ViewPager和Fragment

[lqgyt1]

如图所示，ViewPager和Fragment配合使用后，发现ViewPager在退出后，fragment没有退出，
导致我在左边的菜单里面切换的时候，重新弄进入“本地”时，Fragment没有刷新，就什么都没显示了。
通过LOG打印，发现fragment在创建后，生命周期没有再变化过。但是ViewPager是有DetachedFromWindow



使用方法就是网上流传的最基本的FragmentPagerAdapter和ViewPager。

求大神指教！

[lqgyt1]

http://download.csdn.net/detail/lqgyt1/6633105 专门写了个小的Demo来反馈我的问题，对于Fragment和ViewPager感兴趣的，可以一起讨论。

[2在路上]

mark一下学习一下。。。

[lqgyt1]

这年头还是得靠自己。。自己实现FragmentAdapater，速占楼层，给分喽。

/*
 * Copyright (C) 2011 The Android Open Source Project
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package com.tubban.viewpager;

import android.os.Parcelable;
import android.support.v4.app.Fragment;
import android.support.v4.app.FragmentManager;
import android.support.v4.app.FragmentStatePagerAdapter;
import android.support.v4.app.FragmentTransaction;
import android.support.v4.view.PagerAdapter;
import android.util.Log;
import android.view.View;
import android.view.ViewGroup;

/**
 * Implementation of {@link android.support.v4.view.PagerAdapter} that
 * represents each page as a {@link Fragment} that is persistently
 * kept in the fragment manager as long as the user can return to the page.
 *
 * <p>This version of the pager is best for use when there are a handful of
 * typically more static fragments to be paged through, such as a set of tabs.
 * The fragment of each page the user visits will be kept in memory, though its
 * view hierarchy may be destroyed when not visible.  This can result in using
 * a significant amount of memory since fragment instances can hold on to an
 * arbitrary amount of state.  For larger sets of pages, consider
 * {@link FragmentStatePagerAdapter}.
 *
 * <p>When using FragmentPagerAdapter the host ViewPager must have a
 * valid ID set.</p>
 *
 * <p>Subclasses only need to implement {@link #getItem(int)}
 * and {@link #getCount()} to have a working adapter.
 *
 * <p>Here is an example implementation of a pager containing fragments of
 * lists:
 *
 * {@sample development/samples/Support4Demos/src/com/example/android/supportv4/app/FragmentPagerSupport.java
 *      complete}
 *
 * <p>The <code>R.layout.fragment_pager</code> resource of the top-level fragment is:
 *
 * {@sample development/samples/Support4Demos/res/layout/fragment_pager.xml
 *      complete}
 *
 * <p>The <code>R.layout.fragment_pager_list</code> resource containing each
 * individual fragment's layout is:
 *
 * {@sample development/samples/Support4Demos/res/layout/fragment_pager_list.xml
 *      complete}
 */
public abstract class MyFragmentViewAdapater extends PagerAdapter {
    private static final String TAG = "FragmentPagerAdapter";
    private static final boolean DEBUG = true;

    private final FragmentManager mFragmentManager;

    public MyFragmentViewAdapater(FragmentManager fm) {
        mFragmentManager = fm;
    }

    /**
     * Return the Fragment associated with a specified position.
     */
    public abstract Fragment getItem(int position);

    @Override
    public void startUpdate(ViewGroup container) {
    }

    @Override
    public Object instantiateItem(ViewGroup container, int position) {
        Fragment fragment = getItem(position);
        if(!fragment.isAdded()){
        	FragmentTransaction ft = mFragmentManager.beginTransaction();
        	ft.add(fragment, fragment.getClass().getName());
        	ft.commit();
        	mFragmentManager.executePendingTransactions();
        }
        if(fragment.getView().getParent() == null){
        	container.addView(fragment.getView()); // 为viewpager增加布局
        }

        return fragment.getView();
    }

    @Override
    public void destroyItem(ViewGroup container, int position, Object object) {
    	container.removeView((View) object);
    }


    @Override
    public boolean isViewFromObject(View view, Object object) {
        return view == object;
    }

    @Override
    public Parcelable saveState() {
        return null;
    }

    @Override
    public void restoreState(Parcelable state, ClassLoader loader) {
    }

    private static String makeFragmentName(int viewId, int index) {
        return "android:switcher:" + viewId + ":" + index;
    }
}