Использование HttpResponseCache делает приложение аварии

Question

Я пытаюсь использовать HttpResponseCache кэшировать данные сети, но когда я кладу установить код кэша OnCreate и OnPause методы, приложение аварии. Я использовал код от HttpResponseCache documentation. и ошибки компиляции появляются, как показано ниже. после использования

@TargetApi (Build.VERSION_CODES.ICE_CREAM_SANDWICH)

решить ошибки он исчезнет, ​​то, я бегу приложение, но по-прежнему падает. , когда я удаляю этот код, он возвращается к нормальному поведению.

protected void onCreate(Bundle savedInstanceState) { 
     ... 

     try { 
      File httpCacheDir = new File(context.getCacheDir(), "http"); 
      long httpCacheSize = 10 * 1024 * 1024; // 10 MiB 
      HttpResponseCache.install(httpCacheDir, httpCacheSize); //error 
     } catch (IOException e) { 
      Log.i(TAG, "HTTP response cache installation failed:" + e); 
     } 
    } 

    protected void onStop() { 
     ... 

     HttpResponseCache cache = HttpResponseCache.getInstalled();//error 
     if (cache != null) { 
      cache.flush();//error 
     } 
    }} 

Я начинающий ученик, поэтому я буду признателен, если кто-нибудь сможет помочь. вот MainActivity код

public class MainActivity extends AppCompatActivity { 


    private MovieAdapter movieAdapter; 
    private Context context; 



    @TargetApi(Build.VERSION_CODES.ICE_CREAM_SANDWICH) 
    @Override 
    protected void onCreate(Bundle savedInstanceState) { 
     super.onCreate(savedInstanceState); 
     setContentView(R.layout.activity_main); 


     // ------ caching data ------------------ 
     try { 
      File httpCacheDir = new File(context.getCacheDir(), "http"); 
      long httpCacheSize = 2 * 1024 * 1024; // 10 MiB 
      HttpResponseCache.install(httpCacheDir, httpCacheSize); //error 
     } catch (IOException e) { 
      Log.i("caching failed", "HTTP response cache installation failed:" + e); 
     } 

     //----------------------- 

     DataSyncTask dataSyncTask = new DataSyncTask(); 
     dataSyncTask.execute(); 
    } 


     @Override 
    public boolean onCreateOptionsMenu(Menu menu) { 
     MenuInflater inflater = getMenuInflater(); 
     inflater.inflate(R.menu.menu_main, menu); 
     return true; 
    } 



    @Override 
    public boolean onOptionsItemSelected(MenuItem item) { 
     int id = item.getItemId(); 

     if (id == R.id.action_settings) { 
      startActivity(new Intent(this, SettingsActivity.class)); 

      return true; 
     } 
     return super.onOptionsItemSelected(item); 
    } 


    private class DataSyncTask extends AsyncTask<Void, Void, ArrayList<Movie>> { 

     @Override 
     protected ArrayList<Movie> doInBackground(Void... params) { 
      JSONHttpClient jsonHttpClient = new JSONHttpClient(MainActivity.this); 
      JSONDataParser finalData = new JSONDataParser(); 
      /* 
      using shared preference to obtain data 
      */ 
      SharedPreferences sharedPreferences = 
        PreferenceManager.getDefaultSharedPreferences(getApplicationContext()); 

      String sortingOrder = sharedPreferences.getString(
        getString(R.string.pref_findMovies_key), 
        getString(R.string.pref_popular_value)); 

      String streamData = jsonHttpClient.getData(sortingOrder); 
      return finalData.getParsedData(streamData); 

     } 

     @Override 
     protected void onPostExecute(final ArrayList<Movie> movies) { 


      movieAdapter = new MovieAdapter(getApplicationContext(), movies); 
      GridView gridView = (GridView) findViewById(R.id.movies_grid); 
      gridView.setAdapter(movieAdapter); 
      gridView.setOnItemClickListener(new AdapterView.OnItemClickListener() { 
       @Override 
       public void onItemClick(AdapterView<?> adapterView, View view, int i, long l) { 
        Movie movie = (Movie) adapterView.getItemAtPosition(i); 
        Intent intent = new Intent(MainActivity.this, DetailActivity.class); 
        intent.putExtra("MovieTitle", movie.getTitle()); 
        intent.putExtra("voteAverage", movie.getVoteAverage()); 
        intent.putExtra("ReleaseDate", movie.getReleaseDate()); 
        intent.putExtra("MovieOverview", movie.getOverview()); 
        intent.putExtra("PosterPath", movie.getPosterPath()); 

        startActivity(intent); 
       } 
      }); 

     } 
    } 

    @Override 
    protected void onResume() { 
     DataSyncTask dataSyncTask = new DataSyncTask(); 
     dataSyncTask.execute(); 
     super.onResume(); 

    } 

    @TargetApi(Build.VERSION_CODES.ICE_CREAM_SANDWICH) 
    @Override 
    protected void onStop() { 
     HttpResponseCache cache = HttpResponseCache.getInstalled(); 
     if (cache != null) { 
      cache.flush(); 
     } 
     super.onStop(); 
    } 
} 

, что появляются в LogCat после аварии приложения

12-19 19:22:58.465 17548-17548/com.example.geekymind.displayjsondatafrominternet W/dalvikvm﹕ VFY: unable to find class referenced in signature (Landroid/view/SearchEvent;) 
12-19 19:22:58.465 17548-17548/com.example.geekymind.displayjsondatafrominternet I/dalvikvm﹕ Could not find method android.view.Window$Callback.onSearchRequested, referenced from method android.support.v7.internal.view.WindowCallbackWrapper.onSearchRequested 
12-19 19:22:58.465 17548-17548/com.example.geekymind.displayjsondatafrominternet W/dalvikvm﹕ VFY: unable to resolve interface method 14585: Landroid/view/Window$Callback;.onSearchRequested (Landroid/view/SearchEvent;)Z 
12-19 19:22:58.465 17548-17548/com.example.geekymind.displayjsondatafrominternet I/dalvikvm﹕ Could not find method android.view.Window$Callback.onWindowStartingActionMode, referenced from method android.support.v7.internal.view.WindowCallbackWrapper.onWindowStartingActionMode 
12-19 19:22:58.465 17548-17548/com.example.geekymind.displayjsondatafrominternet W/dalvikvm﹕ VFY: unable to resolve interface method 14589: Landroid/view/Window$Callback;.onWindowStartingActionMode (Landroid/view/ActionMode$Callback;I)Landroid/view/ActionMode; 
12-19 19:22:58.505 17548-17548/com.example.geekymind.displayjsondatafrominternet I/dalvikvm﹕ Could not find method android.content.res.TypedArray.getChangingConfigurations, referenced from method android.support.v7.internal.widget.TintTypedArray.getChangingConfigurations 
12-19 19:22:58.505 17548-17548/com.example.geekymind.displayjsondatafrominternet W/dalvikvm﹕ VFY: unable to resolve virtual method 451: Landroid/content/res/TypedArray;.getChangingConfigurations()I 
12-19 19:22:58.515 17548-17548/com.example.geekymind.displayjsondatafrominternet I/dalvikvm﹕ Could not find method android.content.res.TypedArray.getType, referenced from method android.support.v7.internal.widget.TintTypedArray.getType 
12-19 19:22:58.515 17548-17548/com.example.geekymind.displayjsondatafrominternet W/dalvikvm﹕ VFY: unable to resolve virtual method 473: Landroid/content/res/TypedArray;.getType (I)I 
12-19 19:22:58.585 17548-17548/com.example.geekymind.displayjsondatafrominternet W/dalvikvm﹕ threadid=1: thread exiting with uncaught exception (group=0x415ffc80) 

Answer 1

По HttpResponseCache Docs:

Включить кэширование всех HTTP запросов вашего приложения с помощью установки кэша при запуск приложения.

Таким образом, вы должны использовать как:

MyApplication.java:

public class MyApplication extends Application { 

    private final Context mContext = this; 

    public void onCreate() { 
     super.onCreate(); 

     // Install the cache 
     try { 
      File httpCacheDir = new File(mContext.getCacheDir(), "http"); 
      long httpCacheSize = 10 * 1024 * 1024; // 10 MiB 
      HttpResponseCache.install(httpCacheDir, httpCacheSize); 
     } catch (IOException e) { 
      Log.i("CacheHttpUrlConnection", "HTTP response cache installation failed:" + e); 
     } 

     // Register for activity lifecycle callbacks, 
     // specifically interested in activity stop callbacks. 
     registerActivityLifecycleCallbacks(
       new MyApplicationActivityLifeCycleCallbacks()); 
    } 

    // method to flush cache contents to the filesystem 
    public void flushCache() { 
     HttpResponseCache cache = HttpResponseCache.getInstalled(); 
     if (cache != null) { 
      cache.flush(); 
     } 
    } 

    private class MyApplicationActivityLifeCycleCallbacks implements ActivityLifecycleCallbacks { 
     @Override 
     public void onActivityCreated(Activity activity, Bundle savedInstanceState) { 
     } 

     @Override 
     public void onActivityStarted(Activity activity) { 
     } 

     @Override 
     public void onActivityResumed(Activity activity) { 
     } 

     @Override 
     public void onActivityPaused(Activity activity) { 
     } 

     public void onActivityStopped(Activity activity) { 
      flushCache(); 
     } 

     @Override 
     public void onActivitySaveInstanceState(Activity activity, Bundle outState) { 
     } 

     @Override 
     public void onActivityDestroyed(Activity activity) { 
     } 
    } 
} 

MainActivity.java:

Внутри doInBackground из AsyncTask Класс:

... 
URL url = new URL(address); 
HttpURLConnection urlConnection = (HttpURLConnection) url.openConnection(); 
int maxStale = 60 * 60 * 24 * 28; // tolerate 4-weeks stale 
urlConnection.addRequestProperty("Cache-Control", "max-stale=" + maxStale); 
// Checks cache 
if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.ICE_CREAM_SANDWICH) { 
    cache = HttpResponseCache.getInstalled(); 
    if (cache != null) { 
     cacheInfo = "Request count: " 
       + cache.getRequestCount() + ", hit count " 
       + cache.getHitCount() + ", network count " 
       + cache.getNetworkCount() + " size = " 
       + cache.size() + " <-----------------"; 
     Log.i(LOG_TAG, cacheInfo); 
    } 
} 
// Gets stream 
Log.i(LOG_TAG, "RespCode: " + urlConnection.getResponseCode()); 
if (urlConnection.getResponseCode() < HttpURLConnection.HTTP_BAD_REQUEST) { 
    inputStream = urlConnection.getInputStream(); 
} else { 
    inputStream = urlConnection.getErrorStream(); 
} 
// Parses stream to string 
BufferedReader bufferedReader = new BufferedReader(new InputStreamReader(inputStream)); 
String temp, response = ""; 
while ((temp = bufferedReader.readLine()) != null) { 
    response += temp; 
} 
... 

AndroidManifest.xml:

<?xml version="1.0" encoding="utf-8"?> 
<manifest xmlns:android="http://schemas.android.com/apk/res/android" 
    package="com.example.cachehttpurlconnection" > 

    <uses-permission android:name="android.permission.INTERNET" /> 

    <application 
     android:allowBackup="true" 
     android:icon="@mipmap/ic_launcher" 
     android:label="@string/app_name" 
     android:supportsRtl="true" 
     android:theme="@style/AppTheme" 
     android:name="com.example.cachehttpurlconnection.MyApplication" > 
     <activity android:name=".MainActivity" > 
      <intent-filter> 
       <action android:name="android.intent.action.MAIN" /> 

       <category android:name="android.intent.category.LAUNCHER" /> 
      </intent-filter> 
     </activity> 
    </application> 

</manifest>