在片段完成 onCreateView 之前从 ViewPager 获取视图

Question

现在我在片段中有一个 ViewPager。我需要获取/使用 ViewPager 第一页中的一些视图。我的问题是如何在片段中完成 onCreateView 方法之前获得这些视图？

这是我的一些代码：

MyFragment.java：

@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
    mFragmentLayout = inflater.inflate(R.layout.profile_fragment, container, false);

    ViewPager viewPager = (ViewPager) findViewById(R.id.view_pager);
    MyPagerAdapter myPagerAdapter = new MyPagerAdapter(getContext());
    viewPager.setAdapter(myPagerAdapter);

    View firstView = myPagerAdapter.getFirstView();

    // I need to get the view of the first page and find TextView inside that view.
    // My problem is that firstView is null
    // since viewPager doesn't call instantiateItem yet when below sentence runs.
    mTextView = (TextView) firstView.findViewById(R.id.text);
    return mFragmentLayout;
}

MyPagerAdapter.java：

private View firstView;

@Override
public Object instantiateItem(ViewGroup collection, int position) {
    View layout = mInflater.inflate(R.layout.mixin, collection, false);

    // Other logic to set the page

    if (position == 0) {
        firstView = layout;
    }
    collection.addView(layout);
    return layout;
}

public View getFirstView() {
    return firstView;
}

看起来当我调用 getFirstView() 时 ViewPager 没有开始启动，所以我得到了 null；

我也可以将片段中的视图传递到 ViewPager，但我不知道该怎么做，因为它仅适用于第一页。如何只设置第一页的视图。

Answer 1

改变 ViewPager viewPager = (ViewPager) findViewById(R.id.view_pager);

到

ViewPager viewPager = (ViewPager) mFragmentLayout.findViewById(R.id.view_pager);

从你的 infaleted 布局中获取 ViewPager

@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
    mFragmentLayout = inflater.inflate(R.layout.profile_fragment, container, false);

    ViewPager viewPager = (ViewPager) mFragmentLayout.findViewById(R.id.view_pager);
    MyPagerAdapter myPagerAdapter = new MyPagerAdapter(getContext());
    viewPager.setAdapter(myPagerAdapter);

    View firstView = myPagerAdapter.getFirstView();

    // I need to get the view of the first page and find TextView inside that view.
    // My problem is that firstView is null
    // since viewPager doesn't call instantiateItem yet when below sentence runs.
    mTextView = (TextView) firstView.findViewById(R.id.text);
    return mFragmentLayout;
}