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

心已赠人 2024-02-17 16:22 41阅读 0赞

**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：

![Center][]

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：

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 {
    
    	@Override
    	protected 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);
    			}
    		}
    
    		@Override
    		public int getCount() {
    			return fragments.size();
    		}
    
    		@Override
    		public Fragment getItem(int pos) {
    			return fragments.get(pos);
    		}
    
    		@Override
    		public 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 {
    
    	@Override
    	public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
    		return inflater.inflate(R.layout.pagefragment, container, false);
    	}
    
    	@Override
    	public 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);
    			}
    		}
    
    		@Override
    		public String getPageTitle(int pos) {
    			return "卡" + pos;
    		}
    
    		@Override
    		public int getCount() {
    			return fragments.size();
    		}
    
    		@Override
    		public Fragment getItem(int pos) {
    			return	fragments.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！

[Center]: https://image.dandelioncloud.cn/pgy_files/images/2024/01/30/4a1ff53ceeed448abe874bf97561e6e8.png