第一步：建立類RoundCircleDrawable繼承Drawable

/**
 * 圓角矩形
 * @Project    App_View
 * @Package    com.android.view.drawable
 * @author     chenlin
 * @version    1.0
 * @Date       2016年4月21日
 * @Note       TODO
 */
public class RoundCircleDrawable extends Drawable{
    private Paint mPaint;//畫筆
    private int mWidth;//圖片寬與長度的最小值
 

    private int mRadius;//半徑
    private int mRound;//圓角
    private RectF mRectF;//矩形
    private Bitmap mBitmap;//圖片
    private Type mType = Type.TYPE_ROUND;//預設是矩形

    //設定型別
    enum Type{
        TYPE_ROUND, TYPE_CICLE;
    }

    public RoundCircleDrawable(Bitmap bitmap){
        this.mBitmap = bitmap;

        //初始化畫筆
 

        mPaint = new Paint();
        mPaint.setAntiAlias(true);
        BitmapShader shader = new BitmapShader(mBitmap, TileMode.CLAMP, TileMode.CLAMP);
        mPaint.setShader(shader);

        mWidth = Math.min(mBitmap.getWidth(), mBitmap.getHeight());
        mRadius = mWidth / 2;
    }

    /**
     * 向外提供設定圖片型別的方法
     * @param
 
 type
     */
    public void setType(Type type){
        this.mType = type;
    }

    /**
     * 暴露給外面設定圓角的大小
     * 
     * @param round
     */
    public void setRound(int round) {
        this.mRound = round;
    }

    @Override
    public void setBounds(int left, int top, int right, int bottom) {
        super.setBounds(left, top, right, bottom);
        mRectF = new RectF(left, top, right, bottom);
    }

    @Override
    public void draw(Canvas canvas) {
        if (mType == Type.TYPE_ROUND) {
            canvas.drawRoundRect(mRectF, mRound, mRound, mPaint);
        }else {
            canvas.drawCircle(mWidth / 2, mWidth / 2, mRadius, mPaint);
        }
    }

    @Override
    public int getIntrinsicWidth() {
        if (mType == Type.TYPE_CICLE) {
            return mWidth;
        }else {
            return mBitmap.getWidth();
        }
    }

    @Override
    public int getIntrinsicHeight() {
        if (mType == Type.TYPE_CICLE) {
            return mWidth;
        }else {
            return mBitmap.getHeight();
        }
    }

    @Override
    public void setAlpha(int alpha) {
        mPaint.setAlpha(alpha);
    }

    @Override
    public void setColorFilter(ColorFilter cf) {
        mPaint.setColorFilter(cf);
    }

    @Override
    public int getOpacity() {
        return PixelFormat.TRANSLUCENT;
    }

}

2.實現方法

public class RoundActivity extends Activity {

    private ImageView mImageView;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_round_drawable);
        mImageView = (ImageView) findViewById(R.id.iv_round);
        Bitmap bitmap = BitmapFactory.decodeResource(getResources(), R.drawable.aa);
        //RoundImageDrawable drawable = new RoundImageDrawable(bitmap);
        //drawable.setRound(30);

        RoundCircleDrawable drawable = new RoundCircleDrawable(bitmap);
        drawable.setRound(50);
        mImageView.setImageDrawable(drawable);
    }
}

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