package me.qixingchen.mdbilibili.widget;
import android.content.Context;
import android.support.v4.view.PagerAdapter;
import android.support.v4.view.ViewPager;
import android.util.AttributeSet;
import java.util.ArrayList;
import java.util.List;
/**
* Created by qixingchen on 15/12/4.
* pager无限循环
*/
public class LoopViewPager extends ViewPager {
private static final boolean DEFAULT_BOUNDARY_CASHING = false;
private List<OnPageChangeListener> mOnPageChangeListeners = new ArrayList<>();
private LoopPagerAdapter mAdapter;
private boolean mBoundaryCaching = DEFAULT_BOUNDARY_CASHING;
private OnPageChangeListener onPageChangeListener = new OnPageChangeListener() {
private float mPreviousOffset = -1;
private float mPreviousPosition = -1;
@Override
public void onPageSelected(int position) {
int realPosition = mAdapter.toRealPosition(position);
if (mPreviousPosition != realPosition) {
mPreviousPosition = realPosition;
for (OnPageChangeListener listener : mOnPageChangeListeners) {
listener.onPageSelected(realPosition);
}
}
}
@Override
public void onPageScrolled(int position, float positionOffset,
int positionOffsetPixels) {
int realPosition = position;
if (mAdapter == null) {
return;
}
if (mAdapter != null) {
realPosition = mAdapter.toRealPosition(position);
if (positionOffset == 0
&& mPreviousOffset == 0
&& (position == 0 || position == mAdapter.getCount() - 1)) {
setCurrentItem(realPosition, false);
}
}
mPreviousOffset = positionOffset;
for (OnPageChangeListener listener : mOnPageChangeListeners) {
if (realPosition != mAdapter.getRealCount() - 1) {
listener.onPageScrolled(realPosition,
positionOffset, positionOffsetPixels);
} else {
if (positionOffset > .5) {
listener.onPageScrolled(0, 0, 0);
} else {
listener.onPageScrolled(realPosition,
0, 0);
}
}
}
}
@Override
public void onPageScrollStateChanged(int state) {
if (mAdapter != null) {
int position = LoopViewPager.super.getCurrentItem();
int realPosition = mAdapter.toRealPosition(position);
if (state == ViewPager.SCROLL_STATE_IDLE
&& (position == 0 || position == mAdapter.getCount() - 1)) {
setCurrentItem(realPosition, false);
}
}
for (OnPageChangeListener listener : mOnPageChangeListeners) {
listener.onPageScrollStateChanged(state);
}
}
};
public LoopViewPager(Context context) {
super(context);
init();
}
public LoopViewPager(Context context, AttributeSet attrs) {
super(context, attrs);
init();
}
/**
* helper function which may be used when implementing FragmentPagerAdapter
*
* @param position
* @param count
*
* @return (position-1)%count
*/
public static int toRealPosition(int position, int count) {
position = position - 1;
if (position < 0) {
position += count;
} else {
position = position % count;
}
return position;
}
/**
* If set to true, the boundary views (i.e. first and last) will never be destroyed
* This may help to prevent "blinking" of some views
*
* @param flag
*/
public void setBoundaryCaching(boolean flag) {
mBoundaryCaching = flag;
if (mAdapter != null) {
mAdapter.setBoundaryCaching(flag);
}
}
@Override
public PagerAdapter getAdapter() {
return mAdapter != null ? mAdapter.getRealAdapter() : mAdapter;
}
@Override
public void setAdapter(PagerAdapter adapter) {
mAdapter = new LoopPagerAdapter(adapter);
mAdapter.setBoundaryCaching(mBoundaryCaching);
super.setAdapter(mAdapter);
setCurrentItem(0, false);
}
@Override
public int getCurrentItem() {
return mAdapter != null ? mAdapter.toRealPosition(super.getCurrentItem()) : 0;
}
;
@Override
public void setCurrentItem(int item) {
if (getCurrentItem() != item) {
setCurrentItem(item, true);
}
}
public void setCurrentItem(int item, boolean smoothScroll) {
int realItem = mAdapter.toInnerPosition(item);
super.setCurrentItem(realItem, smoothScroll);
}
@Override
public void addOnPageChangeListener(OnPageChangeListener listener) {
mOnPageChangeListeners.add(listener);
}
private void init() {
super.addOnPageChangeListener(onPageChangeListener);
}
}