Android开发中我们会经常遇到图片过多或操作不当造成OOM异常，有时虽然是解决了这个问题但却会影响程序的运行效率，例如：当用户在快速滑动滚动条的过程中，我们程序在仍在艰难的加载服务器端的图片，这样给用户造成了极不好的体验。其实网络上关于图片的异步加载和缓存的讲解很多，但是其实，写一个这方面的程序还是比较麻烦的，要考虑多线程，缓存，内存溢出等很多方面，针对这一光大开发者都会遇到的问题，一些牛人们已经帮我们解决了这一问题，今天我为大家介绍一款很流行的开源类库，可以很很好的解决大家的烦恼！
public class MyApplication extends Application{
@Override
public void onCreate() {
super.onCreate();
initImageLoader(getApplicationContext());
}
/**初始化图片加载类配置信息**/
public static void initImageLoader(Context context) {
// This configuration tuning is custom. You can tune every option, you may tune some of them,
// or you can create default configuration by
// ImageLoaderConfiguration.createDefault(this);
// method.
ImageLoaderConfiguration config = new ImageLoaderConfiguration.Builder(context)
.threadPriority(Thread.NORM_PRIORITY - 2)//加载图片的线程数
.denyCacheImageMultipleSizesInMemory() //解码图像的大尺寸将在内存中缓存先前解码图像的小尺寸。
.discCacheFileNameGenerator(new Md5FileNameGenerator())//设置磁盘缓存文件名称
.tasksProcessingOrder(QueueProcessingType.LIFO)//设置加载显示图片队列进程
.writeDebugLogs() // Remove for release app
.build();
// Initialize ImageLoader with configuration.
ImageLoader.getInstance().init(config);
}
}
别忘了在AndroidManifest.xml中
android:name=".MyApplication"
/**
* listView中使用ImageLoader
* @author ZHF
*
*/
public class ImageListActivity extends AbsListViewBaseActivity {
DisplayImageOptions options; //配置图片加载及显示选项
String[] imageUrls;
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.ac_image_list);
//获取url数组
Bundle bundle = getIntent().getExtras();
imageUrls = bundle.getStringArray(Extra.IMAGES);
//配置图片加载及显示选项（还有一些其他的配置，查阅doc文档吧）
options = new DisplayImageOptions.Builder()
.showStubImage(R.drawable.ic_stub) //在ImageView加载过程中显示图片
.showImageForEmptyUri(R.drawable.ic_empty) //image连接地址为空时
.showImageOnFail(R.drawable.ic_error) //image加载失败
.cacheInMemory(true) //加载图片时会在内存中加载缓存
.cacheOnDisc(true) //加载图片时会在磁盘中加载缓存
.displayer(new RoundedBitmapDisplayer(20)) //设置用户加载图片task(这里是圆角图片显示)
.build();
listView = (ListView) findViewById(android.R.id.list);
//绑定适配器
listView.setAdapter(new ItemAdapter());
listView.setOnItemClickListener(new OnItemClickListener() {
@Override
public void onItemClick(AdapterView<?> parent, View view, int position, long id) {
startImagePagerActivity(position);
}
});
}
@Override
public void onBackPressed() {
AnimateFirstDisplayListener.displayedImages.clear();
super.onBackPressed();
}
private void startImagePagerActivity(int position) {
Intent intent = new Intent(this, ImagePagerActivity.class);
intent.putExtra(Extra.IMAGES, imageUrls);
intent.putExtra(Extra.IMAGE_POSITION, position);
startActivity(intent);
}
/**自定义图片适配器**/
class ItemAdapter extends BaseAdapter {
private ImageLoadingListener animateFirstListener = new AnimateFirstDisplayListener();
private class ViewHolder {
public TextView text;
public ImageView image;
}
@Override
public int getCount() {
return imageUrls.length;
}
@Override
public Object getItem(int position) {
return position;
}
@Override
public long getItemId(int position) {
return position;
}
@Override
public View getView(final int position, View convertView, ViewGroup parent) {
View view = convertView;
final ViewHolder holder;
if (convertView == null) {
view = getLayoutInflater().inflate(R.layout.item_list_image, parent, false);
holder = new ViewHolder();
holder.text = (TextView) view.findViewById(R.id.text);
holder.image = (ImageView) view.findViewById(R.id.image);
view.setTag(holder);
} else {
holder = (ViewHolder) view.getTag();
}
holder.text.setText("Item " + (position + 1));
//Adds display image task to execution pool. Image will be set to ImageView when it's turn.
imageLoader.displayImage(imageUrls[position], holder.image, options, animateFirstListener);
return view;
}
}
/**图片加载监听事件**/
private static class AnimateFirstDisplayListener extends SimpleImageLoadingListener {
static final List<String> displayedImages = Collections.synchronizedList(new LinkedList<String>());
@Override
public void onLoadingComplete(String imageUri, View view, Bitmap loadedImage) {
if (loadedImage != null) {
ImageView imageView = (ImageView) view;
boolean firstDisplay = !displayedImages.contains(imageUri);
if (firstDisplay) {
FadeInBitmapDisplayer.animate(imageView, 500); //设置image隐藏动画500ms
displayedImages.add(imageUri); //将图片uri添加到集合中
}
}
}
}
}
