Question

我正在处理新闻应用，我希望每次都在ListView向下滑动更新MainActivity 这是我MainActivity下面的代码：

package com.infinitystone.mani.news;

import android.app.LoaderManager;
import android.app.LoaderManager.LoaderCallbacks;
import android.content.Context;
import android.content.Loader;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.net.ConnectivityManager;
import android.net.NetworkInfo;
import android.net.Uri;
import android.os.Bundle;
import android.support.customtabs.CustomTabsIntent;
import android.support.v4.content.ContextCompat;
import android.support.v7.app.AppCompatActivity;
import android.view.View;
import android.widget.AdapterView;
import android.widget.ListView;
import android.widget.TextView;

import java.util.ArrayList;
import java.util.List;

public class MainActivity extends AppCompatActivity implements LoaderCallbacks<List<News>> {

    public static final String LOG_TAG = MainActivity.class.getName();

    private static final int NEWS_LOADER_ID = 1;

    private TextView mEmptyView;

    private NewsAdapter mAdapter;

    private static final String GUARDIAN_REQUEST_URL = "http://content.guardianapis.com/search?order-by=newest&show-fields=thumbnail&page-size=20&api-key=2f3badbb-4a58-44b8-9800-9ee2a0f445f9";

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

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

        mEmptyView = (TextView) findViewById(R.id.empty_view);
        newsList.setEmptyView(mEmptyView);

        mAdapter = new NewsAdapter(this, new ArrayList<News>());
        newsList.setAdapter(mAdapter);

        newsList.setOnItemClickListener(new AdapterView.OnItemClickListener() {
            @Override
            public void onItemClick(AdapterView<?> parent, View view, int position, long id) {
                News currentNews = mAdapter.getItem(position);
                Uri uri = Uri.parse(currentNews.getUrl());

                CustomTabsIntent.Builder builder = new CustomTabsIntent.Builder();

                builder.setToolbarColor(ContextCompat.getColor(MainActivity.this, R.color.colorPrimary));
                builder.setSecondaryToolbarColor(ContextCompat.getColor(MainActivity.this, R.color.colorPrimaryDark));

                builder.setShowTitle(true);

                final Bitmap backButton = BitmapFactory.decodeResource(getResources(), R.drawable.ic_arrow_back_white_24dp);
                builder.setCloseButtonIcon(backButton);

                CustomTabsIntent customTabsIntent = builder.build();
                customTabsIntent.launchUrl(MainActivity.this, uri);

            }
        });

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

        NetworkInfo networkInfo = connMgr.getActiveNetworkInfo();

        if(networkInfo != null && networkInfo.isConnected()){
            LoaderManager loaderManager = getLoaderManager();

            loaderManager.initLoader(NEWS_LOADER_ID, null, this);
        }

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

            mEmptyView.setText(R.string.no_internet);
        }
    }

    @Override
    public Loader<List<News>> onCreateLoader(int i, Bundle bundle) {
        // Create a new loader for the given URL
        return new NewsLoader(this, GUARDIAN_REQUEST_URL);
    }

    @Override
    public void onLoadFinished(Loader<List<News>> loader, List<News> news) {
        View loadingIndicator = findViewById(R.id.loading_indicator);
        loadingIndicator.setVisibility(View.GONE);

        mEmptyView.setText(R.string.no_news);

        mAdapter.clear();

        if (news != null && !news.isEmpty()) {
            mAdapter.addAll(news);
        }
    }

    @Override
    public void onLoaderReset(Loader<List<News>> loader) {
        // Loader reset, so we can clear out our existing data.
        mAdapter.clear();
    }
}

我已在android.support.v4.widget.SwipeRefreshLayout档案中添加了activity_main.xml 如何在java代码中实现SwipeRefreshLayout？获取新闻数据的代码：

package com.infinitystone.mani.news;


import android.text.TextUtils;
import android.util.Log;

import org.json.JSONArray;
import org.json.JSONException;
import org.json.JSONObject;

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.net.HttpURLConnection;
import java.net.MalformedURLException;
import java.net.URL;
import java.nio.charset.Charset;
import java.util.ArrayList;
import java.util.List;

import static com.infinitystone.mani.news.MainActivity.LOG_TAG;

public class QueryUtils {


    private QueryUtils() {

    }

    public static List<News> fetchNewsData(String requestUrl) {
        URL url = createUrl(requestUrl);

        String jsonResponse = null;
        try {
            jsonResponse = makeHttpRequest(url);
        } catch (IOException e) {
            Log.e(LOG_TAG, "Problem making the HTTP request.", e);
        }

        List<News> news = extractFeaturesFromJson(jsonResponse);

        return news;
    }

    private static URL createUrl(String stringUrl) {
        URL url = null;
        try {
            url = new URL(stringUrl);
        } catch (MalformedURLException e) {
            Log.e(LOG_TAG, "Problem building the URL ", e);
        }
        return url;
    }

    private static String makeHttpRequest(URL url) throws IOException {
        String jsonResponse = "";

        // If the URL is null, then return early.
        if (url == null) {
            return jsonResponse;
        }

        HttpURLConnection urlConnection = null;
        InputStream inputStream = null;
        try {
            urlConnection = (HttpURLConnection) url.openConnection();
            urlConnection.setReadTimeout(10000 /* milliseconds */);
            urlConnection.setConnectTimeout(15000 /* milliseconds */);
            urlConnection.setRequestMethod("GET");
            urlConnection.connect();

            // If the request was successful (response code 200),
            // then read the input stream and parse the response.
            if (urlConnection.getResponseCode() == 200) {
                inputStream = urlConnection.getInputStream();
                jsonResponse = readFromStream(inputStream);
            } else {
                Log.e(LOG_TAG, "Error response code: " + urlConnection.getResponseCode());
            }
        } catch (IOException e) {
            Log.e(LOG_TAG, "Problem retrieving the earthquake JSON results.", e);
        } finally {
            if (urlConnection != null) {
                urlConnection.disconnect();
            }
            if (inputStream != null) {
                // Closing the input stream could throw an IOException, which is why
                // the makeHttpRequest(URL url) method signature specifies than an IOException
                // could be thrown.
                inputStream.close();
            }
        }
        return jsonResponse;
    }

    private static String readFromStream(InputStream inputStream) throws IOException {
        StringBuilder output = new StringBuilder();
        if (inputStream != null) {
            InputStreamReader inputStreamReader = new InputStreamReader(inputStream, Charset.forName("UTF-8"));
            BufferedReader reader = new BufferedReader(inputStreamReader);
            String line = reader.readLine();
            while (line != null) {
                output.append(line);
                line = reader.readLine();
            }
        }
        return output.toString();
    }

    private static List<News> extractFeaturesFromJson(String newsJSON) {

        if (TextUtils.isEmpty(newsJSON)) {
            return null;
        }

        List<News> news = new ArrayList<>();

        try {
            JSONObject rootObject = new JSONObject(newsJSON);

            JSONObject responseObject = rootObject.getJSONObject("response");

            JSONArray resultsArray = responseObject.getJSONArray("results");

            for (int i = 0; i < resultsArray.length(); i++) {
                JSONObject currentNews = resultsArray.getJSONObject(i);

                String title = currentNews.getString("webTitle");

                String titleUrl = currentNews.getString("webUrl");

                String date = currentNews.getString("webPublicationDate");

                JSONObject fields = currentNews.getJSONObject("fields");

                String thumbnail = fields.getString("thumbnail");

                News news1 = new News(title, thumbnail, date, titleUrl);

                news.add(news1);
            }
        } catch (JSONException e) {
            Log.e("QueryUtils", "Problem parsing the earthquake JSON results", e);
        }

        return news;
    }
}

Answer 1

获取滑动的参考以刷新布局。

private SwipeRefreshLayout swipeRefreshLayout;

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

    swipeRefreshLayout = (SwipeRefreshLayout) view.findViewById(R.id.refresh);

    swipeRefreshLayout.setOnRefreshListener(this);

    // ... your other codes...

}

现在，让你的活动实现监听器。

public class MainActivity extends AppCompatActivity implements LoaderCallbacks<List<News>>, SwipeRefreshLayout.OnRefreshListener {

    // ... 

}

最后实现那些方法

 @Override
  public void onRefresh(){
     swipeRefreshLayout.setRefreshing(true);

     newsList = fetchNewsData(GUARDIAN_REQUEST_URL);
     mAdapter.notifyDataSetChanged(); 

     swipeRefreshLayout.setRefreshing(false);

  }

编辑：

以下是MainActivity的完整代码。请使用此功能，如果有效，请告诉我。

import android.app.LoaderManager;
import android.app.LoaderManager.LoaderCallbacks;
import android.content.Context;
import android.content.Loader;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.net.ConnectivityManager;
import android.net.NetworkInfo;
import android.net.Uri;
import android.os.Bundle;
import android.support.customtabs.CustomTabsIntent;
import android.support.v4.content.ContextCompat;
import android.support.v4.widget.SwipeRefreshLayout;
import android.support.v7.app.AppCompatActivity;
import android.view.View;
import android.widget.AdapterView;
import android.widget.ListView;
import android.widget.TextView;

import java.util.ArrayList;
import java.util.List;

public class MainActivity extends AppCompatActivity implements LoaderCallbacks<List<News>>, SwipeRefreshLayout.OnRefreshListener {

    public static final String LOG_TAG = MainActivity.class.getName();

    private static final int NEWS_LOADER_ID = 1;

    private TextView mEmptyView;

    private NewsAdapter mAdapter;

    private static final String GUARDIAN_REQUEST_URL = "http://content.guardianapis.com/search?order-by=newest&show-fields=thumbnail&page-size=20&api-key=2f3badbb-4a58-44b8-9800-9ee2a0f445f9";

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

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

        mEmptyView = (TextView) findViewById(R.id.empty_view);
        newsList.setEmptyView(mEmptyView);

        mAdapter = new NewsAdapter(this, new ArrayList<News>());
        newsList.setAdapter(mAdapter);

        swipeRefreshLayout = (SwipeRefreshLayout) view.findViewById(R.id.refresh);

        swipeRefreshLayout.setOnRefreshListener(this);

        newsList.setOnItemClickListener(new AdapterView.OnItemClickListener() {
            @Override
            public void onItemClick(AdapterView<?> parent, View view, int position, long id) {
                News currentNews = mAdapter.getItem(position);
                Uri uri = Uri.parse(currentNews.getUrl());

                CustomTabsIntent.Builder builder = new CustomTabsIntent.Builder();

                builder.setToolbarColor(ContextCompat.getColor(MainActivity.this, R.color.colorPrimary));
                builder.setSecondaryToolbarColor(ContextCompat.getColor(MainActivity.this, R.color.colorPrimaryDark));

                builder.setShowTitle(true);

                final Bitmap backButton = BitmapFactory.decodeResource(getResources(), R.drawable.ic_arrow_back_white_24dp);
                builder.setCloseButtonIcon(backButton);

                CustomTabsIntent customTabsIntent = builder.build();
                customTabsIntent.launchUrl(MainActivity.this, uri);

            }
        });

        updateNewsList();


    }

    private void updateNewsList(){
        ConnectivityManager connMgr = (ConnectivityManager) getSystemService(Context.CONNECTIVITY_SERVICE);

        NetworkInfo networkInfo = connMgr.getActiveNetworkInfo();

        if(networkInfo != null && networkInfo.isConnected()){
            LoaderManager loaderManager = getLoaderManager();

            loaderManager.initLoader(NEWS_LOADER_ID, null, this);
        }

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

            mEmptyView.setText(R.string.no_internet);
        }
    }

    @Override
    public Loader<List<News>> onCreateLoader(int i, Bundle bundle) {
        // Create a new loader for the given URL
        return new NewsLoader(this, GUARDIAN_REQUEST_URL);
    }

    @Override
    public void onLoadFinished(Loader<List<News>> loader, List<News> news) {
        View loadingIndicator = findViewById(R.id.loading_indicator);
        loadingIndicator.setVisibility(View.GONE);

        mEmptyView.setText(R.string.no_news);

        mAdapter.clear();

        if (news != null && !news.isEmpty()) {
            mAdapter.addAll(news);
        }
    }

    @Override
    public void onLoaderReset(Loader<List<News>> loader) {
        // Loader reset, so we can clear out our existing data.
        mAdapter.clear();
    }


    @Override
    public void onRefresh() {
       swipeRefreshLayout.setRefreshing(true);
       updateNewsList();
       swipeRefreshLayout.setRefreshing(false);

    }
}

Answer 2

尝试this回应刷新手势，它应该会有所帮助。

Answer 3

as per my above comment使用 SwipeRefreshLayout

只要用户可以通过垂直滑动手势刷新视图内容，就应该使用SwipeRefreshLayout。实例化此视图的活动应添加OnRefreshListener，以便在刷卡刷新手势完成时通知。 SwipeRefreshLayout将在每次手势再次完成时通知侦听器;

将 setOnRefreshListener 设置为SwipeRefreshLayout

void setOnRefreshListener (SwipeRefreshLayout.OnRefreshListener listener)

设置要在通过滑动手势触发刷新时通知的侦听器。

示例代码

SwipeRefreshLayout mSwipeRefreshView;
mSwipeRefreshView = (SwipeRefreshLayout) findViewById(R.id.homeScreenSwipeRefreshView);

mSwipeRefreshView.setOnRefreshListener(new SwipeRefreshLayout.OnRefreshListener() {
            @Override
            public void onRefresh() {

                // make your api request here
            }
        });

当您的api请求完成后，请使用 setRefreshing(false)

setRefreshing(boolean refreshing)
通知小部件刷新状态已更改。

mSwipeRefreshView.setRefreshing(false);

如何在列表视图中添加滑动到刷新

3 个答案: