Android中的GridView图片异步加载

packageandroid.album.activity;
importjava.io.File;
importjava.util.ArrayList;
importandroid.album.R;
importandroid.album.core.AsyncLoadImage;
importandroid.album.util.Listeners;
importandroid.album.util.MenuID;
importandroid.album.util.Public;
importandroid.album.util.UnitConverter;
importandroid.album.view.BorderImageView;
importandroid.app.Activity;
importandroid.app.ProgressDialog;
importandroid.content.Context;
importandroid.content.Intent;
importandroid.graphics.Color;
importandroid.os.Bundle;
importandroid.os.Handler;
importandroid.os.Message;
importandroid.util.DisplayMetrics;
importandroid.view.ContextMenu;
importandroid.view.ContextMenu.ContextMenuInfo;
importandroid.view.Menu;
importandroid.view.MenuItem;
importandroid.view.View;
importandroid.view.View.OnClickListener;
importandroid.view.ViewGroup;
importandroid.widget.AdapterView;
importandroid.widget.AdapterView.AdapterContextMenuInfo;
importandroid.widget.AdapterView.OnItemClickListener;
importandroid.widget.BaseAdapter;
importandroid.widget.GridView;
importandroid.widget.ImageButton;
importandroid.widget.ImageView;
importandroid.widget.TextView;
/**
*****************************************************************
*文件名称:ListFolderImages.java
*创建时间:2011-7-915:00
*文件描述:显示指定文件夹下的图片列表
*编写人员:Bryant
*****************************************************************
*/
publicclassListFolderImagesActivityextendsActivityimplements
OnItemClickListener{
privateImageButtonbtnBack;
privateTextViewtvFolderName;
/**
*文件夹下的图片列表
*/
privateArrayList<String>imageList=newArrayList<String>();
privateStringfolderPath;
privateGridViewgridview;
privateImageAdapteradapter;
privateintscreenWidth;
privateintimageViewWidth;
privateintimageViewHeight;
@Override
publicvoidonCreate(BundlesavedInstanceState){
super.onCreate(savedInstanceState);
setContentView(R.layout.list_folder_images);
DisplayMetricsdm=newDisplayMetrics();
getWindowManager().getDefaultDisplay().getMetrics(dm);
screenWidth=dm.widthPixels;
imageViewWidth=(screenWidth-UnitConverter.dip2px(this,20))/3;
imageViewHeight=imageViewWidth;
Intentintent=getIntent();
folderPath=intent.getStringExtra("folderPath");
tvFolderName=(TextView)findViewById(R.id.tvFolderName);
tvFolderName.setText(intent.getStringExtra("folderName"));
//返回
btnBack=(ImageButton)findViewById(R.id.btnBack);
btnBack.setOnTouchListener(Listeners.iBtnListener);
btnBack.setOnClickListener(newOnClickListener(){
@Override
publicvoidonClick(Viewv){
ListFolderImagesActivity.this.finish();
}
});
startScanImageFolders();
gridview=(GridView)findViewById(R.id.grid_view);
adapter=newImageAdapter(this);
gridview.setAdapter(adapter);
gridview.setOnItemClickListener(this);
registerForContextMenu(gridview);
}
publicvoidstartScanImageFolders(){
finalProgressDialogprogressDialog=ProgressDialog
.show(ListFolderImagesActivity.this,ListFolderImagesActivity.this.getString(R.string.waiting),
ListFolderImagesActivity.this.getString(R.string.folder_scanning),false);
newThread(){
publicvoidrun(){
imageList=getImagesFromFolder(folderPath);
Messagemessage=newMessage();
message.what=1;
handler.sendMessage(message);
progressDialog.dismiss();
}
}.start();
}
/**
*获取指定文件夹中的图片
*
*@return
*/
publicstaticArrayList<String>getImagesFromFolder(StringfolderPath){
ArrayList<String>imageList=newArrayList<String>();
Filefile=newFile(folderPath);
File[]files=file.listFiles(newImageFileFilter());
for(Filef:files){
imageList.add(f.getPath());
}
returnimageList;
}
publicclassImageAdapterextendsBaseAdapter{
privateContextmContext;
publicImageAdapter(Contextc){
mContext=c;
}
publicintgetCount(){
returnimageList.size();
}
publicObjectgetItem(intposition){
returnimageList.get(position);
}
publiclonggetItemId(intposition){
returnposition;
}
publicViewgetView(intposition,ViewconvertView,ViewGroupparent){
if(convertView==null){
finalImageViewimageView;
imageView=newBorderImageView(mContext,Color.GRAY);
imageView.setLayoutParams(newGridView.LayoutParams(imageViewWidth,imageViewHeight));
imageView.setScaleType(ImageView.ScaleType.CENTER_CROP);
convertView=imageView;
imageLoader.loadDrawable(imageList.get(position),newImageCallback(){
publicvoidimageLoaded(DrawableimageDrawable,StringimageUrl){
imageView.setImageDrawable(imageDrawable);
}
});
}
returnconvertView;
}
}
*刷新UI
*/
finalHandlerhandler=newHandler(){
publicvoidhandleMessage(Messagemsg){
switch(msg.what){
case1:
adapter.notifyDataSetChanged();
break;
}
super.handleMessage(msg);
}
};
}
publicclassAsyncImageLoader{
privateMap<String,SoftReference<Drawable>>imageCache=newHashMap<String,SoftReference<Drawable>>();
publicDrawableloadDrawable(finalStringimageUrl,finalImageCallbackcallback){
if(imageCache.containsKey(imageUrl)){
SoftReference<Drawable>softReference=imageCache.get(imageUrl);
if(softReference.get()!=null){
returnsoftReference.get();
}
}
finalHandlerhandler=newHandler(){
@Override
publicvoidhandleMessage(Messagemsg){
callback.imageLoaded((Drawable)msg.obj,imageUrl);
}
};
newThread(){
publicvoidrun(){
Drawabledrawable=loadImageFromUrl(imageUrl);
imageCache.put(imageUrl,newSoftReference<Drawable>(drawable));
handler.sendMessage(handler.obtainMessage(0,drawable));
};
}.start();
returnnull;
}
protectedDrawableloadImageFromUrl(StringimageUrl){
try{
returnDrawable.createFromPath(imageUrl);
}catch(Exceptione){
thrownewRuntimeException(e);
}
}
publicinterfaceImageCallback{
publicvoidimageLoaded(DrawableimageDrawable,StringimageUrl);
}
}

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