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  esvalues 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>  

 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;
        }
    }
}

<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>

<?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>  

[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]