension。圆角的半径。会被下面每个特定的圆角属性重写。

android:topLeftRadius

Dimension。top-left 圆角的半径。

android:topRightRadius

Dimension。top-right 圆角的半径。

android:bottomLeftRadius

Dimension。 bottom-left圆角的半径。

android:bottomRightRadius

Dimension。bottom-right圆角的半径。

注意：每个圆角半径值都必须大于1，否侧就没有圆角。

             下面的话不明白，我直接设置圆角为0就可以不圆了，其余的设置有圆角，一样的可行。不知道它为什么要这么讲。

（If you want specific cornersto not be rounded, a work-around is to useandroid:radius to set a default cornerradius greater than 1, but then override each and every corner with the values you reallywant, providing zero ("0dp") where you don't want rounded corners.）

<gradient>

指定这个shape的渐变颜色。

属性：

android:angle

Integer。渐变的角度。 0 代表从 left 到 right。90 代表bottom到 top。必须是45的倍数，默认为0

android:centerX

Float。渐变中心的相对X坐标，在0到1.0之间。

android:centerY

Float。渐变中心的相对Y坐标，在0到1.0之间。

android:centerColor

Color。可选的颜色值。基于startColor和endColor之间。

android:endColor

Color。 结束的颜色。

android:gradientRadius

Float 。渐变的半径。只有在 android:type="radial"才使用

android:startColor

Color。开始的颜色值。

android:type

Keyword。渐变的模式，下面值之一：值描述"linear"线形渐变。这也是默认的模式"radial"辐射渐变。startColor即辐射中心的颜色"sweep"扫描线渐变。

android:useLevel

Boolean。如果在LevelListDrawable中使用，则为true

<padding>

     内容与视图边界的距离

属性：

android:left

Dimension。左边填充距离.

android:top

Dimension。顶部填充距离.

android:right

Dimension。右边填充距离.

android:bottom

Dimension。底部填充距离.

<size>

这个shape的大小。

属性：

android:height

Dimension。这个shape的高度。

android:width

Dimension。这个shape的宽度。

注意：默认情况下，这个shape会缩放到与他所在容器大小成正比。当你在一个ImageView中使用这个shape，你可以使用 android:scaleType="center"来限制这种缩放。

<solid>

填充这个shape的纯色

属性：

android:color

Color。颜色值，十六进制数，或者一个Color资源

<stroke>

这个shape使用的笔画，当android:shape="line"的时候，必须设置改元素。

属性：

android:width

Dimension。笔画的粗细。

android:color

Color。笔画的颜色

android:dashGap

Dimension。每画一条线就间隔多少。只有当android:dashWidth也设置了才有效。

android:dashWidth

Dimension。每画一条线的长度。只有当 android:dashGap也设置了才有效。

示例：

XML file saved at res/drawable/gradient_box.xml:

<span class="pun"><?</span><span class="pln">xml version</span><span class="pun">=</span><span class="str">"1.0"</span><span class="pln"> encoding</span><span class="pun">=</span><span class="str">"utf-8"</span><span class="pun">?></span><span class="pln"></span><span class="tag"><shape</span><span class="pln"> </span><span class="atn">xmlns:android</span><span class="pun">=</span><span class="atv">"http://schemas.android.com/apk/res/android"</span><span class="pln">    </span><span class="atn">android:shape</span><span class="pun">=</span><span class="atv">"rectangle"</span><span class="tag">></span><span class="pln">    </span><span class="tag"><gradient</span><span class="pln">        </span><span class="atn">android:startColor</span><span class="pun">=</span><span class="atv">"#FFFF0000"</span><span class="pln">        </span><span class="atn">android:endColor</span><span class="pun">=</span><span class="atv">"#80FF00FF"</span><span class="pln">        </span><span class="atn">android:angle</span><span class="pun">=</span><span class="atv">"45"</span><span class="tag">/></span><span class="pln">    </span><span class="tag"><padding</span><span class="pln"> </span><span class="atn">android:left</span><span class="pun">=</span><span class="atv">"7dp"</span><span class="pln">        </span><span class="atn">android:top</span><span class="pun">=</span><span class="atv">"7dp"</span><span class="pln">        </span><span class="atn">android:right</span><span class="pun">=</span><span class="atv">"7dp"</span><span class="pln">        </span><span class="atn">android:bottom</span><span class="pun">=</span><span class="atv">"7dp"</span><span class="pln"> </span><span class="tag">/></span><span class="pln">    </span><span class="tag"><corners</span><span class="pln"> </span><span class="atn">android:radius</span><span class="pun">=</span><span class="atv">"8dp"</span><span class="pln"> </span><span class="tag">/></span><span class="pln"></span><span class="tag"></shape></span>

This layout XML applies the shape drawable to a View:

<span class="tag"><TextView</span><span class="pln">    </span><span class="atn">android:background</span><span class="pun">=</span><span class="atv">"@drawable/gradient_box"</span><span class="pln">    </span><span class="atn">android:layout_height</span><span class="pun">=</span><span class="atv">"wrap_content"</span><span class="pln">    </span><span class="atn">android:layout_width</span><span class="pun">=</span><span class="atv">"wrap_content"</span><span class="pln"> </span><span class="tag">/></span>

This application code gets the shape drawable and applies it to a View:

<span class="typ">Resources</span><span class="pln"> res </span><span class="pun">=</span><span class="pln"> </span><code><a><span class="pln">getResources</span><span class="pun">()</span></a></code><span class="pun">;</span><span class="pln"></span><span class="typ">Drawable</span><span class="pln"> shape </span><span class="pun">=</span><span class="pln"> res</span><span class="pun">.</span><span class="pln"> </span><code><a><span class="pln">getDrawable</span></a></code><span class="pun">(</span><span class="pln">R</span><span class="pun">.</span><span class="pln">drawable</span><span class="pun">.</span><span class="pln">gradient_box</span><span class="pun">);</span><span class="pln"></span><span class="typ">TextView</span><span class="pln"> tv </span><span class="pun">=</span><span class="pln"> </span><span class="pun">(</span><span class="typ">TextView</span><span class="pun">)</span><span class="pln">findViewByID</span><span class="pun">(</span><span class="pln">R</span><span class="pun">.</span><span class="pln">id</span><span class="pun">.</span><span class="pln">textview</span><span class="pun">);</span><span class="pln">tv</span><span class="pun">.</span><span class="pln">setBackground</span><span class="pun">(</span><span class="pln">shape</span><span class="pun">);</span>

参考：

• ShapeDrawable

下面是API的Demo：

[java] view plaincopyprint?

1. package com.example.shapedrawable;  
2.   
3.   
4. import android.app.Activity;  
5. import android.content.Context;  
6. import android.graphics.Canvas;  
7. import android.graphics.Paint;  
8. import android.graphics.Path;  
9. import android.graphics.Picture;  
10. import android.graphics.Rect;  
11. import android.graphics.drawable.Drawable;  
12. import android.graphics.drawable.GradientDrawable;  
13. import android.graphics.drawable.ShapeDrawable;  
14. import android.os.Bundle;  
15. import android.util.AttributeSet;  
16. import android.view.View;  
17. import android.view.ViewGroup;  
18. import android.view.ViewParent;  
19. import android.widget.TextView;  
20.   
21. public class MainActivity extends GraphicsActivity {  
22.   
23.   @Override  
24.   protected void onCreate(Bundle savedInstanceState) {  
25.     super.onCreate(savedInstanceState);  
26.    setContentView(new SampleView(this));  
27.   }  
28.   
29.   private static class SampleView extends View {  
30.     private Path mPath;  
31.     private Paint mPaint;  
32.     private Rect mRect;  
33.     private GradientDrawable mDrawable;  
34.   
35.     public SampleView(Context context) {  
36.       super(context);  
37.       setFocusable(true);  
38.   
39.       mPath = new Path();  
40.       mPaint = new Paint(Paint.ANTI_ALIAS_FLAG);  
41.       mRect = new Rect(0, 0, 120, 120);  
42.   
43.       mDrawable = new GradientDrawable(  
44.           GradientDrawable.Orientation.TL_BR, new int[] { 0xFFFF0000,  
45.               0xFF00FF00, 0xFF0000FF });  
46.       mDrawable.setShape(GradientDrawable.RECTANGLE);  
47.       mDrawable.setGradientRadius((float) (Math.sqrt(2) * 60));  
48.     }  
49.   
50.     static void setCornerRadii(GradientDrawable drawable, float r0,  
51.         float r1, float r2, float r3) {  
52.       drawable.setCornerRadii(new float[] { r0, r0, r1, r1, r2, r2, r3,  
53.           r3 });  
54.     }  
55.   
56.   
57.     //重点的绘制过程  
58.     @Override  
59.     protected void onDraw(Canvas canvas) {  
60.   
61.       mDrawable.setBounds(mRect);  
62.   
63.       float r = 16;  
64.   
65.       canvas.save();  
66.       canvas.translate(10, 10);  
67.       mDrawable.setGradientType(GradientDrawable.LINEAR_GRADIENT);  
68.       setCornerRadii(mDrawable, r, r, 0, 0);  
69.       mDrawable.draw(canvas);  
70.       canvas.restore();  
71.   
72.       canvas.save();  
73.       canvas.translate(10 + mRect.width() + 10, 10);  
74.       mDrawable.setGradientType(GradientDrawable.RADIAL_GRADIENT);  
75.       setCornerRadii(mDrawable, 0, 0, r, r);  
76.       mDrawable.draw(canvas);  
77.       canvas.restore();  
78.   
79.       canvas.translate(0, mRect.height() + 10);  
80.   
81.       canvas.save();  
82.       canvas.translate(10, 10);  
83.       mDrawable.setGradientType(GradientDrawable.SWEEP_GRADIENT);  
84.       setCornerRadii(mDrawable, 0, r, r, 0);  
85.       mDrawable.draw(canvas);  
86.       canvas.restore();  
87.   
88.       canvas.save();  
89.       canvas.translate(10 + mRect.width() + 10, 10);  
90.       mDrawable.setGradientType(GradientDrawable.LINEAR_GRADIENT);  
91.       setCornerRadii(mDrawable, r, 0, 0, r);  
92.       mDrawable.draw(canvas);  
93.       canvas.restore();  
94.   
95.       canvas.translate(0, mRect.height() + 10);  
96.   
97.       canvas.save();  
98.       canvas.translate(10, 10);  
99.       mDrawable.setGradientType(GradientDrawable.RADIAL_GRADIENT);  
100.       setCornerRadii(mDrawable, r, 0, r, 0);  
101.       mDrawable.draw(canvas);  
102.       canvas.restore();  
103.   
104.       canvas.save();  
105.       canvas.translate(10 + mRect.width() + 10, 10);  
106.       mDrawable.setGradientType(GradientDrawable.SWEEP_GRADIENT);  
107.       setCornerRadii(mDrawable, 0, r, 0, r);  
108.       mDrawable.draw(canvas);  
109.       canvas.restore();  
110.     }  
111.   }  
112. }  
113.   
114. class GraphicsActivity extends Activity {  
115.   // set to true to test Picture  
116.   private static final boolean TEST_PICTURE = false;  
117.   
118.   @Override  
119.   protected void onCreate(Bundle savedInstanceState) {  
120.     super.onCreate(savedInstanceState);  
121.   }  
122.   
123.   @Override  
124.   public void setContentView(View view) {  
125.     if (TEST_PICTURE) {  
126.       ViewGroup vg = new PictureLayout(this);  
127.       vg.addView(view);  
128.       view = vg;  
129.     }  
130.   
131.     super.setContentView(view);  
132.   }  
133. }  
134.   
135. class PictureLayout extends ViewGroup {  
136.   private final Picture mPicture = new Picture();  
137.   
138.   public PictureLayout(Context context) {  
139.     super(context);  
140.   }  
141.   
142.   public PictureLayout(Context context, AttributeSet attrs) {  
143.     super(context, attrs);  
144.   }  
145.   
146.   @Override  
147.   public void addView(View child) {  
148.     if (getChildCount() > 1) {  
149.       throw new IllegalStateException(  
150.           "PictureLayout can host only one direct child");  
151.     }  
152.   
153.     super.addView(child);  
154.   }  
155.   
156.   @Override  
157.   public void addView(View child, int index) {  
158.     if (getChildCount() > 1) {  
159.       throw new IllegalStateException(  
160.           "PictureLayout can host only one direct child");  
161.     }  
162.   
163.     super.addView(child, index);  
164.   }  
165.   
166.   @Override  
167.   public void addView(View child, LayoutParams params) {  
168.     if (getChildCount() > 1) {  
169.       throw new IllegalStateException(  
170.           "PictureLayout can host only one direct child");  
171.     }  
172.   
173.     super.addView(child, params);  
174.   }  
175.   
176.   @Override  
177.   public void addView(View child, int index, LayoutParams params) {  
178.     if (getChildCount() > 1) {  
179.       throw new IllegalStateException(  
180.           "PictureLayout can host only one direct child");  
181.     }  
182.   
183.     super.addView(child, index, params);  
184.   }  
185.   
186.   @Override  
187.   protected LayoutParams generateDefaultLayoutParams() {  
188.     return new LayoutParams(LayoutParams.MATCH_PARENT,  
189.         LayoutParams.MATCH_PARENT);  
190.   }  
191.   
192.   @Override  
193.   protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {  
194.     final int count = getChildCount();  
195.   
196.     int maxHeight = 0;  
197.     int maxWidth = 0;  
198.   
199.     for (int i = 0; i < count; i++) {  
200.       final View child = getChildAt(i);  
201.       if (child.getVisibility() != GONE) {  
202.         measureChild(child, widthMeasureSpec, heightMeasureSpec);  
203.       }  
204.     }  
205.   
206.     maxWidth += getPaddingLeft() + getPaddingRight();  
207.     maxHeight += getPaddingTop() + getPaddingBottom();  
208.   
209.     Drawable drawable = getBackground();  
210.     if (drawable != null) {  
211.       maxHeight = Math.max(maxHeight, drawable.getMinimumHeight());  
212.       maxWidth = Math.max(maxWidth, drawable.getMinimumWidth());  
213.     }  
214.   
215.     setMeasuredDimension(resolveSize(maxWidth, widthMeasureSpec),  
216.         resolveSize(maxHeight, heightMeasureSpec));  
217.   }  
218.   
219.   private void drawPict(Canvas canvas, int x, int y, int w, int h, float sx,  
220.       float sy) {  
221.     canvas.save();  
222.     canvas.translate(x, y);  
223.     canvas.clipRect(0, 0, w, h);  
224.     canvas.scale(0.5f, 0.5f);  
225.     canvas.scale(sx, sy, w, h);  
226.     canvas.drawPicture(mPicture);  
227.     canvas.restore();  
228.   }  
229.   
230.   @Override  
231.   protected void dispatchDraw(Canvas canvas) {  
232.     super.dispatchDraw(mPicture.beginRecording(getWidth(), getHeight()));  
233.     mPicture.endRecording();  
234.   
235.     int x = getWidth() / 2;  
236.     int y = getHeight() / 2;  
237.   
238.     if (false) {  
239.       canvas.drawPicture(mPicture);  
240.     } else {  
241.       drawPict(canvas, 0, 0, x, y, 1, 1);  
242.       drawPict(canvas, x, 0, x, y, -1, 1);  
243.       drawPict(canvas, 0, y, x, y, 1, -1);  
244.       drawPict(canvas, x, y, x, y, -1, -1);  
245.     }  
246.   }  
247.   
248.   @Override  
249.   public ViewParent invalidateChildInParent(int[] location, Rect dirty) {  
250.     location[0] = getLeft();  
251.     location[1] = getTop();  
252.     dirty.set(0, 0, getWidth(), getHeight());  
253.     return getParent();  
254.   }  
255.   
256.   @Override  
257.   protected void onLayout(boolean changed, int l, int t, int r, int b) {  
258.     final int count = super.getChildCount();  
259.   
260.     for (int i = 0; i < count; i++) {  
261.       final View child = getChildAt(i);  
262.       if (child.getVisibility() != GONE) {  
263.         final int childLeft = getPaddingLeft();  
264.         final int childTop = getPaddingTop();  
265.         child.layout(childLeft, childTop,  
266.             childLeft + child.getMeasuredWidth(),  
267.             childTop + child.getMeasuredHeight());  
268.   
269.       }  
270.     }  
271.   }  
272. }  

package com.example.shapedrawable;import android.app.Activity;import android.content.Context;import android.graphics.Canvas;import android.graphics.Paint;import android.graphics.Path;import android.graphics.Picture;import android.graphics.Rect;import android.graphics.drawable.Drawable;import android.graphics.drawable.GradientDrawable;import android.graphics.drawable.ShapeDrawable;import android.os.Bundle;import android.util.AttributeSet;import android.view.View;import android.view.ViewGroup;import android.view.ViewParent;import android.widget.TextView;public class MainActivity extends GraphicsActivity {  @Override  protected void onCreate(Bundle savedInstanceState) {    super.onCreate(savedInstanceState);   setContentView(new SampleView(this));  }  private static class SampleView extends View {    private Path mPath;    private Paint mPaint;    private Rect mRect;    private GradientDrawable mDrawable;    public SampleView(Context context) {      super(context);      setFocusable(true);      mPath = new Path();      mPaint = new Paint(Paint.ANTI_ALIAS_FLAG);      mRect = new Rect(0, 0, 120, 120);      mDrawable = new GradientDrawable(          GradientDrawable.Orientation.TL_BR, new int[] { 0xFFFF0000,              0xFF00FF00, 0xFF0000FF });      mDrawable.setShape(GradientDrawable.RECTANGLE);      mDrawable.setGradientRadius((float) (Math.sqrt(2) * 60));    }    static void setCornerRadii(GradientDrawable drawable, float r0,        float r1, float r2, float r3) {      drawable.setCornerRadii(new float[] { r0, r0, r1, r1, r2, r2, r3,          r3 });    }    //重点的绘制过程    @Override    protected void onDraw(Canvas canvas) {      mDrawable.setBounds(mRect);      float r = 16;      canvas.save();      canvas.translate(10, 10);      mDrawable.setGradientType(GradientDrawable.LINEAR_GRADIENT);      setCornerRadii(mDrawable, r, r, 0, 0);      mDrawable.draw(canvas);      canvas.restore();      canvas.save();      canvas.translate(10 + mRect.width() + 10, 10);      mDrawable.setGradientType(GradientDrawable.RADIAL_GRADIENT);      setCornerRadii(mDrawable, 0, 0, r, r);      mDrawable.draw(canvas);      canvas.restore();      canvas.translate(0, mRect.height() + 10);      canvas.save();      canvas.translate(10, 10);      mDrawable.setGradientType(GradientDrawable.SWEEP_GRADIENT);      setCornerRadii(mDrawable, 0, r, r, 0);      mDrawable.draw(canvas);      canvas.restore();      canvas.save();      canvas.translate(10 + mRect.width() + 10, 10);      mDrawable.setGradientType(GradientDrawable.LINEAR_GRADIENT);      setCornerRadii(mDrawable, r, 0, 0, r);      mDrawable.draw(canvas);      canvas.restore();      canvas.translate(0, mRect.height() + 10);      canvas.save();      canvas.translate(10, 10);      mDrawable.setGradientType(GradientDrawable.RADIAL_GRADIENT);      setCornerRadii(mDrawable, r, 0, r, 0);      mDrawable.draw(canvas);      canvas.restore();      canvas.save();      canvas.translate(10 + mRect.width() + 10, 10);      mDrawable.setGradientType(GradientDrawable.SWEEP_GRADIENT);      setCornerRadii(mDrawable, 0, r, 0, r);      mDrawable.draw(canvas);      canvas.restore();    }  }}class GraphicsActivity extends Activity {  // set to true to test Picture  private static final boolean TEST_PICTURE = false;  @Override  protected void onCreate(Bundle savedInstanceState) {    super.onCreate(savedInstanceState);  }  @Override  public void setContentView(View view) {    if (TEST_PICTURE) {      ViewGroup vg = new PictureLayout(this);      vg.addView(view);      view = vg;    }    super.setContentView(view);  }}class PictureLayout extends ViewGroup {  private final Picture mPicture = new Picture();  public PictureLayout(Context context) {    super(context);  }  public PictureLayout(Context context, AttributeSet attrs) {    super(context, attrs);  }  @Override  public void addView(View child) {    if (getChildCount() > 1) {      throw new IllegalStateException(          "PictureLayout can host only one direct child");    }    super.addView(child);  }  @Override  public void addView(View child, int index) {    if (getChildCount() > 1) {      throw new IllegalStateException(          "PictureLayout can host only one direct child");    }    super.addView(child, index);  }  @Override  public void addView(View child, LayoutParams params) {    if (getChildCount() > 1) {      throw new IllegalStateException(          "PictureLayout can host only one direct child");    }    super.addView(child, params);  }  @Override  public void addView(View child, int index, LayoutParams params) {    if (getChildCount() > 1) {      throw new IllegalStateException(          "PictureLayout can host only one direct child");    }    super.addView(child, index, params);  }  @Override  protected LayoutParams generateDefaultLayoutParams() {    return new LayoutParams(LayoutParams.MATCH_PARENT,        LayoutParams.MATCH_PARENT);  }  @Override  protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {    final int count = getChildCount();    int maxHeight = 0;    int maxWidth = 0;    for (int i = 0; i < count; i++) {      final View child = getChildAt(i);      if (child.getVisibility() != GONE) {        measureChild(child, widthMeasureSpec, heightMeasureSpec);      }    }    maxWidth += getPaddingLeft() + getPaddingRight();    maxHeight += getPaddingTop() + getPaddingBottom();    Drawable drawable = getBackground();    if (drawable != null) {      maxHeight = Math.max(maxHeight, drawable.getMinimumHeight());      maxWidth = Math.max(maxWidth, drawable.getMinimumWidth());    }    setMeasuredDimension(resolveSize(maxWidth, widthMeasureSpec),        resolveSize(maxHeight, heightMeasureSpec));  }  private void drawPict(Canvas canvas, int x, int y, int w, int h, float sx,      float sy) {    canvas.save();    canvas.translate(x, y);    canvas.clipRect(0, 0, w, h);    canvas.scale(0.5f, 0.5f);    canvas.scale(sx, sy, w, h);    canvas.drawPicture(mPicture);    canvas.restore();  }  @Override  protected void dispatchDraw(Canvas canvas) {    super.dispatchDraw(mPicture.beginRecording(getWidth(), getHeight()));    mPicture.endRecording();    int x = getWidth() / 2;    int y = getHeight() / 2;    if (false) {      canvas.drawPicture(mPicture);    } else {      drawPict(canvas, 0, 0, x, y, 1, 1);      drawPict(canvas, x, 0, x, y, -1, 1);      drawPict(canvas, 0, y, x, y, 1, -1);      drawPict(canvas, x, y, x, y, -1, -1);    }  }  @Override  public ViewParent invalidateChildInParent(int[] location, Rect dirty) {    location[0] = getLeft();    location[1] = getTop();    dirty.set(0, 0, getWidth(), getHeight());    return getParent();  }  @Override  protected void onLayout(boolean changed, int l, int t, int r, int b) {    final int count = super.getChildCount();    for (int i = 0; i < count; i++) {      final View child = getChildAt(i);      if (child.getVisibility() != GONE) {        final int childLeft = getPaddingLeft();        final int childTop = getPaddingTop();        child.layout(childLeft, childTop,            childLeft + child.getMeasuredWidth(),            childTop + child.getMeasuredHeight());      }    }  }}

三、ShapeDrawable的使用

ShapeDrawable没有发现如何在XML文件中定义使用，所以应该不属于Drawable Resource。这个留到后面学习Graphics在看。