自定义ImageView实现圆形头像 利用Xferomede实现

不说废话，直接上代码，用的话直接把代码拷过去就行，不用别的配置

import android.content.Context;import android.graphics.Bitmap;import android.graphics.Canvas;import android.graphics.Color;import android.graphics.Matrix;import android.graphics.Paint;import android.graphics.PixelFormat;import android.graphics.PorterDuff;import android.graphics.PorterDuffXfermode;import android.graphics.Xfermode;import android.graphics.drawable.Drawable;import android.support.annotation.Nullable;import android.support.v7.widget.AppCompatImageView;import android.util.AttributeSet;/** * @author : sLiKangli *         创建日期 :  2017/6/4. *         类的作用 :  图片显示为圆形的View */public class RoundPictureView extends AppCompatImageView {    private Paint mPaint;    //画笔过滤模式，显示下层    private Xfermode xfermode = new PorterDuffXfermode(PorterDuff.Mode.DST_IN);    //这个控件的宽和高    private int mHeight;    private int mWidth;    public RoundPictureView(Context context) {        this(context, null);    }    public RoundPictureView(Context context, @Nullable AttributeSet attrs) {        this(context, attrs, 0);    }    public RoundPictureView(Context context, @Nullable AttributeSet attrs, int defStyleAttr) {        super(context, attrs, defStyleAttr);        init();    }    private void init() {        //初始化画笔        mPaint = new Paint(Paint.ANTI_ALIAS_FLAG);        mPaint.setColor(Color.WHITE);    }    @Override    protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {        super.onMeasure(widthMeasureSpec, heightMeasureSpec);        //得到宽和高，且必须相等        mWidth = getMeasuredWidth();        mHeight = getMeasuredHeight();        if(mWidth != mHeight){            throw new IllegalArgumentException("width and height of view required equals");        }    }    @Override    protected void onDraw(Canvas canvas) {        //保存图层，不知道为什么要这一步，不加就错        canvas.saveLayer(0, 0, mWidth, mHeight, null,                Canvas.MATRIX_SAVE_FLAG |                        Canvas.CLIP_SAVE_FLAG |                        Canvas.HAS_ALPHA_LAYER_SAVE_FLAG |                        Canvas.FULL_COLOR_LAYER_SAVE_FLAG |                        Canvas.CLIP_TO_LAYER_SAVE_FLAG);        //得到bitmap        Bitmap bitmap = drawable2Bitmap(getDrawable());        //把图片缩放到合适的比例        float xScale = (float) (mWidth*1.0/bitmap.getWidth());        float yScale = (float) (mHeight*1.0/bitmap.getHeight());        Matrix matrix = new Matrix();        matrix.setScale(xScale, yScale);         //画图片        canvas.drawBitmap(bitmap, matrix, mPaint);        //设置过滤模式        mPaint.setXfermode(xfermode);        //画圆        canvas.drawBitmap(getRoundBitmap(), 0,0, mPaint);        //必须的一步，去掉过滤模式，否则图片显示不出来        mPaint.setXfermode(null);    }    /**     * drawable 转 bitmap     */    private Bitmap drawable2Bitmap(Drawable drawable){        Bitmap bitmap = Bitmap.createBitmap(                drawable.getIntrinsicWidth(),                drawable.getIntrinsicHeight(),                drawable.getOpacity() != PixelFormat.OPAQUE ? Bitmap.Config.ARGB_8888                        : Bitmap.Config.RGB_565);        Canvas canvas = new Canvas(bitmap);        drawable.setBounds(0, 0, drawable.getIntrinsicWidth(), drawable.getIntrinsicHeight());        drawable.draw(canvas);        return bitmap;    }    /**     * 画一个圆形的bitmap     */    private Bitmap getRoundBitmap(){        Bitmap bitmap = Bitmap.createBitmap(mWidth, mHeight, Bitmap.Config.ARGB_8888);        Canvas canvas = new Canvas(bitmap);        Paint paint = new Paint(Paint.ANTI_ALIAS_FLAG);        paint.setColor(Color.WHITE);        canvas.drawCircle(mWidth/2, mHeight/2, mWidth/2, paint);        return bitmap;    }}