Question

我的ViewPager的前两页总是相同的，因为切换到第一个元素（索引0）时不会调用适配器。所有其他片段都可以正常工作。使用getItem()中的位置会返回完全奇怪的位置，因此我使用的是ViewPager的getCurrentItem()方法。 TimetableActivity：

public class TimetableActivity extends FragmentActivity {

private ViewPager mPager;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.screen_slide);

    ActionBar actionBar = getActionBar();
    actionBar.setTitle("Stundenplan");
    actionBar.setIcon(new ColorDrawable(getResources().getColor(android.R.color.transparent)));

    mPager = (ViewPager) findViewById(R.id.pager);
    PagerAdapter mPagerAdapter = new ScreenSlidePagerAdapter(getSupportFragmentManager(), mPager);
    mPager.setAdapter(mPagerAdapter);
}

@Override
public void onBackPressed() {
    if (mPager.getCurrentItem() == 0) {
        super.onBackPressed();
    } else {
        mPager.setCurrentItem(mPager.getCurrentItem() - 1);
    }
}}

ScreenSlidePagerAdapter：

public class ScreenSlidePagerAdapter extends FragmentStatePagerAdapter {

private ViewPager pager;

public ScreenSlidePagerAdapter(FragmentManager fm, ViewPager pager) {
    super(fm);
    this.pager = pager;
}

@Override
public Fragment getItem(int position) {
    System.out.println("Current Item: " + pager.getCurrentItem());
    return ScreenSlidePageFragment.newInstance(pager.getCurrentItem());
}

@Override
public int getCount() {
    return 10;
}}

ScreenSlidePageFragment：

public class ScreenSlidePageFragment extends Fragment {

private List<TableRow> rows;
private int position;

@Nullable
@Override
public View onCreateView(LayoutInflater inflater, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState) {
    ViewGroup rootView = (ViewGroup) inflater.inflate(R.layout.activity_timetable, container, false);
    return rootView;
}

public static ScreenSlidePageFragment newInstance(int num) {
    ScreenSlidePageFragment f = new ScreenSlidePageFragment();

    Bundle args = new Bundle();
    args.putInt("position", num);
    f.setArguments(args);

    return f;
}

@Override
public void onCreate(@Nullable Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);

    System.out.println("Called");

    ActionBar actionBar = getActivity().getActionBar();
    position = getArguments() != null ? getArguments().getInt("position") : 1;

    System.out.println(position);

    SimpleDateFormat format = new SimpleDateFormat("dd.MM.yyyy");
    Calendar c = Calendar.getInstance();
    if (position == 5) {
        actionBar.setTitle("Stundenplan (" + format.format(c.getTime()) + ")");
    } else if (position < 5) {
        int daysBack = 5 - position;
        c.add(Calendar.DAY_OF_MONTH, daysBack * -1);
        actionBar.setTitle("Stundenplan (" + format.format(c.getTime()) + ")");
    } else {
        int daysForward = position - 5;
        c.add(Calendar.DAY_OF_MONTH, daysForward);
        actionBar.setTitle("Stundenplan (" + format.format(c.getTime()) + ")");
    }
}}

所以问题是getCurrentItem()似乎永远不会是0。任何人都可以帮助我吗？

Answer 1

你怎么知道getCurrentItem不是0，你在调试中看过它的值还是注意到按下后活动还没有完成？因为如果它是第二选择你需要知道FragmentActivity onBackPressed（）会弹出片段backstack，直到它为空，然后才结束活动。所以你可能想直接调用finish（）而不是super.onBackPressed（）。

android viewpager将当前项设置为0

1 个答案: