重写ViewPager实现单个帖子进入左右切换和不缓存问题

需要解决问题：单个帖子进入时候可以实现左右切换，并且是在不知道帖子总数的情况下，就是不知道ViewPagerAdapter的getCount数量。

由于帖子内容的数据图片和布局比较复杂，所以不让ViewPager缓存，否则消耗内存太大。

重写ViewPager

public class LazyViewPager extends ViewGroup {

private boolean isCanScroll = true;

public boolean isCanScroll() {
return isCanScroll;
}

public void setCanScroll(boolean isCanScroll) {
this.isCanScroll = isCanScroll;
}

private static final String TAG = "LazyViewPager";
private static final boolean DEBUG = false;

private static final boolean USE_CACHE = false;

<span style="color:#ff0000;">private static final int DEFAULT_OFFSCREEN_PAGES = 0;//默认的加载页面,ViewPager是1个,所以会加载两个Fragment</span>
private static final int MAX_SETTLE_DURATION = 600; // ms

重写ViewPager的setAdapter可以实现单个帖子指定跳转到的页数
public void setAdapter(PagerAdapter adapter,int position) {
if (mAdapter != null) {
mAdapter.unregisterDataSetObserver(mObserver);
mAdapter.startUpdate(this);
for (int i = 0; i < mItems.size(); i++) {
final ItemInfo ii = mItems.get(i);
mAdapter.destroyItem(this, ii.position, ii.object);
}
mAdapter.finishUpdate(this);
mItems.clear();
removeAllViews();
mCurItem = 0;
scrollTo(0, 0);
}

mAdapter = adapter;

if (mAdapter != null) {
if (mObserver == null) {
mObserver = new PagerObserver();
}
mAdapter.registerDataSetObserver(mObserver);
mPopulatePending = false;
if (mRestoredCurItem >= 0) {
mAdapter.restoreState(mRestoredAdapterState, mRestoredClassLoader);
<span style="color:#ff0000;"> if(position>0){
setCurrentItemInternal(position, false, true);
}else{
setCurrentItemInternal(mRestoredCurItem, false, true);
}</span>
mRestoredCurItem = -1;
mRestoredAdapterState = null;
mRestoredClassLoader = null;
} else {
populate(position);
}
}
}

不过前提是设置这个ViewPager的Adapter的getCount的数量为1000或者Integer.Max

如果要实现ViewPager的Fragment不重复执行onCreateView方法，需要重写destroyItem

private class MyFragmentAdapter extends FragmentPagerAdapter{

public MyFragmentAdapter(FragmentManager fm) {
super(fm);
// TODO Auto-generated constructor stub
}

@Override
public Fragment getItem(int arg0) {
// TODO Auto-generated method stub
MyFragment fragment = new MyFragment(arg0);
return fragment;
}

@Override
public int getCount() {
// TODO Auto-generated method stub
return 10;
}

@Override
public void destroyItem(ViewGroup container, int position, Object object) {
// TODO Auto-generated method stub
// super.destroyItem(container, position, object);
}

@Override
public void destroyItem(View container, int position, Object object) {
// TODO Auto-generated method stub
// super.destroyItem(container, position, object);
}
}

如果要设置ViewPager实现左右无限切换，可以通过重写Adapter的getItem（）方法，

@Override
public Fragment getItem(int arg0) {
// TODO Auto-generated method stub
MyFragment fragment = fragments.get(arg0%4);
return fragment;
}

前提是getCount是个很大的数

复制去Google翻译翻译结果
新MyFragment（为arg0）