Android 重定义ImageView可显示出圆形或圆角形图片效果

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，然后进行裁剪圆形的bitmap，然后在onDraw（）进行绘制圆形图片输出。

核心代码：

/**
* 获取圆角位图的方法
* @param bitmap 需要转化成圆角的位图
* @param pixels 圆角的度数，数值越大，圆角越大
* @return 处理后的圆角位图
*/
private Bitmap getCircleBitmap(Bitmap bitmap, int pixels) {
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());
paint.setAntiAlias(true);
canvas.drawARGB(0, 0, 0, 0);
paint.setColor(color);
int x = bitmap.getWidth();
//这是圆drawCircle
//canvas.drawCircle(x / 2, x / 2, x / 2, paint);
//这是圆角drawRoundRect
canvas.drawRoundRect(new RectF(rect), pixels, pixels, paint);
paint.setXfermode(new PorterDuffXfermode(Mode.SRC_IN));
canvas.drawBitmap(bitmap, rect, rect, paint);
return output;

}

转载自：/article/1211904.html

例子如下：



自定义的圆形的ImageView类的实现代码如下：

package com.rainwii.entity;
//包名
import android.content.Context;
import android.graphics.Bitmap;
import android.graphics.Bitmap.Config;
import android.graphics.Canvas;
import android.graphics.Paint;
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;

/**
* * 自定义的圆形ImageView，可以直接当组件在布局中使用。
*
* @author caizhiming
* */
public class XCRoundImageView extends ImageView {
private Paint paint;

public XCRoundImageView(Context context) {
this(context, null);
}

public XCRoundImageView(Context context, AttributeSet attrs) {
this(context, attrs, 0);
}

public XCRoundImageView(Context context, AttributeSet attrs, int defStyle) {
super(context, attrs, defStyle);
paint = new Paint();

}

/**
* * 绘制圆形图片
*
* @author caizhiming
*/
@Override
protected void onDraw(Canvas canvas) {

Drawable drawable = getDrawable();
if (null != drawable) {
Bitmap bitmap = ((BitmapDrawable) drawable).getBitmap();
Bitmap b = getCircleBitmap(bitmap, 14);
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);
}
}

/**
* * 获取圆形图片方法
*
* @param bitmap
* @param pixels
* @return Bitmap
* @author caizhiming
*/
private Bitmap getCircleBitmap(Bitmap bitmap, int pixels) {
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());
paint.setAntiAlias(true);
canvas.drawARGB(0, 0, 0, 0);
paint.setColor(color);
int x = bitmap.getWidth();
canvas.drawCircle(x / 2, x / 2, x / 2, paint);
paint.setXfermode(new PorterDuffXfermode(Mode.SRC_IN));
canvas.drawBitmap(bitmap, rect, rect, paint);
return output;

}
}

完成这个自定义类后，就可以使用这个类了，就是把这个当组件在布局中使用即可，比如：

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent" >
<com.rainwii.entity.XCRoundImageView
android:id="@+id/roundImageView"
　　　　android:layout_centerInParent="true"
　　　 android:layout_width="200dp"
　　　　android:layout_height="200dp"
　　　　android:src="@drawable/roundimageview"
/>
</RelativeLayout>

补充学员资料：http://blog.csdn.net/akon_vm/article/details/7418210

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