如何使Volley NetworkImageView脱机工作 [英] How to make Volley NetworkImageView worke offline

问题描述

我使用Volley NetworkImageView从Internet下载图像并显示在我的listview中.现在，我想使Volley NetworkImageView在没有可用网络的情况下显示保存的图像. Volley已经通过URL作为键缓存了图像，因为当我使用

I use Volley NetworkImageView to download images from internet and show in my listview. Now I want to make Volley NetworkImageView show saved images when there is no network available. Volley has already cached images by URL as a key because when I use

Entry entry = SingletonRequestQueue.getInstance(context).getRequestQueue().getCache().get(imageURL);

entry.data不为null.但是我的问题是图像分辨率很高，我不能使用

the entry.data is not null. But my problem is that image resolutions are high and I can not use

Bitmap b = BitmapFactory.decodeByteArray(entry.data, 0, entry.data.length);

因为它会产生很多滞后，所以我不得不重新发明轮子，因为我必须再次创建asynctask，以查看listview何时滚动以取消解码，回收bitmap，在内存缓存中创建，找到最佳样本值和...

because it creates a lot of lag and I have to reinvent the wheel because again I must create asynctask see when listview has scrolled to cancel decoding, recycling the bitmap, creating in memory cache, finding best insample value and ...

如此好，Idea只是做一些技巧，使Volley NetworkImageView 使用其自己的DiskLRUCache 在没有网络时显示它们.

so better Idea is just do some tricks that make Volley NetworkImageView use its own DiskLRUCache to show them when there is no network.

有什么主意吗?

我的代码:

public class SingletonRequestQueue {


    private static SingletonRequestQueue mInstance;
    private RequestQueue mRequestQueue;
    private ImageLoader mImageLoader;
    private static Context mCtx;
    private LruBitmapCache mLruBitmapCache;

    private SingletonRequestQueue(Context context) {
        mCtx = context;
        mRequestQueue = getRequestQueue();
        mLruBitmapCache = new LruBitmapCache(LruBitmapCache.getCacheSize(context));
        mImageLoader = new ImageLoader(mRequestQueue,mLruBitmapCache);

    }

    public static synchronized SingletonRequestQueue getInstance(Context context) {
        if (mInstance == null) {
            mInstance = new SingletonRequestQueue(context);
        }
        return mInstance;
    }

    public RequestQueue getRequestQueue() {
        if (mRequestQueue == null) {

            // getApplicationContext() is key, it keeps you from leaking the
            // Activity or BroadcastReceiver if someone passes one in.

            mRequestQueue = Volley.newRequestQueue(mCtx.getApplicationContext(),new OkHttpStack());
//          mRequestQueue = Volley.newRequestQueue(mCtx.getApplicationContext());
        }
        return mRequestQueue;
    }

    public <T> void addToRequestQueue(Request<T> req) {
        getRequestQueue().add(req);
    } 

    public ImageLoader getImageLoader() {
        return mImageLoader;
    }

    public LruBitmapCache getLruBitmapCache() {
        return mLruBitmapCache;
    }

    public void setLruBitmapCache(LruBitmapCache lruBitmapCache) {
        mLruBitmapCache = lruBitmapCache;
    }


}

并在我的适配器中:

public IssueListAdapter(Context context, int resource, List<Issue> objects) {
        super(context, resource, objects);
        this.context = context;
        this.mIssueList = objects;
        mImageLoader = SingletonRequestQueue.getInstance(context).getImageLoader();
}

public static class ViewHolder{

    public  NetworkImageView mNetworkImageView;
    public  TextView mFee;
    public  TextView mName;
}


@Override
public View getView(int position, View convertView, ViewGroup parent) {


    ViewHolder holder;

    if(convertView == null){
        holder = new ViewHolder();
        LayoutInflater inflater =    
                (LayoutInflater) context.getSystemService(Activity.LAYOUT_INFLATER_SERVICE);
        convertView = inflater.inflate(R.layout.gridview_issuelist_item, parent, false);

        holder.mNetworkImageView = (NetworkImageView)convertView.findViewById(R.id.NetworkImageView_MainActivity_issue_image);
        holder.mName = (TextView)convertView.findViewById(R.id.TextView_MainActivity_name);
        holder.mFee = (TextView)convertView.findViewById(R.id.TextView_MainActivity_fee);
        Utility.settingTypfaceFont(context, holder.mName);
        Utility.settingTypfaceFont(context, holder.mFee);

        convertView.setTag(holder);

    }else{
        holder = (ViewHolder)(convertView.getTag());
    }

    final Issue issue = mIssueList.get(position);
    holder.mName.setText(issue.getTitle());
    holder.mFee.setText(String.valueOf(issue.getFee()));
    String imageURL = issue.getPublicCover();

    holder.mNetworkImageView.setImageUrl(imageURL, mImageLoader);
    holder.mNetworkImageView.setDefaultImageResId(R.drawable.placeholder2);;

    /*
    Entry entry = SingletonRequestQueue.getInstance(context).getRequestQueue().getCache().get(imageURL);
    if(entry != null && entry.data != null){
        byte[] imageByte = entry.data;
        loadBitmap(imageByte, holder.mNetworkImageView,imageURL);
    }else{
        holder.mNetworkImageView.setImageUrl(imageURL, mImageLoader);
    }*/

    return convertView;
}

@Override
public int getCount() {
    if(mIssueList != null){
        return mIssueList.size();           
    }
    else{
        return 0;
    }
}

public List<Issue> getIssueList() {
    return mIssueList;
}

}

推荐答案

只需在BasicNetwork类中添加此行

Just add this line in BasicNetwork class

if (!ConnectivityUtils.isNetworkEnabled(CardApplication.getContext()) && request instanceof ImageRequest) {
            VolleyLog.e("Cached response", "No Network Connectivity for Url=", request.getUrl());
            return new NetworkResponse(HttpStatus.SC_NOT_MODIFIED,
                    request.getCacheEntry().data, responseHeaders, true);
        }

对于数据请求到期，您可以使用自己的HttpHeaderParser更改Cached.Entry

and for data request expiry you can change the Cached.Entry using using own HttpHeaderParser

这是链接详细解释事情

这篇关于如何使Volley NetworkImageView脱机工作的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！