我一直在尝试在我的应用程序中实现LruCache，但是在连接点和在不同组件之间传递位图时遇到困难。
我想知道如何在我的应用程序中集成LruCache。我也希望了解实现LruCache的过程，所以越详细越好
第一类是AsyncTask图片加载程序，第二类是我的自定义适配器
异步任务
public class GetImagesBitmap extends AsyncTask<ImageView, Void, Bitmap>{
InputStream inputStream;
ImageView imageView = null;
String path;
@Override
protected Bitmap doInBackground(ImageView... imageViews) {
this.imageView = imageViews[0];
return download_Image((String)imageView.getTag());
}
@Override
protected void onPostExecute(Bitmap result) {
imageView.setImageBitmap(result);
}
private Bitmap download_Image(String url) {
final AndroidHttpClient client = AndroidHttpClient.newInstance("Android");
HttpGet httpGet = new HttpGet(url);
try {
HttpResponse httpResponse = client.execute(httpGet);
final int statusCode = httpResponse.getStatusLine().getStatusCode();
if (statusCode != HttpStatus.SC_OK) {
Log.w("ImageDownloader", "Error " + statusCode
+ " while retrieving bitmap from " + url);
return null;
}
final HttpEntity entity = httpResponse.getEntity();
if(entity != null){
inputStream = null;
inputStream = entity.getContent();
final Bitmap bitmap = BitmapFactory.decodeStream(inputStream);
return bitmap;
}
if(inputStream != null){
inputStream.close();
}
entity.consumeContent();
} catch (IOException e) {
httpGet.abort();
Log.w("ImageDownloader", "Error while retrieving bitmap from " + url);
}finally{
if(client != null){
client.close();
}
}
return null;
}
}
自定义视图适配器类
public class CustomListingListAdapter extends ArrayAdapter<HashMap<String, String>> {
private ArrayList<HashMap<String, String>> data;
private Context context;
private LayoutInflater mInflater;
private int viewId;
private String[] tag;
HashMap<String, String> currentData = new HashMap<String, String>();
//private static final String TAG_CONTENT = "content";
//private static final String TAG_RATING = "rating";
private static final String TAG_NAME = "name";
private static final String TAG_IMAGE_PATH = "image_path";
private static final String TAG_PRODUCT_ID = "product_id";
private static final String TAG_RATING = "rating";
public CustomListingListAdapter(Context c,
ArrayList<HashMap<String, String>> data,
int viewId, String[] tag) {
super( c, viewId, data);
this.context = c;
this.data= data;
this.viewId = viewId ;
}
@Override
public int getCount() {
return data.size();
}
@Override
public View getView(int position, View convertView, ViewGroup parent) {
View vi = convertView;
Holder holder;
if (convertView == null) {
// Inflate the view since it does not exist
if (vi == null) {
mInflater = (LayoutInflater) getContext().getSystemService(Context.LAYOUT_INFLATER_SERVICE);
vi = mInflater.inflate(R.layout.list_item_layout, null);
}
holder = new Holder();
holder.Name = (TextView) vi.findViewById(R.id.name);
holder.pid = (TextView) vi.findViewById(R.id.pid);
holder.imageView = (ImageView) vi.findViewById(R.id.list_image);
holder.ratingView = (ImageView) vi.findViewById(R.id.num_stars);
vi.setTag(holder);
}else {
holder = (Holder) vi.getTag();
}
currentData = (HashMap<String, String>) data.get(position);
holder.imageView.setTag(currentData.get(TAG_IMAGE_PATH));
if (currentData != null) {
holder.Name.setText(currentData.get(TAG_NAME));
holder.pid.setText(currentData.get(TAG_PRODUCT_ID));
}
new GetImagesBitmap().execute(holder.imageView);
return vi;
}
private static class Holder {
public ImageView imageView;
public ImageView ratingView;
public TextView pid;
public TextView Name;
}
}
最佳答案
您的工作方向正确，但我无法确定您在代码中的List / GridView中的视图回收位置。您确实确实在重用传递给getView的convertView，但是在每个getView中启动一个新的AsyncTask将导致任务加载图像，但是如果回收由其启动的视图，则将它们插入错误的列表行中。我的建议是检查Google新的网络库Volley。它具有NetworkImageView类，该类将异步将图像加载到ImageView中。我建议在磁盘和内存中进行缓存的原因是为您处理视图回收。
凌空抽射：
https://developers.google.com/events/io/sessions/325304728
如果您想自己解决这个问题，请查看Android Developer博客文章，内容涉及在ListView中加载位图。它演示了如何使用AsyncTasks进行演示，但是可以正确处理视图回收。
文章：
http://developer.android.com/training/displaying-bitmaps/process-bitmap.html
最后一点提示：不要为每个网络调用实例化一个新的HttpClient。创建一个需要花费一些时间，首选的方法是将一个配置为多线程的HttpClient保留为Singleton实例，并将其用于网络调用。另外，您可以为每个请求创建一个新的HttpUrlConnection。对于那个班级来说还可以。
编辑：对不起，我只是意识到我实际上没有回答这个问题。要为Bimap实现LruCache，您可以通过一些调整从支持库扩展LruCache类。这是我用于缓存Bitamp以便与Volley库一起使用的类：
// From com.android.volley.toolbox.ImageLoader
public interface ImageCache {
public Bitmap getBitmap(String url);
public void putBitmap(String url, Bitmap bitmap);
}
// My ImageCache implementation
public class BitmapLruCache extends LruCache<String, Bitmap> implements ImageCache {
private static final int DEFAULT_CACHE_SIZE = (int) (Runtime.getRuntime().maxMemory() / 1024) / 8;
public BitmapLruCache() {
this(DEFAULT_CACHE_SIZE);
}
public BitmapLruCache(int maxSize) {
super(maxSize);
}
@Override
public Bitmap getBitmap(String url) {
return get(url);
}
@Override
public void putBitmap(String url, Bitmap bitmap) {
put(url, bitmap);
}
@Override
protected int sizeOf(String key, Bitmap value) {
return value == null ? 0 : value.getRowBytes() * value.getHeight() / 1024;
}
}
关于android - 使用LruCache将位图存储在内存中，我们在Stack Overflow上找到一个类似的问题：https://stackoverflow.com/questions/18369123/