android - 屏幕旋转时Listview不保存项目 - Android Studio

Question

好的，我有一个通过 JSON 获取数据的新闻程序。它有一个自定义适配器，主要包括字符串和图像。屏幕顶部有一个搜索按钮和用于搜索条件的 editText。这还没有起作用，但稍后会很容易修复。无论如何它工作正常，但是当我旋转屏幕时，数据消失了，你必须再次按下搜索按钮。但实际上它永远不会重新加载数据。我希望它是主要活动中的内容，所以我将其包含在此处。任何帮助，将不胜感激！

package com.example.android.newsreport;

import android.app.LoaderManager.LoaderCallbacks;
import android.content.Context;
import android.content.DialogInterface;
import android.content.Intent;
import android.content.Loader;
import android.net.ConnectivityManager;
import android.net.NetworkInfo;
import android.net.Uri;
import android.os.Bundle;
import android.view.View;
import android.view.inputmethod.InputMethodManager;
import android.widget.AdapterView;
import android.widget.EditText;
import android.widget.ListView;
import android.widget.TextView;
import androidx.appcompat.app.AlertDialog;
import androidx.appcompat.app.AppCompatActivity;
import java.util.ArrayList;
import java.util.List;

public class NewsReportActivity extends AppCompatActivity
        implements LoaderCallbacks<List<Story>> {
    private static final String LOG_TAG = NewsReportActivity.class.getName();
    private  String NewsApiUrl ="http://newsapi.org/v2/top-headlines?sources=bbc-news&apiKey=021abbfbc4de4c33b1644057d5f2be58";
    /**
     * Constant value for the Book loader ID. We can choose any integer.
     * This really only comes into play if you're using multiple loaders.
     */
    private static final int BOOK_LOADER_ID = 1;
    private static String TAG = "MainActivity";
    /** Adapter for the list of books */
    private StoryAdapter mAdapter;
    private StoryAdapter saveStateAdapter;

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


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


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

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

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


        // Set the adapter on the {@link ListView}
        // so the list can be populated in the user interface
        newsListView.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.
        newsListView.setOnItemClickListener(new AdapterView.OnItemClickListener() {
            @Override
            public void onItemClick(AdapterView<?> adapterView, View view, int position, long l) {
                // Find the current book that was clicked on
                Story currentstory = mAdapter.getItem(position);

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

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

                // 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<Story>> onCreateLoader(int i, Bundle bundle) {
        // Create a new loader for the given URL
        return new StoryLoader(this, NewsApiUrl);
    }



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

        // 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<Story>> loader) {
        // Loader reset, so we can clear out our existing data.
        mAdapter.clear();

    }
    public void goQuery(View view){
        EditText mySearchTextView = findViewById(R.id.searchEdit);
        if (mySearchTextView.getText().length() < 1) return;
        // ListView newsListView = (ListView) findViewById(R.id.list);
        //  TextView bookwormTextView = (TextView) findViewById(R.id.empty_view);



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

        NewsApiUrl = "http://newsapi.org/v2/top-headlines?sources=bbc-news&apiKey=021abbfbc4de4c33b1644057d5f2be58";
        ConnectivityManager connMgr = (ConnectivityManager)
                getSystemService(Context.CONNECTIVITY_SERVICE);

        // Get details on the currently active default data network
        NetworkInfo networkInfo = connMgr.getActiveNetworkInfo();
        // Get a reference to the LoaderManager, in order to interact with loaders.
        android.app.LoaderManager loaderManager = getLoaderManager();
        loaderManager.destroyLoader(BOOK_LOADER_ID);
        mAdapter.clear();
        mAdapter.notifyDataSetChanged();

        // If there is a network connection, fetch data
        if (networkInfo != null && networkInfo.isConnected()) {

// Initialize the loader. Pass in the int ID constant defined above and pass in null for
            // the bundle. Pass in this activity for the LoaderCallbacks parameter (which is valid
            // because this activity implements the LoaderCallbacks interface).

            loaderManager.initLoader(BOOK_LOADER_ID, null, this);

        } else {
            // Otherwise, display error
            // First, hide loading indicator so error message will be visible
            loadingIndicator.setVisibility(View.GONE);

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

        InputMethodManager imm = (InputMethodManager)getSystemService(Context.INPUT_METHOD_SERVICE);

        imm.hideSoftInputFromWindow(mySearchTextView.getWindowToken(), 0);
    }


}

标签： androidlistviewrotationadapterscreen