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 ）