android ImageView 的几点经验总结

最近作图片的显示，遇到了些问题，简单总结
1）可以用imageswicher和imageview结合在来做，这样会用到setfectory（），华而不实
最要命的是如果图片的大小超过屏幕，实现比较困难，目前是没有找到方法

2）最简单的方法是用imageview，图片直接fit_center,android会根据图片的大小自动调节
保持图片的比例。如果图片分辨率超过屏幕，android也会自动的调整到屏幕能放下整张的图片
在放大图片的时候，可以用imageview的setframe（） 和setscale（）方法，可以把图片放大
到超过屏幕，原理就是imageview放大，图片跟着放大。同时也是可以添加各种animation.
大致如下：

animation animation = animationutils.loadanimation(main.this, r.anim.my_scale_action);
imageview.setlayoutparams(new gallery.layoutparams(206, 206));
imageview.startanimation(animation);

写一个自己的myimageview类，代码如下，可以直接用

package com.practice.imageviewpic;

import android.app.activity; 
import android.content.context; 
import android.graphics.*; 
import android.graphics.drawable.bitmapdrawable; 
import android.os.bundle; 
import android.util.attributeset;
import android.util.log;
import android.view.motionevent; 
import android.view.view;
import android.view.viewgroup.layoutparams;
import android.widget.button;
import android.widget.imageview; 
import android.widget.imageview.scaletype; 
import android.widget.linearlayout;
    //创建一个自己的imageview类 
    class myimageview extends imageview { 
        private float scale = 0.1f; 

      //两点触屏后之间的长度 
        private float beforelenght; 
        private float afterlenght; 

        //单点移动的前后坐标值 
        private float afterx,aftery; 
        private float beforex,beforey; 

        public myimageview(context context) { 
            super(context); 
        } 
        public myimageview(context context, attributeset attrs) { 
        this(context, attrs, 0);

        }
        public myimageview(context context, attributeset attrs, int defstyle) {
            super(context, attrs, defstyle);
        }
        //用来设置imageview的位置 
        private void setlocation(int x,int y) { 
            this.setframe(this.getleft()+x, this.gettop()+y, this.getright()+x, this.getbottom()+y); 
        } 

         
        /*
         * 用来放大缩小imageview
         * 因为图片是填充imageview的，所以也就有放大缩小图片的效果
         * flag为0是放大图片，为1是小于图片
         */ 
        public void setscale(float temp,int flag) { 

            if(flag==0) { 
                this.setframe(this.getleft()-(int)(temp*this.getwidth()),  
                              this.gettop()-(int)(temp*this.getheight()),  
                              this.getright()+(int)(temp*this.getwidth()),  
                              this.getbottom()+(int)(temp*this.getheight()));    
            }else { 
                this.setframe(this.getleft()+(int)(temp*this.getwidth()),  
                              this.gettop()+(int)(temp*this.getheight()),  
                              this.getright()-(int)(temp*this.getwidth()),  
                              this.getbottom()-(int)(temp*this.getheight())); 
            } 
        } 

        //绘制边框       
         @override 
          protected void ondraw(canvas canvas) { 
              super.ondraw(canvas);     
              rect rec=canvas.getclipbounds(); 
              rec.left++;
              rec.top++;
              rec.bottom--; 
              rec.right--; 
              paint paint=new paint(); 
              paint.setcolor(color.red); 
              paint.setstyle(paint.style.stroke); 
              canvas.drawrect(rec, paint); 
          } 

          
        /* 让图片跟随手指触屏的位置移动
         * beforex、y是用来保存前一位置的坐标
         * afterx、y是用来保存当前位置的坐标
         * 它们的差值就是imageview各坐标的增加或减少值
         */ 
        public void movewithfinger(motionevent event) { 

            switch(event.getaction()) { 

            case motionevent.action_down: 
            //log.d(tag, "down ..");
                beforex = event.getx(); 
                beforey = event.gety(); 
                break; 
            case motionevent.action_move: 

            //log.d(tag, "move ..");
                afterx = event.getx(); 
                aftery = event.gety(); 

                this.setlocation((int)(afterx-beforex),(int)(aftery-beforey)); 

                beforex = afterx; 
                beforey = aftery; 
                break; 

            case motionevent.action_up: 
            //log.d(tag, "up ..");
                break; 
            } 
        } 

        /*
         * 通过多点触屏放大或缩小图像
         * beforelenght用来保存前一时间两点之间的距离
         * afterlenght用来保存当前时间两点之间的距离
         */ 
        public void scalewithfinger(motionevent event) { 
            float movex = event.getx(1) - event.getx(0); 
            float movey = event.gety(1) - event.gety(0); 

            switch(event.getaction()) { 
            case motionevent.action_down: 
                beforelenght = (float) math.sqrt( (movex*movex) + (movey*movey) ); 
                break; 
            case motionevent.action_move: 
                //得到两个点之间的长度 
                afterlenght = (float) math.sqrt( (movex*movex) + (movey*movey) ); 

                float gaplenght = afterlenght - beforelenght; 

                if(gaplenght == 0) { 
                    break; 
                } 

                //如果当前时间两点距离大于前一时间两点距离，则传0，否则传1 
                if(gaplenght>0) { 
                    this.setscale(scale,0); 
                }else { 
                    this.setscale(scale,1); 
                } 

                beforelenght = afterlenght; 
                break; 
            } 
        } 

   //这里来监听屏幕触控时间 
   @override 
    public boolean ontouchevent(motionevent event) { 

       /*
        * 判定用户是否触摸到了图片
        * 如果是单点触摸则调用控制图片移动的方法
        * 如果是2点触控则调用控制图片大小的方法
        */ 
        if(event.gety() > this.gettop() && event.gety() < this.getbottom() 
                && event.getx() > this.getleft() && event.getx() < this.getright()) { 
            if(event.getpointercount() == 2) { 
            this.scalewithfinger(event); 
            }else if(event.getpointercount() == 1) { 
            this.movewithfinger(event); 
            }            
        } 
        return true; 
    }        

}