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好的 这个 Android ( Java ) 应用程序搜索 Google App API 并在列表视图中显示书籍。它使用自定义适配器和异步加载器。我有一个应用程序的骨架，但只有一次搜索。之后，一切都停留在屏幕上，新的搜索不会发生，或者似乎不会发生。

我让它在创建时从 MainActivity 工作，但随后将其移至按钮和 EditText。

我认为问题主要存在于这个文件中。

如果有人可以提供帮助，那就太好了！查看 goQuery 按钮单击下的最后一部分。谢谢。

公共类 MainActivity 扩展 AppCompatActivity 实现 LoaderCallbacks> { private static final String LOG_TAG = MainActivity.class.getName(); 私有字符串 GOOGLE_REQUEST_URL = " https://www.googleapis.com/books/v1/volumes?q=android&maxResults=10 "; /** * Book loader ID 的常量值。我们可以选择任何整数。* 这真的只有在你使用多个加载器时才会起作用。*/ 私有静态最终 int BOOK_LOADER_ID = 1;

/** Adapter for the list of books */
private BookWormAdapter mAdapter;

/** TextView that is displayed when the list is empty */
private TextView mEmptyStateTextView;

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


    ListView bookwormListView = (ListView) findViewById(R.id.list);

    mEmptyStateTextView = (TextView) findViewById(R.id.empty_view);
    bookwormListView.setEmptyView(mEmptyStateTextView);

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

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

    // Set an item click listener on the ListView, which sends an intent to a web browser
    // to open a website with more information about the selected book.
    bookwormListView.setOnItemClickListener(new AdapterView.OnItemClickListener() {
        @Override
        public void onItemClick(AdapterView<?> adapterView, View view, int position, long l) {
            // Find the current book that was clicked on
            Book currentBook = mAdapter.getItem(position);

            // Convert the String URL into a URI object (to pass into the Intent constructor)
            Uri bookwormUri = Uri.parse(currentBook.getPreviewLink());

            // Create a new intent to view the book URI
            Intent websiteIntent = new Intent(Intent.ACTION_VIEW, bookwormUri);

            // Send the intent to launch a new activity
            startActivity(websiteIntent);
        }
    });

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


@Override
public Loader<List<Book>> onCreateLoader(int i, Bundle bundle) {
    // Create a new loader for the given URL
    //Log.i(LOG_TAG, "onCreateLoader: TEST Created Loader!");
    return new BookWormLoader(this, GOOGLE_REQUEST_URL);
}



@Override
public void onLoadFinished(Loader<List<Book>> loader, List<Book> bookworms) {
    // Hide loading indicator because the data has been loaded
    View loadingIndicator = findViewById(R.id.loading_indicator);
    loadingIndicator.setVisibility(View.GONE);
    //  Log.i(LOG_TAG, "onLoadFinished: On Load finished!");
    // Set empty state text to display "No books found."
    mEmptyStateTextView.setText(R.string.no_books);

    // Clear the adapter of previous book data
    mAdapter.clear();

    // If there is a valid list of {@link Book}s, then add them to the adapter's
    // data set. This will trigger the ListView to update.
    if (bookworms != null && !bookworms.isEmpty()) {
        mAdapter.addAll(bookworms);
        //mAdapter.notifyDataSetChanged();
    }
}

@Override
public void onLoaderReset(Loader<List<Book>> loader) {
    // Loader reset, so we can clear out our existing data.
    mAdapter.clear();
    //  Log.i(LOG_TAG, "onLoaderReset: TEST On Loader Reset!");
}
public void goQuery(View view){
    EditText mySearchTextView = findViewById(R.id.searchEdit);

    `enter code here`if (mySearchTextView.getText().length() < 1) return;

    //mAdapter.clear();
  // mAdapter.notifyDataSetChanged();


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

    GOOGLE_REQUEST_URL = "https://www.googleapis.com/books/v1/volumes?q="+mySearchTextView.getText()+"&maxResults=20";

    // 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
    NetworkInfo networkInfo = connMgr.getActiveNetworkInfo();

    // If there is a network connection, fetch data
    if (networkInfo != null && networkInfo.isConnected()) {
        // Get a reference to the LoaderManager, in order to interact with loaders.
        android.app.LoaderManager loaderManager = getLoaderManager();

// 初始化加载器。传入上面定义的 int ID 常量，并为 // bundle 传入 null。为 LoaderCallbacks 参数传入此活动（这是有效的 // 因为此活动实现了 LoaderCallbacks 接口）。loaderManager.initLoader(BOOK_LOADER_ID, null, this); } else { // 否则，显示错误 // 首先，隐藏加载指示器，以便显示错误消息 loadingIndicator.setVisibility(View.GONE);

        // Update empty state with no connection error message
        mEmptyStateTextView.setText(R.string.no_internet_connection);
    }

}

}

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1 回答 1

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我将它添加到 buttonClick 中，它现在正在工作。不知道这是不是真的Kosher？

loaderManager.destroyLoader(BOOK_LOADER_ID); mAdapter.clear(); mAdapter.notifyDataSetChanged() enter code here;

于 2020-03-27T20:02:29.730 回答