自定义控件之 圆形 / 圆角 ImageView

一、问题在哪里？

问题来源于app开发中一个很常见的场景——用户头像要展示成圆的：

   

[转载请保留本文地址：http://www.cnblogs.com/goagent/p/5159126.html] 

 二、怎么搞？

机智的我，第一想法就是，切一张中间圆形透明、四周与底色相同、尺寸与头像相同的蒙板图片，盖在头像上不就完事了嘛，哈哈哈！

在背景纯色的前提下，这的确能简单解决问题，但是如果背景没有这么简单呢？

在这种不规则背景下，有两个问题：

1)　　背景图常常是适应手机宽度缩放，而头像的尺寸又是固定宽高DP的，所以固定的蒙板图片是没法保证在不同机型上都和背景图案吻合的。

2)　　在这种非纯色背景下，哪天想调整一下头像位置就得重新换图片蒙板，实在是太难维护了……

所以呢，既然头像图片肯定是方的，那就就让ImageView圆起来吧。

 [转载请保留本文地址：http://www.cnblogs.com/goagent/p/5159126.html] 

三、开始干活

基本思路是，自定义一个ImageView，通过重写onDraw方法画出一个圆形的图片来：

 1 public class ImageViewPlus extends ImageView{
 2     private Paint mPaintBitmap = new Paint(Paint.ANTI_ALIAS_FLAG);
 3     private Bitmap mRawBitmap;
 4     private BitmapShader mShader;
 5     private Matrix mMatrix = new Matrix();
 6     
 7     public ImageViewPlus(Context context, AttributeSet attrs) {
 8         super(context, attrs);
 9     }
10     
11     @Override
12     protected void onDraw(Canvas canvas) {
13         Bitmap rawBitmap = getBitmap(getDrawable());
14         if (rawBitmap != null){
15             int viewWidth = getWidth();
16             int viewHeight = getHeight();
17             int viewMinSize = Math.min(viewWidth, viewHeight);
18             float dstWidth = viewMinSize;
19             float dstHeight = viewMinSize;
20             if (mShader == null || !rawBitmap.equals(mRawBitmap)){
21                 mRawBitmap = rawBitmap;
22                 mShader = new BitmapShader(mRawBitmap, TileMode.CLAMP, TileMode.CLAMP);
23             }
24             if (mShader != null){
25                 mMatrix.setScale(dstWidth / rawBitmap.getWidth(), dstHeight / rawBitmap.getHeight());
26                 mShader.setLocalMatrix(mMatrix);
27             }
28             mPaintBitmap.setShader(mShader);
29             float radius = viewMinSize / 2.0f;
30             canvas.drawCircle(radius, radius, radius, mPaintBitmap);
31         } else {
32             super.onDraw(canvas);
33         }
34     }
35 
36     private Bitmap getBitmap(Drawable drawable){
37         if (drawable instanceof BitmapDrawable){
38             return ((BitmapDrawable)drawable).getBitmap();
39         } else if (drawable instanceof ColorDrawable){
40             Rect rect = drawable.getBounds();
41             int width = rect.right - rect.left;
42             int height = rect.bottom - rect.top;
43             int color = ((ColorDrawable)drawable).getColor();
44             Bitmap bitmap = Bitmap.createBitmap(width, height, Bitmap.Config.ARGB_8888);
45             Canvas canvas = new Canvas(bitmap);
46             canvas.drawARGB(Color.alpha(color), Color.red(color), Color.green(color), Color.blue(color));
47             return bitmap;
48         } else {
49             return null;
50         }
51     }
52 }

分析一下代码：

 canvas.drawCircle 决定了画出来的形状是圆形，而圆形的内容则是通过 mPaintBitmap.setShader 搞定的。

其中，BitmapShader需要设置Bitmap填充ImageView的方式(CLAMP：拉伸边缘, MIRROR：镜像, REPEAT：整图重复)。

这里其实设成什么不重要，因为我们实际需要的是将Bitmap按比例缩放成跟ImageView一样大，而不是预置的三种效果。

所以，别忘了 mMatrix.setScale 和 mShader.setLocalMatrix 一起用，将图片缩放一下。

  [转载请保留本文地址：http://www.cnblogs.com/goagent/p/5159126.html] 

四、更多玩法 —— 支持边框

看下面的效果图，如果想给圆形的头像上加一个边框，该怎么搞呢？

      

 1 public class ImageViewPlus extends ImageView{
 2     private Paint mPaintBitmap = new Paint(Paint.ANTI_ALIAS_FLAG);
 3     private Paint mPaintBorder = new Paint(Paint.ANTI_ALIAS_FLAG);
 4     private Bitmap mRawBitmap;
 5     private BitmapShader mShader;
 6     private Matrix mMatrix = new Matrix();
 7     private float mBorderWidth = dip2px(15);
 8     private int mBorderColor = 0xFF0080FF;
 9     
10     public ImageViewPlus(Context context, AttributeSet attrs) {
11         super(context, attrs);
12     }
13     
14     @Override
15     protected void onDraw(Canvas canvas) {
16         Bitmap rawBitmap = getBitmap(getDrawable());
17         if (rawBitmap != null){
18             int viewWidth = getWidth();
19             int viewHeight = getHeight();
20             int viewMinSize = Math.min(viewWidth, viewHeight);
21             float dstWidth = viewMinSize;
22             float dstHeight = viewMinSize;
23             if (mShader == null || !rawBitmap.equals(mRawBitmap)){
24                 mRawBitmap = rawBitmap;
25                 mShader = new BitmapShader(mRawBitmap, TileMode.CLAMP, TileMode.CLAMP);
26             }
27             if (mShader != null){
28                 mMatrix.setScale((dstWidth - mBorderWidth * 2) / rawBitmap.getWidth(), (dstHeight - mBorderWidth * 2) / rawBitmap.getHeight());
29                 mShader.setLocalMatrix(mMatrix);
30             }
31             mPaintBitmap.setShader(mShader);
32             mPaintBorder.setStyle(Paint.Style.STROKE);
33             mPaintBorder.setStrokeWidth(mBorderWidth);
34             mPaintBorder.setColor(mBorderColor);
35             float radius = viewMinSize / 2.0f;
36             canvas.drawCircle(radius, radius, radius - mBorderWidth / 2.0f, mPaintBorder);
37             canvas.translate(mBorderWidth, mBorderWidth);
38             canvas.drawCircle(radius - mBorderWidth, radius - mBorderWidth, radius - mBorderWidth, mPaintBitmap);
39         } else {
40             super.onDraw(canvas);
41         }
42     }
43 
44     private Bitmap getBitmap(Drawable drawable){
45         if (drawable instanceof BitmapDrawable){
46             return ((BitmapDrawable)drawable).getBitmap();
47         } else if (drawable instanceof ColorDrawable){
48             Rect rect = drawable.getBounds();
49             int width = rect.right - rect.left;
50             int height = rect.bottom - rect.top;
51             int color = ((ColorDrawable)drawable).getColor();
52             Bitmap bitmap = Bitmap.createBitmap(width, height, Bitmap.Config.ARGB_8888);
53             Canvas canvas = new Canvas(bitmap);
54             canvas.drawARGB(Color.alpha(color), Color.red(color), Color.green(color), Color.blue(color));
55             return bitmap;
56         } else {
57             return null;
58         }
59     }
60     
61     private int dip2px(int dipVal)
62     {
63         float scale = getResources().getDisplayMetrics().density;
64         return (int)(dipVal * scale + 0.5f);
65     }
66 }

View Code

看代码中，加边框实际上就是用实心纯色的 Paint 画了一个圆边，在此基础上画上原来的头像即可。

需要的注意的地方有三个：

1)　　圆框的半径不是 radius ，而应该是 radius - mBorderWidth / 2.0f 。想象着拿着笔去画线，线其实是画在右图中白色圈的位置，只不过它很粗。

2)　　在ImageView大小不变的基础上，头像的实际大小要比没有边框的时候小了，所以 mMatrix.setScale 的时候要把边框的宽度去掉。

3)　　画头像Bitmap的时候不能直接 canvas.drawCircle(radius, radius, radius - mBorderWidth, mPaintBitmap) ，这样你会发现头像的右侧和下方边缘被拉伸了（右图）

   　　为什么呢？因为 Paint 默认是以左上角为基准开始绘制的，此时头像的实际区域是右图中的红框，而超过红框的部分（圆形的右侧和下方），自然被 TileMode.CLAMP效果沿边缘拉伸了。

   　　所以，需要通过挪动坐标系的位置和调整圆心，才能把头像画在正确的区域（右图绿框）中。

 [转载请保留本文地址：http://www.cnblogs.com/goagent/p/5159126.html] 

五、更多玩法 —— 支持xml配置

既然有了边框，那如果想配置边框的宽度和颜色该如何是好呢？

基本上两个思路：

1)　　给ImageViewPlus加上set接口，设置完成之后通过 invalidate(); 重绘一下即可；

2)　　在xml里就支持配置一些自定义属性，这样用起来会方便很多。

这里重点说一下支持xml配置自定义属性。

自定义控件要支持xml配置自定义属性的话，首先需要在 \res\values 里去定义属性： 

 1 <?xml version="1.0" encoding="utf-8"?>  
 2 <resources>  
 3     <attr name="borderColor" format="color" />
 4     <attr name="borderWidth" format="dimension" />
 5 
 6     <declare-styleable name="ImageViewPlus">  
 7         <attr name="borderColor" />
 8         <attr name="borderWidth" />
 9     </declare-styleable>  
10 </resources>  

View attrs_imageviewplus.xml

 然后在ImageViewPlus的构造函数中去读取这些自定义属性：

 1     private static final int DEFAULT_BORDER_COLOR = Color.TRANSPARENT;
 2     private static final int DEFAULT_BORDER_WIDTH = 0;
 3     
 4     public ImageViewPlus(Context context, AttributeSet attrs) {
 5         super(context, attrs);
 6         //取xml文件中设定的参数
 7         TypedArray ta = context.obtainStyledAttributes(attrs, R.styleable.ImageViewPlus);
 8         mBorderColor = ta.getColor(R.styleable.ImageViewPlus_borderColor, DEFAULT_BORDER_COLOR);
 9         mBorderWidth = ta.getDimensionPixelSize(R.styleable.ImageViewPlus_borderWidth, dip2px(DEFAULT_BORDER_WIDTH));
10         ta.recycle();
11     }

View Code

 在xml布局中使用自定义属性：

 1 <RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
 2     xmlns:tools="http://schemas.android.com/tools"
 3     xmlns:snser="http://schemas.android.com/apk/res/cc.snser.imageviewplus"
 4     android:layout_width="match_parent"
 5     android:layout_height="match_parent"
 6     android:background="@drawable/wallpaper"
 7     android:orientation="vertical"
 8     tools:context="${relativePackage}.${activityClass}" >
 9     
10     <cc.snser.imageviewplus.ImageViewPlus
11         android:id="@+id/imgplus"
12         android:layout_width="200dp"
13         android:layout_height="300dp"
14         android:layout_marginBottom="50dp"
15         android:layout_centerHorizontal="true"
16         android:layout_alignParentBottom="true"
17         android:src="@drawable/img_square"
18         snser:borderColor="#FF0080FF"
19         snser:borderWidth="15dp" />
20     
21 </RelativeLayout>

View Code

 [转载请保留本文地址：http://www.cnblogs.com/goagent/p/5159126.html] 

六、更多玩法 —— 圆角ImageView

搞定了圆形ImageView以及对应的边框，那如何实现下面这种圆角的ImageView呢？

 

其实原理上一样，把 canvas.drawCircle 对应改成 canvas.drawRoundRect 就OK了，直接贴代码吧：

  1 public class ImageViewPlus extends ImageView{
  2     /**
  3      * android.widget.ImageView
  4      */
  5     public static final int TYPE_NONE = 0;
  6     /**
  7      * 圆形
  8      */
  9     public static final int TYPE_CIRCLE = 1;
 10     /**
 11      * 圆角矩形
 12      */
 13     public static final int TYPE_ROUNDED_RECT = 2;    
 14     
 15     private static final int DEFAULT_TYPE = TYPE_NONE;
 16     private static final int DEFAULT_BORDER_COLOR = Color.TRANSPARENT;
 17     private static final int DEFAULT_BORDER_WIDTH = 0;
 18     private static final int DEFAULT_RECT_ROUND_RADIUS = 0;
 19     
 20     private int mType;
 21     private int mBorderColor;
 22     private int mBorderWidth;
 23     private int mRectRoundRadius;
 24     
 25     private Paint mPaintBitmap = new Paint(Paint.ANTI_ALIAS_FLAG);
 26     private Paint mPaintBorder = new Paint(Paint.ANTI_ALIAS_FLAG);
 27     
 28     private RectF mRectBorder = new RectF();
 29     private RectF mRectBitmap = new RectF();
 30     
 31     private Bitmap mRawBitmap;
 32     private BitmapShader mShader;
 33     private Matrix mMatrix = new Matrix();
 34     
 35     public ImageViewPlus(Context context, AttributeSet attrs) {
 36         super(context, attrs);
 37         //取xml文件中设定的参数
 38         TypedArray ta = context.obtainStyledAttributes(attrs, R.styleable.ImageViewPlus);
 39         mType = ta.getInt(R.styleable.ImageViewPlus_type, DEFAULT_TYPE);
 40         mBorderColor = ta.getColor(R.styleable.ImageViewPlus_borderColor, DEFAULT_BORDER_COLOR);
 41         mBorderWidth = ta.getDimensionPixelSize(R.styleable.ImageViewPlus_borderWidth, dip2px(DEFAULT_BORDER_WIDTH));
 42         mRectRoundRadius = ta.getDimensionPixelSize(R.styleable.ImageViewPlus_rectRoundRadius, dip2px(DEFAULT_RECT_ROUND_RADIUS));
 43         ta.recycle();
 44     }
 45     
 46     @Override
 47     protected void onDraw(Canvas canvas) {
 48         Bitmap rawBitmap = getBitmap(getDrawable());
 49         
 50         if (rawBitmap != null && mType != TYPE_NONE){
 51             int viewWidth = getWidth();
 52             int viewHeight = getHeight();
 53             int viewMinSize = Math.min(viewWidth, viewHeight);
 54             float dstWidth = mType == TYPE_CIRCLE ? viewMinSize : viewWidth;
 55             float dstHeight = mType == TYPE_CIRCLE ? viewMinSize : viewHeight;
 56             float halfBorderWidth = mBorderWidth / 2.0f;
 57             float doubleBorderWidth = mBorderWidth * 2;
 58             
 59             if (mShader == null || !rawBitmap.equals(mRawBitmap)){
 60                 mRawBitmap = rawBitmap;
 61                 mShader = new BitmapShader(mRawBitmap, TileMode.CLAMP, TileMode.CLAMP);
 62             }
 63             if (mShader != null){
 64                 mMatrix.setScale((dstWidth - doubleBorderWidth) / rawBitmap.getWidth(), (dstHeight - doubleBorderWidth) / rawBitmap.getHeight());
 65                 mShader.setLocalMatrix(mMatrix);
 66             }
 67             
 68             mPaintBitmap.setShader(mShader);
 69             mPaintBorder.setStyle(Paint.Style.STROKE);
 70             mPaintBorder.setStrokeWidth(mBorderWidth);
 71             mPaintBorder.setColor(mBorderWidth > 0 ? mBorderColor : Color.TRANSPARENT);
 72             
 73             if (mType == TYPE_CIRCLE){
 74                 float radius = viewMinSize / 2.0f;
 75                 canvas.drawCircle(radius, radius, radius - halfBorderWidth, mPaintBorder);
 76                 canvas.translate(mBorderWidth, mBorderWidth);
 77                 canvas.drawCircle(radius - mBorderWidth, radius - mBorderWidth, radius - mBorderWidth, mPaintBitmap);
 78             } else if (mType == TYPE_ROUNDED_RECT){
 79                 mRectBorder.set(halfBorderWidth, halfBorderWidth, dstWidth - halfBorderWidth, dstHeight - halfBorderWidth);
 80                 mRectBitmap.set(0.0f, 0.0f, dstWidth - doubleBorderWidth, dstHeight - doubleBorderWidth);
 81                 float borderRadius = mRectRoundRadius - halfBorderWidth > 0.0f ? mRectRoundRadius - halfBorderWidth : 0.0f;
 82                 float bitmapRadius = mRectRoundRadius - mBorderWidth > 0.0f ? mRectRoundRadius - mBorderWidth : 0.0f;
 83                 canvas.drawRoundRect(mRectBorder, borderRadius, borderRadius, mPaintBorder);
 84                 canvas.translate(mBorderWidth, mBorderWidth);
 85                 canvas.drawRoundRect(mRectBitmap, bitmapRadius, bitmapRadius, mPaintBitmap);
 86             }
 87         } else {
 88             super.onDraw(canvas);
 89         }
 90     }
 91 
 92     private int dip2px(int dipVal)
 93     {
 94         float scale = getResources().getDisplayMetrics().density;
 95         return (int)(dipVal * scale + 0.5f);
 96     }
 97     
 98     private Bitmap getBitmap(Drawable drawable){
 99         if (drawable instanceof BitmapDrawable){
100             return ((BitmapDrawable)drawable).getBitmap();
101         } else if (drawable instanceof ColorDrawable){
102             Rect rect = drawable.getBounds();
103             int width = rect.right - rect.left;
104             int height = rect.bottom - rect.top;
105             int color = ((ColorDrawable)drawable).getColor();
106             Bitmap bitmap = Bitmap.createBitmap(width, height, Bitmap.Config.ARGB_8888);
107             Canvas canvas = new Canvas(bitmap);
108             canvas.drawARGB(Color.alpha(color), Color.red(color), Color.green(color), Color.blue(color));
109             return bitmap;
110         } else {
111             return null;
112         }
113     }
114 }

View ImageViewPlus.java

 1 <RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
 2     xmlns:tools="http://schemas.android.com/tools"
 3     xmlns:snser="http://schemas.android.com/apk/res/cc.snser.imageviewplus"
 4     android:layout_width="match_parent"
 5     android:layout_height="match_parent"
 6     android:background="@drawable/wallpaper"
 7     android:orientation="vertical"
 8     tools:context="${relativePackage}.${activityClass}" >
 9     
10     <cc.snser.imageviewplus.ImageViewPlus
11         android:id="@+id/imgplus"
12         android:layout_width="200dp"
13         android:layout_height="300dp"
14         android:layout_marginBottom="50dp"
15         android:layout_centerHorizontal="true"
16         android:layout_alignParentBottom="true"
17         android:src="@drawable/img_rectangle"
18         snser:type="rounded_rect"
19         snser:borderColor="#FF0080FF"
20         snser:borderWidth="10dp"
21         snser:rectRoundRadius="30dp" />
22     
23 </RelativeLayout>

View layout

 1 <?xml version="1.0" encoding="utf-8"?>  
 2 <resources>  
 3     <attr name="type">  
 4         <enum name="none" value="0" />  
 5         <enum name="circle" value="1" />  
 6         <enum name="rounded_rect" value="2" />
 7     </attr>
 8     <attr name="borderColor" format="color" />
 9     <attr name="borderWidth" format="dimension" />
10     <attr name="rectRoundRadius" format="dimension" />
11 
12     <declare-styleable name="ImageViewPlus">  
13         <attr name="type" />
14         <attr name="borderColor" />
15         <attr name="borderWidth" />
16         <attr name="rectRoundRadius" />
17     </declare-styleable>
18 </resources>  

View attrs_imageviewplus.xml

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七、完结

 

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