Implementing Circular Scrolling In PagerAdapter
I am using PagerAdapter for horizontal swiping for showing newspaper pages in my app.
Currently I want to implement the circular scrolling in this app.Right now what I have done is whenever I am getting on last page I try to set the currentItem to first pagei.e that functionality working for last page to first page,but the problem is that how can I go to last page from first page.
Here I am pasting my code related to pagerAdapter & 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);
}
}
}
});
Also the PagerAdapter i.e AwesomweAdapter in my case,is also as folllows:-
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);
}
Please give me any suggestions/changes in my code (if applicable) for it. Thanks in Advance.
Answer
I could achieve this by overriding onPageSelected method of OnPageChangeListener. Consider you have three pages in this order A<->B<->C. To goal is to reach C if we scroll right from A and similarly to reach A if we scroll left from C.
To do this, define your to have 5 pages (3+2), and organize the pages as follows:
C<->A<->B<->C<->A
Now in the onPageSelected method, check and if position if 0, change it to 3 (getCount()-2) and if position is 4 (getCount()-1), change it to 1. Make sure to use the method:
setCurrentItem(item, smoothScroll)
Here is complete code for CircularPagerAdaptor Class :
package zolender.adapters;
import android.content.Context;
import android.os.Parcelable;
import android.support.v4.view.PagerAdapter;
import android.support.v4.view.ViewPager;
import android.support.v4.view.ViewPager.OnPageChangeListener;
import android.view.LayoutInflater;
import android.view.View;
public class CircularPagerAdapter extends PagerAdapter{
private int[] pageIDsArray;
private int count;
public CircularPagerAdapter(final ViewPager pager, int... pageIDs) {
super();
int actualNoOfIDs = pageIDs.length;
count = actualNoOfIDs + 2;
pageIDsArray = new int[count];
for (int i = 0; i < actualNoOfIDs; i++) {
pageIDsArray[i + 1] = pageIDs[i];
}
pageIDsArray[0] = pageIDs[actualNoOfIDs - 1];
pageIDsArray[count - 1] = pageIDs[0];
pager.setOnPageChangeListener(new OnPageChangeListener() {
@Override
public void onPageSelected(int position) {
int pageCount = getCount();
if (position == 0){
pager.setCurrentItem(pageCount-2,false);
} else if (position == pageCount-1){
pager.setCurrentItem(1,false);
}
}
@Override
public void onPageScrolled(int position, float positionOffset, int positionOffsetPixels) {
// TODO Auto-generated method stub
}
@Override
public void onPageScrollStateChanged(int state) {
// TODO Auto-generated method stub
}
});
}
public int getCount() {
return count;
}
public Object instantiateItem(View container, int position) {
LayoutInflater inflater = (LayoutInflater) container.getContext()
.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
int pageId = pageIDsArray[position];
View view = inflater.inflate(pageId, null);
((ViewPager) container).addView(view, 0);
return view;
}
@Override
public void destroyItem(View container, int position, Object object) {
((ViewPager) container).removeView((View) object);
}
@Override
public void finishUpdate(View container) {
// TODO Auto-generated method stub
}
@Override
public boolean isViewFromObject(View view, Object object) {
return view == ((View) object);
}
@Override
public void restoreState(Parcelable state, ClassLoader loader) {
// TODO Auto-generated method stub
}
@Override
public Parcelable saveState() {
// TODO Auto-generated method stub
return null;
}
@Override
public void startUpdate(View container) {
// TODO Auto-generated method stub
}
}
And here is how you can use it:
myPager = (ViewPager) findViewById(R.id.myfivepanelpager);
PagerAdapter adapter = new CircularPagerAdapter(myPager, new int[]{R.layout.farleft, R.layout.left, R.layout.middle, R.layout.right, R.layout.farright});
myPager.setAdapter(adapter);
myPager.setCurrentItem(3);