如何知道Android ActionBar选项卡式活动中哪个选项卡在视图中(How to know which tab is in view in an Android ActionBar Tabbed Activity)

 所以我使用ViewPager使用ActionBar Tabbed Activity创建了一个Android应用程序项目。 我还创建了两个片段类，并附加了相应的片段布局。 在选择相应的选项卡时，我将片段返回到SectionsPagerAdapter。 
 
public class SectionsPagerAdapter extends FragmentPagerAdapter {

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

    @Override
    public Fragment getItem(int position) {
        // getItem is called to instantiate the fragment for the given page.
        // Return a PlaceholderFragment (defined as a static inner class below).
        switch (position) {
        case 0:
            return new fragmentAddSize();
        case 1:
            return new fragmentMySizes();
    }
    return null;
    }
} 
 
 现在我对此有一些疑问。 我的印象是，每次选择一个选项卡时，它都会调用片段类并进入片段的onCreateView，但它只发生一次。 
 
 我想要实现的是知道何时选择选项卡并且相应的片段在视图中。 因此，每当我切换标签时，它只会弹出标签1或标签2中的标签符号。 

So I created an Android application project using ActionBar Tabbed Activity using ViewPager. I've also created two fragment classes and attached corresponding fragment layout with them. As the respective tab is selected I return fragment to SectionsPagerAdapter.
 
public class SectionsPagerAdapter extends FragmentPagerAdapter {

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

    @Override
    public Fragment getItem(int position) {
        // getItem is called to instantiate the fragment for the given page.
        // Return a PlaceholderFragment (defined as a static inner class below).
        switch (position) {
        case 0:
            return new fragmentAddSize();
        case 1:
            return new fragmentMySizes();
    }
    return null;
    }
} 
 
Now I have some questions about this. I was under the impression that every time a tab is selected, it calls the fragment class and goes into the onCreateView of the fragment but it only happens once.
 
What I want to achieve is to know when the tabs are selected and the corresponding fragment is in view. So that everytime i switch tabs it just pops a tab sying you are in tab 1 or tab2.

原文：https://stackoverflow.com/questions/26657971