我使用的是ViewPager的变体,它不是在水平方向上滚动,而是在垂直方向上滚动.
VerticalViewPager：
https://android.googlesource.com/platform/packages/apps/DeskClock/+/master/src/com/android/deskclock/VerticalViewPager.java
android.support.v4.app.FragmentStatePagerAdapter用于设置VerticalViewPager中的内容.
每次调用FragmentStatePagerAdapter的getItem()时,我都会从FragmentStatePagerAdapter创建并返回一个新的android.support.v4.app.Fragment实例,如下所示：
@Override
public Fragment getItem(int position) {
return PreviewFragment.getNewFragmentInstance(position);
}
PreviewFragment呈现可能不适合屏幕的内容.
为了显示不适合屏幕的所有内容,android.support.v4.widget.nestedScrollView用作PreviewFragment布局的父元素.
问题：
PreviewFragment的内容按预期滚动到位置0.
但是,为了切换到下一页,必须多次执行甩动或滑动操作,因此向位置1的页面滑动是非常困难的.
此外,投掷或滑回到位置0非常困难或几乎不可能.
需要：
Fling或滑动或切换到PreviewFragment的下一个实例应该是平滑的.
换句话说,滚动内容应该是平滑的,同时请记住,滑动到下一页也应该顺利工作.
Link to the sample project as mentioned above
解决方法
Github Link – https://github.com/karanatwal/vertical-viewpager-nestedscrollview
以下是VerticalViewPager代码 –
@Override
public boolean onInterceptTouchEvent(MotionEvent ev) {
boolean toIntercept = super.onInterceptTouchEvent(flipXY(ev));
// Return MotionEvent to normal
float x = ev.getX();
flipXY(ev);
int direction=1;
switch (ev.getAction()) {
case MotionEvent.ACTION_DOWN:
mStartDragX = x;
break;
case MotionEvent.ACTION_MOVE:
if (mStartDragX < x ) {
direction=-1;
} else if (mStartDragX > x) {
direction=1;
}
MainActivity.MyPagerAdapter adapter = (MainActivity.MyPagerAdapter)this.getAdapter();
if (adapter.getCurrentFragment() instanceof FragmentViewPager){
FragmentViewPager fragmentViewPager = (FragmentViewPager)adapter.getCurrentFragment();
toIntercept = !fragmentViewPager.getnestedScrollView().canScrollVertically(direction);
int range = fragmentViewPager.getnestedScrollView().computeVerticalScrollRange();
int offset = fragmentViewPager.getnestedScrollView().computeVerticalScrollOffset();
int extent = fragmentViewPager.getnestedScrollView().computeVerticalScrollExtent();
int percentage = (int)(100.0 * offset / (float)(range - extent));
System.out.println(" range: "+range);
System.out.print(" offset: "+offset);
System.out.print(" extent: "+extent);
System.out.print(" percentage: "+percentage);
System.out.print(" direction: "+direction);
if (fragmentViewPager.getnestedScrollView().computeVerticalScrollOffset()==0 && direction==-1){
//top
return true;
}
else if (percentage>99 && direction==1){
//bottom
return true;
}else {
//scroll nestedscrollview
return false;
}
}
break;
}
return toIntercept;
}
你的MyPagerAdapter –
public class MyPagerAdapter extends FragmentStatePagerAdapter {
public MyPagerAdapter(FragmentManager fm) {
super(fm);
}
private Fragment mCurrentFragment;
public Fragment getCurrentFragment() {
return mCurrentFragment;
}
//...
@Override
public void setPrimaryItem(ViewGroup container,int position,Object object) {
if (getCurrentFragment() != object) {
mCurrentFragment = ((Fragment) object);
}
super.setPrimaryItem(container,position,object);
}
@Override
public android.support.v4.app.Fragment getItem(int pos) {
switch (pos) {
case 0:
return FragmentViewPager.newInstance("Title Start",R.drawable.ic_launcher_background);
case 1:
return FragmentViewPager.newInstance("Rock",R.drawable.rock);
case 2:
return FragmentViewPager.newInstance("Paper",R.drawable.paper);
case 3:
return FragmentViewPager.newInstance("Scissors",R.drawable.scissors);
case 4:
return FragmentViewPager.newInstance("Title End",R.drawable.ic_launcher_background);
default:
return FragmentViewPager.newInstance("Default Title",R.drawable.rock);
}
}
@Override
public int getCount() {
return 5;
}
}
为了避免受限制的API方法 – 使用以下逻辑作为替代
//offset,range and extent
int scrollY = scrollView.getScrollY();
int scrollContentHeight = scrollView.getChildAt(0).getHeight();
int screenHeight = Utility.getScreenHeight(context);
int statusBarHeight = Utility.getStatusBarHeight(context);
double percent = ((((float) scrollY) / ((float) (scrollContentHeight - screenHeight + statusBarHeight))));
您只需要滚动百分比和滑动方向.在SO上找到滚动百分比和滑动方向有很多问题,如this和this.你应该为它做一点R& D.