Android设置圆角图，如两个圆角--工具类

刺骨的言语ヽ痛彻心扉 2022-07-11 12:05 353阅读 0赞

先看效果图：  
![这里写图片描述][SouthEast]  
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();

![这里写图片描述][SouthEast 1]  
（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  
![这里写图片描述][SouthEast 2]

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);
        }
    }

[SouthEast]: /images/20220711/f0ac876c9bcf446a8a02052f6919bc29.png
[SouthEast 1]: /images/20220711/fcfc21522da04a719d57ecc32a51e93c.png
[SouthEast 2]: /images/20220711/dac67342fd024847a5c0cee70d4c0ec8.png