【Android学习笔记】圆角矩形ImageView自定义控件的实现与使用

　　在做安卓项目的过程中，我们总会遇到需要以圆角矩形控件来显示图标、图片或者按钮的需求，解决办法有两种，一种是在drawable下创建shape布局xml文件，另一种是自定义一个继承于ImageView的自定义控件类来实现，下面是具体的实现办法。

　　首先我们命名一个XCRoundRectImageView类，并继承于ImageView。代码如下：

 1 import android.content.Context;
 2 import android.graphics.Bitmap;
 3 import android.graphics.Bitmap.Config;
 4 import android.graphics.Canvas;
 5 import android.graphics.Paint;
 6 import android.graphics.PixelFormat;
 7 import android.graphics.RectF;
 8 import android.graphics.PorterDuff.Mode;
 9 import android.graphics.PorterDuffXfermode;
10 import android.graphics.Rect;
11 import android.graphics.drawable.BitmapDrawable;
12 import android.graphics.drawable.Drawable;
13 import android.util.AttributeSet;
14 import android.widget.ImageView;
15
16 17
18 /**
19  * Created by Yang on 2016-03-18.
20  * 自定义的圆角矩形ImageView，可以直接当组件在布局中使用。
21  */
22 public class XCRoundRectImageView extends ImageView {
23     private Paint paint;
24
25     public XCRoundRectImageView(Context context) {
26         this(context, null);
27     }
28
29     public XCRoundRectImageView(Context context, AttributeSet attrs) {
30         this(context, attrs, 0);
31     }
32
33     public XCRoundRectImageView(Context context, AttributeSet attrs, int defStyle) {
34         super(context, attrs, defStyle);
35         paint = new Paint();
36     }
37
38     /**
39      * 绘制圆角矩形图片
40      */
41     @Override
42     protected void onDraw(Canvas canvas) {
43         Drawable drawable = getDrawable();
44         if (null != drawable) {
45             Bitmap bitmap = null;
46             if (drawable instanceof BitmapDrawable) {
47                 bitmap = ((BitmapDrawable) drawable).getBitmap();
48             } else if (drawable instanceof AsyncDrawable) {
49                 bitmap = Bitmap.createBitmap(getWidth(),
50                         getHeight(),
51                         drawable.getOpacity() != PixelFormat.OPAQUE ? Bitmap.Config.ARGB_8888 : Bitmap.Config.RGB_565);
52                 Canvas canvas1 = new Canvas(bitmap);
53                 drawable.setBounds(0, 0, getWidth(), getHeight());
54                 drawable.draw(canvas1);
55             }
56             //10为设置的圆角矩形圆角角度大小，可修改
57             Bitmap b = getRoundBitmap(bitmap, 10);
58             final Rect rectSrc = new Rect(0, 0, b.getWidth(), b.getHeight());
59             final Rect rectDest = new Rect(0, 0, getWidth(), getHeight());
60             paint.reset();
61             canvas.drawBitmap(b, rectSrc, rectDest, paint);
62         } else {
63             super.onDraw(canvas);
64         }
65     }
66
67     /**
68      * 获取圆角矩形图片方法
69      * @param bitmap
70      * @return Bitmap
71      */
72     private Bitmap getRoundBitmap(Bitmap bitmap, int roundPx) {
73         Bitmap output = Bitmap.createBitmap(bitmap.getWidth(), bitmap.getHeight(), Config.ARGB_8888);
74         Canvas canvas = new Canvas(output);
75         final int color = 0xff424242;
76         final Rect rect = new Rect(0, 0, bitmap.getWidth(), bitmap.getHeight());
77         final RectF rectF = new RectF(rect);
78         paint.setAntiAlias(true);
79         canvas.drawARGB(0, 0, 0, 0);
80         paint.setColor(color);
81         int x = bitmap.getWidth();
82         canvas.drawRoundRect(rectF, roundPx, roundPx, paint);
83         paint.setXfermode(new PorterDuffXfermode(Mode.SRC_IN));
84         canvas.drawBitmap(bitmap, rect, rect, paint);
85         return output;
86     }
87 }

只需要在需要圆角矩形的地方引用自定义控件即可，代码如下

<<!--你的包名-->.view.XCRoundRectImageView
                    android:id="@+id/xCRoundRectImageView"
                    android:layout_width="wrap_content"
                    android:layout_height="wrap_content"/>