如何在列表视图中添加滑动刷新

Question

I am working on a news app and I want to update the ListView every time by swiping down in the MainActivity
This is the code of my MainActivity below:

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();
    }
}  

I have already added the android.support.v4.widget.SwipeRefreshLayout in my activity_main.xml file
How can I implement the SwipeRefreshLayout in java code ?
Code for fetching the news data:

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

Get a reference to your swipe to refresh layout.

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...

}

Now, make your activity implement the listener.

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

    // ... 

}

Finally implement those methods

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

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

     swipeRefreshLayout.setRefreshing(false);

  }

EDIT:

Here is the complete code for MainActivity . Please use this and let me know if this works.

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

试试这个响应刷新手势，它应该会有所帮助。

Answer 3

as per my above comment use SwipeRefreshLayout

The SwipeRefreshLayout should be used whenever the user can refresh the contents of a view via a vertical swipe gesture. The activity that instantiates this view should add an OnRefreshListener to be notified whenever the swipe to refresh gesture is completed. The SwipeRefreshLayout will notify the listener each and every time the gesture is completed again;

than set setOnRefreshListener to your SwipeRefreshLayout

void setOnRefreshListener (SwipeRefreshLayout.OnRefreshListener listener)

Set the listener to be notified when a refresh is triggered via the swipe gesture.

sample code

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

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

                // make your api request here
            }
        });

when your api request complted than use setRefreshing(false)

 setRefreshing(boolean refreshing)

Notify the widget that refresh state has changed.

mSwipeRefreshView.setRefreshing(false);