在使用Viewpager和fragment处理中会出现预加载的问题，最近看别人的代码，终于找到了一个很好的处理方法

能有效的解决预加载的问题，在fragment都继承一个重写setUserVisibleHint类的基类

如图是效果图

其实在是一个fragment中，用Viewpager和fragment再展示3个界面

不过如果你是在activity中实现Viewpager和fragment的结合不要这么麻烦  这句代码就够了 viewPager.setOffscreenPageLimit(3)不用重写什么MyLazyFragment 了；但是用viewPager.setOffscreenPageLimit(3)实际上是一次性把几个ViewPager都加载出来以后就不加载了；用懒加载的处理，实际上是滑到第二个界面时再加载二个的数据。

如下是主要代码

最后写的程序代码连接：http://download.csdn.net/detail/qq_29774291/9620872

package com.ithello.suibianxie.activity.notice;

import android.support.v4.app.Fragment;

public abstract class MyLazyFragment extends Fragment {

    protected boolean isVisible;

    /**

     * 在这里实现Fragment数据的缓加载.

     *

     * @param isVisibleToUser

     */

    @Override

    public void setUserVisibleHint(boolean isVisibleToUser) {

        super.setUserVisibleHint(isVisibleToUser);

        if (getUserVisibleHint()) {

            isVisible = true;

            onVisible();

        } else {

            isVisible = false;

            onInvisible();

        }

    }

    protected abstract void onVisible();

    protected abstract void onInvisible();

}

其中第一个fragment的处理方法和其他的不同

package com.ithello.suibianxie.activity.fragment;

import org.xutils.x;

import org.xutils.common.Callback;

import org.xutils.http.RequestParams;

import android.os.Bundle;

import android.util.Log;

import android.view.LayoutInflater;

import android.view.View;

import android.view.ViewGroup;

import android.widget.TextView;

import com.ithello.suibianxie.R;

import com.ithello.suibianxie.activity.notice.MyLazyFragment;

import com.ithello.suibianxie.common.GlobalData;

import com.ithello.suibianxie.util.Constant;

public class VideoListFragment extends MyLazyFragment{

    private boolean isPrepared;

    private boolean isFirstLoad = false;

    private TextView tView;

    @Override

    public View onCreateView(LayoutInflater inflater, ViewGroup container,

            Bundle savedInstanceState) {

        // TODO Auto-generated method stub

        //return inflater.inflate(R.layout.videolistfragment, container, false);

        View view = inflater.inflate(R.layout.videolistfragment, null);

        isPrepared = true;

        initView(view);

        System.out.println("1");

        firstLoad();

        return view;

    }

    private void initView(View view) {

        // TODO Auto-generated method stub

        tView=(TextView)view.findViewById(R.id.tv_videofragment);

    }

    @Override

    protected void onVisible() {

        // TODO Auto-generated method stub

        Log.d("jiejie", "11 isPreparen:" + isPrepared + ", isVisible" + isVisible);

        if(!isPrepared || !isVisible){

            return;

        }

        if(!isFirstLoad){

            isFirstLoad = true;

            //firstLoad();

        }

    }

    private void firstLoad() {

        // TODO Auto-generated method stub

        requestDates();

    }

    private void requestDates() {

        // TODO Auto-generated method stub

        RequestParams params = new RequestParams(Constant.findAppArticleList_url);

        params.addBodyParameter("rc", GlobalData.getGlobalData().getRc());

        params.addBodyParameter("page", 1+"");

        params.addBodyParameter("rows", 10 +"");

        params.addBodyParameter("appOS", "android");

        x.http().get(params, new Callback.CommonCallback<String>() {

            @Override

            public void onCancelled(CancelledException arg0) {

                // TODO Auto-generated method stub

            }

            @Override

            public void onError(Throwable arg0, boolean arg1) {

                // TODO Auto-generated method stub

            }

            @Override

            public void onFinished() {

                // TODO Auto-generated method stub

            }

            @Override

            public void onSuccess(String arg0) {

                // TODO Auto-generated method stub

                Log.d("jiejie", arg0);

                tView.setText(arg0);

            }

        });

    }

    @Override

    protected void onInvisible() {

        // TODO Auto-generated method stub

    }

}
package com.ithello.suibianxie.activity.fragment;

import java.util.ArrayList;

import java.util.List;

import org.json.JSONArray;

import org.json.JSONException;

import org.json.JSONObject;

import org.xutils.x;

import org.xutils.common.Callback;

import org.xutils.http.RequestParams;

import android.os.Bundle;

import android.text.format.DateUtils;

import android.util.Log;

import android.view.LayoutInflater;

import android.view.View;

import android.view.ViewGroup;

import android.widget.ListView;

import com.handmark.pulltorefresh.library.PullToRefreshBase;

import com.handmark.pulltorefresh.library.PullToRefreshBase.OnLastItemVisibleListener;

import com.handmark.pulltorefresh.library.PullToRefreshBase.OnRefreshListener;

import com.handmark.pulltorefresh.library.PullToRefreshListView;

import com.ithello.suibianxie.R;

import com.ithello.suibianxie.activity.notice.MyLazyFragment;

import com.ithello.suibianxie.adapter.ArticleAdapter;

import com.ithello.suibianxie.common.GlobalData;

import com.ithello.suibianxie.entity.Article;

import com.ithello.suibianxie.util.Constant;

public class ArticleFragment extends MyLazyFragment {

    // private List<Article> list = new ArrayList<Article>();

    private List<JSONObject> list = new ArrayList<JSONObject>();

    private PullToRefreshListView mPullToRefreshListView;

    private ListView listView;

    private ArticleAdapter mAdapter;

    private int page = 0;

    private int rows = 10;

    private int total = 0;

    // private String urlString

    // ="http://111.39.245.155:9527/dtbt/findAppArticleList.action";

    // 标志位，标志已经初始化完成

    private boolean isPrepared;

    private boolean isFirstLoad = false;

    @Override

    public View onCreateView(LayoutInflater inflater, ViewGroup container,

            Bundle savedInstanceState) {

        // TODO Auto-generated method stub

        // return super.onCreateView(inflater, container, savedInstanceState);

        // return inflater.inflate(R.layout.articlefragment, container, false);

        View view = inflater.inflate(R.layout.articlefragment, null);

        initListView(view);

        isPrepared = true;

        System.out.println("2");

        return view;

    }

    @Override

    protected void onVisible() {

        // TODO Auto-generated method stub

        Log.d("jiejie", "22  isPrepared:" + isPrepared + ", isVisible" + isVisible);

        if (!isPrepared || !isVisible) {

            return;

        }

        if (!isFirstLoad) {

            isFirstLoad = true;

            firstLoad();

        }

    }

    @Override

    protected void onInvisible() {

        // TODO Auto-generated method stub

    }

    private void firstLoad() {

        // TODO Auto-generated method stub

//        mAdapter.notifyDataSetChanged();

//        list.clear();

        page = 1;

        requestDate(page);

    }

    private void initListView(View view) {

        // TODO Auto-generated method stub

        listView = (ListView)view.findViewById(R.id.art_listview);

    }

    /**

     * 进行网络的请求

     *

     * @param page2

     */

    protected void requestDate(int page2) {

        // TODO Auto-generated method stub

        RequestParams params = new RequestParams(

                Constant.findAppArticleList_url);

        params.addBodyParameter("rc", GlobalData.getGlobalData().getRc());

        params.addBodyParameter("page", page2 + "");

        params.addBodyParameter("rows", rows + "");

        params.addBodyParameter("appOS", "android");

        x.http().get(params, new Callback.CommonCallback<String>() {

            @Override

            public void onCancelled(CancelledException arg0) {

                // TODO Auto-generated method stub

            }

            @Override

            public void onError(Throwable arg0, boolean arg1) {

                // TODO Auto-generated method stub

            }

            @Override

            public void onFinished() {

                // TODO Auto-generated method stub

            }

            @Override

            public void onSuccess(String arg0) {

                // TODO Auto-generated method stub

                System.out.println(arg0);

                Log.d("jiejie", arg0);

                if(arg0 != null){

                    try {

                        JSONObject object= new JSONObject(arg0);

                        JSONArray array = object.getJSONArray("rows");

                        JSONObject dataJsonObject;

                        for(int i = 0 ; i<array.length();i++){

                            dataJsonObject =array.getJSONObject(i);

                            list.add(dataJsonObject);

                        }

                    } catch (JSONException e) {

                        // TODO Auto-generated catch block

                        e.printStackTrace();

                    }

                    mAdapter = new ArticleAdapter(getActivity(), list);

                    listView.setAdapter(mAdapter);

                }

            }

        });

    }

}
package com.ithello.suibianxie.activity.fragment;

import org.xutils.x;

import org.xutils.common.Callback;

import org.xutils.http.RequestParams;

import android.os.Bundle;

import android.util.Log;

import android.view.LayoutInflater;

import android.view.View;

import android.view.ViewGroup;

import android.widget.TextView;

import com.ithello.suibianxie.R;

import com.ithello.suibianxie.activity.notice.MyLazyFragment;

import com.ithello.suibianxie.common.GlobalData;

import com.ithello.suibianxie.util.Constant;

public class NoticeFragment extends MyLazyFragment{

    private boolean isPrepared;

    private boolean  isFirstLoad = false;

    private TextView tView ;

    @Override

    public View onCreateView(LayoutInflater inflater, ViewGroup container,

            Bundle savedInstanceState) {

        // TODO Auto-generated method stub

        //return inflater.inflate(R.layout.noticefragment, container, false);

        View view = inflater.inflate(R.layout.noticefragment, null);

        isPrepared = true;

        initView(view);

        System.out.println("3");

        return view;

    }

    private void initView(View view) {

        // TODO Auto-generated method stub

        tView = (TextView)view.findViewById(R.id.tv_notice);

    }

    @Override

    protected void onVisible() {

        // TODO Auto-generated method stub

        Log.d("jiejie", "33 isPreparen" + isPrepared + ", isVisibletrue" + isVisible);

        if(!isPrepared || !isVisible){

            return;

        }

        if(!isFirstLoad){

            isFirstLoad = true;

            firstLoad();

        }

    }

    @Override

    protected void onInvisible() {

        // TODO Auto-generated method stub

    }

    private void firstLoad() {

        // TODO Auto-generated method stub

        stHttoop();

    }

    private void stHttoop() {

        // TODO Auto-generated method stub

        RequestParams params = new RequestParams(Constant.findAppArticleList_url);

        params.addBodyParameter("rc", GlobalData.getGlobalData().getRc());

        params.addBodyParameter("page", 1+"");

        params.addBodyParameter("rows", 10 +"");

        params.addBodyParameter("appOS", "android");

        x.http().get(params, new Callback.CommonCallback<String>() {

            @Override

            public void onCancelled(CancelledException arg0) {

                // TODO Auto-generated method stub

            }

            @Override

            public void onError(Throwable arg0, boolean arg1) {

                // TODO Auto-generated method stub

            }

            @Override

            public void onFinished() {

                // TODO Auto-generated method stub

            }

            @Override

            public void onSuccess(String arg0) {

                // TODO Auto-generated method stub

                Log.d("jiejie", arg0);

                tView.setText(arg0);

            }

        });

    }

}

其中Viewpager和fragment的结合我用的是IndicatorViewPager来实现的

package com.ithello.suibianxie.fragment;

import com.ithello.suibianxie.R;

import com.ithello.suibianxie.activity.fragment.ArticleFragment;

import com.ithello.suibianxie.activity.fragment.NoticeFragment;

import com.ithello.suibianxie.activity.fragment.VideoListFragment;

import com.potato.viewpagerindicator.view.indicator.IndicatorViewPager;

import com.potato.viewpagerindicator.view.indicator.adapter.IndicatorFragmentPagerAdapter;

import com.potato.viewpagerindicator.view.indicator.indicator.Indicator;

import com.potato.viewpagerindicator.view.indicator.slidebar.ColorBar;

import com.potato.viewpagerindicator.view.indicator.transition.OnTransitionTextListener;

import android.content.res.Resources;

import android.os.Bundle;

import android.support.v4.app.Fragment;

import android.support.v4.app.FragmentManager;

import android.support.v4.view.ViewPager;

import android.view.LayoutInflater;

import android.view.View;

import android.view.ViewGroup;

import android.widget.RelativeLayout;

import android.widget.TextView;

/**

 * 第三个fragment

 * @author zh

 *

 */

public class MThreeFragment extends Fragment{

    private IndicatorViewPager indicatorViewPager;

    @Override

    public View onCreateView(LayoutInflater inflater, ViewGroup container,

            Bundle savedInstanceState) {

        // TODO Auto-generated method stub

        return inflater.inflate(R.layout.mthreefragment, container, false);

    }

    @Override

    public void onActivityCreated(Bundle savedInstanceState) {

        // TODO Auto-generated method stub

        super.onActivityCreated(savedInstanceState);

        setView();

    }

    private void setView() {

        // TODO Auto-generated method stub

        Resources res = getResources();

        ViewPager viewPager =(ViewPager)getActivity().findViewById(R.id.fragment_training_home_viewPager);

        Indicator indicator =(Indicator)getActivity().findViewById(R.id.fragment_training_home_fixedindicatorview);

        int color =getResources().getColor(R.color.tab_indicator_daab3c);

        indicator.setScrollBar(new ColorBar(getActivity(), color, 2));

        float unSelectSize = 14;

        float selectSize = unSelectSize * 1.0f;

        int selectColor =res.getColor(R.color.tab_title_color_select_daab3c);

        int unSelectColor = res.getColor(R.color.tab_title_color_normal_e8d6ab);

        indicator.setOnTransitionListener(new OnTransitionTextListener().setColor(selectColor, unSelectColor).setSize(selectSize, unSelectSize));

        viewPager.setOffscreenPageLimit(3);

        indicatorViewPager = new IndicatorViewPager(indicator, viewPager);

        indicatorViewPager.setAdapter(new MyAdapter(getChildFragmentManager()));

    }

    private String[] tabNames ={"视频","文章","通知"};

    private class MyAdapter extends IndicatorFragmentPagerAdapter{

        public MyAdapter(FragmentManager fragmentManager) {

            super(fragmentManager);

            // TODO Auto-generated constructor stub

        }

        @Override

        public int getCount() {

            // TODO Auto-generated method stub

            return 3;

        }

        @Override

        public Fragment getFragmentForPage(int position) {

            // TODO Auto-generated method stub

            Bundle bundle = new Bundle();

            if(position ==0){

                VideoListFragment videoListFragment = new VideoListFragment();

                videoListFragment.setArguments(bundle);

                return videoListFragment;

            }else if (position == 1) {

                ArticleFragment articleFragment = new ArticleFragment();

                articleFragment.setArguments(bundle);

                return articleFragment;

            }else if (position ==2) {

                NoticeFragment noticeFragment = new NoticeFragment();

                noticeFragment.setArguments(bundle);

                return noticeFragment;

            }

            VideoListFragment mainFragment = new VideoListFragment();

            mainFragment.setArguments(bundle);

            return mainFragment;

        }

        @Override

        public View getViewForTab(int position, View convertView, ViewGroup container) {

            // TODO Auto-generated method stub

            if(convertView == null){

                if(position ==0){

                    convertView = View.inflate(getActivity(), R.layout.title_bae_left, null);

                }else if (position ==1) {

                    convertView = View.inflate(getActivity(), R.layout.title_bar_middle, null);

                }else if (position == 2) {

                    convertView = View.inflate(getActivity(), R.layout.title_bar_right, null);

                }

            }

            RelativeLayout layout = (RelativeLayout)convertView;

            TextView tView = (TextView)layout.findViewById(R.id.tv);

            tView.setText(tabNames[position]);

            return convertView;

        }

    }

}

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