怎么在Android中利用ImageView控件实现一个圆角功能

import android.content.Context;import android.content.res.TypedArray;import android.graphics.Bitmap;import android.graphics.Bitmap.Config;import android.graphics.BitmapFactory;import android.graphics.Canvas;import android.graphics.Matrix;import android.graphics.Paint;import android.graphics.PorterDuff;import android.graphics.PorterDuffXfermode;import android.graphics.RectF;import android.graphics.drawable.BitmapDrawable;import android.graphics.drawable.Drawable;import android.util.AttributeSet;import android.widget.ImageView;import com.towatt.charge.towatt.R;public class CustomImageView extends android.support.v7.widget.AppCompatImageView { private Paint paint; private Paint paintBorder; private Bitmap mclass="lazy" data-srcBitmap;  private float mRadius; private boolean mIsCircle; public CustomImageView(final Context context) {  this(context, null); } public CustomImageView(Context context, AttributeSet attrs) {  this(context, attrs, R.attr.customImageViewStyle); } public CustomImageView(Context context, AttributeSet attrs, int defStyle) {  super(context, attrs, defStyle);  TypedArray ta = context.obtainStyledAttributes(attrs,    R.styleable.CustomImageView, defStyle, 0);  mRadius = ta.getDimension(R.styleable.CustomImageView_radius, 0);  mIsCircle = ta.getBoolean(R.styleable.CustomImageView_circle, false);  int class="lazy" data-srcResource = attrs.getAttributeResourceValue(    "http://schemas.android.com/apk/res/android", "class="lazy" data-src", 0);  if (class="lazy" data-srcResource != 0)   mclass="lazy" data-srcBitmap = BitmapFactory.decodeResource(getResources(),     class="lazy" data-srcResource);  ta.recycle();  paint = new Paint();  paint.setAntiAlias(true);  paintBorder = new Paint();  paintBorder.setAntiAlias(true); } @Override public void onDraw(Canvas canvas) {  int width = canvas.getWidth() - getPaddingLeft() - getPaddingRight();  int height = canvas.getHeight() - getPaddingTop() - getPaddingBottom();  Bitmap image = drawableToBitmap(getDrawable());  if (mIsCircle) {   Bitmap reSizeImage = reSizeImageC(image, width, height);   canvas.drawBitmap(createCircleImage(reSizeImage, width, height),     getPaddingLeft(), getPaddingTop(), null);  } else {   Bitmap reSizeImage = reSizeImage(image, width, height);   canvas.drawBitmap(createRoundImage(reSizeImage, width, height),     getPaddingLeft(), getPaddingTop(), null);  } }  private Bitmap createRoundImage(Bitmap source, int width, int height) {  Paint paint = new Paint();  paint.setAntiAlias(true);  Bitmap target = Bitmap.createBitmap(width, height, Config.ARGB_8888);  Canvas canvas = new Canvas(target);  RectF rect = new RectF(0, 0, width, height);  canvas.drawRoundRect(rect, mRadius, mRadius, paint);  // 核心代码取两个图片的交集部分  paint.setXfermode(new PorterDuffXfermode(PorterDuff.Mode.class="lazy" data-src_IN));  canvas.drawBitmap(source, 0, 0, paint);  return target; }  private Bitmap createCircleImage(Bitmap source, int width, int height) {  Paint paint = new Paint();  paint.setAntiAlias(true);  Bitmap target = Bitmap.createBitmap(width, height, Config.ARGB_8888);  Canvas canvas = new Canvas(target);  canvas.drawCircle(width / 2, height / 2, Math.min(width, height) / 2,    paint);  // 核心代码取两个图片的交集部分  paint.setXfermode(new PorterDuffXfermode(PorterDuff.Mode.class="lazy" data-src_IN));  canvas.drawBitmap(source, (width - source.getWidth()) / 2,    (height - source.getHeight()) / 2, paint);  return target; } @Override protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {  int width = MeasureSpec.getSize(widthMeasureSpec);  int height = MeasureSpec.getSize(heightMeasureSpec);  setMeasuredDimension(width, height); }  private Bitmap drawableToBitmap(Drawable drawable) {  if (drawable == null) {   if (mclass="lazy" data-srcBitmap != null) {    return mclass="lazy" data-srcBitmap;   } else {    return null;   }  } else if (drawable instanceof BitmapDrawable) {   return ((BitmapDrawable) drawable).getBitmap();  }  Bitmap bitmap = Bitmap.createBitmap(drawable.getIntrinsicWidth(),    drawable.getIntrinsicHeight(), Bitmap.Config.ARGB_8888);  Canvas canvas = new Canvas(bitmap);  drawable.setBounds(0, 0, canvas.getWidth(), canvas.getHeight());  drawable.draw(canvas);  return bitmap; }  private Bitmap reSizeImage(Bitmap bitmap, int newWidth, int newHeight) {  int width = bitmap.getWidth();  int height = bitmap.getHeight();  // 计算出缩放比  float scaleWidth = ((float) newWidth) / width;  float scaleHeight = ((float) newHeight) / height;  // 矩阵缩放bitmap  Matrix matrix = new Matrix();  matrix.postScale(scaleWidth, scaleHeight);  return Bitmap.createBitmap(bitmap, 0, 0, width, height, matrix, true); }  private Bitmap reSizeImageC(Bitmap bitmap, int newWidth, int newHeight) {  int width = bitmap.getWidth();  int height = bitmap.getHeight();  int x = (newWidth - width) / 2;  int y = (newHeight - height) / 2;  if (x > 0 && y > 0) {   return Bitmap.createBitmap(bitmap, 0, 0, width, height, null, true);  }  float scale = 1;  if (width > height) {   // 按照宽度进行等比缩放   scale = ((float) newWidth) / width;  } else {   // 按照高度进行等比缩放   // 计算出缩放比   scale = ((float) newHeight) / height;  }  Matrix matrix = new Matrix();  matrix.postScale(scale, scale);  return Bitmap.createBitmap(bitmap, 0, 0, width, height, matrix, true); }}