Question

我有一个listview，我已经在ScrollListener上实现了，所以当列表到达底部时会加载更多数据。但在我的情况下，列表不止一次（三次）加载数据，我找不到导致这种情况的原因。那么有人可以帮助我！

以下是代码：

public class GameListing extends FragmentActivity implements OnScrollListener {

    private ListView list;
    private GameListingAdapter adapter;
    private ArrayList<Game> games;
    private TextView title;
    private ImageView back, menu;
    private SlidingMenu slidingMenu;
    private int jsonStart = 20;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.game_listing);
        initWidgets();
        list.setOnItemClickListener(new OnItemClickListener() {
            @Override
            public void onItemClick(AdapterView<?> arg0, View arg1,
                    int position, long arg3) {
                Intent i = new Intent(GameListing.this, GameDetails.class);
                i.putExtra("game_details", games.get(position));
                startActivity(i);
            }
        });
    }

    @SuppressWarnings("unchecked")
    private void initWidgets() {
        menu = (ImageView) findViewById(R.id.game_listing_menu);
        list = (ListView) findViewById(R.id.game_listing_list);
        title = (TextView) findViewById(R.id.game_listing_title);
        back = (ImageView) findViewById(R.id.game_listing_back);
        back.setOnClickListener(new OnClickListener() {

            @Override
            public void onClick(View arg0) {
                finish();
            }
        });

        try {
            games = (ArrayList<Game>) getIntent().getSerializableExtra(
                    "selectedGames");
            title.setText(games.get(0).getBelongTo().toUpperCase());
            adapter = new GameListingAdapter(this, games);
            list.setAdapter(adapter);
            list.setOnScrollListener(this);
        } catch (Exception e) {
            e.printStackTrace();
        }
        displayMenu();
    }

    private void displayMenu() {
        slidingMenu = new SlidingMenu(this);
        slidingMenu.setMode(SlidingMenu.RIGHT);
        slidingMenu.setTouchModeAbove(SlidingMenu.TOUCHMODE_FULLSCREEN);
        slidingMenu.setShadowWidthRes(R.dimen.slidingmenu_shadow_width);
        slidingMenu.setShadowDrawable(R.drawable.slidingmenu_shadow);
        slidingMenu.setBehindOffsetRes(R.dimen.slidingmenu_offset);
        slidingMenu.setFadeDegree(0.35f);
        slidingMenu.attachToActivity(this, SlidingMenu.SLIDING_CONTENT);
        slidingMenu.setMenu(R.layout.slidingmenu);

        menu.setOnClickListener(new OnClickListener() {

            @Override
            public void onClick(View v) {
                slidingMenu.toggle();
            }
        });
    }

    @Override
    public boolean onKeyDown(int keyCode, KeyEvent event) {
        if (keyCode == KeyEvent.KEYCODE_MENU) {
            slidingMenu.toggle();
            return true;
        }
        return super.onKeyDown(keyCode, event);
    }

    @Override
    public void onBackPressed() {
        if (slidingMenu.isMenuShowing()) {
            slidingMenu.toggle();
        } else {
            super.onBackPressed();
        }
    }

    @Override
    public void onScroll(AbsListView view, int firstVisibleItem,
            int visibleItemCount, int totalItemCount) {
        if (list.getFirstVisiblePosition() > (games.size() - 7)) {
            try {
                loadJSON();
            } catch (JSONException e) {
                e.printStackTrace();
            }
        }
    }

    @Override
    public void onScrollStateChanged(AbsListView view, int scrollState) {
    }

    public void loadJSON() throws JSONException {
        AsyncTask<Void, Void, Void> task = new AsyncTask<Void, Void, Void>() {

            @Override
            protected void onPreExecute() {
                super.onPreExecute();

            }

            @Override
            protected Void doInBackground(Void... params) {
                JSONArray json = new JSONParser()
                        .getJSONFromUrl(AppConstants.JsonURL
                                + games.get(0).getBelongTo()
                                + AppConstants.JsonLimit + jsonStart + ","
                                + (jsonStart + 20));
                loadGamesJson(json);
                jsonStart += 20;
                Log.v("--", jsonStart + " jsonStart");
                return null;
            }

            @Override
            protected void onPostExecute(Void result) {
                super.onPostExecute(result);
                adapter.notifyDataSetChanged();

            }
        };
        task.execute();
    }

    private void loadGamesJson(JSONArray json) {
        try {
            for (int i = 0; i < json.length(); i++) {
                JSONObject gameObj = json.getJSONObject(i)
                        .getJSONObject("game");
                int id = gameObj.getInt("id");
                String name = gameObj.getString("name");
                String date = gameObj.getString("release_date");
                String timeStamp = gameObj.getString("timeStamp");
                String rating = gameObj.getString("rating");
                String description = gameObj.getString("description");
                String belongsTo = gameObj.getString("belongto");

                String publisher = gameObj.getString("publisher")
                        .replace("\"", "").replace("[", "").replace("]", "");

                String platform = gameObj.getString("platform")
                        .replace("\"", "").replace("[", "").replace("]", "");

                String genre = gameObj.getString("genre").replace("\"", "")
                        .replace("[", "").replace("]", "");

                String developer = gameObj.getString("developer")
                        .replace("\"", "").replace("[", "").replace("]", "");
                String video = "";
                for (int n = 1; n <= 3; n++) {
                    video += gameObj.getString("video" + n) + ",";
                }

                video = video.substring(0, video.length() - 1);
                String gameImage = gameObj.getString("game_img");
                games.add(new Game(id, name, date, timeStamp, rating,
                        description, publisher, gameImage, developer, platform,
                        genre, belongsTo, video, false));
            }

        } catch (JSONException e) {
            e.printStackTrace();
        }
    }

}

Answer 1

我找到了一个解决方案，似乎就像@Prasad所指的那样。我在课堂上添加了这个：

private int visibleThreshold = 5;
        private int currentPage = 0;
        private int previousTotal = 0;
        private boolean loading = true;

这就是我onScroll()的样子

@Override
    public void onScroll(AbsListView view, int firstVisibleItem,
            int visibleItemCount, int totalItemCount) {
        if (loading) {
            if (totalItemCount > previousTotal) {
                loading = false;
                previousTotal = totalItemCount;
                currentPage++;
            }
        }
        if (!loading
                && (totalItemCount - visibleItemCount) <= (firstVisibleItem + visibleThreshold)) {
            // I load the next page of gigs using a background task,
            // but you can call any function here.
            try {
                loadJSON();
            } catch (JSONException e) {
                e.printStackTrace();
            }
            loading = true;
        }

    }

在加载新的json时，在asynctask中将加载设置为false。我还建议您查看this。

列表视图加载更多滚动执行三次

1 个答案: