java - 空 View 不显示在 ListView 中

Question

我正在尝试没有互联网连接时显示空 View 没有互联网连接，并且在未找到书籍时不显示任何书籍

这是我的代码

public class MainActivity extends AppCompatActivity {
private static final String BOOK_REQUEST_URL = "https://www.googleapis.com/books/v1/volumes?q=";
public static final String LOG_TAG = MainActivity.class.getName();
// search button
private Button search_button;
// edit text to use for search
private EditText editText;
// string used to get string from edit text.
private String queryWord = null;
private TextView emptyTextView;
private ListView bookListView;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    search_button = (Button) findViewById(R.id.next_button);
    editText = (EditText) findViewById(R.id.edit_text);
    emptyTextView = (TextView) findViewById(R.id.empty_view);

    bookListView = (ListView) findViewById(R.id.list_view);

    // Get a reference to the ConnectivityManager to check state of network connectivity
    ConnectivityManager connMgr = (ConnectivityManager)
            getSystemService(Context.CONNECTIVITY_SERVICE);

    // Get details on the currently active default data network
    final NetworkInfo networkInfo = connMgr.getActiveNetworkInfo();

这里我想在没有连接时给我没有互联网连接`

 search_button.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            if (networkInfo != null && networkInfo.isConnected()) {

                new GetBook().execute(BOOK_REQUEST_URL);
            } else {

                emptyTextView.setText(R.string.NoConnect);
                bookListView.setEmptyView(emptyTextView);

            }
        }

    });
    new GetBook().execute(BOOK_REQUEST_URL);
}
//  method to get string from edit text.
public String getBook() {
    queryWord = editText.getText().toString();
    if (queryWord == null) {
        bookListView.setEmptyView(emptyTextView);
    }
    return queryWord;
}

/**
 * Update the UI with the given book information.
 */
private void updateUi(List<Book> books) {

    // Find a reference to the {@link ListView} in the layout

    // Create a new {@link ArrayAdapter} of book
    final BookAdapter adapter = new BookAdapter(this, books);

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

}
// inner class for to support methods do in the background.
private class GetBook extends AsyncTask<String, Void, List<Book>> {

    @Override
    protected List<Book> doInBackground(String... urls) {
        String word_search = getBook();
        // Don't perform the request if there are no URLs, or the first URL is null.
        if (urls.length < 1 || urls[0] == null) {
            return null;
        }
        List<Book> result = QueryUtils.fetchBookName(urls[0], word_search);
        return result;
    }

    /**
     * This method is invoked on the main UI thread after the background work has been
     * completed.
     * <p>
     * It IS okay to modify the UI within this method. We take the {@link Book} object
     * (which was returned from the doInBackground() method) and update the views on the screen.
     */

这里我想不显示列表书

    @Override
        protected void onPostExecute(List<Book> book) {

            emptyTextView.setText(R.string.nobook);
            bookListView.setEmptyView(emptyTextView);

            // Hide loading indicator because the data has been loaded
            View loadingIndicator = findViewById(R.id.loading_indicator);
            loadingIndicator.setVisibility(View.GONE);
            if ((book != null) && !book.isEmpty()) {
                updateUi(book);
            }

        }
    }
}

我尝试了更多步骤，但没有任何反应

Answer 1

try this

View  emptyV = getActivity().getLayoutInflater().inflate(R.layout.empty_view, null);
                    TextView tvMSG = (TextView) emptyV.findViewById(R.id.tvMSG);
                    tvMSG.setText("No product available.");
                    ViewGroup viewGroup= (ViewGroup) listView.getParent();                  
                    viewGroup.addView(emptyV, new ViewGroup.LayoutParams(ViewGroup.LayoutParams.MATCH_PARENT,
                            ViewGroup.LayoutParams.MATCH_PARENT)); 
                    listView.setEmptyView(emptyV);