圆形图片 ImageView

package com.example.m_evolution;

import android.content.Context;
import android.graphics.Bitmap;
import android.graphics.Canvas;
import android.graphics.Paint;
import android.graphics.PorterDuff;
import android.graphics.PorterDuffXfermode;
import android.graphics.Rect;
import android.graphics.drawable.BitmapDrawable;
import android.graphics.drawable.Drawable;
import android.support.annotation.Nullable;
import android.util.AttributeSet;
import android.widget.ImageView;

public class CircleImageView extends ImageView {
    private Paint paint;

    public CircleImageView(Context context) {
        super(context);
        paint = new Paint();
    }

    public CircleImageView(Context context, @Nullable AttributeSet attrs) {
        super(context, attrs);
        paint = new Paint();
    }

    public CircleImageView(Context context, @Nullable AttributeSet attrs, int defStyleAttr) {
        super(context, attrs, defStyleAttr);
        paint = new Paint();
    }

    //显示时调用的函数
    @Override
    protected void onDraw(Canvas canvas) {
        Drawable drawable = getDrawable();  //获取drawable
        if (drawable != null) {
            Bitmap bitmap = ((BitmapDrawable) drawable).getBitmap();//转换成bitmap
            Bitmap bitmap_circle = getCircleBitmap(bitmap);  //将bitmap图片剪切成圆形
            final Rect rectSrc = new Rect(0, 0, bitmap_circle.getWidth(), bitmap_circle.getHeight());
            final Rect rectDest = new Rect(0,0,getWidth(),getHeight());
            paint.reset();
            canvas.drawBitmap(bitmap_circle, rectSrc, rectDest, paint);
        }
        else{
            super.onDraw(canvas);
        }
    }

    //将bitmap图片剪切成圆形
    private Bitmap getCircleBitmap(Bitmap bitmap) {
        Bitmap output = Bitmap.createBitmap(bitmap.getWidth(),bitmap.getHeight(), Bitmap.Config.ARGB_8888);
        Canvas canvas = new Canvas(output);

        final int color = 0xff424242;

        final Rect rect = new Rect(0, 0, bitmap.getWidth(), bitmap.getHeight());
        paint.setAntiAlias(true);
        canvas.drawARGB(0, 0, 0, 0);
        paint.setColor(color);
        int x = bitmap.getWidth();

        canvas.drawCircle(x / 2, x / 2, x / 2, paint);
        paint.setXfermode(new PorterDuffXfermode(PorterDuff.Mode.SRC_IN));
        canvas.drawBitmap(bitmap, rect, rect, paint);
        return output;

    }
}