Android（ViewPager中的ViewPager）ViewPager FragmentPagerAdapter嵌套子ViewPager FragmentPagerAdapter页面不能正常显示

Android（ViewPager中的ViewPager）ViewPager FragmentPagerAdapter嵌套子ViewPager FragmentPagerAdapter页面不能正常显示问题

Android的ViewPager如果只使用一“层” FragmentPagerAdapter构建ViewPager，那么将不会导致本文题目中所说的问题，当ViewPager再次嵌套一个ViewPager时候，如果细节地方使用不当将导致页面不能正常显示问题。

比如，如图所示：

这是一个典型的ViewPager嵌套ViewPager的框架布局。底部0,1,2,3是一个SlidingTabLayout，SlidingTabLayout，SlidingTabLayout上面是一个ViewPager，其布局文件代码：

<RelativeLayout        xmlns:android="http://schemas.android.com/apk/res/android"        xmlns:tools="http://schemas.android.com/tools"        xmlns:app="http://schemas.android.com/apk/res-auto"        android:layout_width="match_parent"        android:layout_height="match_parent"        android:orientation="vertical" >        <android.support.v4.view.ViewPager            android:id="@+id/viewPager"            android:layout_width="match_parent"            android:layout_height="wrap_content"            android:layout_above="@+id/slidingTabLayout" />        <zhangphil.viewpagerdebug.SlidingTabLayout            android:id="@+id/slidingTabLayout"            android:layout_width="match_parent"            android:layout_height="wrap_content"            android:layout_alignParentBottom="true"/>            </RelativeLayout>

Java代码：

package zhangphil.viewpagerdebug;import java.util.ArrayList;import android.os.Bundle;import android.support.v4.app.Fragment;import android.support.v4.app.FragmentActivity;import android.support.v4.app.FragmentManager;import android.support.v4.app.FragmentPagerAdapter;import android.support.v4.view.ViewPager;public class MainActivity extends FragmentActivity {@Overrideprotected void onCreate(Bundle savedInstanceState) {super.onCreate(savedInstanceState);setContentView(R.layout.activity_main);MyViewPagerAdapter adapter = new MyViewPagerAdapter(this.getSupportFragmentManager());ViewPager viewPager = (ViewPager) findViewById(R.id.viewPager);viewPager.setAdapter(adapter);SlidingTabLayout mSlidingTabLayout = (SlidingTabLayout) findViewById(R.id.slidingTabLayout);mSlidingTabLayout.setViewPager(viewPager);}private class MyViewPagerAdapter extends FragmentPagerAdapter {private ArrayList<Fragment> fragments;public MyViewPagerAdapter(FragmentManager fm) {super(fm);fragments = new ArrayList<Fragment>();for (int i = 0; i < 4; i++) {PageFragment f=new PageFragment();fragments.add(f);}}@Overridepublic int getCount() {return fragments.size();}@Overridepublic Fragment getItem(int pos) {return fragments.get(pos);}@Overridepublic CharSequence getPageTitle(int pos) {return "" + pos;}}}

将ViewPager与SlidingTabLayout联结起来。在此ViewPager中的MyViewPagerAdapter中喂给每一个ViewPager的子page又一个ViewPager——也是如果使用不当将引起问题的PageFragment：

package zhangphil.viewpagerdebug;import java.util.ArrayList;import android.os.Bundle;import android.support.design.widget.TabLayout;import android.support.v4.app.Fragment;import android.support.v4.app.FragmentManager;import android.support.v4.app.FragmentPagerAdapter;import android.support.v4.view.ViewPager;import android.view.LayoutInflater;import android.view.View;import android.view.ViewGroup;public class PageFragment extends Fragment {@Overridepublic View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {return inflater.inflate(R.layout.pagefragment, container, false);}@Overridepublic void onViewCreated(View view, Bundle savedInstanceState) {super.onViewCreated(view, savedInstanceState);TabLayout tabLayout = (TabLayout) view.findViewById(R.id.tabLayout);tabLayout.setSmoothScrollingEnabled(true);MyViewPagerAdapter pagerAdapter = new MyViewPagerAdapter(this.getChildFragmentManager());ViewPager viewPager = (ViewPager) view.findViewById(R.id.viewpager);viewPager.setAdapter(pagerAdapter);tabLayout.setupWithViewPager(viewPager);}private class MyViewPagerAdapter extends FragmentPagerAdapter {private ArrayList<Fragment> fragments;public MyViewPagerAdapter(FragmentManager fm) {super(fm);fragments = new ArrayList<Fragment>();for (int i = 0; i < 5; i++) {Fragment f=new ContentFragment();fragments.add(f);}}@Overridepublic String getPageTitle(int pos) {return "卡" + pos;}@Overridepublic int getCount() {return fragments.size();}@Overridepublic Fragment getItem(int pos) {returnfragments.get(pos);}}}

PageFragment的布局：

<?xml version="1.0" encoding="utf-8"?><RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"    xmlns:app="http://schemas.android.com/apk/res-auto"     android:layout_width="match_parent"    android:layout_height="match_parent" >    <android.support.design.widget.TabLayout        android:id="@+id/tabLayout"        android:layout_width="match_parent"        android:layout_height="wrap_content"        android:layout_alignParentTop="true"        app:tabGravity="fill"        app:tabMode="fixed" >    </android.support.design.widget.TabLayout>     <android.support.v4.view.ViewPager        android:id="@+id/viewpager"        android:layout_width="match_parent"        android:layout_height="wrap_content"        android:layout_below="@+id/tabLayout"        android:layout_alignParentBottom="true" />    </RelativeLayout>

PageFragment就是图中顶部的卡0，卡1，卡2，卡3，卡4分别显示的每一个page。ContentFragment只是一个继承自ListFragment的、仅仅显示一行数据的演示Fragment。
PageFragment作为第二层、第二级ViewPager（ViewPager中的ViewPager）在PageFragment中创建此PageFragment的FragmentPagerAdapter时候，切记要传递给FragmentPagerAdapter的构造函数参数FragmentManager为：getChildFragmentManager() 而不是像父ViewPager中
那样直接随意的直接getFragmentManager()。如果PageFragment直接仍然用getFragmentManager()构造其FragmentPagerAdapter，将导致第二层、第二级的ViewPager不能正常显示。切记切记！

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