android自定义view 图片的应用

1xml布局

2新建一个activity

package com.example.dingview;

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;
import android.graphics.drawable.BitmapDrawable;
import android.graphics.drawable.Drawable;
import android.support.v7.widget.AppCompatImageView;
import android.util.AttributeSet;

public class CircleHeaderView extends AppCompatImageView {

    private int radius;

    public CircleHeaderView(Context context) {
        super(context);
    }

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

    //测量 测量自定义view的宽高
    @Override
    protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
        super.onMeasure(widthMeasureSpec, heightMeasureSpec);
        //获取当期view的宽高
        int measuredWidth = getMeasuredWidth();
        int measuredHeight = getMeasuredHeight();
        radius = Math.min(measuredWidth, measuredHeight) / 2;
    }
    //布局

    @Override
    protected void onLayout(boolean changed, int left, int top, int right, int bottom) {
        super.onLayout(changed, left, top, right, bottom);
    }

    @Override
    protected void onDraw(Canvas canvas) {
        //super.onDraw(canvas);
        Paint paint = new Paint();
        float mScale=1;
        paint.setColor(getResources().getColor(R.color.colorAccent));
        BitmapDrawable drawable =(BitmapDrawable) getDrawable();
        if (drawable!=null){
            Bitmap bitmap = drawable.getBitmap();
            BitmapShader bitmapShader = new BitmapShader(bitmap, Shader.TileMode.CLAMP, Shader.TileMode.CLAMP);
            mScale=(radius*2.0f)/Math.min(bitmap.getHeight(),bitmap.getWidth());

            Matrix matrix = new Matrix();
            matrix.setScale(mScale, mScale);
            bitmapShader.setLocalMatrix(matrix);
            paint.setShader(bitmapShader);
            canvas.drawCircle(radius,radius,radius,paint);
        }else{
            super.onDraw(canvas);
        }
    }
}

3效果图