Android開發之自定義圓角矩形圖片ImageView的實現

android中的ImageView只能顯示矩形的圖片，這樣一來不能知足咱們其餘的需求，好比要顯示圓角矩形的圖片，這個時候，咱們就須要自定義ImageView了，其原理就是首先獲取到圖片的Bitmap，而後進行裁剪對應的圓角矩形的bitmap，而後在onDraw（）進行繪製圓角矩形圖片輸出。

效果圖以下：

自定義的圓形的ImageView類的實現代碼以下：

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;

/**
 * 自定義的圓角矩形ImageView，能夠直接當組件在佈局中使用。
 * @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();
    }  
  
    /**
     * 繪製圓角矩形圖片
     * @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);  
        }  
    }  
  
    /**
     * 獲取圓角矩形圖片方法
     * @param bitmap
     * @param roundPx,通常設置成14
     * @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;  
        
        
    }  
}

完成這個自定義類後，就能夠使用這個類了，就是把這個當組件在佈局中使用便可，好比：

<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.xc.xcskin.view.XCRoundRectImageView
        android:id="@+id/roundRectImageView"  
        android:layout_centerInParent="true" 
        android:layout_width="200dp"   
        android:layout_height="200dp"
        android:src="@drawable/roundimageview"
          />
    
    
        
    

</RelativeLayout>