Android开发：ImageView阴影和图层效果

Android开发：ImageView阴影和图层效果：

1. import Android.app.Activity;  
2. import Android.content.Context;  
3. import Android.graphics.Bitmap;  
4. import Android.graphics.BitmapFactory;  
5. import Android.graphics.Canvas;  
6. import Android.graphics.Color;  
7. import Android.graphics.Paint;  
8. import Android.graphics.PorterDuff;  
9. import Android.graphics.PorterDuff.Mode;  
10. import Android.graphics.PorterDuffXfermode;  
11. import Android.graphics.Rect;  
12. import Android.graphics.RectF;  
13. import Android.graphics.drawable.Drawable;  
14. import Android.os.Bundle;  
15. import Android.view.View;  
16.   
17. public class MyCanvasActivity extends Activity {  
18.     /** Called when the activity is first created. */  
19.     @Override  
20.     public void onCreate(Bundle savedInstanceState) {  
21.         super.onCreate(savedInstanceState);  
22.         setContentView(new ImageEffect(this));  
23.     }  
24.       
25.   class ImageEffect extends View{  
26.       Paint paint;  
27.      public ImageEffect(Context context){  
28.          super(context);  
29.          paint= new Paint(); //初始化画笔，为后面阴影效果使用。   
30.          paint.setAntiAlias(true);//去除锯齿。   
31.          paint.setShadowLayer(5f, 5.0f, 5.0f, Color.BLACK); //设置阴影层，这是关键。   
32.          paint.setXfermode(new PorterDuffXfermode(Mode.SRC_IN));  
33.            
34.      }  
35.      public void onDraw(Canvas canvas){  
36.          super.onDraw(canvas);  
37.          int posX  = 20;  
38.          int posY = 50;  
39.          int PicWidth,PicHeight;  
40.            
41.         Drawable drawable = getResources().getDrawable(R.drawable.pic);  
42.         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。   
43.         Drawable drawTest = getResources().getDrawable(R.drawable.pic);  
44.         Bitmap bmp = BitmapFactory.decodeResource(getResources(), R.drawable.pic);  
45.         PicWidth = drawable.getIntrinsicWidth();  
46.         PicHeight = drawable.getIntrinsicHeight();  
47.           
48.         drawTest.setBounds(posX, (2 * posY) + PicHeight, posX + PicWidth, (2 * posY) + 2 * PicHeight );  
49.         drawable.setBounds(posX,posY,posX+PicWidth,posY+PicHeight);  
50.         dbe.setBounds(0, 0, PicWidth, PicHeight);  
51.           
52.         canvas.drawColor(Color.WHITE);//设置画布颜色   
53.         canvas.save(Canvas.MATRIX_SAVE_FLAG);  
54.         dbe.setColorFilter(0x7f000000,PorterDuff.Mode.SRC_IN);  
55.         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。   
56.         canvas.skew(-0.9F, 0.0F);//图像倾斜效果。   
57.         canvas.scale(1.0f, 0.5f);//图像（其实是画布）缩放，Y方向缩小为1/2。   
58.         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。   
59.         drawable.clearColorFilter();  
60.         canvas.restore();  
61.           
62.        canvas.save(Canvas.MATRIX_SAVE_FLAG);  
63.         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。   
64.         canvas.restore();  
65.           
66.         //默认无效果原图   
67.         canvas.save(Canvas.MATRIX_SAVE_FLAG);  
68.         drawTest.draw(canvas);  
69.         canvas.restore();  
70.           
71.         //图片阴影效果   
72.         Rect rect = new Rect(2*posX + PicWidth + 3, 2*posY + PicHeight + 3, 2*posX + 2*PicWidth - 2, 2*posY + 2*PicHeight - 2);  
73.         //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   
74.           
75.         RectF rectF = new RectF(rect);  
76.         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。   
77.         canvas.drawBitmap(bmp, 2*posX + PicWidth, 2*posY + PicHeight, null);//画上原图。   
78.         canvas.restore();  
79.         }  
80.   }  
81. }