根据哪个页面更改 viewpager 上方的 textview？

Question

我有一个 activity，它有 2 个按钮（上一个、下一个）和两个按钮之间的文本视图。下面是一个viewpager。

我想将 textview 更改为它们所在页面的标题。

这里是 class 这一切发生的地方：

public class MyWorkout extends BaseActivity {

NonSwipeableViewPager vp;
TextView txtViewTitle;

@Override
protected void onCreate(@Nullable Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.my_workout);
    mToolBar = activateToolbar();
    setUpNavigationDrawer();
    getSupportActionBar().setTitle("My Workout");

    Intent intent = getIntent();
    String workouttitle = intent.getStringExtra("workout");
    switch(workouttitle) {
        case "w29" : {
            getSupportActionBar().setTitle("My Workout - Workout 29");
            break;
        }
        case "w30" : {
            getSupportActionBar().setTitle("My Workout - Workout 30");
            break;
        }
    }

    Button btnPrev = (Button) findViewById(R.id.btnPrevious);
    Button btnNext = (Button) findViewById(R.id.btnNext);
    vp = (NonSwipeableViewPager) findViewById(R.id.view_pager);
    txtViewTitle = (TextView) findViewById(R.id.txtViewTitle);
    this.addPages(vp);

    //THIS IS WHAT I HAVE TRIED
    if (vp.getCurrentItem() == 0) {
        txtViewTitle.setText("Week One, Monday");
    }
    if (vp.getCurrentItem() == 1) {
        txtViewTitle.setText("Week One, Wednesday");
    }

    btnNext.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            MoveNext();
        }
    });

    btnPrev.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            MovePrevious();
        }
    });

}
public void MoveNext() {
    //it doesn't matter if you're already in the last item
    vp.setCurrentItem(vp.getCurrentItem() + 1);
}

public void MovePrevious() {
    //it doesn't matter if you're already in the first item
    vp.setCurrentItem(vp.getCurrentItem() - 1);
}

private void addPages(NonSwipeableViewPager pager) {
    MyFragPagerAdapter adapter = new MyFragPagerAdapter(getSupportFragmentManager());
    Intent intent = getIntent();
    String workout = intent.getStringExtra("workout");
    Bundle args = new Bundle();
    args.putString("workout", workout);

    Week1Mon week1MonFragment = new Week1Mon();
    week1MonFragment.setArguments(args);
    adapter.addPage(week1MonFragment);
    Week1Wed week1WedFragment = new Week1Wed();
    week1WedFragment.setArguments(args);
    adapter.addPage(week1WedFragment);
    Week1Fri week1Fri = new Week1Fri();
    week1Fri.setArguments(args);
    adapter.addPage(week1Fri);
    Week2Mon week2MonFragment = new Week2Mon();
    week2MonFragment.setArguments(args);
    adapter.addPage(week2MonFragment);
    Week2Wed week2WedFragment = new Week2Wed();
    week2WedFragment.setArguments(args);
    adapter.addPage(week2WedFragment);
    Week2Fri week2Fri = new Week2Fri();
    week2Fri.setArguments(args);
    adapter.addPage(week2Fri);

    pager.setAdapter(adapter);
}
}

我试过的部分：

if (vp.getCurrentItem() == 0) {
        txtViewTitle.setText("Week One, Monday");
    }
    if (vp.getCurrentItem() == 1) {
        txtViewTitle.setText("Week One, Wednesday");
    }

这会将文本视图设置为第一周，即星期一。不幸的是，当用户点击 Next 按钮时它并没有改变。我也希望有更好的方法，因为我不想 "assume" 当前项目是星期几，因为每周都不一样。我还需要弄清楚如何在打开应用程序时设置当前页面，因为它保存位置是共享 pref 并且我必须在上面的 class 中加载它，并以某种方式将页面设置为当前页面（最好是标题）

这是 MyFragPagerAdapter：

public class MyFragPagerAdapter extends FragmentPagerAdapter {

ArrayList<Fragment> pages = new ArrayList<>();

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

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

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

public void addPage(Fragment f) {
    pages.add(f);
}

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

感谢您的帮助，如果您需要查看更多代码，请告诉我！

Answer 1

可以使用，

viewPager.addOnPageChangeListener(new OnPageChangeListener() {
public void onPageScrollStateChanged(int state) {}
public void onPageScrolled(int position, float positionOffset, int positionOffsetPixels) {}

public void onPageSelected(int position) {
    // Check if this is the page you want.
}});

根据哪个页面更改 viewpager 上方的 textview？

Changing a textview above viewpager depending on what page?

android

textview

android-adapter

android-viewpager