Android使用Drawable实现圆角矩形

第一步：写个类继承drawable,重写里面的方法，实现的核心代码在draw里
关键技术：BitmapShader
public BitmapShader(Bitmap bitmap,Shader.TileMode tileX,Shader.TileMode tileY)
调用这个方法来产生一个画有一个位图的渲染器（Shader）。
bitmap 在渲染器内使用的位图
tileX The tiling mode for x to draw the bitmap in. 在位图上X方向渲染器平铺模式
tileY The tiling mode for y to draw the bitmap in. 在位图上Y方向渲染器平铺模式
TileMode：
CLAMP ：如果渲染器超出原始边界范围，会复制范围内边缘染色。
REPEAT ：横向和纵向的重复渲染器图片，平铺。
MIRROR ：横向和纵向的重复渲染器图片，这个和REPEAT重复方式不一样，他是以镜像方式平铺。

/**
* 四种屏幕尺寸分类：: small, normal, large, and xlarge
* 四种密度分类: ldpi (low), mdpi (medium), hdpi (high), and xhdpi (extra high)
* 四种屏幕的DPI：ldpi是120dpi，mdpi是160dpi，hdpi是240dpi，xhdpi是320dpi
* 四种屏幕对应density：0.75,1,1.5,2
* 四种图片资源文件夹：drawable-ldpi,drawable-mdpi,drawable-hdpi,drawable-xhdpi
*/

/** * 圆角 *  * @Project App_View * @Package com.android.view.drawable * @author chenlin * @version 1.0 * @Note TODO */public class RoundImageDrawable extends Drawable {    private Paint mPaint;    private Bitmap mBitmap;    private RectF mRectF;    private int mRound;    public RoundImageDrawable(Bitmap bitmap) {        this.mBitmap = bitmap;        mPaint = new Paint();        mPaint.setAntiAlias(true);        BitmapShader shader = new BitmapShader(mBitmap, TileMode.CLAMP, TileMode.CLAMP);        mPaint.setShader(shader);    }    /**     * 初始化区域     */    @Override    public void setBounds(int left, int top, int right, int bottom) {        mRectF = new RectF(left, top, right, bottom);        super.setBounds(left, top, right, bottom);    }    /**     * 核心代码： 绘制圆角     */    @Override    public void draw(Canvas canvas) {        canvas.drawRoundRect(mRectF, mRound, mRound, mPaint);    }    /**     * 暴露给外面设置圆角的大小     *      * @param round     */    public void setRound(int round) {        this.mRound = round;    }    /**     * getIntrinsicWidth、getIntrinsicHeight主要是为了在View使用wrap_content的时候，     * 提供一下尺寸，默认为-1可不是我们希望的     */    @Override    public int getIntrinsicHeight() {        return mBitmap.getHeight();    }    @Override    public int getIntrinsicWidth() {        return mBitmap.getWidth();    }    /**     * 根据画笔设定drawable的透明度     */    @Override    public void setAlpha(int alpha) {        mPaint.setAlpha(alpha);    }    /**     * 根据画笔设定drawable的颜色过滤器     */    @Override    public void setColorFilter(ColorFilter cf) {        mPaint.setColorFilter(cf);    }    @Override    public int getOpacity() {        return PixelFormat.TRANSLUCENT;    }}

第二步：实现类

public class RoundActivity extends Activity {    private ImageView mImageView;    @Override    protected void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        setContentView(R.layout.activity_round_drawable);        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);        mImageView.setImageDrawable(drawable);  }}

activity_round_drawable.xml

<?xml version="1.0" encoding="utf-8"?><LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"    android:layout_width="match_parent"    android:layout_height="match_parent"    android:orientation="vertical" >    <ImageView        android:id="@+id/iv_round"        android:layout_width="wrap_content"        android:layout_height="wrap_content"        android:scaleType="fitXY" /></LinearLayout>

绘制圆形图片
核心代码：
mWidth = Math.min(bitmap.getWidth(), bitmap.getHeight());
canvas.drawCircle(mWidth / 2, mWidth / 2, mRadius, mPaint);

/** * 圆形 * @Project    App_View * @Package    com.android.view.drawable * @author     chenlin * @version    1.0 * @Note       TODO */public class CircleImageDrawable extends Drawable {    private Bitmap mBitmap;    private Paint mPaint;    private int mWidth;      private int mRadius;        public CircleImageDrawable(Bitmap bitmap){        this.mBitmap = bitmap;        mPaint.setAntiAlias(true);        BitmapShader shader = new BitmapShader(mBitmap, TileMode.CLAMP, TileMode.CLAMP);        mPaint.setShader(shader);        mWidth = Math.min(bitmap.getWidth(), bitmap.getHeight());        mRadius = mWidth / 2;    }    /**     * 核心代码     */    @Override    public void draw(Canvas canvas) {        canvas.drawCircle(mWidth / 2, mWidth / 2, mRadius, mPaint);    }    /**     * getIntrinsicWidth、getIntrinsicHeight主要是为了在View使用wrap_content的时候，     * 提供一下尺寸，默认为-1可不是我们希望的     */    @Override    public int getIntrinsicHeight() {        return mWidth;    }    @Override    public int getIntrinsicWidth() {        return mWidth;    }    @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;    }}