使用android自动加载更多项目

Question

我有这段代码可以从网站上获取JSON数据，并且运行良好

我想做的是，加载10个项目，当用户滚动到底部时，它加载另外10个项目...等，直到项目完成

public class MainActivity extends Activity  {
    private static final String TAG = MainActivity.class.getSimpleName();
    private ListView listView;
    private FeedListAdapter listAdapter;
    private List<FeedItem> feedItems;

    //Feeds URL - Your Website URL where you uploaded the admin panel
    private String URL_FEED = "http://EXAMPLE.COM";


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




        //Getting feeds from the website into listview 
        listView = (ListView) findViewById(R.id.list);
        feedItems = new ArrayList<FeedItem>();
        listAdapter = new FeedListAdapter(this, feedItems);
        listView.setAdapter(listAdapter);



            // making fresh volley request and getting json
            JsonObjectRequest jsonReq = new JsonObjectRequest(Method.GET,
                    URL_FEED, null, new Response.Listener<JSONObject>() {

                        @Override
                        public void onResponse(JSONObject response) {
                            VolleyLog.d(TAG, "Response: " + response.toString());
                            if (response != null) {
                                parseJsonFeed(response);
                            }
                        }
                    }, new Response.ErrorListener() {

                        @Override
                        public void onErrorResponse(VolleyError error) {
                            VolleyLog.d(TAG, "Error: " + error.getMessage());
                        }
                    });

            // Adding request to volley request queue
            AppController.getInstance().addToRequestQueue(jsonReq);


    }

    /**
     * Parsing json reponse and passing the data to feed view list adapter
     * */
    private void parseJsonFeed(JSONObject response) {
        try {
            JSONArray feedArray = response.getJSONArray("feed");

            for (int i = 0; i < feedArray.length(); i++) {
                JSONObject feedObj = (JSONObject) feedArray.get(i);

                FeedItem item = new FeedItem();
                item.setId(feedObj.getInt("id"));
                item.setName(feedObj.getString("name"));

                // Image might be null sometimes
                String image = feedObj.isNull("image") ? null : feedObj
                        .getString("image");
                item.setImge(image);
                item.setStatus(feedObj.getString("status"));
                item.setProfilePic(feedObj.getString("profilePic"));
                item.setTimeStamp(feedObj.getString("timeStamp"));

                // url might be null sometimes
                String feedUrl = feedObj.isNull("url") ? null : feedObj
                        .getString("url");
                item.setUrl(feedUrl);

                feedItems.add(item);
            }

            // notify data changes to list adapater
            listAdapter.notifyDataSetChanged();
        } catch (JSONException e) {
            e.printStackTrace();
        }
    }


    ///Menus functions
    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        getMenuInflater().inflate(R.menu.main, menu);
        return true;
    }

    @Override
    public boolean onOptionsItemSelected(MenuItem item) {
        int itemId = item.getItemId();

        switch (itemId) {
        case R.id.action_logout:
            session.logoutUser();
            break;
        case R.id.myProfile:
            Intent intent2 = new Intent(this, ProfileActivity.class);
            startActivity(intent2);
            break;
        case R.id.addPhoto:
            Intent intent1 = new Intent(this, UploadPhoto.class);
            startActivity(intent1);
            break;
        }

        // TODO Auto-generated method stub
        return super.onOptionsItemSelected(item);
    }



}

Answer 1

实现onscrolllistener()

public void onScroll(AbsListView view, int firstVisibleItem, int visibleItemCount, int totalItemCount) {
    this.currentFirstVisibleItem = firstVisibleItem;
    this.currentVisibleItemCount = visibleItemCount;
}

public void onScrollStateChanged(AbsListView view, int scrollState) {
    this.currentScrollState = scrollState;
    this.isScrollCompleted();
 }

private void isScrollCompleted() {
    if (this.currentVisibleItemCount > 0 && this.currentScrollState == SCROLL_STATE_IDLE) {
        /*** In this way I detect if there's been a scroll which has completed ***/
        /*** do the work for load more date! ***/
        if(!isLoading){
             isLoading = true;
             GetMoreJsonData();
        }
    }
}

当您实现并将此侦听器添加到listview时，这将检测到listview的末尾，因为滚动位置位于list的末尾只是获得了更多数据。 在加载数据期间，滚动位置结束时，您需要一个标志来立即加载数据。 因此，如果正在加载数据，并且在此期间您向上滚动然后向下滚动，则将不会获得更多要复制的数据。

您可以创建一个新方法，并移动发出新的齐射请求并在其中获取json的代码：

private void GetMoreJsonData()
{
    // making fresh volley request and getting json
    JsonObjectRequest jsonReq = new JsonObjectRequest(Method.GET,
            URL_FEED, null, new Response.Listener<JSONObject>() {
                @Override
                public void onResponse(JSONObject response) {
                    VolleyLog.d(TAG, "Response: " + response.toString());
                    if (response != null) {
                        parseJsonFeed(response);
                    }
                }
            }, new Response.ErrorListener() {
                @Override
                public void onErrorResponse(VolleyError error) {
                    VolleyLog.d(TAG, "Error: " + error.getMessage());
                }
            });

    // Adding request to volley request queue
    AppController.getInstance().addToRequestQueue(jsonReq);     
}

发送json请求时不要忘记获得10-10个项目