这是一个不错的技巧,但对我来说,它工作得很好:
我有一个可以正常工作的FragmentPagerAdapter
,但我想知道的是,如果FragmentPagerAdapter
在最后一个视图上,我如何让它循环回到第一个视图并像往常一样继续运行
这是我正在使用的示例代码
public class FragmentPager extends FragmentActivity {
MyAdapter mAdapter;
ViewPager mPager;
static final int NUM_ITEMS = 5;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
mAdapter = new MyAdapter(getSupportFragmentManager());
mPager = (ViewPager)findViewById(R.id.pager);
mPager.setAdapter(mAdapter);
}
public static class MyAdapter extends FragmentPagerAdapter {
public MyAdapter(FragmentManager fm) {
super(fm);
}
@Override
public int getCount() {
return NUM_ITEMS;
}
@Override
public Fragment getItem(int position) {
return MyFragment.newInstance(position);
}
}
public static class MyFragment extends ListFragment{
int mNum;
/**
* Create a new instance of CountingFragment, providing "num"
* as an argument.
*/
static MyFragment newInstance(int num) {
MyFragment f = new MyFragment();
// Supply num input as an argument.
Bundle args = new Bundle();
args.putInt("num", num);
f.setArguments(args);
return f;
}
/**
* When creating, retrieve this instance's number from its arguments.
*/
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
mNum = getArguments() != null ? getArguments().getInt("num") : 1;
}
/**
* The Fragment's UI is just a simple text view showing its
* instance number.
*/
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View v = inflater.inflate(R.layout.fragment_pager_list, container, false);
View tv = v.findViewById(R.id.text);
((TextView)tv).setText("Fragment #" + mNum);
return v;
}
@Override
public void onActivityCreated(Bundle savedInstanceState) {
super.onActivityCreated(savedInstanceState);
setListAdapter(new ArrayAdapter<String>(getActivity(),
android.R.layout.simple_list_item_1, new String[] {"test1","test2","test3","test4","Test5"}));
}
@Override
public void onListItemClick(ListView l, View v, int position, long id) {
Log.i("FragmentList", "Item clicked: " + id);
}
}
}
基本上来说,到最后时,如何显示第一个片段,就像它会出现在其他片段上一样?
即A->B
, B->C
,C->A
和后退A->C
,C->B
,B->A
这是我的解决方案,我有“ n”个屏幕(在这种情况下为5个),由于我想返回列表末尾的第一个屏幕,因此我“添加了另一个屏幕”,它只是最后一个屏幕,也可以反向操作。基本上,我现在有“ n”个屏幕+2(在这种情况下,现在是7)。屏幕设置如下:copy of C
,A
,B
,C
,copy of A
,然后设置手势侦听器以监视某些页面上的滑动。
如果在列表的末尾(“ A的副本”,并且检测到向左滑动> a certain number of pixels
,我将移至页面A
,并继续以正常的页面旋转方式向后滑动。
朝相反方向刷卡时也是如此。
问题
从末尾页面之一移动以模拟循环时确实会有点慢,因为ViewPager
会在当前当前页面之前和之后加载页面,但是由于您位于页面列表的末尾或开头它不会像通常那样加载下一页,因为从技术上讲没有下一页。仅当您对每个列表行都有复杂的自定义视图时,才会发生这种情况]
您不能将其与动画一起用于页面滚动,因为当您从复制的页面移动到实际页面(即从A到A的副本)时,它看起来不会无缝,并且会产生动画效果。>>
而且它似乎有时甚至卡在页面的末尾,我不知道为什么
这是我的完整演示应用程序,基于android开发人员网站上的viewpager示例
public class FragmentPager extends FragmentActivity{
MyAdapter mAdapter;
public static ViewPager mPager;
static int currentPage = 1;
static final int NUM_ITEMS = 7;
public static View vContainer;
float dxInitial=0;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
mAdapter = new MyAdapter(getSupportFragmentManager());
mPager = (ViewPager)findViewById(R.id.pager);
mPager.setAdapter(mAdapter);
mPager.setCurrentItem(1,false);
mPager.setOnTouchListener(new OnTouchListener(){
@Override
public boolean onTouch(View v, MotionEvent event) {
if(event.getAction() == MotionEvent.ACTION_DOWN){
dxInitial=event.getX();
Log.d("INITIAL X", String.valueOf(dxInitial));
}else if(event.getAction() == MotionEvent.ACTION_MOVE){
if(event.getX() - dxInitial > 100 && currentPage==1){
mPager.setCurrentItem(6,false);
}else if(dxInitial - event.getX() > 100 && currentPage==5){
mPager.setCurrentItem(0,false);
}else if(dxInitial - event.getX() > 50 && currentPage==6){
mPager.setCurrentItem(1,false);
}else if(event.getX() - dxInitial > 50 && currentPage==0){
mPager.setCurrentItem(5,false);
}
}
/*if(Math.abs(dx) > Math.abs(dy)) {
if(dx>75){ directiion = "right";
}else if{
direction = "left";
}
} else {
if(dy>0) direction = "down";
else direction = "up";
}*/
return false;
}
});
mPager.setOnPageChangeListener(new OnPageChangeListener(){
@Override
public void onPageScrollStateChanged(int state) {
// TODO Auto-generated method stub
if(state == ViewPager.SCROLL_STATE_IDLE){
}
}
@Override
public void onPageScrolled(int position, float positionOffset, int positionOffsetPixels) {
}
@Override
public void onPageSelected(int arg0) {
currentPage=arg0;
}
});
}
public static class MyAdapter extends FragmentPagerAdapter{
public MyAdapter(FragmentManager fm) {
super(fm);
}
@Override
public int getCount() {
return NUM_ITEMS;
}
@Override
public Fragment getItem(int position) {
return MyFragment.newInstance(position);
}
@Override
public Object instantiateItem(View container, int position) {
vContainer=container;
return super.instantiateItem(container, position);
}
}
public static class MyFragment extends ListFragment{
int mNum;
/**
* Create a new instance of CountingFragment, providing "num"
* as an argument.
*/
static MyFragment newInstance(int num) {
MyFragment f = new MyFragment();
// Supply num input as an argument.
Bundle args = new Bundle();
args.putInt("num", num);
f.setArguments(args);
return f;
}
/**
* When creating, retrieve this instance's number from its arguments.
*/
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
mNum = getArguments() != null ? getArguments().getInt("num") : 1;
}
/**
* The Fragment's UI is just a simple text view showing its
* instance number.
*/
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View v = inflater.inflate(R.layout.fragment_pager_list, container, false);
View tv = v.findViewById(R.id.text);
if(mNum == 6){
mNum=1;
}else if(mNum==7){
mNum=5;
}else if(mNum==0){
mNum=5;
}
((TextView)tv).setText("Fragment #" + mNum);
return v;
}
@Override
public void onActivityCreated(Bundle savedInstanceState) {
super.onActivityCreated(savedInstanceState);
setListAdapter(new ArrayAdapter<String>(getActivity(),
android.R.layout.simple_list_item_1, new String[] {"test1","test2","test3","test4","Test5"}));
}
@Override
public void onListItemClick(ListView l, View v, int position, long id) {
Log.i("FragmentList", "Item clicked: " + id);
}
}
}
这是一个不错的技巧,但对我来说,它工作得很好:
@Override
public int getCount() {
return NUM_ITEMS * 1000;
}
这会使您的页面“循环播放” 1000x不要忘了对getItem使用%操作,像这样
@Override
public Fragment getItem(int position) {
position = position % 1000;
return MyFragment.newInstance(position);
}
根据tyczj的回答,我提出了一个解决方案,该解决方案用于处理在创建适配器后加载轮播项目(例如,从服务器加载项目)并且不抓取触摸侦听器,而是等待的空闲状态。 ViewPager2。就我而言,我有一个“用户个人资料”轮播。
根据tycjz的回答,如果我们有一组项A B C D
,则ViewPager2在功能上以C A B C D A
结尾,但我们在位置1而不是0处开始ViewPager2,因此它在A
处结束。
inner class UserProfileSlidePagerAdapter(fa: FragmentActivity) : FragmentStateAdapter(fa) { var profileToJumpTo: Int? = null override fun getItemCount(): Int { if (userIdsForLocalUsers.size > 0) { return userIdsForLocalUsers.size + 2 } return userIdsForLocalUsers.size } override fun createFragment(position: Int): Fragment { var positionToUse = position - 1 if (position > userIdsForLocalUsers.size) { positionToUse = 0 } if (positionToUse < 0) { positionToUse = userIdsForLocalUsers.size - 1 } val userId = userIdsForLocalUsers[positionToUse] [email protected][userId].let {userProfile -> return CarouselUserProfileFragment.newInstance(userProfile!!) } } }
在按如下方式管理PageAdapter的“按1偏移”定位问题后,可以确定发生ViewPager2
onPageSelected
事件时是处于循环的开始还是结束,然后选择要跳转到的页面当页面处于onPageScrollStateChanged
的空闲状态时。因此,在ViewPager2存在的Fragment
中:this.profiles_view_pager.registerOnPageChangeCallback(object: ViewPager2.OnPageChangeCallback() { override fun onPageScrollStateChanged(state: Int) { if (state == ViewPager2.SCROLL_STATE_IDLE) { val adapter = [email protected]_view_pager.adapter as ProfileViewModel.UserProfileSlidePagerAdapter val profileToJumpTo = adapter.profileToJumpTo profileToJumpTo?.let { [email protected]_view_pager.setCurrentItem(profileToJumpTo, false) adapter.profileToJumpTo = null } } super.onPageScrollStateChanged(state) } override fun onPageSelected(position: Int) { val adapter = [email protected]_view_pager.adapter as ProfileViewModel.UserProfileSlidePagerAdapter adapter.itemCount.let { itemCount -> if (position == 0) { adapter.profileToJumpTo = itemCount - 2 } if (position == itemCount - 1) { adapter.profileToJumpTo = 1 } } super.onPageSelected(position) } })
我还观看了LiveData,将当前项目设置为“ +1”。
this.profileViewModel.loadUserProfilesResult.observe(viewLifecycleOwner, Observer { this.profiles_view_pager.setCurrentItem(1, false) })
这是一个不错的技巧,但对我来说,它工作得很好:
根据tyczj的回答,我提出了一个解决方案,该解决方案用于处理在创建适配器后加载轮播项目(例如,从服务器加载项目)并且不抓取触摸侦听器,而是等待的空闲状态。 ViewPager2。就我而言,我有一个“用户个人资料”轮播。