file：// android_assets /和http://someurl.com/之間的區別？

Question

我有一個android應用程序，它從Web上的JSON文件加載圖像。 JSON文件在其中包含一個帶有圖像位置的URL。通常，應用程序讀取JSON文件以從Web地址下載圖像。但現在我想從我的資產文件夾下載文件，並閱讀資產目錄中的JSON文件（我正在使用file：// android_assets）。

我的第一個問題是，爲什麼不能讀取我的資產文件夾中的JSON文件？

我的JSON文件，而不是真正需要解決我的第一個問題，但我只是將它張貼：

舊JSON：

[ 
{ 
    "id": "1", 
    "title": "Blue Calmness", 
    "thumburl": "http://someurl.com/1.jpg", 
    "previewurl": "http://someurl.com/1.jpg", 
    "url": "http://someurl.com/1.jpg", 
    "text": "Give your background a special message! An inspirational image, the texture and its calm blue color are stimulating and representing the silent word of the see. For a positive look at the world." 
} 
] 

新JSON：

[ 
{ 
    "id": "1", 
    "title": "Blue Calmness", 
    "thumburl": "file:///android_assets/1.jpg", 
    "previewurl": "file:///android_assets/1.jpg", 
    "url": "file:///android_assets/1.jpg", 
    "text": "Give your background a special message! An inspirational image, the texture and its calm blue color are stimulating and representing the silent word of the see. For a positive look at the world." 
} 
] 

但我得到的錯誤消息：

04-29 21:52:42.169: E/AndroidRuntime(23408): FATAL EXCEPTION: main 
    04-29 21:52:42.169: E/AndroidRuntime(23408): java.lang.RuntimeException: java.lang.IllegalArgumentException: Host name may not be null 
    04-29 21:52:42.169: E/AndroidRuntime(23408):  at app.wallpaper.main.ScroidWallpaperGallery$FillGalleryTask.handleUncaughtException(ScroidWallpaperGallery.java:415) 
    04-29 21:52:42.169: E/AndroidRuntime(23408):  at app.wallpaper.util.threading.LongTimeRunningOperation$InnerAsyncTask.onPostExecute(LongTimeRunningOperation.java:87) 
    04-29 21:52:42.169: E/AndroidRuntime(23408):  at android.os.AsyncTask.finish(AsyncTask.java:631) 
    04-29 21:52:42.169: E/AndroidRuntime(23408):  at android.os.AsyncTask.access    $600(AsyncTask.java:177) 
    04-29 21:52:42.169: E/AndroidRuntime(23408):  at android.os.AsyncTask$InternalHandler.handleMessage(AsyncTask.java:644) 
    04-29 21:52:42.169: E/AndroidRuntime(23408):  at android.os.Handler.dispatchMessage(Handler.java:99) 
    04-29 21:52:42.169: E/AndroidRuntime(23408):  at android.os.Looper.loop(Looper.java:137) 
    04-29 21:52:42.169: E/AndroidRuntime(23408):  at android.app.ActivityThread.main(ActivityThread.java:5041) 
    04-29 21:52:42.169: E/AndroidRuntime(23408):  at java.lang.reflect.Method.invokeNative(Native Method) 
    04-29 21:52:42.169: E/AndroidRuntime(23408):  at java.lang.reflect.Method.invoke(Method.java:511) 
    04-29 21:52:42.169: E/AndroidRuntime(23408):  at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:793) 
    04-29 21:52:42.169: E/AndroidRuntime(23408):  at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:560) 
    04-29 21:52:42.169: E/AndroidRuntime(23408):  at dalvik.system.NativeStart.main(Native Method) 
    04-29 21:52:42.169: E/AndroidRuntime(23408): Caused by: java.lang.IllegalArgumentException: Host name may not be null 
    04-29 21:52:42.169: E/AndroidRuntime(23408):  at org.apache.http.HttpHost.<init>(HttpHost.java:83) 
    04-29 21:52:42.169: E/AndroidRuntime(23408):  at org.apache.http.impl.client.AbstractHttpClient.determineTarget(AbstractHttpClient.java:497) 
    04-29 21:52:42.169: E/AndroidRuntime(23408):  at org.apache.http.impl.client.AbstractHttpClient.execute(AbstractHttpClient.java:626) 
    04-29 21:52:42.169: E/AndroidRuntime(23408):  at org.apache.http.impl.client.AbstractHttpClient.execute(AbstractHttpClient.java:616) 
    04-29 21:52:42.169: E/AndroidRuntime(23408):  at app.wallpaper.main.dao.wallpapers.WallpaperDAO.download(WallpaperDAO.java:105) 
    04-29 21:52:42.169: E/AndroidRuntime(23408):  at app.wallpaper.main.dao.wallpapers.WallpaperDAO.getAvailableWallpapers(WallpaperDAO.java:61) 
    04-29 21:52:42.169: E/AndroidRuntime(23408):  at app.wallpaper.main.core.wallpapers.WallpaperManager.loadAvailableWallpapers(WallpaperManager.java:92) 
    04-29 21:52:42.169: E/AndroidRuntime(23408):  at app.wallpaper.main.ScroidWallpaperGallery$FillGalleryTask.onRun(ScroidWallpaperGallery.java:425) 
    04-29 21:52:42.169: E/AndroidRuntime(23408):  at app.wallpaper.main.ScroidWallpaperGallery$FillGalleryTask.onRun(ScroidWallpaperGallery.java:1) 
    04-29 21:52:42.169: E/AndroidRuntime(23408):  at app.wallpaper.util.threading.LongTimeRunningOperation$InnerAsyncTask.doInBackground(LongTimeRunningOperation.java:73) 
    04-29 21:52:42.169: E/AndroidRuntime(23408):  at app.wallpaper.util.threading.LongTimeRunningOperation$InnerAsyncTask.doInBackground(LongTimeRunningOperation.java:1) 
    04-29 21:52:42.169: E/AndroidRuntime(23408):  at android.os.AsyncTask$2.call(AsyncTask.java:287) 
    04-29 21:52:42.169: E/AndroidRuntime(23408):  at java.util.concurrent.FutureTask.run(FutureTask.java:234) 
    04-29 21:52:42.169: E/AndroidRuntime(23408):  at android.os.AsyncTask$SerialExecutor$1.run(AsyncTask.java:230) 
    04-29 21:52:42.169: E/AndroidRuntime(23408):  at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1080) 
    04-29 21:52:42.169: E/AndroidRuntime(23408):  at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:573) 
    04-29 21:52:42.169: E/AndroidRuntime(23408):  at java.lang.Thread.run(Thread.java:856) 

@Inject 
WallpaperDAO(IWallpaperParser wallpaperParser) { 
    super(); 

    this.wallpaperParser = wallpaperParser; 
} 


/* (non-Javadoc) 
* @see app.wallpaper.main.dao.wallpapers.IWallpaperDAO#getAvailableWallpapers(android.content.Context) 
*/ 
public Wallpaper[] getAvailableWallpapers(Context context) throws WallpaperListReceivingException {  
    try { 
     String data = this.download(URI.create(context.getString(R.string.galleryUrl)), 
            new TextFileHttpResponseHandler(), 
            MAX_DOWNLOAD_RETRIES); 

     List<Wallpaper> wallpapers = this.wallpaperParser.parse(data); 

     return wallpapers.toArray(new Wallpaper[wallpapers.size()]); 
    } 
    catch (IllegalStateException ex) { 
     throw new WallpaperListReceivingException(context.getString(R.string.receivingException), ex); 
    } 
    catch (IOException ex) { 
     throw new WallpaperListReceivingException(context.getString(R.string.receivingException), ex); 
    } 
    catch (ParseException ex) { 
     throw new WallpaperListReceivingException(context.getString(R.string.parseExceptionText), ex); 
    } 
} 

哪裏GALLERYURL是文件：//android_assets/myfile.json

現在我想知道，爲什麼不能從的android我的資產文件夾加載我JSON文件我的代碼從服務器下載JSON ，雖然它可以從我的網絡服務器。有沒有辦法解決這個問題。

任何幫助表示讚賞！

Answer 1

file：///表示一個不同於HTTP URI的URI，它指向您資產目錄中包含的數據。您的下載方式顯然是爲HTTP網址設計的。

爲了從資產目錄加載數據，您可以特別使用AssetManager和open方法。

例如：

AssetManager assetMgr = this.getAssets() 
InputStream is = assetMgr.open("1.jpg");