我正在使用PagerAdapter进行横向滑动，以便在我的应用中显示报纸页面。
目前我想在这个应用程序中实现循环滚动。现在我所做的是whenever I am getting on last page I try to set the currentItem to first page，即该功能适用于最后一页到第一页，但问题是如何进入最后一页从第一页开始。
在这里，我粘贴了与pagerAdapter＆amp; amp; onPageChangeListener： -
awesomeAdapter = new AwesomePagerAdapter(awesomePager);
awesomePager.setAdapter(awesomeAdapter);
awesomePager.setPageMargin(10);
awesomePager.setOnPageChangeListener(new OnPageChangeListener() {
int lastPosition;
float posOffset = 0;
@Override
public void onPageSelected(int position) {
viewerPage = position;
CommonLogic.logMessage("Viewer Page:- "+ viewerPage, TAG, Log.VERBOSE);
posOffset = 0;
}
@Override
public void onPageScrolled(int position,float positionOffset,int positionOffsetPixels) {
if (positionOffset == 0 && positionOffsetPixels == 0 && position != 0) {
lastPosition = position;
}
posOffset -= positionOffset;
CommonLogic.logMessage(" Position:- "
+ position + " Position Offset:- " + positionOffset
+ " Position Offset Variable:- "
+ posOffset
+ " Position Offset Pixels:- "
+ positionOffsetPixels
+ " Last Position " + lastPosition,
TAG, Log.VERBOSE);
CommonLogic.logMessage(" Last Position "
+ lastPosition, TAG, Log.VERBOSE);
}
@Override
public void onPageScrollStateChanged(int state) {
// To Detect the Last Page & This Sets it to first page.This working fine.
if (state == ViewPager.SCROLL_STATE_DRAGGING && viewerPage == (uris.size() - 1)) {
CommonLogic.logMessage("Scroll State Changed ", TAG,Log.VERBOSE);
postDelayed(new Runnable() {
@Override
public void run() {
awesomePager.setCurrentItem(0, true);
}
}, 200);
}
// I have also used this to detect whether the user is on first & try to move on last page,but it is not working well.
else if (state == ViewPager.SCROLL_STATE_DRAGGING && (lastPosition == 0 || lastPosition == (uris.size() - 1)) && viewerPage == 0 && posOffset <= 0) {
CommonLogic.logMessage( "Scroll State Changed ", TAG,Log.VERBOSE);
postDelayed(new Runnable() {
@Override
public void run() {
awesomePager.setCurrentItem((uris.size() - 1), true);
}
}, 200);
}
}
}
});
在我的情况下，PagerAdapter即AwesomweAdapter也是如下： -
private class AwesomePagerAdapter extends PagerAdapter {
ViewPager pdfContainer;
DocumentNewView documentNewView;
CustomViewPager customViewPager;
public AwesomePagerAdapter(CustomViewPager awesomePager) {
this.customViewPager = awesomePager;
}
@Override
public int getItemPosition(Object object) {
return POSITION_NONE;
}
@Override
public int getCount() {
return uris.size();
}
public DocumentNewView addViewAt(int position, DocumentNewView mainView) {
CommonLogic.logMessage("Position of View:- " + position, TAG,
Log.VERBOSE);
pdfContainer.addView(mainView);
return mainView;
}
/**
* Create the page for the given position. The adapter is responsible
* for adding the view to the container given here, although it only
* must ensure this is done by the time it returns from
* {@link #finishUpdate()}.
*
* @param container
* The containing View in which the page will be shown.
* @param position
* The page position to be instantiated.
* @return Returns an Object representing the new page. This does not
* need to be a View, but can be some other container of the
* page.
*/
@Override
public Object instantiateItem(View collection, int position) {
CommonLogic
.logMessage("Instantiate Item Called ", TAG, Log.VERBOSE);
documentNewView = new DocumentNewView(cxt, display, customViewPager);
documentNewView.setPdfContext(new PdfContext());
CodecDocument codecDocument = documentNewView.open(uris
.get(position));
documentNewView.renderDocument(codecDocument);
documentNewView.setMaxZoom(4f);
documentNewView.setVerticalScrollBarEnabled(true);
codecDocument = null;
this.pdfContainer = (ViewPager) collection;
return addViewAt(position, documentNewView);
}
/**
* Remove a page for the given position. The adapter is responsible for
* removing the view from its container, although it only must ensure
* this is done by the time it returns from {@link #finishUpdate()}.
*
* @param container
* The containing View from which the page will be removed.
* @param position
* The page position to be removed.
* @param object
* The same object that was returned by
* {@link #instantiateItem(View, int)}.
*/
@Override
public void destroyItem(View collection, int position, Object view) {
pdfContainer.removeView((DocumentNewView) view);
}
/**
* Called when the a change in the shown pages has been completed. At
* this point you must ensure that all of the pages have actually been
* added or removed from the container as appropriate.
*
* @param container
* The containing View which is displaying this adapter's
* page views.
*/
@Override
public void finishUpdate(View arg0) {
CommonLogic.logMessage("Finish Update Called ", TAG, Log.VERBOSE);
}
@Override
public void restoreState(Parcelable arg0, ClassLoader arg1) {
}
@Override
public Parcelable saveState() {
return null;
}
@Override
public void startUpdate(View arg0) {
CommonLogic.logMessage("State Update Called ", TAG, Log.VERBOSE);
}
@Override
public boolean isViewFromObject(View view, Object object) {
return view == ((DocumentNewView) object);
}
请在我的代码（如果适用）中为我提供任何建议/更改。 提前致谢。
答案 0 :(得分：21)
我可以通过覆盖onPageSelected的{{1}}方法来实现这一点。考虑按此顺序排列有三个页面OnPageChangeListener。如果我们从A<->B<->C向右滚动，目标就是C，如果我们从A向左滚动，则与A类似。
要执行此操作，请将您的页面定义为5页（3 + 2），然后按如下方式组织页面：
<强> C C的 <->A<->B<->C<->
现在在A方法中，检查以及onPageSelected的位置，将其更改为0（3），如果位置为getCount()-2（{ {1}}），将其更改为4。请务必使用以下方法：
getCount()-1以下是 CircularPagerAdaptor 类的完整代码：
1以下是您可以使用它的方法：
setCurrentItem(item, smoothScroll)
答案 1 :(得分：8)
我还需要一个循环的ViewPager。这就是我所做的。我假设你从某个地方获得了pageCount值。
...
pager = (ViewPager) findViewById(R.id.pager);
//Gesture detection
final GestureDetector gestureDetector = new GestureDetector(new MyGestureDetector());
pager.setOnTouchListener(new OnTouchListener() {
@Override
public boolean onTouch(View v, MotionEvent event) {
return gestureDetector.onTouchEvent(event);
}
});
//pagelistener is just for getting selected page
pager.setOnPageChangeListener(new OnPageChangeListener() {
@Override
public void onPageSelected(int position) {
selectedPage = position;
}
@Override
public void onPageScrolled(int position, float positionOffset, int positionOffsetPixels) {
}
@Override
public void onPageScrollStateChanged(int state) {
}
});
这是GestureDetector。 复制自here
class MyGestureDetector extends SimpleOnGestureListener {
@Override
public boolean onFling(MotionEvent e1, MotionEvent e2, float velocityX, float velocityY) {
int SWIPE_MIN_DISTANCE = Utils.ConvertToPixel(mContext, 50);
int SWIPE_MAX_OFF_PATH = Utils.ConvertToPixel(mContext, 250);
int SWIPE_THRESHOLD_VELOCITY = Utils.ConvertToPixel(mContext, 200);
try {
if (Math.abs(e1.getY() - e2.getY()) > SWIPE_MAX_OFF_PATH)
return false;
// right to left swipe
if(e1.getX() - e2.getX() > SWIPE_MIN_DISTANCE
&& Math.abs(velocityX) > SWIPE_THRESHOLD_VELOCITY
&& selectedPage == (pageCount - 1)) {
pager.setCurrentItem(0);
return true;
} else if (e2.getX() - e1.getX() > SWIPE_MIN_DISTANCE
&& Math.abs(velocityX) > SWIPE_THRESHOLD_VELOCITY
&& selectedPage == 0) {
pager.setCurrentItem(pageCount - 1);
return true;
}
} catch (Exception e) {
// nothing
}
return false;
}
}
答案 2 :(得分：4)
扩展Z0lenDer的答案，当使用常规ViewPager而不需要为每个关联视图释放内存时，存储创建的视图而不是布局更有效标识。如果想要在切换项目时摆脱任何延迟和闪烁，这是必要的。
使用onPageSelected时动画也存在问题，因为在进行切换之前不会让幻灯片完成。我发现避免这种情况的唯一方法是仅在滚动状态更改为SCROLL_STATE_IDLE并且仅在onPageSelected中设置当前项目时执行切换。
private int currentPage = 0;
...
pager.setOnPageChangeListener(new OnPageChangeListener() {
@Override
public void onPageSelected(int position) {
currentPage = position;
}
@Override
public void onPageScrolled(int position, float positionOffset, int positionOffsetPixels) {
}
@Override
public void onPageScrollStateChanged(int state) {
// TODO Auto-generated method stub
Log.d(TAG, "onPageScrollStateChanged: " + state);
if (state == ViewPager.SCROLL_STATE_IDLE) {
int pageCount = getCount();
if (currentPage == 0){
pager.setCurrentItem(pageCount-2,false);
} else if (currentPage == pageCount-1){
pager.setCurrentItem(1,false);
}
}
}
});
答案 3 :(得分：0)
试试这个
((ViewPager) container)
.setOnPageChangeListener(new OnPageChangeListener() {
@Override
public void onPageSelected(int position) {
Log.i("TAG", "pos::" + position);
}
@Override
public void onPageScrollStateChanged(int state) {
// TODO Auto-generated method stub
int currentPage = pager.getCurrentItem();
Log.i("TAG", "currentPage::" + currentPage);
Log.i("TAG", "currentState::" + currentState);
Log.i("TAG", "previousState::" + previousState);
if (currentPage == 4 || currentPage == 0) {
previousState = currentState;
currentState = state;
if (previousState == 1 && currentState == 0) {
pager.setCurrentItem(currentPage == 0 ? 4 : 0);
}
}
}
@Override
public void onPageScrolled(int arg0, float arg1,
int arg2) {
// TODO Auto-generated method stub
}
});
return
这应该放在
里面 @Override
public Object instantiateItem(final View container, int position) {}
答案 4 :(得分：0)
viewPager.setAdapter(adapter);
viewPager.setCurrentItem(1, false); //going to page 1;
final int[] pagePosition = new int[1];
viewPager.addOnPageChangeListener(new ViewPager.OnPageChangeListener() {
@Override
public void onPageScrolled(int position, float positionOffset, int positionOffsetPixels) {
}
@Override
public void onPageSelected(int position) {
pagePosition[0] = position;
}
@Override
public void onPageScrollStateChanged(int state) { //state changes from 2 to 0 during a swipe
if (state == 0 && pagePosition[0] == 0){
viewPager.setCurrentItem(4, false);
} else if (state == 0 && pagePosition[0] == 5){
viewPager.setCurrentItem(1, false);
}
}
});
答案 5 :(得分：0)
这有帮助
private class CircularViewPagerHandler implements ViewPager.OnPageChangeListener {
private ViewPager mViewPager;
private int mCurrentPosition;
private int mScrollState;
private int mPreviousPosition;
public CircularViewPagerHandler(final ViewPager viewPager) {
mViewPager = viewPager;
}
@Override
public void onPageSelected(final int position) {
mCurrentPosition = position;
mPreviousPosition = position-1;
}
@Override
public void onPageScrollStateChanged(final int state) {
if (state == ViewPager.SCROLL_STATE_IDLE) {
setNextItemIfNeeded();
}
mScrollState = state;
}
private void setNextItemIfNeeded() {
if (!isScrollStateSettling()) {
handleSetNextItem();
}
}
private boolean isScrollStateSettling() {
return mScrollState == ViewPager.SCROLL_STATE_SETTLING; //indicated page is settling to it's final position
}
private void handleSetNextItem() {
final int lastPosition = mViewPager.getAdapter().getCount() - 1;
if (mCurrentPosition == 0) {
mViewPager.setCurrentItem(lastPosition,false);
} else if (mCurrentPosition == lastPosition) {
mViewPager.setCurrentItem(0, false);
}
}
@Override
public void onPageScrolled(final int position, final float positionOffset, final int positionOffsetPixels) {
}
}
这是@ tobi_b的answer