Android学习笔记-绘制圆形ImageView实例

package com.jay.demo.imageviewdemo;

import android.content.Context;
import android.graphics.Bitmap;
import android.graphics.Canvas;
import android.graphics.Paint;
import android.graphics.PaintFlagsDrawFilter;
import android.graphics.Path;
import android.graphics.Rect;
import android.graphics.Region;
import android.util.AttributeSet;
import android.widget.ImageView;

/**
 * Created by coder-pig on 2015/7/18 0018.
 */
public class RoundImageView extends ImageView {

    private Bitmap mBitmap;
    private Rect mRect = new Rect();
    private PaintFlagsDrawFilter pdf = new PaintFlagsDrawFilter(0, Paint.ANTI_ALIAS_FLAG);
    private Paint mPaint = new Paint();
    private Path mPath=new Path();
    public RoundImageView(Context context, AttributeSet attrs) {
        super(context, attrs);
        init();
    }


    //传入一个Bitmap对象
    public void setBitmap(Bitmap bitmap) {
        this.mBitmap = bitmap;
    }


    private void init() {
        mPaint.setStyle(Paint.Style.STROKE);
        mPaint.setFlags(Paint.ANTI_ALIAS_FLAG);
        mPaint.setAntiAlias(true);// 抗锯尺
    }


    @Override
    protected void onDraw(Canvas canvas) {
        super.onDraw(canvas);
        if(mBitmap == null)
        {
            return;
        }
        mRect.set(0,0,getWidth(),getHeight());
        canvas.save();
        canvas.setDrawFilter(pdf);
        mPath.addCircle(getWidth() / 2, getWidth() / 2, getHeight() / 2, Path.Direction.CCW);
        canvas.clipPath(mPath, Region.Op.REPLACE);
        canvas.drawBitmap(mBitmap, null, mRect, mPaint);
        canvas.restore();
    }
}

<com.jay.demo.imageviewdemo.RoundImageView
        android:id="@+id/img_round"
        android:layout_width="200dp"
        android:layout_height="200dp"
        android:layout_margin="5px"/>

package com.jay.demo.imageviewdemo;

import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.os.Bundle;
import android.support.v7.app.AppCompatActivity;

public class MainActivity extends AppCompatActivity {

    private RoundImageView img_round;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        img_round = (RoundImageView) findViewById(R.id.img_round);
        Bitmap bitmap = BitmapFactory.decodeResource(getResources(),R.mipmap.meinv);
        img_round.setBitmap(bitmap);
    }
}