使用ViewPager切換Fragment時，防止頻繁調用OnCreatView，fragmentoncreat

使用ViewPager切換Fragment時，防止頻繁調用OnCreatView，fragmentoncreat

使用ViewPager切換Fragment，我原先使用系統內建的適配器FragmentPagerAdapter。

切換fragment時，頻繁調用oncreatview()。

查看FragmentPagerAdapter的源碼，發現兩個關鍵的地方

 1 @Override 2     public Object instantiateItem(ViewGroup container, int position) { 3         if (mCurTransaction == null) { 4             mCurTransaction = mFragmentManager.beginTransaction(); 5         } 6  7         final long itemId = getItemId(position); 8  9         // Do we already have this fragment?10         String name = makeFragmentName(container.getId(), itemId);11         Fragment fragment = mFragmentManager.findFragmentByTag(name);12         if (fragment != null) {13             if (DEBUG) Log.v(TAG, "Attaching item #" + itemId + ": f=" + fragment);14            //該處使用attach導致頻繁調用oncreatview15             mCurTransaction.attach(fragment);16 17         } else {18             fragment = getItem(position);19             if (DEBUG) Log.v(TAG, "Adding item #" + itemId + ": f=" + fragment);20             mCurTransaction.add(container.getId(), fragment,21                     makeFragmentName(container.getId(), itemId));22         }23         if (fragment != mCurrentPrimaryItem) {24             fragment.setMenuVisibility(false);25             fragment.setUserVisibleHint(false);26         }27 28         return fragment;29     }30 31     @Override32     public void destroyItem(ViewGroup container, int position, Object object) {33         if (mCurTransaction == null) {34             mCurTransaction = mFragmentManager.beginTransaction();35         }36         if (DEBUG) Log.v(TAG, "Detaching item #" + getItemId(position) + ": f=" + object37                 + " v=" + ((Fragment)object).getView());38         //該處使用detach導致頻繁調用oncreatview39         mCurTransaction.detach((Fragment)object);40     }

attach和detach的頻繁使用導致了fragment頻繁調用oncreatview。

找到元兇了，接下來就好辦了。

自訂一個適配器，將attach改為show，將detach改為hide。

完美解決問題。

@Override    public Object instantiateItem(ViewGroup container, int position) {        if (mCurTransaction == null) {            mCurTransaction = mFragmentManager.beginTransaction();        }        final long itemId = getItemId(position);        // Do we already have this fragment?        String name = makeFragmentName(container.getId(), itemId);        Fragment fragment = mFragmentManager.findFragmentByTag(name);        if (fragment != null) {            if (DEBUG) Log.v(TAG, "Attaching item #" + itemId + ": f=" + fragment);            //用show而不用attach，防止頻繁調用oncreatview            mCurTransaction.show(fragment);        } else {            fragment = getItem(position);            if (DEBUG) Log.v(TAG, "Adding item #" + itemId + ": f=" + fragment);            mCurTransaction.add(container.getId(), fragment,                    makeFragmentName(container.getId(), itemId));        }        if (fragment != mCurrentPrimaryItem) {            fragment.setMenuVisibility(false);            fragment.setUserVisibleHint(false);        }        return fragment;    }    @Override    public void destroyItem(ViewGroup container, int position, Object object) {        if (mCurTransaction == null) {            mCurTransaction = mFragmentManager.beginTransaction();        }        if (DEBUG) Log.v(TAG, "Detaching item #" + getItemId(position) + ": f=" + object                + " v=" + ((Fragment) object).getView());        //用hide而不用detach，防止頻繁調用oncreatview        mCurTransaction.hide((Fragment) object);    }

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