Android开发之自定义圆角矩形图片ImageView

android中的ImageView只能显示矩形的图片，这样一来不能满足我们其他的需求，比如要显示圆角矩形的图片，这个时候，我们就需要自定义ImageView了，其原理就是首先获取到图片的Bitmap，然后进行裁剪对应的圆角矩形的bitmap，然后在onDraw（）进行绘制圆角矩形图片输出。

自定义的圆形的ImageView类的实现代码如下：

package com.xc.xcskin.view;import android.content.Context;import android.graphics.Bitmap;import android.graphics.Bitmap.Config;import android.graphics.Canvas;import android.graphics.Paint;import android.graphics.RectF;import android.graphics.PorterDuff.Mode;import android.graphics.PorterDuffXfermode;import android.graphics.Rect;import android.graphics.drawable.BitmapDrawable;import android.graphics.drawable.Drawable;import android.util.AttributeSet;import android.widget.ImageView;/*** 自定义的圆角矩形ImageView，可以直接当组件在布局中使用。* @author caizhiming**/public class XCRoundRectImageView extends ImageView{private Paint paint;public XCRoundRectImageView(Context context) { this(context,null); } public XCRoundRectImageView(Context context, AttributeSet attrs) { this(context, attrs,0); } public XCRoundRectImageView(Context context, AttributeSet attrs, int defStyle) { super(context, attrs, defStyle); paint = new Paint();} /*** 绘制圆角矩形图片* @author caizhiming*/@Override protected void onDraw(Canvas canvas) { Drawable drawable = getDrawable(); if (null != drawable) { Bitmap bitmap = ((BitmapDrawable) drawable).getBitmap(); Bitmap b = getRoundBitmap(bitmap, 20); final Rect rectSrc = new Rect(0, 0, b.getWidth(), b.getHeight()); final Rect rectDest = new Rect(0,0,getWidth(),getHeight());paint.reset(); canvas.drawBitmap(b, rectSrc, rectDest, paint); } else { super.onDraw(canvas); } } /*** 获取圆角矩形图片方法* @param bitmap* @param roundPx,圆角的弧度* @return Bitmap* @author caizhiming*/private Bitmap getRoundBitmap(Bitmap bitmap, int roundPx) { Bitmap output = Bitmap.createBitmap(bitmap.getWidth(), bitmap.getHeight(), Config.ARGB_8888); Canvas canvas = new Canvas(output); final int color = 0xff424242;final Rect rect = new Rect(0, 0, bitmap.getWidth(), bitmap.getHeight()); final RectF rectF = new RectF(rect);paint.setAntiAlias(true); canvas.drawARGB(0, 0, 0, 0); paint.setColor(color); int x = bitmap.getWidth(); canvas.drawRoundRect(rectF, roundPx, roundPx, paint);paint.setXfermode(new PorterDuffXfermode(Mode.SRC_IN)); canvas.drawBitmap(bitmap, rect, rect, paint); return output; } }

注：getRoundBitmap(Bitmap bitmap, int roundPx)中第二个参数为图片的圆角弧度

xml布局文件中直接引用即可：

<RelativeLayout xmlns:android="/apk/res/android"xmlns:tools="/tools"android:layout_width="match_parent"android:layout_height="match_parent" ><com.xc.xcskin.view.XCRoundRectImageViewandroid:id="@+id/roundRectImageView" android:layout_centerInParent="true" android:layout_width="200dp" android:layout_height="80dp"android:src="@drawable/roundimageview"/></RelativeLayout>

最后：效果图如下：