问题描述
如题，用单Activity，多个Fragment做一个应用，应该如何实现？
问题解答
回答1：强烈不建议这么玩: 如果页面很多, 而且又没管理好Fragment, 那很有可能 OOM...
如果非要这么玩, 请参考FragmentStatePagerAdapter的管理方式. 关键代码如下:
public abstract class FragmentStatePagerAdapter extends PagerAdapter { @Override public Object instantiateItem(ViewGroup container, int position) {// If we already have this item instantiated, there is nothing// to do. This can happen when we are restoring the entire pager// from its saved state, where the fragment manager has already// taken care of restoring the fragments we previously had instantiated.if (mFragments.size() > position) { Fragment f = mFragments.get(position); if (f != null) {return f; }}if (mCurTransaction == null) { mCurTransaction = mFragmentManager.beginTransaction();}Fragment fragment = getItem(position);if (DEBUG) Log.v(TAG, 'Adding item #' + position + ': f=' + fragment);if (mSavedState.size() > position) { Fragment.SavedState fss = mSavedState.get(position); if (fss != null) {fragment.setInitialSavedState(fss); }}while (mFragments.size() <= position) { mFragments.add(null);}fragment.setMenuVisibility(false);fragment.setUserVisibleHint(false);mFragments.set(position, fragment);mCurTransaction.add(container.getId(), fragment);return fragment; } @Override public void destroyItem(ViewGroup container, int position, Object object) {Fragment fragment = (Fragment) object;if (mCurTransaction == null) { mCurTransaction = mFragmentManager.beginTransaction();}if (DEBUG) Log.v(TAG, 'Removing item #' + position + ': f=' + object+ ' v=' + ((Fragment)object).getView());while (mSavedState.size() <= position) { mSavedState.add(null);}mSavedState.set(position, fragment.isAdded()? mFragmentManager.saveFragmentInstanceState(fragment) : null);mFragments.set(position, null);mCurTransaction.remove(fragment); }}
除此之外, Activity有 NavigateUp(向上导航) 和 BackPressed(回退键) 的功能, 因此, 还要管理Fragment的回退栈(和Activity的回退栈是不一样的), 即调用 FragmentTransaction#addToBackStack(String).
回答2：建议同上面的回答一样，尽量不要这样搞。希望你可以分析一下需要处理的几个页面，是否是同样性质的。比如说网易新闻，不同频道所展现的内容是类似的，所以使用Fragment比较合适。但是设置项中，各设置项中内容比较独立，使用不同的Activity比较好。
