Android 简易 自定义ImageView 实现圆形头像

实现思路：

效果：

源码 ：

import android.content.Context;
import android.content.res.TypedArray;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.graphics.BitmapShader;
import android.graphics.Canvas;
import android.graphics.Matrix;
import android.graphics.Paint;
import android.graphics.Shader;
import android.support.annotation.Nullable;
import android.util.AttributeSet;
/**
* Created by 煎鱼 on 2017/11/11.
*/

public class RoundView extends android.support.v7.widget.AppCompatImageView {

private static final String TAG = "RoundView";

private int D_Width;//圆的直径，D_Width = Math.min(width,heigh);

private int src; //通过自定义属性传进来的bitmap的资源码
private  Bitmap b;

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

public RoundView(Context context, @Nullable AttributeSet attrs) {
this(context, attrs,0);
}

public RoundView(Context context, @Nullable AttributeSet attrs, int defStyleAttr) {
super(context, attrs, defStyleAttr);
init(context,attrs);
}

private void init(Context context, AttributeSet attrs) {
//获取自定义属性。
TypedArray ta = context.obtainStyledAttributes(attrs, R.styleable.RoundView);
src = ta.getResourceId( R.styleable.RoundView_src,-1);

if( src== -1 ){
b = BitmapFactory.decodeResource(getResources(), R.drawable.t1);//默认图
}else{
b = BitmapFactory.decodeResource(getResources(), src);
}
}
@Override
protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
int widthMode = MeasureSpec.getMode(widthMeasureSpec);
int width = MeasureSpec.getSize(widthMeasureSpec);
int heighMode = MeasureSpec.getMode(heightMeasureSpec);
int heigh = MeasureSpec.getSize(heightMeasureSpec);

D_Width = Math.min(width,heigh);

alterBitmap();

setMeasuredDimension(width, heigh);
}

private void alterBitmap() {
//先缩小再裁剪：
b = scaleBitmap( b , (float) D_Width/Math.min(b.getWidth(),b.getHeight()) );//计算比例
b = cropBitmap(b);
}

@Override
protected void onDraw(Canvas canvas) {
Paint mPaint = new Paint();
mPaint.setAntiAlias(true);

//以bitmap为填充内容画一个圆
mPaint.setShader(new BitmapShader(b, Shader.TileMode.MIRROR, Shader.TileMode.MIRROR));
canvas.drawCircle(D_Width / 2, D_Width / 2, D_Width / 2, mPaint);
//画外边框
mPaint.reset();
mPaint.setStyle(Paint.Style.STROKE);
mPaint.setStrokeWidth(10);
mPaint.setColor(0xffdddddd);
canvas.drawCircle(D_Width / 2, D_Width / 2, D_Width / 2, mPaint);
}

/**
* 按比例缩放图片
*
* @param origin 原图
* @param ratio  比例
* @return 新的bitmap
*/
private Bitmap scaleBitmap(Bitmap origin, float ratio) {
if (origin == null) {
return null;
}
int width = origin.getWidth();
int height = origin.getHeight();
Matrix matrix = new Matrix();
matrix.postScale(ratio, ratio);
Bitmap newBM = Bitmap.createBitmap(origin, 0, 0, width, height, matrix, true);
if (newBM.equals(origin)) {
return newBM;
}
origin.recycle();
return newBM;
}

/**
* 裁剪成正方形
*
* @param bitmap 原图
* @return 裁剪后的图像
*/
private Bitmap cropBitmap(Bitmap bitmap) {
int w = bitmap.getWidth(); // 得到图片的宽，高
int h = bitmap.getHeight();

int cropWidth = w;
int cropHeight = h;
//在取图片较短边作为正方形的边长，从图片长边的中间进行裁剪
if(w>=h){
cropWidth = h;
return Bitmap.createBitmap(bitmap, (w-h)/2, 0, cropWidth, cropHeight , null, false);
}else{
cropHeight = w;
return Bitmap.createBitmap(bitmap, 0 , (h-w)/2  , cropWidth, cropHeight , null, false);
}
}

}