重寫ImageView

public class CircleImageView extends ImageView {

   private static final ScaleType SCALE_TYPE = ScaleType.CENTER_CROP;
   private static final Bitmap.Config BITMAP_CONFIG = Bitmap.Config.ARGB_8888;
   private static final int COLORDRAWABLE_DIMENSION = 1;
   private static final int DEFAULT_BORDER_WIDTH 
 
= 0;
   private static final int DEFAULT_BORDER_COLOR = Color.BLACK;
   private final RectF mDrawableRect = new RectF();
   private final RectF mBorderRect = new RectF();
   private final Matrix mShaderMatrix = new Matrix();
   private final Paint mBitmapPaint = new Paint();
   private final Paint mBorderPaint 
 
= new Paint();
   private int mBorderColor = DEFAULT_BORDER_COLOR;
   private int mBorderWidth = DEFAULT_BORDER_WIDTH;
   private Bitmap mBitmap;
   private BitmapShader mBitmapShader;
   private int mBitmapWidth;
   private int mBitmapHeight;
   private float mDrawableRadius;
   private float mBorderRadius
 
;
   private boolean mReady;
   private boolean mSetupPending;
   public CircleImageView(final Context context) {
      super(context);
}

   public CircleImageView(final Context context, final AttributeSet attrs) {
      this(context, attrs, 0);
}

   public CircleImageView(final Context context, final AttributeSet attrs,
         final int defStyle) {
      super(context, attrs, defStyle);
      super.setScaleType(SCALE_TYPE);
      final TypedArray a = context.obtainStyledAttributes(attrs,
R.styleable.CircleImageView, defStyle, 0);
mBorderWidth = a.getDimensionPixelSize(
            R.styleable.CircleImageView_border_width, DEFAULT_BORDER_WIDTH);
mBorderColor = a.getColor(R.styleable.CircleImageView_border_color,
DEFAULT_BORDER_COLOR);
a.recycle();
mReady = true;
      if (mSetupPending) {
         setup();
mSetupPending = false;
}
   }

   @Override
public ScaleType getScaleType() {
      return SCALE_TYPE;
}

   @Override
public void setScaleType(final ScaleType scaleType) {
      if (scaleType != SCALE_TYPE) {
         throw new IllegalArgumentException(String.format(
               "ScaleType %s not supported.", scaleType));
}
   }

   @Override
protected void onDraw(final Canvas canvas) {
      if (getDrawable() == null) {
         return;
}

      canvas.drawCircle(getWidth() / 2, getHeight() / 2, mDrawableRadius,
mBitmapPaint);
      if (mBorderWidth != 0) {
         canvas.drawCircle(getWidth() / 2, getHeight() / 2, mBorderRadius,
mBorderPaint);
}
   }

   @Override
protected void onSizeChanged(final int w, final int h, final int oldw,
         final int oldh) {
      super.onSizeChanged(w, h, oldw, oldh);
setup();
}

   public int getBorderColor() {
      return mBorderColor;
}

   public void setBorderColor(final int borderColor) {
      if (borderColor == mBorderColor) {
         return;
}

      mBorderColor = borderColor;
mBorderPaint.setColor(mBorderColor);
invalidate();
}

   public int getBorderWidth() {
      return mBorderWidth;
}

   public void setBorderWidth(final int borderWidth) {
      if (borderWidth == mBorderWidth) {
         return;
}

      mBorderWidth = borderWidth;
setup();
}

   @Override
public void setImageBitmap(final Bitmap bm) {
      super.setImageBitmap(bm);
mBitmap = bm;
setup();
}

   @Override
public void setImageDrawable(final Drawable drawable) {
      super.setImageDrawable(drawable);
mBitmap = getBitmapFromDrawable(drawable);
setup();
}

   @Override
public void setImageResource(final int resId) {
      super.setImageResource(resId);
mBitmap = getBitmapFromDrawable(getDrawable());
setup();
}

   private Bitmap getBitmapFromDrawable(final Drawable drawable) {
      if (drawable == null) {
         return null;
}

      if (drawable instanceof BitmapDrawable) {
         return ((BitmapDrawable) drawable).getBitmap();
}

      try {
         Bitmap bitmap;
         if (drawable instanceof ColorDrawable) {
            bitmap = Bitmap.createBitmap(COLORDRAWABLE_DIMENSION,
COLORDRAWABLE_DIMENSION, BITMAP_CONFIG);
} else {
            bitmap = Bitmap.createBitmap(drawable.getIntrinsicWidth(),
drawable.getIntrinsicHeight(), BITMAP_CONFIG);
}

         final Canvas canvas = new Canvas(bitmap);
drawable.setBounds(0, 0, canvas.getWidth(), canvas.getHeight());
drawable.draw(canvas);
         return bitmap;
} catch (final OutOfMemoryError e) {
         return null;
}
   }

   private void setup() {
      if (!mReady) {
         mSetupPending = true;
         return;
}

      if (mBitmap == null) {
         return;
}

      mBitmapShader = new BitmapShader(mBitmap, Shader.TileMode.CLAMP,
Shader.TileMode.CLAMP);
mBitmapPaint.setAntiAlias(true);
mBitmapPaint.setShader(mBitmapShader);
mBorderPaint.setStyle(Paint.Style.STROKE);
mBorderPaint.setAntiAlias(true);
mBorderPaint.setColor(mBorderColor);
mBorderPaint.setStrokeWidth(mBorderWidth);
mBitmapHeight = mBitmap.getHeight();
mBitmapWidth = mBitmap.getWidth();
mBorderRect.set(0, 0, getWidth(), getHeight());
mBorderRadius = Math.min((mBorderRect.height() - mBorderWidth) / 2,
(mBorderRect.width() - mBorderWidth) / 2);
mDrawableRect.set(mBorderWidth, mBorderWidth, mBorderRect.width()
            - mBorderWidth, mBorderRect.height() - mBorderWidth);
mDrawableRadius = Math.min(mDrawableRect.height() / 2,
mDrawableRect.width() / 2);
updateShaderMatrix();
invalidate();
}

   private void updateShaderMatrix() {
      float scale;
      float dx = 0;
      float dy = 0;
mShaderMatrix.set(null);
      if (mBitmapWidth * mDrawableRect.height() > mDrawableRect.width()
            * mBitmapHeight) {
         scale = mDrawableRect.height() / mBitmapHeight;
dx = (mDrawableRect.width() - mBitmapWidth * scale) * 0.5f;
} else {
         scale = mDrawableRect.width() / mBitmapWidth;
dy = (mDrawableRect.height() - mBitmapHeight * scale) * 0.5f;
}

      mShaderMatrix.setScale(scale, scale);
mShaderMatrix.postTranslate((int) (dx + 0.5f) + mBorderWidth,
(int) (dy + 0.5f) + mBorderWidth);
mBitmapShader.setLocalMatrix(mShaderMatrix);
}

}

使用方法：

在佈局檔案中

<cn.XXX.view.CircleImageView
android:id="@+id/iv_avatar"
android:layout_width="40dp"
android:layout_height="40dp"
android:src="@drawable/avatar"
android:layout_marginLeft="15dp"
android:layout_marginRight="15dp"/>

效果圖