GridView内存及时释放，不需要使用软引用

突然写上瘾了，就把这个得意之作发上来吧，这个内存释放可是花费了我将近一周呢，显示搞懂gridview机制，然后是进行优化，反正是搞死我了。
先说软引用吧，不得不说软引用是个非常好的解决OOM的方法，只要系统内存不够就会释放掉软引用中不需要的bitmap，但是经我测试这个也并不是及时释放的，我一屏显示20张图片的话，有时内存中会存在60多张图片，这个是我不能容忍的，我最多让它存在30张，多了如果我在此时处理一个需要很大内存的动作，系统会提高heapsize，这是会出现OOM的。
我的解决办法：人为及时释放内存，保证内存中图片不超过30张。
原理：gridview有两个参数，getFirstVisiblePosition和getLastVisiblePosition，这两个参数意思是当前显示的第一张图片的position和最后一张图片的position，有了这两个我们就可以有选择的释放内存了，此范围外的都是可以释放的。
我的代码：

[代码]java代码：

/**
*
* Copyright 2012 HISENSE. All rights reserved.
* DirListAdapter.java
*
*/
package com.hisense.hicloud.album.hiview;

import java.util.ArrayList;
import java.util.HashMap;
import java.util.Iterator;
import java.util.Map;
import java.util.Map.Entry;

import android.content.Context;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.util.Log;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.BaseAdapter;
import android.widget.GridView;
import android.widget.ImageView;

import com.hisense.hicloud.album.HiCloudAlbum;
import com.hisense.hicloud.album.HiCloudApplication;
import com.hisense.hicloud.album.R;
import com.hisense.hicloud.album.imagecache.AsyncImageLoader;
import com.hisense.hicloud.album.imagecache.HiImageView;
import com.hisense.hicloud.album.imagecache.LocationImageCache;
import com.hisense.hicloud.album.imagecache.AsyncImageLoader.BitmapCallback;
import com.hisense.hicloud.album.imagecache.LocationImageCache.OnLoadImageListener;
import com.hisense.hicloud.album.scanfiles.ImageListBean;
import com.hisense.hicloud.album.sys.SYSPath;

/**
* @author qiuxiaolong (qiuxiaolong1@hisense.com)
* @date 2012-2-13
*/
public class LocalImageAdapter2 extends BaseAdapter {

private Context context;

private static ArrayList<String> imagePathList;

private LayoutInflater inflater;

private ViewHolder holder = null;

private AsyncImageLoader imageLoader;
private String LocalThumbPath;//本地图片缩略图地址
private static String TAG = "LocalImageAdapter2";
/**存放bitmap与position*/
public static ArrayList<HashMap<String,Object>> bitmapArrayList = new ArrayList<HashMap<String,Object>>();
//获取LocalGridView对象
private GridView gridview;
/**记步，记录getView执行次数,六次一循环*/
private static int local_i = 0;
/**记录gridview中第一张和最后一张图片的position*/
private static int gridviewFirst = 0;
private static int gridviewLast = 0;
public LocalImageAdapter2(){}
public LocalImageAdapter2(Context context,ArrayList<String> callList,GridView gridview) {
this.context = context;
this.imagePathList = callList;
for (String url : imagePathList) {
Log.d("==========Image Url==========", url);
}

inflater = LayoutInflater.from(this.context);
imageLoader = new AsyncImageLoader(true, context);
this.gridview = gridview;
//judge that whether the bitmapArrayList  is null
CloudImageAdapter cloudimageadapter = new CloudImageAdapter();
if(cloudimageadapter.getbitmapArrayListSize() != 0){
//clean the bitmapArrayList
cloudimageadapter.cleanbitmapArrayList();
}
}

public void removeAdpterList(ArrayList<String> removeList)
{
System.out.println("=============删除元数据："+removeList.size());
System.out.println("=============前："+imagePathList.size());
imagePathList.removeAll(removeList);
System.out.println("=============后："+imagePathList.size());
}

public int getCount() {
return imagePathList.size();
}

public Object getItem(int position) {
return imagePathList.get(position);
}

public long getItemId(int position) {
return position;
}
/**return bitmapArrayList size*/
public int getbitmapArrayListSize(){
return bitmapArrayList.size();
}
/**clean bitmapArrayList all*/
public void cleanbitmapArrayList(){
for(int k = 0;k < bitmapArrayList.size();k++){
if(bitmapArrayList.get(k).get("bitmap") != null){
//get bitmap from hashmap
Bitmap bitmap1 = (Bitmap) bitmapArrayList.get(k).get("bitmap");
try{
if(!bitmap1.isRecycled()){
bitmap1.recycle();
Log.i(TAG,"clean bitmapArrayList success,print position:" + (Integer)bitmapArrayList.get(k).get("ID"));
//remove this element
bitmapArrayList.remove(k);
k--;
}
}catch(Exception e){
Log.e(TAG,"clean bitmapArrayList error");
e.printStackTrace();
}
}
}
}
/**clean bitmap that not in gridview*/
public void cleanGridView(){
//select bitmaps what can be recycled
for(int k = 0;k < bitmapArrayList.size();k++){
//keep these bitmaps which between first and last
if((Integer)bitmapArrayList.get(k).get("ID")>=(gridviewFirst-3) && (Integer)bitmapArrayList.get(k).get("ID") <= (gridviewLast + 3)){
//in the range,do nothing
Log.i(TAG,"in the range continue,print the k：" + k + ";and print the position：" + (Integer)bitmapArrayList.get(k).get("ID"));
continue;
}
//get the bitmap from hashmap
Bitmap bitmap1 = (Bitmap) bitmapArrayList.get(k).get("bitmap");
if(bitmap1 != null){
try{
Log.i(TAG,"start to recycle，print the position：" + (Integer)bitmapArrayList.get(k).get("ID") + ";print first position："
+ gridviewFirst + ";print last position：" + gridviewLast);
if(!bitmap1.isRecycled()){
Log.i(TAG,"can be recycled，the id of bitmap：" + bitmap1.toString());
//do the action
bitmap1.recycle();
Log.i(TAG,"success to recycle,print the position:" + (Integer)bitmapArrayList.get(k).get("ID"));
//remove this element
bitmapArrayList.remove(k);
k--;
}
}catch(RuntimeException e){
Log.e(TAG,"the bitmap can't be recycled,print the position:" + (Integer)bitmapArrayList.get(k).get("ID"));
e.printStackTrace();
}
}
}
//do gc
System.gc();
}
public View getView( final int position, View convertView, final ViewGroup parent) {
Log.e(TAG,"print the position：" + position + ";print bitmapArrayList size:" + bitmapArrayList.size());
//get current first position and last position
gridviewFirst = gridview.getFirstVisiblePosition();
gridviewLast = gridview.getLastVisiblePosition();
//do the clean action for every six
if(local_i == 6){
local_i = 0;
//do the clean action
//cleanGridView();
}

if (convertView == null) {
holder = new ViewHolder();
if(HiCloudAlbum.album_orientation == HiCloudAlbum.ALBUM_ORIENTATION_LANDSCAPE)
convertView = inflater.inflate(R.layout.image_local_gridview_item_land, null);
else
convertView = inflater.inflate(R.layout.image_local_gridview_item, null);
holder.img = (HiImageView) convertView
.findViewById(R.id.image_thumbnail);
holder.mask = (ImageView) convertView.findViewById(R.id.masklayer);
holder.uploaded = (ImageView)convertView.findViewById(R.id.uploadedlayer);
convertView.setTag(holder);
} else {
holder = (ViewHolder) convertView.getTag();
}
holder.img.setTag(imagePathList.get(position));

if (LocalGridView.getAlreadUploadList().contains(imagePathList.get(position)))
{
holder.uploaded.setVisibility(View.VISIBLE);
holder.mask.setVisibility(View.GONE);
}else
{
if (LocalGridView.getSelectedItemsList().contains(imagePathList.get(position)))
{
holder.mask.setVisibility(View.VISIBLE);
}else
{
holder.mask.setVisibility(View.GONE);
}
holder.uploaded.setVisibility(View.GONE);
}
//计算本地缩略图存放地址
LocalThumbPath = SYSPath.LocalThumCachePATH + "/" + imagePathList.get(position).substring(imagePathList.get(position).lastIndexOf("/")+1) + "_Thum.jpg";
Bitmap bitmap = null;
boolean flag = false;
Log.d(TAG,"输出LocalThumbPath" + LocalThumbPath);
//if the bitmap is in the bitmapArrayList,then get it from bitmapArrayList
/*for(int i = 0;i<bitmapArrayList.size();i++){
//Comparison the position
if(bitmapArrayList.get(i).get("ID").toString().equals(String.valueOf(position))){
Log.i(TAG,"have the same position,print this position:" + position);
//get bitmap from hashmap
bitmap = (Bitmap)bitmapArrayList.get(i).get("bitmap");
holder.img.setImageBitmap(null);
holder.img.setImageBitmap(bitmap);
//set to be true,then skip getting bitmap from local
flag = true;
break;
}
}*/
if(flag == false){
//mark add
local_i++;
Log.i(TAG,"print the local_i" + local_i);
//get bitmap from local
//bitmap = AsyncImageLoader.getCacheBitmap(LocalThumbPath,position);
bitmap = AsyncImageLoader.getCacheBitmap(imagePathList.get(position));
if (bitmap != null)
{
Log.i(TAG,"success to get the bitmap at section one");
holder.img.setImageBitmap(null);
holder.img.setImageBitmap(bitmap);
//bitmapArrayList add
bitmapArrayListAdd(position,bitmap,"one");
}else{
Log.i(TAG,"can't find bitmap from local,bitmap is null,now start to create thumb picture and get bitmap from it");
//bitmap = BitmapFactory.decodeResource(context.getResources(), R.drawable.fipper_loading);
holder.img.setImageBitmap(null);
imageLoader.loadLocalBitmap(imagePathList.get(position),LocalThumbPath,new BitmapCallback() {
//imageLoader.loadLocalBitmap(imagePathList.get(position),LocalThumbPath, position,new BitmapCallback() {
public void imageLoaded(Bitmap imageBitmap, String imageUrl)
{
// TODO Auto-generated method stub
HiImageView iv = (HiImageView) parent.findViewWithTag(imageUrl);
if (iv != null && imageBitmap != null)
{
Log.i(TAG,"success to get the bitmap at section two");
iv.setImageBitmap(null);
iv.setImageBitmap(imageBitmap);
//bitmapArrayList add
bitmapArrayListAdd(position,imageBitmap,"two");
}
}
});
}
}
return convertView;

}

/**bitmapArrayList add*/
private void bitmapArrayListAdd(int position,Bitmap bitmap,String section){
Log.d(TAG,"at section "+section+" print the id of bitmap:" + bitmap.toString() + ";print the position" + position);
//create map to put information
HashMap<String,Object> map = new HashMap<String,Object>();
map.put("ID", position);
//map.put("bitmap", bitmap);
//add bitmapArrayList
bitmapArrayList.add(map);
Log.d(TAG,"success and over at section " + section);
}
public class ViewHolder {
public HiImageView img;
public ImageView mask;
public ImageView uploaded;
}
}

其中cleanbitmapArrayList方法是不需要整个gridview的时候调用的，它会释放所有的bitmap资源，cleanGridView方法除了自身调用外，比如处理大内存消耗动作而且还要保留此gridview时也可以调用，可清除额外内存，其中有点要说明，Integer)bitmapArrayList.get(k).get("ID")>=(gridviewFirst-3)，之所以减三加三，是我自己做的一个缓存区，可以调大，但是如果不减任何数肯定会报错，如果有try to use a recyclee
bitmap 那就是这里出问题了，数字一般最好为你一行显示的个数。

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这都是12年写的文章了，现在已经有更好的代替方法，直接使用LruCache和DiskLruCache做缓存就行，Android既然已经提供了这么好用的缓存我们就不用再多此一举啦。