RoundImageView.java

package com.com.mr_wrong.GaoFeng;

import android.content.Context;
import android.graphics.Bitmap;
import android.graphics.BitmapShader;
import android.graphics.Canvas;
import android.graphics.Matrix;
import android.graphics.Paint;
import android.graphics.Shader.TileMode;
import android.graphics.drawable.BitmapDrawable;
import android.graphics.drawable.Drawable;
import android.util.AttributeSet;
import android.widget.ImageView;

public class RoundImageView extends ImageView {
    //绘图的paint
    private Paint mBitmapPaint;
    //矩阵 用于放大缩小
    private Matrix mMatrix;
    //渲染图像，使用图像为绘制图像着色
    private BitmapShader mBitmapShader;
    //圆角的半径
    private int mRadius;
    //view的宽度
    private int mWidth;

    public RoundImageView(Context context) {
        this(context, null);
    }

    public RoundImageView(Context context, AttributeSet attrs) {
        super(context, attrs);
        mMatrix = new Matrix();
        mBitmapPaint = new Paint();
        mBitmapPaint.setAntiAlias(true);
    }

    @Override
    protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
        super.onMeasure(widthMeasureSpec, heightMeasureSpec);
        mWidth = Math.min(getMeasuredWidth(), getMeasuredHeight());
        mRadius = mWidth / 2;
        setMeasuredDimension(mWidth, mWidth);
    }

    /**
     * 初始化BitmapShader
     */
    private void setUpShader() {
        Drawable drawable = getDrawable();
        if (drawable == null) {
            return;
        }

        Bitmap bmp = drawableToBitamp(drawable);
        // 将bmp作为着色器，就是在指定区域内绘制bmp
        mBitmapShader = new BitmapShader(bmp, TileMode.CLAMP, TileMode.CLAMP);
        float scale = 1.0f;

        // 拿到bitmap宽或高的小值
        int bSize = Math.min(bmp.getWidth(), bmp.getHeight());
        scale = mWidth * 1.0f / bSize;

        if (!(bmp.getWidth() == getWidth() && bmp.getHeight() == getHeight())) {
            // 如果图片的宽或者高与view的宽高不匹配，计算出需要缩放的比例；缩放后的图片的宽高，一定要大于我们view的宽高；所以我们这里取大值；
            scale = Math.max(getWidth() * 1.0f / bmp.getWidth(),
                    getHeight() * 1.0f / bmp.getHeight());
        }
        // shader的变换矩阵，我们这里主要用于放大或者缩小
        mMatrix.setScale(scale, scale);
        // 设置变换矩阵
        mBitmapShader.setLocalMatrix(mMatrix);
        // 设置shader
        mBitmapPaint.setShader(mBitmapShader);
    }

    @Override
    protected void onDraw(Canvas canvas) {
        if (getDrawable() == null) {
            return;
        }
        setUpShader();
        canvas.drawCircle(mRadius, mRadius, mRadius, mBitmapPaint);
    }


    private Bitmap drawableToBitamp(Drawable drawable) {
        if (drawable instanceof BitmapDrawable) {
            BitmapDrawable bd = (BitmapDrawable) drawable;
            return bd.getBitmap();
        }
        int w = drawable.getIntrinsicWidth();
        int h = drawable.getIntrinsicHeight();
        Bitmap bitmap = Bitmap.createBitmap(w, h, Bitmap.Config.ARGB_8888);
        Canvas canvas = new Canvas(bitmap);
        drawable.setBounds(0, 0, w, h);
        drawable.draw(canvas);
        return bitmap;
    }


}