Android开发：ImageView阴影和图层效果

import android.app.Activity;  

import android.content.Context;  

import android.graphics.Bitmap;  

import android.graphics.BitmapFactory;  

import android.graphics.Canvas;  

import android.graphics.Color;  

import android.graphics.Paint;  

import android.graphics.PorterDuff;  

import android.graphics.PorterDuff.Mode;  

import android.graphics.PorterDuffXfermode;  

import android.graphics.Rect;  

import android.graphics.RectF;  

import android.graphics.drawable.Drawable;  

import android.os.Bundle;  

import android.view.View;  

  

public class MyCanvasActivity extends Activity {  

    /** Called when the activity is first created. */  

    @Override  

    public void onCreate(Bundle savedInstanceState) {  

        super.onCreate(savedInstanceState);  

        setContentView(new ImageEffect(this));  

    }  

      

  class ImageEffect extends View{  

      Paint paint;  

     public ImageEffect(Context context){  

         super(context);  

         paint= new Paint(); //初始化画笔，为后面阴影效果使用。   

         paint.setAntiAlias(true);//去除锯齿。   

         paint.setShadowLayer(5f, 5.0f, 5.0f, Color.BLACK); //设置阴影层，这是关键。   

         paint.setXfermode(new PorterDuffXfermode(Mode.SRC_IN));  

           

     }  

     public void onDraw(Canvas canvas){  

         super.onDraw(canvas);  

         int posX  = 20;  

         int posY = 50;  

         int PicWidth,PicHeight;  

           

        Drawable drawable = getResources().getDrawable(R.drawable.pic);  

        Drawable dbe    = getResources().getDrawable(R.drawable.pic).mutate();//如果不调用mutate方法，则原图也会被改变，因为调用的资源是同一个，所有对象是共享状态的。   

        Drawable drawTest = getResources().getDrawable(R.drawable.pic);  

        Bitmap bmp = BitmapFactory.decodeResource(getResources(), R.drawable.pic);  

        PicWidth = drawable.getIntrinsicWidth();  

        PicHeight = drawable.getIntrinsicHeight();  

          

        drawTest.setBounds(posX, (2 * posY) + PicHeight, posX + PicWidth, (2 * posY) + 2 * PicHeight );  

        drawable.setBounds(posX,posY,posX+PicWidth,posY+PicHeight);  

        dbe.setBounds(0, 0, PicWidth, PicHeight);  

          

        canvas.drawColor(Color.WHITE);//设置画布颜色   

        canvas.save(Canvas.MATRIX_SAVE_FLAG);  

        dbe.setColorFilter(0x7f000000,PorterDuff.Mode.SRC_IN);  

        canvas.translate(posX + (int)(0.9 * PicWidth/2), posY + PicHeight/2);//图像平移为了刚好在原图后形成影子效果。   

        canvas.skew(-0.9F, 0.0F);//图像倾斜效果。   

        canvas.scale(1.0f, 0.5f);//图像（其实是画布）缩放，Y方向缩小为1/2。   

        dbe.draw(canvas);//此处为画原图像影子效果图，比原图先画，则会在下层。   

        drawable.clearColorFilter();  

        canvas.restore();  

          

       canvas.save(Canvas.MATRIX_SAVE_FLAG);  

        drawable.draw(canvas);//此处为画原图像，由于canvas有层次效果，因此会盖在影子之上。   

        canvas.restore();  

          

        //默认无效果原图   

        canvas.save(Canvas.MATRIX_SAVE_FLAG);  

        drawTest.draw(canvas);  

        canvas.restore();  

          

        //图片阴影效果   

        Rect rect = new Rect(2*posX + PicWidth + 3, 2*posY + PicHeight + 3, 2*posX + 2*PicWidth - 2, 2*posY + 2*PicHeight - 2);  

        //由于图片的实际尺寸比显示出来的图像要大一些，因此需要适当更改下大小，以达到较好的效果   

          

        RectF rectF = new RectF(rect);  

        canvas.drawRoundRect(rectF, 10f, 10f, paint);//在原有矩形基础上，画成圆角矩形，同时带有阴影层。   

        canvas.drawBitmap(bmp, 2*posX + PicWidth, 2*posY + PicHeight, null);//画上原图。   

        canvas.restore();  

        }  

  }  

}