在android上使用圆形图像视图

public class CircleImageView extends ImageView {
    private Paint paint;

    public CircleImageView(Context context) {
        super(context);
        init();
    }

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

    public CircleImageView(Context context, AttributeSet attrs, int defStyle) {
        super(context, attrs, defStyle);
        init();
    }

    private void init() {
        paint = new Paint();
        paint.setAntiAlias(true);
    }

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

        if (getWidth() == 0 || getHeight() == 0) {
            return;
        }

        Bitmap bitmap = ((BitmapDrawable) drawable).getBitmap();
        Bitmap scaledBitmap = Bitmap.createScaledBitmap(bitmap, getWidth(), getHeight(), false);

        Bitmap circleBitmap = Bitmap.createBitmap(getWidth(), getHeight(), Bitmap.Config.ARGB_8888);
        Canvas circleCanvas = new Canvas(circleBitmap);
        circleCanvas.drawCircle(getWidth() / 2, getHeight() / 2, getWidth() / 2, paint);
        circleCanvas.drawBitmap(scaledBitmap, 0, 0, paint);

        canvas.drawBitmap(circleBitmap, 0, 0, paint);
    }
}

<com.example.CircleImageView
    android:layout_width="100dp"
    android:layout_height="100dp"
    android:src="@drawable/avatar"
    android:scaleType="centerCrop" />