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：


代码如下:

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


代码如下:

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; 
    }

}