延迟加载实现错误

Question

我正在尝试在选项卡片段中的listview上实现延迟加载，以加载数组abc的元素。我正在尝试加载10个元素，然后当用户向下滚动时，将加载下10个元素。但我的应用程序无法正常工作，因为我无法跳转到UI线程以便更新它（runonUithread（returnRes）;不工作）。告诉你[请看下面的代码并建议实现延迟加载的正确方法。谢谢。

片段类：

package com.example.abe;

import java.util.ArrayList;
import android.annotation.TargetApi;
import android.app.Activity;
import android.content.Context;
import android.os.Build;
import android.os.Bundle;
import android.support.v4.app.ListFragment;
import android.util.Log;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.AbsListView;
import android.widget.AbsListView.OnScrollListener;
import android.widget.ArrayAdapter;
import android.widget.ListView;

@TargetApi(Build.VERSION_CODES.HONEYCOMB)
public class Tab1Fragment extends ListFragment {
    ListView lv;
    Activity act = this.getActivity();
    Context ct = this.getActivity();
    XMLGettersSetters data;
    boolean loadingMore = false;
    String abc[] = new String[50];
    static int count = 0;
    int itemsPerPage = 10;
    ArrayList<String> myListItems;
    ArrayList<String> myListItems2;
    ArrayAdapter<String> adapter;
    static int size = 0;

    @SuppressWarnings("unused")
    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
            Bundle savedInstanceState) {
        if (container == null) {
            return null;
        }
        myListItems2 = new ArrayList<String>();
        adapter = new ArrayAdapter<String>(getActivity().getBaseContext(),
                android.R.layout.simple_list_item_1, myListItems2);
        View root = inflater.inflate(R.layout.tab_frag1_layout, container,
                false);
        lv = (ListView) root.findViewById(android.R.id.list);
        lv.setAdapter(adapter);
        return root;
    }

    @Override
    public void onViewCreated(View view, Bundle savedInstanceState) {
        super.onViewCreated(view, savedInstanceState);
        myListItems = new ArrayList<String>();
        View footerView = ((LayoutInflater) this.getActivity()
                .getSystemService(Context.LAYOUT_INFLATER_SERVICE)).inflate(
                R.layout.listfooter, null, false);
        this.getListView().addFooterView(footerView);
        this.setListAdapter(adapter);
        for (int i = 0; i < 50; i++) {
            abc[i] = "ab" + i;
        }
        this.getListView().setOnScrollListener(new OnScrollListener() {
            @Override
            public void onScrollStateChanged(AbsListView view, int scrollState) {
            }

            @Override
            public void onScroll(AbsListView view, int firstVisibleItem,
                    int visibleItemCount, int totalItemCount) {
                System.out.println(abc.length);
                System.out.println(count);
                int lastInScreen = firstVisibleItem + visibleItemCount;
                System.out.println(lastInScreen);
                if ((lastInScreen == totalItemCount) && !(loadingMore)) {
                    try {
                        Thread thread = new Thread(null, loadMoreListItems);
                        thread.start();
                    } catch (Exception e) {
                        e.printStackTrace();
                    }
                }
            }
        });
        try {
            Thread thread = new Thread(null, loadMoreListItems);
            thread.start();
        } catch (Exception e) {
            e.printStackTrace();
        }
    }

    private Runnable loadMoreListItems = new Runnable() {
        @Override
        public void run() {
            loadingMore = true;
            myListItems = new ArrayList<String>();
            try {
                Thread.sleep(1000);
            } catch (InterruptedException e) {
            }
            size = abc.length;
            for (int i = 0; i < itemsPerPage; i++) {
                if (count < size) {
                    myListItems.add(abc[count].toString());
                    count = count + 1;
                } else {
                    break;
                }
            }
            Log.i("a", "b");
            try {
                act.runOnUiThread(returnRes);
            } catch (Exception e) {
                e.printStackTrace();
            }
            Log.i("a", "b");
        }
    };
    private Runnable returnRes = new Runnable() {
        @Override
        public void run() {
            if (myListItems != null && myListItems.size() > 0) {
                for (int i = 0; i < myListItems.size(); i++)
                    adapter.add(myListItems.get(i));
            }
            lv.setAdapter(adapter);
            Log.i("a", "b");
            adapter.notifyDataSetChanged();
            Log.i("a", "b");
            loadingMore = false;
        }
    };
}

logcat的：

01-18 18:59:21.606: I/System.out(971): 50
01-18 18:59:21.606: I/System.out(971): 0
01-18 18:59:21.606: I/System.out(971): 0
01-18 18:59:21.926: I/System.out(971): 50
01-18 18:59:21.926: I/System.out(971): 0
01-18 18:59:21.926: I/System.out(971): 1
01-18 18:59:22.257: I/System.out(971): 50
01-18 18:59:22.257: I/System.out(971): 0
01-18 18:59:22.257: I/System.out(971): 1
01-18 18:59:22.676: I/a(971): b
01-18 18:59:22.676: W/System.err(971): java.lang.NullPointerException
01-18 18:59:22.715: W/System.err(971):  at com.example.abe.Tab1Fragment$1.run(Tab1Fragment.java:113)
01-18 18:59:22.936: W/System.err(971):  at java.lang.Thread.run(Thread.java:1019)
01-18 18:59:22.936: I/a(971): b

FragmentActivity类：

package com.example.abe;

import java.util.HashMap;
import android.content.Context;
import android.os.Bundle;
import android.support.v4.app.Fragment;
import android.support.v4.app.FragmentActivity;
import android.support.v4.app.FragmentTransaction;
import android.view.View;
import android.widget.TabHost;
import android.widget.TabHost.TabContentFactory;

public class TabsFragmentActivity extends FragmentActivity implements
        TabHost.OnTabChangeListener {

    private TabHost mTabHost;
    private HashMap<String, TabInfo> mapTabInfo = new HashMap<String, TabsFragmentActivity.TabInfo>();
    private TabInfo mLastTab = null;

    private class TabInfo {
        private String tag;
        private Class<?> clss;
        private Bundle args;
        private Fragment fragment;

        TabInfo(String tag, Class<?> clazz, Bundle args) {
            this.tag = tag;
            this.clss = clazz;
            this.args = args;
        }

    }

    class TabFactory implements TabContentFactory {

        private final Context mContext;

        public TabFactory(Context context) {
            mContext = context;
        }

        public View createTabContent(String tag) {
            View v = new View(mContext);
            v.setMinimumWidth(0);
            v.setMinimumHeight(0);
            return v;
        }

    }

    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.tabs_layout);
        initialiseTabHost(savedInstanceState);
        if (savedInstanceState != null) {
            mTabHost.setCurrentTabByTag(savedInstanceState.getString("tab")); // set
                                                                                // the
                                                                                // tab
                                                                                // as
                                                                                // per
                                                                                // the
                                                                                // saved
                                                                                // state
        }
    }

    protected void onSaveInstanceState(Bundle outState) {
        outState.putString("tab", mTabHost.getCurrentTabTag()); // save the tab
                                                                // selected
        super.onSaveInstanceState(outState);
    }

    private void initialiseTabHost(Bundle args) {
        mTabHost = (TabHost) findViewById(android.R.id.tabhost);
        mTabHost.setup();
        TabInfo tabInfo = null;
        TabsFragmentActivity.addTab(this, this.mTabHost, this.mTabHost
                .newTabSpec("Tab1").setIndicator("ST"), (tabInfo = new TabInfo(
                "Tab1", Tab1Fragment.class, args)));
        this.mapTabInfo.put(tabInfo.tag, tabInfo);
        TabsFragmentActivity.addTab(this, this.mTabHost, this.mTabHost
                .newTabSpec("Tab2").setIndicator("CSI"),
                (tabInfo = new TabInfo("Tab2", Tab2Fragment.class, args)));
        this.mapTabInfo.put(tabInfo.tag, tabInfo);
        this.onTabChanged("Tab1");
        mTabHost.setOnTabChangedListener(this);
    }

    private static void addTab(TabsFragmentActivity activity, TabHost tabHost,
            TabHost.TabSpec tabSpec, TabInfo tabInfo) {
        tabSpec.setContent(activity.new TabFactory(activity));
        String tag = tabSpec.getTag();
        tabInfo.fragment = activity.getSupportFragmentManager()
                .findFragmentByTag(tag);
        if (tabInfo.fragment != null && !tabInfo.fragment.isDetached()) {
            FragmentTransaction ft = activity.getSupportFragmentManager()
                    .beginTransaction();
            ft.detach(tabInfo.fragment);
            ft.commit();
            activity.getSupportFragmentManager().executePendingTransactions();
        }
        tabHost.addTab(tabSpec);
    }

    public void onTabChanged(String tag) {
        TabInfo newTab = this.mapTabInfo.get(tag);
        if (mLastTab != newTab) {
            FragmentTransaction ft = this.getSupportFragmentManager()
                    .beginTransaction();
            if (mLastTab != null) {
                if (mLastTab.fragment != null) {
                    ft.detach(mLastTab.fragment);
                }
            }
            if (newTab != null) {
                if (newTab.fragment == null) {
                    newTab.fragment = Fragment.instantiate(this,
                            newTab.clss.getName(), newTab.args);
                    ft.add(R.id.realtabcontent, newTab.fragment, newTab.tag);
                } else {
                    ft.attach(newTab.fragment);
                }
            }
            mLastTab = newTab;
            ft.commit();
            this.getSupportFragmentManager().executePendingTransactions();
        }
    }

}

Answer 1

使用Endless Scrolling ListView。 Here is the link。我已经实现了它。如果你有任何疑问，你可以问。

这是我的TabActivity

import android.app.TabActivity;
import android.content.Context;
import android.content.Intent;
import android.os.Bundle;
import android.view.Menu;
import android.widget.TabHost;
import android.widget.TabHost.OnTabChangeListener;
import android.widget.TabHost.TabSpec;

public class MainActivity extends TabActivity {

    Context context = MainActivity.this;

    TabHost tabHost;
    TabSpec spec;

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

        tabHost = getTabHost();
        // Android tab
        tabHost.addTab(tabHost
                .newTabSpec("Home")
                .setIndicator("Home",
                        getResources().getDrawable(R.drawable.home))
                .setContent(
                        new Intent(this, MyActivityGroup.class)
                                .addFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP)));

        tabHost.addTab(tabHost
                .newTabSpec("Now Reading")
                .setIndicator("Now Reading",
                        getResources().getDrawable(R.drawable.now_reading))
                .setContent(
                        new Intent(this, NowReadingActivityGroup.class)
                                .addFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP)));

        tabHost.addTab(tabHost
                .newTabSpec("Favorites")
                .setIndicator("Favorites",
                        getResources().getDrawable(R.drawable.favorites))
                .setContent(
                        new Intent(this, FavoriteActivityGroup.class)
                                .addFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP)));

        tabHost.addTab(tabHost
                .newTabSpec("Profile")
                .setIndicator("Profile",
                        getResources().getDrawable(R.drawable.profile))
                .setContent(
                        new Intent(this, ProfileActivityGroup.class)
                                .addFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP)));

        tabHost.setCurrentTabByTag("Home");

        tabHost.setOnTabChangedListener(new OnTabChangeListener() {

            @Override
            public void onTabChanged(String tabId) {

            }
        });

    }

    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        getMenuInflater().inflate(R.menu.activity_main, menu);
        return true;
    }

}

这里是ActivityGroup类

import java.util.Stack;
import android.app.Activity;
import android.app.ActivityGroup;
import android.app.LocalActivityManager;
import android.content.Intent;
import android.os.Bundle;
import android.os.Parcelable;
import android.util.Log;
import android.view.Window;

public class MyActivityGroup extends ActivityGroup {
    private Stack<String> stack;

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        if (stack == null) {
            stack = new Stack<String>();
        }

        push("1stStackActivity", new Intent(this, Home.class));

    }

    @Override
    public void finishFromChild(Activity child) {
        pop();
    }

    @Override
    public void onBackPressed() {

        pop();

    }

    public void push(String id, Intent intent) {
        Window window = getLocalActivityManager().startActivity(id,
                intent.addFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP));
        if (window != null) {
            stack.push(id);
            setContentView(window.getDecorView());
        }
    }

    public void pop() {
        if (stack.size() == 1) {

            Home.BookTitle = null;
            Home.BookCoverPhotos = null;
            Home.BookAuther = null;
            Home.BookPublishDate = null;
            Home.language = "all";
            Home.bitmapArray = null;
            Home.BookIDs = null;
            Home.BookRating = null;
            Home.BookDescription = null;
            Home.BookCode = null;
            Home.userFName = null;
            Home.gridViewState = null;
            Home.initialIndex = 0;
            Home.CustomerID = -1;
            Home.checkBookCount = true;
            Home.str = null;
            Home.FlagSharedPreferences = false;

            BookSearchResultActivity.BookTitle = null;
            BookSearchResultActivity.BookCoverPhotos = null;
            BookSearchResultActivity.BookAuther = null;
            BookSearchResultActivity.BookPublishDate = null;
            BookSearchResultActivity.ImageByte = null;
            BookSearchResultActivity.bitmapArray = null;
            BookSearchResultActivity.BookIDs = null;
            BookSearchResultActivity.BookRating = null;
            BookSearchResultActivity.BookDescription = null;

            BookSearchResultActivity.startIndex = 0;
            BookSearchResultActivity.endIndex = 14;
            BookSearchResultActivity.listViewState = null;

            finish();
        }

        LocalActivityManager manager = getLocalActivityManager();
        manager.destroyActivity(stack.pop(), true);
        if (stack.size() > 0) {
            Intent lastIntent = manager.getActivity(stack.peek()).getIntent()
                    .setFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP);
            Window newWindow = manager.startActivity(stack.peek(), lastIntent);
            setContentView(newWindow.getDecorView());
        }
    }
}

这是我的Home Activty Class，它使用EndlessLisnter进行gridview，但你也可以将它用于listview。

public class Home extends Activity {     /** 在第一次创建活动时调用。 * /     static final String URL =“http://www.shiaislamiclibrary.com/requesthandler.ashx”;

static final String KEY_ITEM = "Book"; // parent node
static final String KEY_BOOKAUTHOR = "book_author";
static final String KEY_BOOKRATING = "BookRating";
static final String KEY_BOOKID = "BookID";
static final String KEY_BOOKDESC = "BookDescription";
static final String KEY_BOOKDATEPUBLISHED = "DatePublished";
static final String KEY_BOOKTITLE = "BookTitle";
static final String KEY_BOOKCODE = "BookCode";
static final String KEY_BOOKIMAGE = "BookImage";

static ArrayList<String> BookTitle = null;
static ArrayList<Integer> BookRating = null;
static ArrayList<String> BookDescription = null;
static ArrayList<String> BookCoverPhotos = null;
static ArrayList<String> BookAuther = null;
static ArrayList<String> BookIDs = null;
static ArrayList<String> BookCode = null;
static ArrayList<String> BookPageCount = null;
static ArrayList<String> BookPublishDate = null;
static ArrayList<Bitmap> bitmapArray = null;
static String str = null;


Context ctx = this;
Activity act = this;
Context context = Home.this;
URL bookImageURL = null;
Bitmap bitMapImage = null;
LayoutInflater inflater = null;

GridView gridView;

@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);

    // setContentView(R.layout.home_activity);
    View viewToLoad = LayoutInflater.from(this.getParent()).inflate(
            R.layout.home_activity, null);
    this.setContentView(viewToLoad);

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

    gridView = (GridView) findViewById(R.id.gridview);
    gridView.setOnScrollListener(new EndlessScrollListener());

    if (gridViewState != null) {
        gridView.onRestoreInstanceState(gridViewState);
    }

public void checkConnection() {

    // Check Flight mode ON/OFF

    if (Settings.System.getInt(context.getContentResolver(),
            Settings.System.AIRPLANE_MODE_ON, 0) == 0) {

        if (cm.getActiveNetworkInfo() != null
                && cm.getActiveNetworkInfo().isAvailable()
                && cm.getActiveNetworkInfo().isConnected()) {
            // Avoid to reload the page again and again
            if (str == null) {
                str = "TempString";
                BookTitle = new ArrayList<String>();
                BookRating = new ArrayList<Integer>();
                BookDescription = new ArrayList<String>();
                BookIDs = new ArrayList<String>();
                BookCode = new ArrayList<String>();
                BookCoverPhotos = new ArrayList<String>();
                BookAuther = new ArrayList<String>();
                BookPublishDate = new ArrayList<String>();
                BookPageCount = new ArrayList<String>();
                bitmapArray = new ArrayList<Bitmap>();
                new UIThread().execute(URL, initialIndex + "");
            } else {

                ImageAdapter adapter = new ImageAdapter(context, act);
                gridView.setAdapter(adapter);
                if (gridViewState != null) {
                    gridView.onRestoreInstanceState(gridViewState);
                }
                btnLanguage.setText(language);

            }
        } else {

            connectionFailureDialog("CONNECTION FAILURE...!",
                    "No internet connection found");
        }
    } else {
        new DialogClass(getParent()).airplaneDialog("AIRPLANE MODE...!",
                "Please make sure Airplane mode is Turned Off", "Exit");
    }

}


@Override
protected void onStart() {

    checkConnection();

    gridView.setOnItemClickListener(new OnItemClickListener() {
        @Override
        public void onItemClick(AdapterView<?> arg0, View arg1, int pos,
                long arg3) {

            Intent bookOverViewIntent = new Intent();
            bookOverViewIntent.setClass(getParent(), BookOverView.class);
            bookOverViewIntent.putExtra("BITMAP", bitmapArray.get(pos));
            bookOverViewIntent.putExtra("BOOK_TITLE", BookTitle.get(pos));
            bookOverViewIntent.putExtra("BOOK_AUTHOR", BookAuther.get(pos));
            bookOverViewIntent.putExtra("BOOK_PUBLISH_DATE",
                    BookPublishDate.get(pos));
            bookOverViewIntent.putExtra("BOOK_ID", BookIDs.get(pos));
            bookOverViewIntent.putExtra("BOOK_RATING", BookRating.get(pos));
            bookOverViewIntent.putExtra("BOOK_DESC",
                    BookDescription.get(pos));

            bookOverViewIntent.putExtra("PAGE_NO", "1");
            bookOverViewIntent.putExtra("BOOK_CODE", BookCode.get(pos));
            bookOverViewIntent.putExtra("BOOK_PAGE_COUNT",
                    BookPageCount.get(pos));

            bookOverViewIntent.putExtra("ACTIVITY", "Home");

            MyActivityGroup activityStack = (MyActivityGroup) getParent();
            activityStack.push("BookOverView", bookOverViewIntent);
            gridViewState = gridView.onSaveInstanceState();

        }
    });

private class listAdapter extends BaseAdapter {

    int size;

    @Override
    public int getCount() {

        if (btnFlag.equals("btnLanguage")) {
            size = getResources().getStringArray(
                    R.array.spnr_language_array).length;
        } else if (btnFlag.equals("btnBrowseBy")) {
            size = getResources().getStringArray(R.array.spnr_browse_array).length;
        }
        return size;
    }

    @Override
    public Object getItem(int position) {

        return null;
    }

    @Override
    public long getItemId(int position) {

        return 0;
    }

    @Override
    public View getView(int position, View convertView, ViewGroup parent) {

        View row = null;
        LayoutInflater inflater;
        if (btnFlag.equals("btnLanguage")) {
            inflater = (LayoutInflater) getSystemService(Context.LAYOUT_INFLATER_SERVICE);
            row = inflater.inflate(R.layout.itemslist, parent, false);
            TextView listText = (TextView) row.findViewById(R.id.textView2);
            listText.setText(getResources().getStringArray(
                    R.array.spnr_language_array)[position]);

        } else if (btnFlag.equals("btnBrowseBy")) {
            inflater = (LayoutInflater) getSystemService(Context.LAYOUT_INFLATER_SERVICE);
            row = inflater.inflate(R.layout.itemslist, parent, false);
            TextView listText = (TextView) row.findViewById(R.id.textView2);
            listText.setText(getResources().getStringArray(
                    R.array.spnr_browse_array)[position]);
        }

        return row;
    }

}

private class EndlessScrollListener implements OnScrollListener {

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

    public EndlessScrollListener() {
    }

    @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)) {

            if (checkBookCount) {
                new UIThread().execute(URL, initialIndex + "");
                Log.i("Reached If", "End");
            }

            loading = true;
            gridViewState = gridView.onSaveInstanceState();

        }
    }


private class UIThread extends AsyncTask<String, Integer, String> {

    ProgressDialog progressDialog;

    @Override
    protected void onPreExecute() {
        super.onPreExecute();
        progressDialog = ProgressDialog.show(getParent(),
                "Acumlating Books from server...",
                "This may Take a few seconds.\nPlease Wait...");

    }

    @Override
    protected String doInBackground(String... params) {

        String URL = params[0];
        int lIndex = Integer.valueOf(params[1]);
        XMLParser parser = new XMLParser();
        String XMLString = null;
        XMLString = parser.getXmlFromUrl_FeaturedBooks(URL, lIndex,
                language);
        // Log.i("language = ", language);
        // Log.i("XMLString = ", XMLString);

        if (XMLString != null) {

            initialIndex = lIndex + 14;

            Document doc = parser.getDomElement(XMLString);
            NodeList nlBooksLimit = doc
                    .getElementsByTagName(KEY_ITEM_BOOKs_LIMIT);
            Element eLimit = (Element) nlBooksLimit.item(0);

            totalBookCount = 0;
            try {

                totalBookCount = Integer.valueOf(parser.getValue(eLimit,
                        KEY_ITEM_TOTAL_BOOKS));
                checkBookCount = true;
            } catch (NumberFormatException e) {

                checkBookCount = false;
                totalBookCount = totalBookCount + 0;
            }

            NodeList nl = doc.getElementsByTagName(KEY_ITEM);

            // looping through all item nodes <item>

            Bitmap imageNotFound = BitmapFactory.decodeResource(
                    getResources(), R.drawable.defaultcoverphoto);

            for (int i = 0; i < nl.getLength(); i++) {

                Element e = (Element) nl.item(i);

                try {
                    BookRating.add(Integer.valueOf(parser.getValue(e,
                            KEY_BOOKRATING)));

                } catch (Exception e2) {
                    BookRating.add(0);
                }

                BookDescription.add(parser.getValue(e, KEY_BOOKDESC));
                BookTitle.add(parser.getValue(e, KEY_BOOKTITLE));
                BookCoverPhotos
                        .add("http://shiaislamicbooks.com/books_Snaps/"
                                + parser.getValue(e, KEY_BOOKCODE)
                                + "/1_thumb.jpg");
                int tempCount = BookCoverPhotos.size() - 1;
                BookAuther.add(parser.getValue(e, KEY_BOOKAUTHOR));
                BookPublishDate.add(parser.getValue(e,
                        KEY_BOOKDATEPUBLISHED));
                BookIDs.add(parser.getValue(e, KEY_BOOKID));
                BookCode.add(parser.getValue(e, KEY_BOOKCODE));
                BookPageCount.add(parser.getValue(e, KEY_PAGE_COUNT));

                try {
                    bookImageURL = new URL(BookCoverPhotos.get(tempCount));
                } catch (MalformedURLException e1) {
                    // e1.printStackTrace();
                }

                try {
                    bitMapImage = BitmapFactory.decodeStream(bookImageURL
                            .openConnection().getInputStream());
                    bitmapArray.add(bitMapImage);

                } catch (IOException e2) {
                    // e2.printStackTrace();
                    bitmapArray.add(imageNotFound);
                }
                publishProgress(i + 1);
            }

        } else {
            publishProgress(5000);
        }

        return null;
    }

    @Override
    protected void onProgressUpdate(Integer... values) {
        super.onProgressUpdate(values);
        progressDialog.setMessage(values[0]
                + " Book(s) found \nPlease wait...");
        if (values[0] == 5000) {
            Toast.makeText(context,
                    "Rrequest Time out!\nNo or Slow Internet Connection!",
                    Toast.LENGTH_LONG).show();
        }
    }

    @Override
    protected void onPostExecute(String result) {
        super.onPostExecute(result);
        progressDialog.dismiss();
        ImageAdapter adapter = new ImageAdapter(context, act);
        gridView.setAdapter(adapter);
        if (gridViewState != null) {
            gridView.onRestoreInstanceState(gridViewState);
        }

    }
}


class ViewHolder {
    TextView txt_BooksTitle;
    ImageView img_BookCoverPhoto;
    }
}

在这里你可以注意到，首先我从Asynctask填充我的gridview，然后我将gridview设置为无限列表器

gridView.setOnScrollListener(new EndlessScrollListener());

下次我从Endless listner类中调用asynctask。

    new UIThread().execute(URL, initialIndex + "");

你必须从那里完成所有任务。我在无尽的列表中将这一行称为上述行。

Answer 2

尝试这种方式：

 @Override
 public View onCreateView(LayoutInflater inflater, ViewGroup container,
        Bundle savedInstanceState) {
    if (container == null) {
        myListItems2 = new ArrayList<String>();
        adapter = new ArrayAdapter<String>(getActivity().getBaseContext(), android.R.layout.simple_list_item_1, myListItems2);
        View root = inflater.inflate(R.layout.tab_frag1_layout,
                 container, false);  
       lv = (ListView) root.findViewById(android.R.id.list); 
       lv.setAdapter(adapter);        
    return root;
}

Answer 3

Activity act = this.getActivity();

这作为成员变量将获得null，这将导致NPE

act.runOnUiThread(returnRes);

尝试在运行时询问活动，而不是成员变量：

getActivity().runOnUiThread(returnRes);