ListView异步加载图片实现思路异步加载图片实现思路(优化篇优化篇)
在APP应用中,listview的异步加载图片方式能够带来很好的用户体验,同时也是考量程序性能的一个重要指标。关于listview
的异步加载,网上其实很多示例了,中心思想都差不多,不过很多版本或是有bug,或是有性能问题有待优化。有鉴于此,本
人在网上找了个相对理想的版本并在此基础上进行改造,下面就让在下阐述其原理以探索个中奥秘,与诸君共赏…
贴张效果图先:
异步加载图片基本思想异步加载图片基本思想:
1.先从内存缓存中获取图片显示(内存缓冲)
2.获取不到的话从SD卡里获取(SD卡缓冲)
3.都获取不到的话从网络下载图片并保存到SD卡同时加入内存并显示(视情况看是否要显示)
OK,先上adapter的代码:
代码如下:
public class LoaderAdapter extends BaseAdapter{
private static final String TAG = “LoaderAdapter”;
private boolean mBusy = false;
public void setFlagBusy(boolean busy) {
this.mBusy = busy;
}
private ImageLoader mImageLoader;
private int mCount;
private Context mContext;
private String[] urlArrays;
public LoaderAdapter(int count, Context context, String []url) {
this.mCount = count;
this.mContext = context;
urlArrays = url;
mImageLoader = new ImageLoader(context);
}
public ImageLoader getImageLoader(){
return mImageLoader;
}
@Override
public int getCount() {
return mCount;
}
@Override
public Object getItem(int position) {
return position;
}
@Override
public long getItemId(int position) {
return position;
}
@Override
public View getView(int position, View convertView, ViewGroup parent) {
ViewHolder viewHolder = null;
if (convertView == null) {
convertView = LayoutInflater.from(mContext).inflate(
R.layout.list_item, null);
viewHolder = new ViewHolder();
viewHolder.mTextView = (TextView) convertView
.findViewById(R.id.tv_tips);
viewHolder.mImageView = (ImageView) convertView
.findViewById(R.id.iv_image);
convertView.setTag(viewHolder);
} else {
viewHolder = (ViewHolder) convertView.getTag();
}
String url = “”;
url = urlArrays[position % urlArrays.length];
viewHolder.mImageView.setImageResource(R.drawable.ic_launcher);
if (!mBusy) {
mImageLoader.DisplayImage(url, viewHolder.mImageView, false);
viewHolder.mTextView.setText(“–” + position
+ “–IDLE ||TOUCH_SCROLL”);
} else {
mImageLoader.DisplayImage(url, viewHolder.mImageView, true);
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