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：

   

 

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/snser/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：

 public class ImageViewPlus extends ImageView{
     private Paint mPaintBitmap = new Paint(Paint.ANTI_ALIAS_FLAG);
     private Bitmap mRawBitmap;
     private BitmapShader mShader;
     private Matrix mMatrix = new Matrix();

     public ImageViewPlus(Context context, AttributeSet attrs) {
         super(context, attrs);
     }

     @Override
     protected void onDraw(Canvas canvas) {
         Bitmap rawBitmap = getBitmap(getDrawable());
         if (rawBitmap != null){
             int viewWidth = getWidth();
             int viewHeight = getHeight();
             int viewMinSize = Math.min(viewWidth, viewHeight);
             float dstWidth = viewMinSize;
             float dstHeight = viewMinSize;
             if (mShader == null || !rawBitmap.equals(mRawBitmap)){
                 mRawBitmap = rawBitmap;
                 mShader = new BitmapShader(mRawBitmap, TileMode.CLAMP, TileMode.CLAMP);
             }
             if (mShader != null){
                 mMatrix.setScale(dstWidth / rawBitmap.getWidth(), dstHeight / rawBitmap.getHeight());
                 mShader.setLocalMatrix(mMatrix);
             }
             mPaintBitmap.setShader(mShader);
             float radius = viewMinSize / 2.0f;
             canvas.drawCircle(radius, radius, radius, mPaintBitmap);
         } else {
             super.onDraw(canvas);
         }
     }

     private Bitmap getBitmap(Drawable drawable){
         if (drawable instanceof BitmapDrawable){
             return ((BitmapDrawable)drawable).getBitmap();
         } else if (drawable instanceof ColorDrawable){
             Rect rect = drawable.getBounds();
             int width = rect.right - rect.left;
             int height = rect.bottom - rect.top;
             int color = ((ColorDrawable)drawable).getColor();
             Bitmap bitmap = Bitmap.createBitmap(width, height, Bitmap.Config.ARGB_8888);
             Canvas canvas = new Canvas(bitmap);
             canvas.drawARGB(Color.alpha(color), Color.red(color), Color.green(color), Color.blue(color));
             return bitmap;
         } else {
             return null;
         }
     }
 }

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/snser/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？

   

 public class ImageViewPlus extends ImageView{
     private Paint mPaintBitmap = new Paint(Paint.ANTI_ALIAS_FLAG);
     private Paint mPaintBorder = new Paint(Paint.ANTI_ALIAS_FLAG);
     private Bitmap mRawBitmap;
     private BitmapShader mShader;
     private Matrix mMatrix = new Matrix();
     private float mBorderWidth = dip2px(15);
     private int mBorderColor = 0xFF0080FF;

     public ImageViewPlus(Context context, AttributeSet attrs) {
         super(context, attrs);
     }

     @Override
     protected void onDraw(Canvas canvas) {
         Bitmap rawBitmap = getBitmap(getDrawable());
         if (rawBitmap != null){
             int viewWidth = getWidth();
             int viewHeight = getHeight();
             int viewMinSize = Math.min(viewWidth, viewHeight);
             float dstWidth = viewMinSize;
             float dstHeight = viewMinSize;
             if (mShader == null || !rawBitmap.equals(mRawBitmap)){
                 mRawBitmap = rawBitmap;
                 mShader = new BitmapShader(mRawBitmap, TileMode.CLAMP, TileMode.CLAMP);
             }
             if (mShader != null){
                 mMatrix.setScale((dstWidth - mBorderWidth * 2) / rawBitmap.getWidth(), (dstHeight - mBorderWidth * 2) / rawBitmap.getHeight());
                 mShader.setLocalMatrix(mMatrix);
             }
             mPaintBitmap.setShader(mShader);
             mPaintBorder.setStyle(Paint.Style.STROKE);
             mPaintBorder.setStrokeWidth(mBorderWidth);
             mPaintBorder.setColor(mBorderColor);
             float radius = viewMinSize / 2.0f;
             canvas.drawCircle(radius, radius, radius - mBorderWidth / 2.0f, mPaintBorder);
             canvas.translate(mBorderWidth, mBorderWidth);
             canvas.drawCircle(radius - mBorderWidth, radius - mBorderWidth, radius - mBorderWidth, mPaintBitmap);
         } else {
             super.onDraw(canvas);
         }
     }

     private Bitmap getBitmap(Drawable drawable){
         if (drawable instanceof BitmapDrawable){
             return ((BitmapDrawable)drawable).getBitmap();
         } else if (drawable instanceof ColorDrawable){
             Rect rect = drawable.getBounds();
             int width = rect.right - rect.left;
             int height = rect.bottom - rect.top;
             int color = ((ColorDrawable)drawable).getColor();
             Bitmap bitmap = Bitmap.createBitmap(width, height, Bitmap.Config.ARGB_8888);
             Canvas canvas = new Canvas(bitmap);
             canvas.drawARGB(Color.alpha(color), Color.red(color), Color.green(color), Color.blue(color));
             return bitmap;
         } else {
             return null;
         }
     }

     private int dip2px(int dipVal)
     {
         float scale = getResources().getDisplayMetrics().density;
         return (int)(dipVal * scale + 0.5f);
     }
 }

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/snser/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：

 <?xml version="1.0" encoding="utf-8"?>
 <resources>
     <attr name="borderColor" format="color" />
     <attr name="borderWidth" format="dimension" />

     <declare-styleable name="ImageViewPlus">
         <attr name="borderColor" />
         <attr name="borderWidth" />
     </declare-styleable>
 </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：

     private static final int DEFAULT_BORDER_COLOR = Color.TRANSPARENT;
     private static final int DEFAULT_BORDER_WIDTH = 0;

     public ImageViewPlus(Context context, AttributeSet attrs) {
         super(context, attrs);
         //取xml文件中设定的参数
         TypedArray ta = context.obtainStyledAttributes(attrs, R.styleable.ImageViewPlus);
         mBorderColor = ta.getColor(R.styleable.ImageViewPlus_borderColor, DEFAULT_BORDER_COLOR);
         mBorderWidth = ta.getDimensionPixelSize(R.styleable.ImageViewPlus_borderWidth, dip2px(DEFAULT_BORDER_WIDTH));
         ta.recycle();
     }

在xml布局中使用自定义属性：

 <RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
     xmlns:tools="http://schemas.android.com/tools"
     xmlns:snser="http://schemas.android.com/apk/res/cc.snser.imageviewplus"
     android:layout_width="match_parent"
     android:layout_height="match_parent"
     android:background="@drawable/wallpaper"
     android:orientation="vertical"
     tools:context="${relativePackage}.${activityClass}" >

     <cc.snser.imageviewplus.ImageViewPlus
         android:id="@+id/imgplus"
         android:layout_width="200dp"
         android:layout_height="300dp"
         android:layout_marginBottom="50dp"
         android:layout_centerHorizontal="true"
         android:layout_alignParentBottom="true"
         android:src="@drawable/img_square"
         snser:borderColor="#FF0080FF"
         snser:borderWidth="15dp" />

 </RelativeLayout>

[转载请保留本文地址：http://www.cnblogs.com/snser/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：

 public class ImageViewPlus extends ImageView{
     /**
      * android.widget.ImageView
      */
     public static final int TYPE_NONE = 0;
     /**
      * 圆形
      */
     public static final int TYPE_CIRCLE = 1;
     /**
      * 圆角矩形
      */
     public static final int TYPE_ROUNDED_RECT = 2;    

     private static final int DEFAULT_TYPE = TYPE_NONE;
     private static final int DEFAULT_BORDER_COLOR = Color.TRANSPARENT;
     private static final int DEFAULT_BORDER_WIDTH = 0;
     private static final int DEFAULT_RECT_ROUND_RADIUS = 0;

     private int mType;
     private int mBorderColor;
     private int mBorderWidth;
     private int mRectRoundRadius;

     private Paint mPaintBitmap = new Paint(Paint.ANTI_ALIAS_FLAG);
     private Paint mPaintBorder = new Paint(Paint.ANTI_ALIAS_FLAG);

     private RectF mRectBorder = new RectF();
     private RectF mRectBitmap = new RectF();

     private Bitmap mRawBitmap;
     private BitmapShader mShader;
     private Matrix mMatrix = new Matrix();

     public ImageViewPlus(Context context, AttributeSet attrs) {
         super(context, attrs);
         //取xml文件中设定的参数
         TypedArray ta = context.obtainStyledAttributes(attrs, R.styleable.ImageViewPlus);
         mType = ta.getInt(R.styleable.ImageViewPlus_type, DEFAULT_TYPE);
         mBorderColor = ta.getColor(R.styleable.ImageViewPlus_borderColor, DEFAULT_BORDER_COLOR);
         mBorderWidth = ta.getDimensionPixelSize(R.styleable.ImageViewPlus_borderWidth, dip2px(DEFAULT_BORDER_WIDTH));
         mRectRoundRadius = ta.getDimensionPixelSize(R.styleable.ImageViewPlus_rectRoundRadius, dip2px(DEFAULT_RECT_ROUND_RADIUS));
         ta.recycle();
     }

     @Override
     protected void onDraw(Canvas canvas) {
         Bitmap rawBitmap = getBitmap(getDrawable());

         if (rawBitmap != null && mType != TYPE_NONE){
             int viewWidth = getWidth();
             int viewHeight = getHeight();
             int viewMinSize = Math.min(viewWidth, viewHeight);
             float dstWidth = mType == TYPE_CIRCLE ? viewMinSize : viewWidth;
             float dstHeight = mType == TYPE_CIRCLE ? viewMinSize : viewHeight;
             float halfBorderWidth = mBorderWidth / 2.0f;
             float doubleBorderWidth = mBorderWidth * 2;

             if (mShader == null || !rawBitmap.equals(mRawBitmap)){
                 mRawBitmap = rawBitmap;
                 mShader = new BitmapShader(mRawBitmap, TileMode.CLAMP, TileMode.CLAMP);
             }
             if (mShader != null){
                 mMatrix.setScale((dstWidth - doubleBorderWidth) / rawBitmap.getWidth(), (dstHeight - doubleBorderWidth) / rawBitmap.getHeight());
                 mShader.setLocalMatrix(mMatrix);
             }

             mPaintBitmap.setShader(mShader);
             mPaintBorder.setStyle(Paint.Style.STROKE);
             mPaintBorder.setStrokeWidth(mBorderWidth);
             mPaintBorder.setColor(mBorderWidth > 0 ? mBorderColor : Color.TRANSPARENT);

             if (mType == TYPE_CIRCLE){
                 float radius = viewMinSize / 2.0f;
                 canvas.drawCircle(radius, radius, radius - halfBorderWidth, mPaintBorder);
                 canvas.translate(mBorderWidth, mBorderWidth);
                 canvas.drawCircle(radius - mBorderWidth, radius - mBorderWidth, radius - mBorderWidth, mPaintBitmap);
             } else if (mType == TYPE_ROUNDED_RECT){
                 mRectBorder.set(halfBorderWidth, halfBorderWidth, dstWidth - halfBorderWidth, dstHeight - halfBorderWidth);
                 mRectBitmap.set(0.0f, 0.0f, dstWidth - doubleBorderWidth, dstHeight - doubleBorderWidth);
                 float borderRadius = mRectRoundRadius - halfBorderWidth > 0.0f ? mRectRoundRadius - halfBorderWidth : 0.0f;
                 float bitmapRadius = mRectRoundRadius - mBorderWidth > 0.0f ? mRectRoundRadius - mBorderWidth : 0.0f;
                 canvas.drawRoundRect(mRectBorder, borderRadius, borderRadius, mPaintBorder);
                 canvas.translate(mBorderWidth, mBorderWidth);
                 canvas.drawRoundRect(mRectBitmap, bitmapRadius, bitmapRadius, mPaintBitmap);
             }
         } else {
             super.onDraw(canvas);
         }
     }

     private int dip2px(int dipVal)
     {
         float scale = getResources().getDisplayMetrics().density;
         return (int)(dipVal * scale + 0.5f);
     }

     private Bitmap getBitmap(Drawable drawable){
         if (drawable instanceof BitmapDrawable){
             return ((BitmapDrawable)drawable).getBitmap();
         } else if (drawable instanceof ColorDrawable){
             Rect rect = drawable.getBounds();
             int width = rect.right - rect.left;
             int height = rect.bottom - rect.top;
             int color = ((ColorDrawable)drawable).getColor();
             Bitmap bitmap = Bitmap.createBitmap(width, height, Bitmap.Config.ARGB_8888);
             Canvas canvas = new Canvas(bitmap);
             canvas.drawARGB(Color.alpha(color), Color.red(color), Color.green(color), Color.blue(color));
             return bitmap;
         } else {
             return null;
         }
     }
 }

View ImageViewPlus.java

 <RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
     xmlns:tools="http://schemas.android.com/tools"
     xmlns:snser="http://schemas.android.com/apk/res/cc.snser.imageviewplus"
     android:layout_width="match_parent"
     android:layout_height="match_parent"
     android:background="@drawable/wallpaper"
     android:orientation="vertical"
     tools:context="${relativePackage}.${activityClass}" >

     <cc.snser.imageviewplus.ImageViewPlus
         android:id="@+id/imgplus"
         android:layout_width="200dp"
         android:layout_height="300dp"
         android:layout_marginBottom="50dp"
         android:layout_centerHorizontal="true"
         android:layout_alignParentBottom="true"
         android:src="@drawable/img_rectangle"
         snser:type="rounded_rect"
         snser:borderColor="#FF0080FF"
         snser:borderWidth="10dp"
         snser:rectRoundRadius="30dp" />

 </RelativeLayout>

View layout

 <?xml version="1.0" encoding="utf-8"?>
 <resources>
     <attr name="type">
         <enum name="none" value="0" />
         <enum name="circle" value="1" />
         <enum name="rounded_rect" value="2" />
     </attr>
     <attr name="borderColor" format="color" />
     <attr name="borderWidth" format="dimension" />
     <attr name="rectRoundRadius" format="dimension" />

     <declare-styleable name="ImageViewPlus">
         <attr name="type" />
         <attr name="borderColor" />
         <attr name="borderWidth" />
         <attr name="rectRoundRadius" />
     </declare-styleable>
 </resources>  

View attrs_imageviewplus.xml

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

七、Demo源码

保存下面的图片，扩展名改成zip后解压即可。

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