空视图不在列表视图中显示

Question

当我没有互联网连接时，我试图显示空白视图，而当找不到书时，我不显示书

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();

在这里我想在没有连接时不给我互联网连接

 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.
     */

在这里我不想显示清单书

    @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，却没有反应

Answer 1

尝试这个

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);  

Answer 2

您可以为empty状态添加另一个layout ，并根据list大小进行实用的show/hide 。

这是一个例子：

activity_main.xml中

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout
    xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    android:id="@+id/container"
    android:layout_height="match_parent"
    android:layout_width="match_parent">

    <ListView
        android:id="@+id/list_view"
        android:layout_width="match_parent"
        android:layout_height="match_parent" />

    <RelativeLayout
        android:id="@+id/layout_empty"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_centerVertical="true"
        android:layout_centerHorizontal="true"
        android:visibility="gone"
        android:layout_margin="30dp">

        <ImageView
            android:id="@+id/image_empty"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_centerHorizontal="true"
            android:src="@mipmap/ic_launcher"/>

        <TextView
            android:id="@+id/text_empty"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_centerHorizontal="true"
            android:layout_below="@id/image_empty"
            android:layout_marginTop="16dp"
            android:gravity="center"
            android:textSize="20sp"
            android:textStyle="bold"
            android:textColor="@color/textColorPrimary"
            android:text="Oops!"/>

        <TextView
            android:id="@+id/text_empty_hints"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_centerHorizontal="true"
            android:layout_below="@id/text_empty"
            android:layout_marginTop="16dp"
            android:gravity="center"
            android:textSize="14sp"
            android:textStyle="bold"
            android:textColor="@color/textColorSecondary"
            android:text="No items found"/>
    </RelativeLayout>
</RelativeLayout>

MainActivity.java：

private ListView bookListView;
private RelativeLayout layoutEmpty;

.......
............

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

    bookListView = (ListView) findViewById(R.id.list_view);
    layoutEmpty = (RelativeLayout) findViewById(R.id.layout_empty);

    .......
    ...........
}

private void updateUi(List<Book> books) {

    if(books.size() > 0) {
        layoutEmpty.setVisibility(View.GONE);
        bookListView.setVisibility(View.VISIBLE);
    } else {
        layoutEmpty.setVisibility(View.VISIBLE);
        bookListView.setVisibility(View.GONE);
    }
}

OUTPUT：

希望这会有所帮助〜