Volley.java 文件源码

/**
 * Creates a default instance of the worker pool and calls {@link RequestLauncher#start()} on it.
 * You may set a maximum size of the disk cache in bytes.
 *
 * @param context A {@link Context} to use for creating the cache dir.
 * @param stack An {@link HttpStack} to use for the network, or null for default.
 * @param maxDiskCacheBytes the maximum size of the disk cache, in bytes. Use -1 for default size.
 * @return A started {@link RequestLauncher} instance.
 */
public static RequestLauncher newLauncher(Context context, HttpStack stack, int maxDiskCacheBytes) {
    File cacheDir = new File(context.getCacheDir(), DEFAULT_CACHE_DIR);

    String userAgent = "volley/0";
    try {
        String packageName = context.getPackageName();
        PackageInfo info = context.getPackageManager().getPackageInfo(packageName, 0);
        userAgent = packageName + "/" + info.versionCode;
    } catch (NameNotFoundException e) {
        e.printStackTrace();
    }

    if (stack == null) {
        if (Build.VERSION.SDK_INT >= 9) {
            stack = new HurlStack();
        } else {
            // Prior to Gingerbread, HttpUrlConnection was unreliable.
            // See: http://android-developers.blogspot.com/2011/09/androids-http-clients.html
            stack = new HttpClientStack(AndroidHttpClient.newInstance(userAgent));
        }
    }

    Network network = new BasicNetwork(stack);

    RequestLauncher launcher;
    if (maxDiskCacheBytes <= -1) {
        // No maximum size specified
        launcher = new RequestLauncher(new DiskBasedCache(cacheDir), network);
    } else {
        // Disk cache size specified
        launcher = new RequestLauncher(new DiskBasedCache(cacheDir, maxDiskCacheBytes), network);
    }
    launcher.start();

    return launcher;
}