图片添加背景

android程序中图片的阴影效果

动态的生成图片的阴影，阴影可以随图片的大小改变

 

package com.example.test;

import android.os.Bundle;
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.Mode;
import android.graphics.PorterDuffXfermode;
import android.graphics.PorterDuff;
import android.graphics.Rect;
import android.graphics.RectF;
import android.graphics.drawable.Drawable;
import android.view.Menu;
import android.view.View;

public class MainActivity extends Activity {

    @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));
        }
        @Override
        public void onDraw(Canvas canvas){
            super.onDraw(canvas);
            int posX = 20;
            int posY = 50;
            int PicWidth,PicHegiht;
           
            Drawable drawable = getResources().getDrawable(R.drawable.aa);
            Bitmap bmp = BitmapFactory.decodeResource(getResources(), R.drawable.aa);
           
            PicWidth = drawable.getIntrinsicWidth();
            PicHegiht = drawable.getIntrinsicHeight();
            drawable.setBounds(posX,posY,posX+PicWidth,posY+PicHegiht);
         
            canvas.drawColor(Color.WHITE);//设置画布颜色
           
            //图片阴影效果
            canvas.save(Canvas.MATRIX_SAVE_FLAG);
            Rect rect = new Rect(3, 3, PicWidth - 2,  PicHegiht - 2);//此为理论上的阴影图坐标
           
            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, 0, 0, null);//画上原图。
            canvas.restore();
        }
    }

}