在viewpager交换片段片段、viewpager

2023-09-07 04:36:40 作者：心安理得

我有3个片段，我的一个FragmentPagerAdapter ViewPager：

I have a ViewPager with 3 Fragments and my FragmentPagerAdapter:

private class test_pager extends FragmentPagerAdapter {
    public test_pager(FragmentManager fm) {
        super(fm);
    }

    @Override
    public Fragment getItem(int i) {
        return fragments[i];
    }

    @Override
    public long getItemId(int position) {
        if (position == 1) {
            long res = fragments[position].hashCode()+fragment1_state.hashCode();
            Log.d(TAG, "getItemId for position 1: "+res);
            return res;
        } else
            return fragments[position].hashCode();
    }

    @Override
    public int getCount() {
        return fragments[2] == null ? 2 : 3;
    }

    @Override
    public int getItemPosition(Object object) {
        Fragment fragment = (Fragment) object;
        for (int i=0; i<3; i++)
            if (fragment.equals(fragments[i])){
                if (i==1) {
                    return 1; // not sure if that makes a difference
                }
                return POSITION_UNCHANGED;
            }

        return POSITION_NONE;
    }
}

在页面中的一个（＃1），我不断改变片段被显示。我删除旧片段的方法是这样的：

In one of the page (#1), I keep changing the fragment to be displayed. The way I remove the old fragment is like this:

FragmentManager fm = getSupportFragmentManager();
fm.beginTransaction().remove(old_fragment1).commit();

和则只是改变的值片段[1]

我发现我真的不能添加或替换新一或会抱怨ViewPager试图用另一个标签添加它太...（我在这里做得不对？）

I found that I cannot really add or replace the new one or it will complain the ViewPager is trying to add it too with another tag... (am I doing something wrong here?)

我所显示的片段具有 setRetainInstance（真）; 在其的onCreate 函数

All the fragments I display have setRetainInstance(true); in their onCreate function.

我的问题是，这通常非常适用于前几个替代品，但后来当我尝试重用片段，有时（我还没有真正想通了的模式，同样的片段可能会显示多次出现这种情况之前）它只会显示一个空白页。

My problem is that this usually works well for the first few replacement, but then when I try to reuse a fragment, sometimes (I have not really figured out the pattern, the same fragment may be displayed several times before this happens) it will only show a blank page.

下面是我发现在我的片段的回调函数发生了，我想显示当问题发生：

Here is what I have found happened in the callback functions of my Fragment I am trying to display when the problem happens:

onAttach 被称为（但在那个时候，getView仍然是空） onCreateView 不叫（这是预期） onViewStateRestored 不叫（为什么不呢？） onResume 不叫（我真的认为它会...） onAttach is called (but at that time, getView is still null) onCreateView is not called (that's expected) onViewStateRestored is not called (why not?) onResume is not called (I really thought it would...)

如果它改变任何东西，我使用的支持包，我的活动是 SherlockFragmentActivity

If it changes anything, I am using the support package, my activity is a SherlockFragmentActivity

修改（回答Marco的评论）

EDIT (to answer Marco's comment):

该片段在活动的OnCreate函数实例化，我填一个ArrayList与那些片段：

The fragments are instantiated in the onCreate function of the Activity, I fill an ArrayList with those fragments:

char_tests = new ArrayList<Fragment>(Arrays.asList(
            new FragmentOptionA(), new FragmentOptionB(), new FragmentOptionC()));

该我从列表中选择设置片段[1] （这是所有在UI线程中完成）

The I pick from that list to set fragments[1] (that's all done in the UI thread)

在viewpager交换片段片段、viewpager

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