[英]How to change fragment inside getItem of FragmentStatePagerAdapter
我有这段代码,我想根据某些布尔值更改FragmentStatePageAdapter的第一个片段(在viewpager内部)。
inner class MainFragmentAdapter(fragmentManager: FragmentManager) :
FragmentStatePagerAdapter(fragmentManager) {
override fun getCount(): Int {
return MainView.Fragments.values().size
}
override fun getItem(position: Int): Fragment? {
return when (position) {
0 -> {
if (booleanOne && !booleanTwo) {
FragmentOne.newInstance()
} else if (booleanTwo && !booleanOne) {
FragmentTwo.newInstance()
} else {
FragmentThree.newInstance()
}
}
else -> null
}
}
}
到目前为止,我发现的唯一解决方案是,当我个人知道其中一个布尔值已更改时,我只是做了类似的事情:
_fragmentAdapter = MainFragmentAdapter(getLifecycleFragmentManager())
fragmentViewPager.adapter = _fragmentAdapter
因此,我只是再次设置了适配器,但是这样做似乎不可行。 我不能强迫它再次计算getItem吗?
在您的类中进行这些更改, notifyDataSetChanged()
然后重写getItemPosition()
,它将在每次通知时调用,然后只返回各自的常量POSITION_NONE
如果您想查看新的更改),否则返回POSITION_UNCHANGED
inner class MainFragmentAdapter(fragmentManager: FragmentManager) :
FragmentStatePagerAdapter(fragmentManager) {
override fun getCount(): Int {
return MainView.Fragments.values().size
}
override fun getItem(position: Int): Fragment? {
return when (position) {
0 -> {
if (booleanOne && !booleanTwo) {
FragmentOne.newInstance()
} else if (booleanTwo && !booleanOne) {
FragmentTwo.newInstance()
} else {
FragmentThree.newInstance()
}
notifyDataSetChanged();
}
else -> null
}
}
override fun getItemPosition(@NonNull `object`: Any): Int {
// this method will be called for every fragment in the ViewPager
return if (`object` is FragmentOne) {
POSITION_UNCHANGED // don't force a reload
} else {
// POSITION_NONE means something like: this fragment is no longer valid
// triggering the ViewPager to re-build the instance of this fragment.
POSITION_NONE
}
}
}
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