viewpage里嵌套fragment如何实现

在ViewPage中嵌套Fragment有两种方式：

1. 使用FragmentPagerAdapter

使用FragmentPagerAdapter需要继承它实现一个适配器类，然后在适配器类中重写getItem和getCount方法来返回对应的Fragment和Fragment数量。具体实现如下：

public class MyAdapter extends FragmentPagerAdapter {

    private List<Fragment> mFragments = new ArrayList<>();
    private List<String> mFragmentTitles = new ArrayList<>();

    public MyAdapter(FragmentManager fm) {
        super(fm);
    }

    public void addFragment(Fragment fragment, String title) {
        mFragments.add(fragment);
        mFragmentTitles.add(title);
    }

    @Override
    public Fragment getItem(int position) {
        return mFragments.get(position);
    }

    @Override
    public int getCount() {
        return mFragments.size();
    }

    @Override
    public CharSequence getPageTitle(int position) {
        return mFragmentTitles.get(position);
    }
}

然后在Activity或Fragment中使用ViewPager，并将适配器设置给ViewPager：

MyAdapter adapter = new MyAdapter(getChildFragmentManager());
adapter.addFragment(new FirstFragment(), "First");
adapter.addFragment(new SecondFragment(), "Second");
viewPager.setAdapter(adapter);

2. 使用FragmentStatePagerAdapter

使用FragmentStatePagerAdapter也需要继承它实现一个适配器类，然后在适配器类中重写getItem和getCount方法来返回对应的Fragment和Fragment数量。具体实现如下：

public class MyAdapter extends FragmentStatePagerAdapter {

    private List<Fragment> mFragments = new ArrayList<>();
    private List<String> mFragmentTitles = new ArrayList<>();

    public MyAdapter(FragmentManager fm) {
        super(fm);
    }

    public void addFragment(Fragment fragment, String title) {
        mFragments.add(fragment);
        mFragmentTitles.add(title);
    }

    @Override
    public Fragment getItem(int position) {
        return mFragments.get(position);
    }

    @Override
    public int getCount() {
        return mFragments.size();
    }

    @Override
    public CharSequence getPageTitle(int position) {
        return mFragmentTitles.get(position);
    }
}

然后在Activity或Fragment中使用ViewPager，并将适配器设置给ViewPager：

MyAdapter adapter = new MyAdapter(getChildFragmentManager());
adapter.addFragment(new FirstFragment(), "First");
adapter.addFragment(new SecondFragment(), "Second");
viewPager.setAdapter(adapter);