beim Analysieren von JSON-Buchdaten "kein Buch gefunden" Logik funktioniert nicht in Android

Question

Ich verwende GOOGLE_BOOK_API, um JSON-Daten zu analysieren. Wenn ein Benutzer ein Schlüsselwort in die Suchansicht eingibt, das nicht in der Liste ist, dann funktioniert mEmptyStateTextView nicht, was besagt, dass kein Buch gefunden wurde. Unten ist mein Code.

BookActivity.java // Buch Details

public class BookActivity extends AppCompatActivity { 

/** 
* URL for book data from the google book dataset 
*/ 
private static final String GOOGLE_REQUEST_SEARCH_URL = "https://www.googleapis.com/books/v1/volumes?maxResults=20&q="; 
View loadingIndicator; 
ArrayList<Book> books; 
ConnectivityManager connectivityManager; 
NetworkInfo networkInfo; 
/** 
* Adapter for the list of earthquakes 
*/ 
private BookAdapter mAdapter; 
private TextView mEmptyStateTextView; 

@Override 
protected void onSaveInstanceState(Bundle keepState) { 
    keepState.putParcelableArrayList("booklist", books); 
    Log.v("My Log message", "book is :" + books); 
    super.onSaveInstanceState(keepState); 
} 


@Override 
protected void onCreate(Bundle savedInstanceState) { 
    super.onCreate(savedInstanceState); 

    setContentView(R.layout.activity_book); 
    loadingIndicator = findViewById(R.id.loading_indicator); 
    loadingIndicator.setVisibility(View.GONE); 

    // Find a reference to the {@link ListView} in the layout 
    ListView bookListView = (ListView) findViewById(R.id.list); 

    mEmptyStateTextView = (TextView) findViewById(R.id.empty_view); 
    mEmptyStateTextView.setText(R.string.no_data); 
    bookListView.setEmptyView(mEmptyStateTextView); 

    // Create a new adapter that takes an empty list of books as input 
    mAdapter = new BookAdapter(this, new ArrayList<Book>()); 

    // Set the adapter on the {@link ListView} 
    // so the list can be populated in the user interface 
    bookListView.setAdapter(mAdapter); 

    if (savedInstanceState != null) { 
     books = savedInstanceState.getParcelableArrayList("booklist"); 
     mAdapter.addAll(books); 

    } else { 
     books = new ArrayList<>(); 

    } 
    bookListView.setOnItemClickListener(new AdapterView.OnItemClickListener() { 
     @Override 
     public void onItemClick(AdapterView<?> adapterView, View view, int position, long l) { 
      Book currentBook = mAdapter.getItem(position); 

      Uri bookUri = Uri.parse(currentBook.getUrl()); 

      Intent websiteIntent = new Intent(Intent.ACTION_VIEW, bookUri); 

      startActivity(websiteIntent); 
     } 
    }); 


    /* if (networkInfo != null && networkInfo.isConnected()) { 

     BookAsyncTask task = new BookAsyncTask(); 
     task.execute(GOOGLE_REQUEST_SEARCH_URL); 
    } else { 

     loadingIndicator = findViewById(R.id.loading_indicator); 
     loadingIndicator.setVisibility(View.GONE); 

     mEmptyStateTextView.setText(R.string.no_internet_connection); 
    }*/ 
} 

@Override 
public boolean onCreateOptionsMenu(Menu menu) { 
    MenuInflater inflater = getMenuInflater(); 
    inflater.inflate(R.menu.options_menu, menu); 

    SearchManager searchManager = 
      (SearchManager) getSystemService(Context.SEARCH_SERVICE); 

    MenuItem searchItem = menu.findItem(R.id.search); 
    final SearchView searchView = (SearchView) searchItem.getActionView(); 

    searchView.setSearchableInfo(searchManager.getSearchableInfo(getComponentName())); 
    searchView.setOnQueryTextListener(new SearchView.OnQueryTextListener() { 
     @Override 
     public boolean onQueryTextSubmit(String query) { 

      String urlQuery; 
      query = searchView.getQuery().toString(); 

      connectivityManager = (ConnectivityManager) getSystemService(Context.CONNECTIVITY_SERVICE); 

      networkInfo = connectivityManager.getActiveNetworkInfo(); 
      if (networkInfo != null && networkInfo.isConnected()) { 

       BookAsyncTask task = new BookAsyncTask(); 
       task.execute(GOOGLE_REQUEST_SEARCH_URL); 

       if (!TextUtils.isEmpty(query)) { 

        String encodedQuery = ""; 
        try { 
         encodedQuery = URLEncoder.encode(query, "utf-8"); 
        } catch (UnsupportedEncodingException e) { 
         e.printStackTrace(); 
        } 
        urlQuery = GOOGLE_REQUEST_SEARCH_URL + encodedQuery + "&maxResults=10"; 

        //Toast.makeText(getApplicationContext(), urlQuery, Toast.LENGTH_SHORT).show(); 
        mAdapter.clear(); 
        mEmptyStateTextView.setText(""); // clear any message set previously 
        loadingIndicator.setVisibility(View.VISIBLE); // show loading during search 
        new BookAsyncTask().execute(urlQuery); 
       } 

      } else { 

       Toast.makeText(getApplicationContext(), "Network not available", Toast.LENGTH_SHORT).show(); 
      } 
      return true; 
     } 

     @Override 
     public boolean onQueryTextChange(String newText) { 

      return false; 
     } 
    }); 

    return true; 
} 

private class BookAsyncTask extends AsyncTask<String, Void, ArrayList<Book>> { 
    @Override 
    protected ArrayList<Book> doInBackground(String... urls) { 

     if (urls.length < 1 || urls[0] == null) { 
      return null; 
     } 

     ArrayList<Book> result = QueryUtils.fetchBook(urls[0]); 
     return result; 
    } 

    @Override 
    protected void onPostExecute(ArrayList<Book> result) { 

     loadingIndicator = findViewById(R.id.loading_indicator); 
     loadingIndicator.setVisibility(View.GONE); 

     mAdapter.clear(); 

     if (result == null) { 
      return; 
     } 
     if (result != null && !result.isEmpty()) { 
      books = result; 
      mAdapter.addAll(result); 
     } 

     mEmptyStateTextView.setText(R.string.no_book_found); 

    } 
} 

}

activity_book.xml

<?xml version="1.0" encoding="utf-8"?> 
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android" 
android:layout_width="match_parent" 
android:layout_height="match_parent"> 

<!-- Layout for a list of books --> 
<ListView 
    android:id="@+id/list" 
    android:layout_width="wrap_content" 
    android:layout_height="wrap_content" 
    android:orientation="vertical" 
    android:dividerHeight="0dp" 
    android:divider="@null"/> 

<!-- Empty view is only visible when the list has no items. --> 
<TextView 
    android:id="@+id/empty_view" 
    android:layout_width="wrap_content" 
    android:layout_height="wrap_content" 
    android:layout_centerInParent="true" 
    android:paddingLeft="@dimen/padding_left" 
    android:paddingRight="@dimen/padding_right" 
    android:textAppearance="?android:textAppearanceMedium"/> 

<!-- Loading indicator is only shown before the first load --> 
<ProgressBar 
    android:id="@+id/loading_indicator" 
    android:layout_width="wrap_content" 
    android:layout_height="wrap_content" 
    android:layout_centerInParent="true"/> 

</RelativeLayout> 

Answer 1

Sie rufen BookAsyncTask zweimal in url Methode holen, die erste ist api schlagen https://www.googleapis.com/books/v1/volumes?maxResults=20&q= (das ist falsch params) und die zweite trifft mit den richtigen params.

Und nach Android-Richtlinien (more details) in Bezug auf AsyncTask, nur eine Instanz von AsyncTask kann zu einem Zeitpunkt ausgeführt werden, so dass die zweite richtige URL bekommt Anruf nie und man bekam die Antwort getroffen ersten Treffer, die gefunden kein Buch

sind

Ersetzen Sie Ihre onQueryTextSubmit komplette Methode mit dem unten angegebenen Verfahren,

public boolean onQueryTextSubmit(String query) { 

     String urlQuery; 
     query = searchView.getQuery().toString(); 

     connectivityManager = (ConnectivityManager) getSystemService(Context.CONNECTIVITY_SERVICE); 

     networkInfo = connectivityManager.getActiveNetworkInfo(); 
     if (networkInfo != null && networkInfo.isConnected()) { 

      //BookAsyncTask task = new BookAsyncTask(); //Removing this and below will solve the problem 
      //task.execute(GOOGLE_REQUEST_SEARCH_URL);//Removing this will solve the problem 

      if (!TextUtils.isEmpty(query)) { 

       String encodedQuery = ""; 
       try { 
        encodedQuery = URLEncoder.encode(query, "utf-8"); 
       } catch (UnsupportedEncodingException e) { 
        e.printStackTrace(); 
       } 
       urlQuery = GOOGLE_REQUEST_SEARCH_URL + encodedQuery + "&maxResults=10"; 

       //Toast.makeText(getApplicationContext(), urlQuery, Toast.LENGTH_SHORT).show(); 
       mAdapter.clear(); 
       mEmptyStateTextView.setText(""); // clear any message set previously 
       loadingIndicator.setVisibility(View.VISIBLE); // show loading during search 
       new BookAsyncTask().execute(urlQuery); 
      } 

     } else { 

      Toast.makeText(getApplicationContext(), "Network not available", Toast.LENGTH_SHORT).show(); 
     } 
     return true; 
    } 

EDIT: prüfen auf dieser link ein sehr gutes Tutorial, das die JSON-Daten i holen und analysieren nto JAVA-Modell mit GSON-Framework