6

我参考了 android 开发者网站并使用单例类创建了凌空 NetworkImageView。但是在强制关闭应用程序并再次离线打开我的应用程序后，它不会维护缓存图像。如何使网络图像视图在离线模式下从缓存中获取图像。我正在使用 LruCache。

注意：我在整个应用程序中使用 NetworkImageView。而且我在某处读到，仅当图像 URL 包含缓存标头时才会存储磁盘缓存。我想知道这一点，如果 URL 中没有这样的标题，那么如何强制 volley 存储图像的磁盘缓存？

我的代码：

public class VolleySingletonPattern {

private static VolleySingletonPattern mInstance;
private RequestQueue mRequestQueue;
private ImageLoader mImageLoader;
private static Context mCtx;

private VolleySingletonPattern(Context context) {
    mCtx = context;
    mRequestQueue = getRequestQueue();

    mImageLoader = new ImageLoader(mRequestQueue, new LruBitmapCache(
            LruBitmapCache.getCacheSize(mCtx)));
}

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

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

public ImageLoader getImageLoader() {
    return mImageLoader;
}}

我的 LruCache：

public class LruBitmapCache extends LruCache<String, Bitmap>
    implements ImageCache {

public LruBitmapCache(int maxSize) {
    super(maxSize);
}

public LruBitmapCache(Context ctx) {
    this(getCacheSize(ctx));
}

@Override
protected int sizeOf(String key, Bitmap value) {
    return value.getRowBytes() * value.getHeight();
}

@Override
public Bitmap getBitmap(String url) {
    return get(url);
}

@Override
public void putBitmap(String url, Bitmap bitmap) {
    put(url, bitmap);
}

// Returns a cache size equal to approximately three screens worth of images.
public static int getCacheSize(Context ctx) {
    final DisplayMetrics displayMetrics = ctx.getResources().
            getDisplayMetrics();
    final int screenWidth = displayMetrics.widthPixels;
    final int screenHeight = displayMetrics.heightPixels;
    // 4 bytes per pixel
    final int screenBytes = screenWidth * screenHeight * 4;

    return screenBytes * 3;
}}
4

1 回答 1

0

我已经使用了this，并且正在为我工​​作。您需要添加这些权限。

<uses-permission android:name="android.permission.INTERNET" />
<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />
于 2016-02-06T08:33:54.887 回答