Android设置圆角图，如两个圆角--工具类

先看效果图：

实现圆角图有很多种方式，本文采用paint.setXfermode(new PorterDuffXfermode(PorterDuff.Mode.SRC_IN));关于Xfermode类的使用，我会独立博客详细介绍。

工具类可以设置任意两个圆角，或者四个圆角。是不是有点小激动。

此处并未使用自定义控件，而是工具类。
实现原理：
1.先定义出透明的画板大小
2.将需要显示的图片贴到画板上
最关键的就是画板的定义，下面以右对角线为例，详见代码中clipRightDiagonal();

（注意：图中6，交集为，有笔误，应为“并集为”，请自行屏蔽，望不误导。）

那么问题来了。
Android中canvas中如何画矩形？
RectF和Rect都表示的是一个矩形的区域，他们的构造方法类似，详细请看官方文档，这里以RectF为例，如下：
RectF() :构造一个无参的矩形；
RectF（float left,float top,float right,float bottom）构造一个指定了4个参数的矩形 ，这些参数都是坐标，即矩形的宽width = right - left ，高height = bottom - top；如下图所示

RectF(Rect F r)根据指定的RectF对象来构造一个RectF对象(对象的左边坐标不变) 。
RectF(Rect r)根据给定的Rect对象来构造一个RectF对象。
这就是RectF的功能了，Rect 也具有这个功能。两者的区别在于：
RectF 中的参数是单精度浮点型的；
Rect 中的参数是整形的。

工具类代码如下：

package com.interjoy.demoguagualka;

import android.graphics.Bitmap;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Paint;
import android.graphics.PorterDuff;
import android.graphics.PorterDuffXfermode;
import android.graphics.Rect;
import android.graphics.RectF;

/**
 * Created by ylwang on 2017/1/24.
 */
public class BitmapFillet {

    public static final int ALL = 347120;
    public static final int TOP = 547120;
    public static final int LEFT = 647120;
    public static final int RIGHT = 747120;
    public static final int BOTTOM = 847120;
    public static final int LEFT_DIAGONAL = 0x123;//左对角线
    public static final int RIGHT_DIAGONAL = 0x223;//右对角线

    /**
     * 指定图片的切边，对图片进行圆角处理
     *
     * @param type    具体参见：{@link BitmapFillet.ALL} , {@link BitmapFillet.TOP} ,
     *                {@link BitmapFillet.LEFT} , {@link BitmapFillet.RIGHT} , {@link BitmapFillet.BOTTOM}
     * @param bitmap  需要被切圆角的图片
     * @param roundPx 要切的像素大小
     * @return
     */
    public static Bitmap fillet(int type, Bitmap bitmap, int roundPx) {
        try {
            // 其原理就是：先建立一个与图片大小相同的透明的Bitmap画板
            // 然后在画板上画出一个想要的形状的区域。
            // 最后把源图片帖上。
            final int width = bitmap.getWidth();
            final int height = bitmap.getHeight();

            Bitmap paintingBoard = Bitmap.createBitmap(width, height, Bitmap.Config.ARGB_8888);
            Canvas canvas = new Canvas(paintingBoard);
            canvas.drawARGB(Color.TRANSPARENT, Color.TRANSPARENT, Color.TRANSPARENT, Color.TRANSPARENT);

            final Paint paint = new Paint();
            paint.setAntiAlias(true);
            paint.setColor(Color.BLACK);
            if (TOP == type) {
                clipTop(canvas, paint, roundPx, width, height);
            } else if (LEFT == type) {
                clipLeft(canvas, paint, roundPx, width, height);
            } else if (RIGHT == type) {
                clipRight(canvas, paint, roundPx, width, height);
            } else if (BOTTOM == type) {
                clipBottom(canvas, paint, roundPx, width, height);
            } else if (LEFT_DIAGONAL == type) {
                clipLeftDiagonal(canvas, paint, roundPx, width, height);
            } else if (RIGHT_DIAGONAL == type) {
                clipRightDiagonal(canvas, paint, roundPx, width, height);
            } else {
                clipAll(canvas, paint, roundPx, width, height);
            }

            paint.setXfermode(new PorterDuffXfermode(PorterDuff.Mode.SRC_IN));
            //帖子图
            final Rect src = new Rect(0, 0, width, height);
            final Rect dst = src;
            canvas.drawBitmap(bitmap, src, dst, paint);
            return paintingBoard;
        } catch (Exception exp) {
            return bitmap;
        }
    }

    private static void clipLeft(final Canvas canvas, final Paint paint, int offset, int width, int height) {
        final Rect block = new Rect(offset, 0, width, height);
        canvas.drawRect(block, paint);
        final RectF rectF = new RectF(0, 0, offset * 2, height);
        canvas.drawRoundRect(rectF, offset, offset, paint);
    }

    private static void clipRight(final Canvas canvas, final Paint paint, int offset, int width, int height) {
        final Rect block = new Rect(0, 0, width - offset, height);
        canvas.drawRect(block, paint);
        final RectF rectF = new RectF(width - offset * 2, 0, width, height);
        canvas.drawRoundRect(rectF, offset, offset, paint);
    }

    private static void clipTop(final Canvas canvas, final Paint paint, int offset, int width, int height) {
        final Rect block = new Rect(0, offset, width, height);
        canvas.drawRect(block, paint);
        final RectF rectF = new RectF(0, 0, width, offset * 2);
        canvas.drawRoundRect(rectF, offset, offset, paint);
    }

    private static void clipBottom(final Canvas canvas, final Paint paint, int offset, int width, int height) {
        final Rect block = new Rect(0, 0, width, height - offset);
        canvas.drawRect(block, paint);
        final RectF rectF = new RectF(0, height - offset * 2, width, height);
        canvas.drawRoundRect(rectF, offset, offset, paint);
    }

    private static void clipAll(final Canvas canvas, final Paint paint, int offset, int width, int height) {
        final RectF rectF = new RectF(0, 0, width, height);
        canvas.drawRoundRect(rectF, offset, offset, paint);
    }

    private static void clipLeftDiagonal(Canvas canvas, Paint paint, int offset, int width, int height) {
        Rect rect1 = new Rect(offset, 0, width, height - offset);
        canvas.drawRect(rect1, paint);
        Rect rect2 = new Rect(0, offset, width - offset, height);
        canvas.drawRect(rect2, paint);
        canvas.drawCircle(offset, offset, offset, paint);
        canvas.drawCircle(width - offset, height - offset, offset, paint);
    }

    private static void clipRightDiagonal(Canvas canvas, Paint paint, int offset, int width, int height) {
        Rect rect1 = new Rect(0, 0, width - offset, height - offset);
        canvas.drawRect(rect1, paint);
        Rect rect2 = new Rect(offset, offset, width, height);
        canvas.drawRect(rect2, paint);
        canvas.drawCircle(width - offset, offset, offset, paint);
        canvas.drawCircle(offset, height - offset, offset, paint);
    }
}

代码中调用

public class ThirdActivity extends Activity {
    private ImageView iv_test1,iv_test2;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        requestWindowFeature(Window.FEATURE_NO_TITLE);
        setContentView(R.layout.activity_third);
        init();
    }

    private void init() {
        iv_test1 = (ImageView) findViewById(R.id.iv_test1);
        Bitmap src1 = BitmapFactory.decodeResource(getResources(), R.drawable.chuanpu);
        Bitmap bitmap1 = BitmapFillet.fillet(BitmapFillet.RIGHT_DIAGONAL, src1,200);
        iv_test1.setImageBitmap(bitmap1);

        iv_test2= (ImageView) findViewById(R.id.iv_test2);
        Bitmap src2 = BitmapFactory.decodeResource(getResources(), R.drawable.yuanyuan);
        Bitmap bitmap2 = BitmapFillet.fillet(BitmapFillet.BOTTOM, src2,150);
        iv_test2.setImageBitmap(bitmap2);
    }
}