androidx下的fragment的lazy懒加载问题详解
网上关于androidx的fragment懒加载文章已经有很多,各有侧重。几乎都点到了sexMaxLifecycle和修改FragmentPagerAdapter。很少看到经过实践的文章,谨以此文,更加详尽的把实践后的结果记录下来,赠予有缘人。
一、前置准备工作
几个关于androidx的fragment懒加载方案,都离不开如下几个包:
- androidx.fragment:fragment:1.1.0-alpha07 以上,支持setMaxLifecycle方法即可
- androidx.viewpager:viewpager:1.0.0 以上,如果涉及到viewpager内的fragment使用
我在实际测试代码中使用了如下版本,可供参考:
- androidx.fragment:fragment:1.2.4
- androidx.viewpager:viewpager:1.0.0
- FlycoTabLayout
还准备了4个Activity与5个Fragment:
- AddShowHideFragmentActivity 通过add show显示的案例
- AddShowHideFragmentInFragmentActivity 嵌套在fragment中的,通过add show显示的fragment案例
- ViewPagerFragmentActivity 通过ViewPager滑动显示的案例
- ViewPagerFragmentInFragmentActivity 嵌套在fragment中的,通过ViewPager滑动显示的案例
- AddFragmentInFragment 操作add show的fragment
- ViewPagerFragmentInFragment 操作ViewPager的fragment
- BlankFragment1 打印生命周期日志的空页面1
- BlankFragment2 打印生命周期日志的空页面2
- BlankFragment3 打印生命周期日志的空页面3
相应的几个简单布局文件:
文件:fragment_main.xml
加载ViewPager控件和AddShow使用的FrameLayout,以及测试跳转后返回的TextView按钮。
fragment_main.xml
<?xml version="1.0" encoding="utf-8"?> <androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android" xmlns:app="http://schemas.android.com/apk/res-auto" xmlns:tools="http://schemas.android.com/tools" android:layout_width="match_parent" android:layout_height="match_parent" > <androidx.viewpager.widget.ViewPager android:id="@+id/vp_fragment" android:layout_width="match_parent" android:layout_height="200dp" app:layout_constraintLeft_toLeftOf="parent" app:layout_constraintTop_toTopOf="parent" /> <com.flyco.tablayout.CommonTabLayout android:id="@+id/tab_title" android:layout_width="match_parent" android:layout_height="50dp" android:background="@color/colorPrimary" app:tl_indicator_color="@color/colorAccent" app:tl_indicator_height="2dp" app:tl_indicator_width="30dp" app:tl_tab_space_equal="true" app:tl_textBold="SELECT" app:tl_textSelectColor="#000000" app:tl_textUnselectColor="#333333" app:layout_constraintTop_toBottomOf="@id/vp_fragment" app:layout_constraintLeft_toLeftOf="parent" /> <FrameLayout android:id="@+id/fl_in_content" android:layout_width="match_parent" android:layout_height="200dp" app:layout_constraintTop_toBottomOf="@id/tab_title" /> <TextView android:id="@+id/tv_next" android:layout_width="match_parent" android:layout_height="50dp" android:text="next" android:gravity="center" app:layout_constraintBottom_toBottomOf="parent" /> </androidx.constraintlayout.widget.ConstraintLayout>
文件:activity_lazy_fragment.xml
这里是测试fragment嵌套情况下的布局,fl_content用来加载fragment
activity_lazy_fragment.xml
<?xml version="1.0" encoding="utf-8"?> <androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android" xmlns:app="http://schemas.android.com/apk/res-auto" xmlns:tools="http://schemas.android.com/tools" android:layout_width="match_parent" android:layout_height="match_parent" tools:context=".lazyFragment.ViewPagerFragmentActivity"> <FrameLayout android:id="@+id/fl_content" android:layout_width="match_parent" android:layout_height="match_parent" app:layout_constraintTop_toTopOf="parent" app:layout_constraintBottom_toBottomOf="parent" app:layout_constraintLeft_toLeftOf="parent" app:layout_constraintRight_toRightOf="parent" /> </androidx.constraintlayout.widget.ConstraintLayout>
文件:fragment_blank.xml
这一个空fragment就没什么讲究了
fragment_blank.xml
<?xml version="1.0" encoding="utf-8"?> <FrameLayout xmlns:android="http://schemas.android.com/apk/res/android" xmlns:tools="http://schemas.android.com/tools" android:layout_width="match_parent" android:layout_height="match_parent" > <TextView android:id="@+id/tv_fragment" android:layout_width="match_parent" android:layout_height="match_parent" android:text="" /> </FrameLayout>
二、具体代码分析
1) ViewPager+Fragment
最常见的使用方式,由ViewPager滑动显示多个Fragment,直接上代码:
activity页面代码
其中就是个简单的viewpager设置adapter然后加载fragment集合显示
/** * viewpager内的fragment懒加载 */ public class ViewPagerFragmentActivity extends BindActivity implements BlankFragment1.OnFragmentInteractionListener , BlankFragment2.OnFragmentInteractionListener, BlankFragment3.OnFragmentInteractionListener { private static final String KEY_FRAGMENT_1 = "1"; private static final String KEY_FRAGMENT_2 = "2"; private static final String KEY_FRAGMENT_3 = "3"; @BindView(R.id.vp_fragment) ViewPager vp; @BindView(R.id.tv_next) TextView tv_next; BlankFragment1 blankFragment1; BlankFragment2 blankFragment2; BlankFragment3 blankFragment3; List<Fragment> fragmentList; @Override protected int setLayoutID() { return R.layout.fragment_main; } @Override protected void initViews(Bundle savedInstanceState) { tv_next.setOnClickListener(new View.OnClickListener() { @Override public void onClick(View v) { Intent intent=new Intent(mContext, MMKVActivity.class); startActivity(intent); } }); if(savedInstanceState != null){ blankFragment1 = (BlankFragment1)getSupportFragmentManager().getFragment(savedInstanceState,KEY_FRAGMENT_1); blankFragment2 = (BlankFragment2)getSupportFragmentManager().getFragment(savedInstanceState,KEY_FRAGMENT_2); blankFragment3 = (BlankFragment3)getSupportFragmentManager().getFragment(savedInstanceState,KEY_FRAGMENT_3); } fragmentList=new ArrayList<>(); if (blankFragment1==null){ fragmentList.add(blankFragment1=BlankFragment1.newInstance("11111","")); }else { fragmentList.add(blankFragment1); } if (blankFragment2==null){ fragmentList.add(blankFragment2=BlankFragment2.newInstance("22222","")); }else { fragmentList.add(blankFragment2); } if (blankFragment3==null){ fragmentList.add(blankFragment3=BlankFragment3.newInstance("333333","")); }else { fragmentList.add(blankFragment3); } vp.setAdapter(new BaseFragmentXPagerAdapter(getSupportFragmentManager(),fragmentList,null)); } @Override public void onFragmentInteraction(Uri uri) { } @Override protected void onSaveInstanceState(Bundle outState) { if(blankFragment1 != null&&blankFragment1.isAdded()) { getSupportFragmentManager().putFragment(outState,KEY_FRAGMENT_1,blankFragment1); } if(blankFragment2 != null&&blankFragment2.isAdded()){ getSupportFragmentManager().putFragment(outState,KEY_FRAGMENT_2,blankFragment2); } if(blankFragment3 != null&&blankFragment3.isAdded()){ getSupportFragmentManager().putFragment(outState,KEY_FRAGMENT_3,blankFragment3); } super.onSaveInstanceState(outState); } }
BaseFragmentXPagerAdapter页面代码
新版FragmentPagerAdapter多了2个常量
@Retention(RetentionPolicy.SOURCE) @IntDef({BEHAVIOR_SET_USER_VISIBLE_HINT, BEHAVIOR_RESUME_ONLY_CURRENT_FRAGMENT}) private @interface Behavior { }
用在了构造方法中
/** * Constructor for {@link FragmentPagerAdapter}. * * If {@link #BEHAVIOR_RESUME_ONLY_CURRENT_FRAGMENT} is passed in, then only the current * Fragment is in the {@link Lifecycle.State#RESUMED} state. All other fragments are capped at * {@link Lifecycle.State#STARTED}. If {@link #BEHAVIOR_SET_USER_VISIBLE_HINT} is passed, all * fragments are in the {@link Lifecycle.State#RESUMED} state and there will be callbacks to * {@link Fragment#setUserVisibleHint(boolean)}. * * @param fm fragment manager that will interact with this adapter * @param behavior determines if only current fragments are in a resumed state */ public FragmentPagerAdapter(@NonNull FragmentManager fm, @Behavior int behavior) { mFragmentManager = fm; mBehavior = behavior; }
我们只需要在构造adapter时,使用BEHAVIOR_RESUME_ONLY_CURRENT_FRAGMENT
这个常量就行
/** * support lazy init */ public class BaseFragmentXPagerAdapter extends FragmentPagerAdapter { private List<Fragment> mFragmentList = new ArrayList<>(); private List<String> mFragmentTitleList = new ArrayList<>(); public BaseFragmentXPagerAdapter(@NonNull FragmentManager fm,List<Fragment> fragmentList,List<String> fragmentTitleList) { this(fm,fragmentList,fragmentTitleList,BEHAVIOR_RESUME_ONLY_CURRENT_FRAGMENT); } public BaseFragmentXPagerAdapter(@NonNull FragmentManager fm,List<Fragment> fragmentList,List<String> fragmentTitleList, int behavior) { super(fm, behavior); if (fragmentList!=null){ mFragmentList.addAll(fragmentList); } if (fragmentTitleList!=null){ mFragmentTitleList.addAll(fragmentTitleList); } } public BaseFragmentXPagerAdapter(@NonNull FragmentManager fm,Fragment[] fragmentList,String[] fragmentTitleList) { this(fm,fragmentList,fragmentTitleList,BEHAVIOR_RESUME_ONLY_CURRENT_FRAGMENT); } public BaseFragmentXPagerAdapter(@NonNull FragmentManager fm,Fragment[] fragmentList,String[] fragmentTitleList, int behavior) { super(fm, behavior); if (fragmentList!=null){ for (int i = 0; i < fragmentList.length; i++) { mFragmentList.add(fragmentList[i]); } } if (fragmentTitleList!=null){ for (int i = 0; i < fragmentTitleList.length; i++) { mFragmentTitleList.add(fragmentTitleList[i]); } } } @NonNull @Override public Fragment getItem(int position) { if (mFragmentList!=null&&!mFragmentList.isEmpty()){ return mFragmentList.get(position); }else { return null; } } @Override public int getCount() { if (mFragmentList!=null&&!mFragmentList.isEmpty()){ return mFragmentList.size(); }else { return 0; } } @Nullable @Override public CharSequence getPageTitle(int position) { if (mFragmentTitleList!=null&&!mFragmentTitleList.isEmpty()&&position<mFragmentTitleList.size()){ return mFragmentTitleList.get(position); }else { return null; } } }
最终打印生命周期日志,确认结果,viewPager+fragment搭配pagerAdapter的behavior在各种情况下的日志,可以看出新版viewPager+pagerAdapter实测下来,Fragment的onResume生命周期只会在当前页显示时调用:
首次进入 显示第一页
ViewPagerFragmentActivity--->onCreate
ViewPagerFragmentActivity--->onStart
ViewPagerFragmentActivity--->onResume
BlankFragment1--->onAttach
BlankFragment1--->onCreate
BlankFragment2--->onAttach
BlankFragment2--->onCreate
BlankFragment1--->onViewCreated
BlankFragment1--->onActivityCreated
BlankFragment1--->onStart
BlankFragment2--->onViewCreated
BlankFragment2--->onActivityCreated
BlankFragment2--->onStart
BlankFragment1--->onResume <<=================== 当前页
滑动到第二页
BlankFragment3--->onAttach
BlankFragment3--->onCreate
BlankFragment3--->onViewCreated
BlankFragment3--->onActivityCreated
BlankFragment3--->onStart
BlankFragment1--->onPause
BlankFragment2--->onResume <<=================== 当前页
锁屏
BlankFragment2--->onPause
ViewPagerFragmentActivity--->onPause
BlankFragment1--->onStop
BlankFragment2--->onStop
BlankFragment3--->onStop
ViewPagerFragmentActivity--->onStop
ViewPagerFragmentActivity--->onSaveInstanceState
解锁屏幕
ViewPagerFragmentActivity--->onRestart
BlankFragment1--->onStart
BlankFragment2--->onStart
BlankFragment3--->onStart
ViewPagerFragmentActivity--->onStart
ViewPagerFragmentActivity--->onResume
BlankFragment2--->onResume <<=================== 当前页
HOME回到桌面
BlankFragment2--->onPause
ViewPagerFragmentActivity--->onPause
BlankFragment1--->onStop
BlankFragment2--->onStop
BlankFragment3--->onStop
ViewPagerFragmentActivity--->onStop
ViewPagerFragmentActivity--->onSaveInstanceState
返回app页面
ViewPagerFragmentActivity--->onRestart
BlankFragment1--->onStart
BlankFragment2--->onStart
BlankFragment3--->onStart
ViewPagerFragmentActivity--->onStart
ViewPagerFragmentActivity--->onResume
BlankFragment2--->onResume <<=================== 当前页
跳转新页面
BlankFragment2--->onPause
ViewPagerFragmentActivity--->onPause
MMKVActivity--->onCreate
MMKVActivity--->onStart
MMKVActivity--->onResume
BlankFragment1--->onStop
BlankFragment2--->onStop
BlankFragment3--->onStop
ViewPagerFragmentActivity--->onStop
ViewPagerFragmentActivity--->onSaveInstanceState
返回ViewPager的页面
MMKVActivity--->onPause
ViewPagerFragmentActivity--->onRestart
BlankFragment1--->onStart
BlankFragment2--->onStart
BlankFragment3--->onStart
ViewPagerFragmentActivity--->onStart
ViewPagerFragmentActivity--->onResume
BlankFragment2--->onResume <<=================== 当前页
MMKVActivity--->onStop
MMKVActivity--->onDestroy
2) Fragment嵌套Fragment内的ViewPager+Fragment
外层的activity只是add一个fragment
/** * fragment内的viewpager内的fragment懒加载 */ public class ViewPagerFragmentInFragmentActivity extends BindActivity implements ViewPagerFragmentInFragment.OnFragmentInteractionListener ,BlankFragment1.OnFragmentInteractionListener, BlankFragment2.OnFragmentInteractionListener, BlankFragment3.OnFragmentInteractionListener { @Override protected int setLayoutID() { return R.layout.activity_lazy_fragment; } @Override protected void initViews(Bundle savedInstanceState) { FragmentTransaction transaction=getSupportFragmentManager().beginTransaction(); transaction.add(R.id.fl_content, ViewPagerFragmentInFragment.newInstance("","")); transaction.commit(); } @Override public void onFragmentInteraction(Uri uri) { } @Override protected void onSaveInstanceState(Bundle outState) { super.onSaveInstanceState(outState); } }
嵌套用的fragment类,ViewPagerFragmentInFragment
/** * viewpager在一个fragment内 */ public class ViewPagerFragmentInFragment extends BaseFragment { private static final String ARG_PARAM1 = "param1"; private static final String ARG_PARAM2 = "param2"; private String mParam1; private String mParam2; private OnFragmentInteractionListener mListener; private static final String KEY_FRAGMENT_1 = "1"; private static final String KEY_FRAGMENT_2 = "2"; private static final String KEY_FRAGMENT_3 = "3"; @BindView(R.id.vp_fragment) ViewPager vp; @BindView(R.id.tv_next) TextView tv_next; BlankFragment1 blankFragment1; BlankFragment2 blankFragment2; BlankFragment3 blankFragment3; List<Fragment> fragmentList; public ViewPagerFragmentInFragment() { } public static ViewPagerFragmentInFragment newInstance(String param1, String param2) { ViewPagerFragmentInFragment fragment = new ViewPagerFragmentInFragment(); Bundle args = new Bundle(); args.putString(ARG_PARAM1, param1); args.putString(ARG_PARAM2, param2); fragment.setArguments(args); return fragment; } @Override public void onSaveInstanceState(@NonNull Bundle outState) { if(blankFragment1 != null&&blankFragment1.isAdded()) { mActivity.getSupportFragmentManager().putFragment(outState,KEY_FRAGMENT_1,blankFragment1); } if(blankFragment2 != null&&blankFragment2.isAdded()){ mActivity.getSupportFragmentManager().putFragment(outState,KEY_FRAGMENT_2,blankFragment2); } if(blankFragment3 != null&&blankFragment3.isAdded()){ mActivity.getSupportFragmentManager().putFragment(outState,KEY_FRAGMENT_3,blankFragment3); } super.onSaveInstanceState(outState); } @Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); if (getArguments() != null) { mParam1 = getArguments().getString(ARG_PARAM1); mParam2 = getArguments().getString(ARG_PARAM2); } } @Override public void onViewCreated(@NonNull View view, @Nullable Bundle savedInstanceState) { super.onViewCreated(view, savedInstanceState); tv_next.setOnClickListener(new View.OnClickListener() { @Override public void onClick(View v) { Intent intent=new Intent(mContext, MMKVActivity.class); startActivity(intent); } }); if(savedInstanceState != null){ blankFragment1 = (BlankFragment1)mActivity.getSupportFragmentManager().getFragment(savedInstanceState,KEY_FRAGMENT_1); blankFragment2 = (BlankFragment2)mActivity.getSupportFragmentManager().getFragment(savedInstanceState,KEY_FRAGMENT_2); blankFragment3 = (BlankFragment3)mActivity.getSupportFragmentManager().getFragment(savedInstanceState,KEY_FRAGMENT_3); } fragmentList=new ArrayList<>(); if (blankFragment1==null){ fragmentList.add(blankFragment1=BlankFragment1.newInstance("11111","")); }else { fragmentList.add(blankFragment1); } if (blankFragment2==null){ fragmentList.add(blankFragment2=BlankFragment2.newInstance("22222","")); }else { fragmentList.add(blankFragment2); } if (blankFragment3==null){ fragmentList.add(blankFragment3=BlankFragment3.newInstance("333333","")); }else { fragmentList.add(blankFragment3); } vp.setAdapter(new BaseFragmentXPagerAdapter(mActivity.getSupportFragmentManager(),fragmentList,null)); } @Override public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) { return inflater.inflate(R.layout.fragment_main, container, false); } public void onButtonPressed(Uri uri) { if (mListener != null) { mListener.onFragmentInteraction(uri); } } @Override public void onAttach(Context context) { super.onAttach(context); if (context instanceof OnFragmentInteractionListener) { mListener = (OnFragmentInteractionListener) context; } else { throw new RuntimeException(context.toString() + " must implement OnFragmentInteractionListener"); } } @Override public void onDetach() { super.onDetach(); mListener = null; } public interface OnFragmentInteractionListener { void onFragmentInteraction(Uri uri); } }
实测日志可以发现,哪怕fragment是嵌套过的,Fragment的onResume生命周期也只会在当前页显示时调用:
首次进入显示第一页
ViewPagerFragmentInFragment--->onStart
ViewPagerFragmentInFragmentActivity--->onStart
ViewPagerFragmentInFragmentActivity--->onResume
ViewPagerFragmentInFragment--->onResume
BlankFragment1--->onAttach
BlankFragment1--->onCreate
BlankFragment2--->onAttach
BlankFragment2--->onCreate
BlankFragment1--->onViewCreated
BlankFragment1--->onActivityCreated
BlankFragment1--->onStart
BlankFragment2--->onViewCreated
BlankFragment2--->onActivityCreated
BlankFragment2--->onStart
BlankFragment1--->onResume <<=================== 当前页
滑动到第二页
BlankFragment3--->onAttach
BlankFragment3--->onCreate
BlankFragment3--->onViewCreated
BlankFragment3--->onActivityCreated
BlankFragment3--->onStart
BlankFragment1--->onPause
BlankFragment2--->onResume <<=================== 当前页
锁屏
ViewPagerFragmentInFragment--->onPause
BlankFragment2--->onPause
ViewPagerFragmentInFragmentActivity--->onPause
ViewPagerFragmentInFragment--->onStop
BlankFragment1--->onStop
BlankFragment2--->onStop
BlankFragment3--->onStop
ViewPagerFragmentInFragmentActivity--->onStop
ViewPagerFragmentInFragmentActivity--->onSaveInstanceState
解锁屏幕
ViewPagerFragmentInFragmentActivity--->onRestart
ViewPagerFragmentInFragment--->onStart
BlankFragment1--->onStart
BlankFragment2--->onStart
BlankFragment3--->onStart
ViewPagerFragmentInFragmentActivity--->onStart
ViewPagerFragmentInFragmentActivity--->onResume
ViewPagerFragmentInFragment--->onResume
BlankFragment2--->onResume <<=================== 当前页
HOME回到桌面
ViewPagerFragmentInFragment--->onPause
BlankFragment2--->onPause
ViewPagerFragmentInFragmentActivity--->onPause
ViewPagerFragmentInFragment--->onStop
BlankFragment1--->onStop
BlankFragment2--->onStop
BlankFragment3--->onStop
ViewPagerFragmentInFragmentActivity--->onStop
ViewPagerFragmentInFragmentActivity--->onSaveInstanceState
返回app页面
ViewPagerFragmentInFragmentActivity--->onRestart
ViewPagerFragmentInFragment--->onStart
BlankFragment1--->onStart
BlankFragment2--->onStart
BlankFragment3--->onStart
ViewPagerFragmentInFragmentActivity--->onStart
ViewPagerFragmentInFragmentActivity--->onResume
ViewPagerFragmentInFragment--->onResume
BlankFragment2--->onResume <<=================== 当前页
跳转新页面
ViewPagerFragmentInFragment--->onPause
BlankFragment2--->onPause
ViewPagerFragmentInFragmentActivity--->onPause
MMKVActivity--->onCreate
MMKVActivity--->onStart
MMKVActivity--->onResume
ViewPagerFragmentInFragment--->onStop
BlankFragment1--->onStop
BlankFragment2--->onStop
BlankFragment3--->onStop
ViewPagerFragmentInFragmentActivity--->onStop
ViewPagerFragmentInFragmentActivity--->onSaveInstanceState
返回ViewPager的页面
MMKVActivity--->onPause
ViewPagerFragmentInFragmentActivity--->onRestart
ViewPagerFragmentInFragment--->onStart
BlankFragment1--->onStart
BlankFragment2--->onStart
BlankFragment3--->onStart
ViewPagerFragmentInFragmentActivity--->onStart
ViewPagerFragmentInFragmentActivity--->onResume
ViewPagerFragmentInFragment--->onResume
BlankFragment2--->onResume <<=================== 当前页
3) 通过add show hide操作多个fragment
activity代码中的一个细节为通过add show的页面,设置transaction.setMaxLifecycle(fragment, Lifecycle.State.RESUMED),让该fragment的生命周期能顺利走到resume;
通过hide隐藏的页面,设置transaction.setMaxLifecycle(fragmentList.get(i), Lifecycle.State.CREATED),使隐藏了的fragment生命周期只能走到创建阶段,无法走到resume方法。
/** * add show hide下的fragment懒加载 */ public class AddShowHideFragmentActivity extends BindActivity implements BlankFragment1.OnFragmentInteractionListener , BlankFragment2.OnFragmentInteractionListener, BlankFragment3.OnFragmentInteractionListener { private static final String KEY_FRAGMENT_1 = "1"; private static final String KEY_FRAGMENT_2 = "2"; private static final String KEY_FRAGMENT_3 = "3"; @BindView(R.id.tab_title) CommonTabLayout commonTabLayout; @BindView(R.id.tv_next) TextView tv_next; BlankFragment1 blankFragment1; BlankFragment2 blankFragment2; BlankFragment3 blankFragment3; List<Fragment> fragmentList; @Override protected int setLayoutID() { return R.layout.fragment_main; } @Override protected void initViews(Bundle savedInstanceState) { tv_next.setOnClickListener(new View.OnClickListener() { @Override public void onClick(View v) { Intent intent=new Intent(mContext, MMKVActivity.class); startActivity(intent); } }); if(savedInstanceState != null){ blankFragment1 = (BlankFragment1)getSupportFragmentManager().getFragment(savedInstanceState,KEY_FRAGMENT_1); blankFragment2 = (BlankFragment2)getSupportFragmentManager().getFragment(savedInstanceState,KEY_FRAGMENT_2); blankFragment3 = (BlankFragment3)getSupportFragmentManager().getFragment(savedInstanceState,KEY_FRAGMENT_3); } fragmentList=new ArrayList<>(); if (blankFragment1==null){ fragmentList.add(blankFragment1=BlankFragment1.newInstance("11111","")); }else { fragmentList.add(blankFragment1); } if (blankFragment2==null){ fragmentList.add(blankFragment2=BlankFragment2.newInstance("22222","")); }else { fragmentList.add(blankFragment2); } if (blankFragment3==null){ fragmentList.add(blankFragment3=BlankFragment3.newInstance("33333","")); }else { fragmentList.add(blankFragment3); } ArrayList<CustomTabEntity> tabEntities = new ArrayList<>(); tabEntities.add(new TabLayoutEntity("商品1")); tabEntities.add(new TabLayoutEntity("评价2")); tabEntities.add(new TabLayoutEntity("详情3")); commonTabLayout.setTabData(tabEntities); commonTabLayout.setCurrentTab(0); showFragment(fragmentList.get(0),false); commonTabLayout.setOnTabSelectListener(new OnTabSelectListener() { @Override public void onTabSelect(int position) { showFragment(fragmentList.get(position),false); } @Override public void onTabReselect(int position) { showFragment(fragmentList.get(position),false); } }); } private void showFragment(Fragment fragment,boolean replace){ FragmentTransaction transaction = getSupportFragmentManager().beginTransaction(); if (replace){ transaction.replace(R.id.fl_in_content,fragment); }else { if (!fragment.isAdded()){ transaction.add(R.id.fl_in_content,fragment,fragment.getClass().getSimpleName()); } hideAllFragment(transaction,fragment); transaction.show(fragment); transaction.setMaxLifecycle(fragment, Lifecycle.State.RESUMED); } transaction.commit(); } private void hideAllFragment(FragmentTransaction transaction,Fragment withoutFragment){ for (int i = 0; i < fragmentList.size(); i++) { if (!fragmentList.get(i).equals(withoutFragment)&&fragmentList.get(i).isAdded()){ transaction.hide(fragmentList.get(i)); transaction.setMaxLifecycle(fragmentList.get(i), Lifecycle.State.CREATED); } } } @Override public void onFragmentInteraction(Uri uri) { } @Override protected void onSaveInstanceState(Bundle outState) { if(blankFragment1 != null&&blankFragment1.isAdded()) { getSupportFragmentManager().putFragment(outState,KEY_FRAGMENT_1,blankFragment1); } if(blankFragment2 != null&&blankFragment2.isAdded()){ getSupportFragmentManager().putFragment(outState,KEY_FRAGMENT_2,blankFragment2); } if(blankFragment3 != null&&blankFragment3.isAdded()){ getSupportFragmentManager().putFragment(outState,KEY_FRAGMENT_3,blankFragment3); } super.onSaveInstanceState(outState); } }
首次进入 显示第一页
AddShowHideFragmentActivity--->onCreate
BlankFragment1--->onAttach
BlankFragment1--->onCreate
BlankFragment1--->onViewCreated
BlankFragment1--->onActivityCreated
BlankFragment1--->onStart
AddShowHideFragmentActivity--->onStart
AddShowHideFragmentActivity--->onResume
BlankFragment1--->onResume <<=================== 当前页
点击显示第二页
BlankFragment2--->onAttach
BlankFragment2--->onCreate
BlankFragment1--->onHiddenChanged=true
BlankFragment1--->onPause
BlankFragment1--->onStop
BlankFragment1--->onDestroyView
BlankFragment2--->onViewCreated
BlankFragment2--->onActivityCreated
BlankFragment2--->onStart
BlankFragment2--->onResume <<=================== 当前页
锁屏
lankFragment2--->onPause
AddShowHideFragmentActivity--->onPause
BlankFragment2--->onStop
AddShowHideFragmentActivity--->onStop
AddShowHideFragmentActivity--->onSaveInstanceState
解锁屏幕
AddShowHideFragmentActivity--->onRestart
BlankFragment2--->onStart
AddShowHideFragmentActivity--->onStart
AddShowHideFragmentActivity--->onResume
BlankFragment2--->onResume <<=================== 当前页
HOME回到桌面
BlankFragment2--->onPause
AddShowHideFragmentActivity--->onPause
BlankFragment2--->onStop
AddShowHideFragmentActivity--->onStop
AddShowHideFragmentActivity--->onSaveInstanceState
返回app页面
AddShowHideFragmentActivity--->onRestart
BlankFragment2--->onStart
AddShowHideFragmentActivity--->onStart
AddShowHideFragmentActivity--->onResume
BlankFragment2--->onResume <<=================== 当前页
跳转新页面
BlankFragment2--->onPause
AddShowHideFragmentActivity--->onPause
MMKVActivity--->onCreate
MMKVActivity--->onStart
MMKVActivity--->onResume
BlankFragment2--->onStop
AddShowHideFragmentActivity--->onStop
AddShowHideFragmentActivity--->onSaveInstanceState
返回ViewPager的页面
MMKVActivity--->onPause
AddShowHideFragmentActivity--->onRestart
BlankFragment2--->onStart
AddShowHideFragmentActivity--->onStart
AddShowHideFragmentActivity--->onResume
BlankFragment2--->onResume <<=================== 当前页
4) Fragment嵌套Fragment内的add show hide Fragment
外层的activity只是add一个fragment
/** * fragment内的viewpager内的fragment懒加载 */ public class AddShowHideFragmentInFragmentActivity extends BindActivity implements AddFragmentInFragment.OnFragmentInteractionListener ,BlankFragment1.OnFragmentInteractionListener, BlankFragment2.OnFragmentInteractionListener, BlankFragment3.OnFragmentInteractionListener { @Override protected int setLayoutID() { return R.layout.activity_lazy_fragment; } @Override protected void initViews(Bundle savedInstanceState) { FragmentTransaction transaction=getSupportFragmentManager().beginTransaction(); transaction.add(R.id.fl_content,AddFragmentInFragment.newInstance("","")); transaction.commit(); } @Override public void onFragmentInteraction(Uri uri) { } @Override protected void onSaveInstanceState(Bundle outState) { super.onSaveInstanceState(outState); } }
内部的fragment代码如下
/** * add hide show显示的fragment 嵌套在 外层fragment内 */ public class AddFragmentInFragment extends BaseFragment { private static final String ARG_PARAM1 = "param1"; private static final String ARG_PARAM2 = "param2"; private String mParam1; private String mParam2; private OnFragmentInteractionListener mListener; private static final String KEY_FRAGMENT_1 = "1"; private static final String KEY_FRAGMENT_2 = "2"; private static final String KEY_FRAGMENT_3 = "3"; @BindView(R.id.tab_title) CommonTabLayout commonTabLayout; @BindView(R.id.tv_next) TextView tv_next; BlankFragment1 blankFragment1; BlankFragment2 blankFragment2; BlankFragment3 blankFragment3; List<Fragment> fragmentList; public AddFragmentInFragment() { } public static AddFragmentInFragment newInstance(String param1, String param2) { AddFragmentInFragment fragment = new AddFragmentInFragment(); Bundle args = new Bundle(); args.putString(ARG_PARAM1, param1); args.putString(ARG_PARAM2, param2); fragment.setArguments(args); return fragment; } @Override public void onSaveInstanceState(@NonNull Bundle outState) { if(blankFragment1 != null&&blankFragment1.isAdded()) { mActivity.getSupportFragmentManager().putFragment(outState,KEY_FRAGMENT_1,blankFragment1); } if(blankFragment2 != null&&blankFragment2.isAdded()){ mActivity.getSupportFragmentManager().putFragment(outState,KEY_FRAGMENT_2,blankFragment2); } if(blankFragment3 != null&&blankFragment3.isAdded()){ mActivity.getSupportFragmentManager().putFragment(outState,KEY_FRAGMENT_3,blankFragment3); } super.onSaveInstanceState(outState); } @Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); if (getArguments() != null) { mParam1 = getArguments().getString(ARG_PARAM1); mParam2 = getArguments().getString(ARG_PARAM2); } } @Override public void onViewCreated(@NonNull View view, @Nullable Bundle savedInstanceState) { super.onViewCreated(view, savedInstanceState); tv_next.setOnClickListener(new View.OnClickListener() { @Override public void onClick(View v) { Intent intent=new Intent(mContext, MMKVActivity.class); startActivity(intent); } }); if(savedInstanceState != null){ blankFragment1 = (BlankFragment1)mActivity.getSupportFragmentManager().getFragment(savedInstanceState,KEY_FRAGMENT_1); blankFragment2 = (BlankFragment2)mActivity.getSupportFragmentManager().getFragment(savedInstanceState,KEY_FRAGMENT_2); blankFragment3 = (BlankFragment3)mActivity.getSupportFragmentManager().getFragment(savedInstanceState,KEY_FRAGMENT_3); } fragmentList=new ArrayList<>(); if (blankFragment1==null){ fragmentList.add(blankFragment1=BlankFragment1.newInstance("11111","")); }else { fragmentList.add(blankFragment1); } if (blankFragment2==null){ fragmentList.add(blankFragment2=BlankFragment2.newInstance("222222","")); }else { fragmentList.add(blankFragment2); } if (blankFragment3==null){ fragmentList.add(blankFragment3=BlankFragment3.newInstance("3333333","")); }else { fragmentList.add(blankFragment3); } ArrayList<CustomTabEntity> tabEntities = new ArrayList<>(); tabEntities.add(new TabLayoutEntity("商品1")); tabEntities.add(new TabLayoutEntity("评价2")); tabEntities.add(new TabLayoutEntity("详情3")); commonTabLayout.setTabData(tabEntities); commonTabLayout.setCurrentTab(0); showFragment(fragmentList.get(0),false); commonTabLayout.setOnTabSelectListener(new OnTabSelectListener() { @Override public void onTabSelect(int position) { showFragment(fragmentList.get(position),false); } @Override public void onTabReselect(int position) { showFragment(fragmentList.get(position),false); } }); } private void showFragment(Fragment fragment,boolean replace){ FragmentTransaction transaction = mActivity.getSupportFragmentManager().beginTransaction(); if (replace){ transaction.replace(R.id.fl_in_content,fragment); }else { if (!fragment.isAdded()){ transaction.add(R.id.fl_in_content,fragment,fragment.getClass().getSimpleName()); } hideAllFragment(transaction,fragment); transaction.show(fragment); transaction.setMaxLifecycle(fragment, Lifecycle.State.RESUMED); } transaction.commit(); } private void hideAllFragment(FragmentTransaction transaction,Fragment withoutFragment){ for (int i = 0; i < fragmentList.size(); i++) { if (!fragmentList.get(i).equals(withoutFragment)&&fragmentList.get(i).isAdded()){ transaction.hide(fragmentList.get(i)); transaction.setMaxLifecycle(fragmentList.get(i), Lifecycle.State.CREATED); } } } @Override public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) { return inflater.inflate(R.layout.fragment_main, container, false); } public void onButtonPressed(Uri uri) { if (mListener != null) { mListener.onFragmentInteraction(uri); } } @Override public void onAttach(Context context) { super.onAttach(context); if (context instanceof OnFragmentInteractionListener) { mListener = (OnFragmentInteractionListener) context; } else { throw new RuntimeException(context.toString() + " must implement OnFragmentInteractionListener"); } } @Override public void onDetach() { super.onDetach(); mListener = null; } public interface OnFragmentInteractionListener { void onFragmentInteraction(Uri uri); } }
实测日志可以发现,哪怕fragment是嵌套过的,Fragment的onResume生命周期也只会在当前页显示时调用:
首次进入 显示第一页
AddShowHideFragmentInFragmentActivity--->onCreate
AddFragmentInFragment--->onAttach
AddFragmentInFragment--->onCreate
AddFragmentInFragment--->onViewCreated
AddFragmentInFragment--->onActivityCreated
BlankFragment1--->onAttach
BlankFragment1--->onCreate
BlankFragment1--->onViewCreated
BlankFragment1--->onActivityCreated
AddFragmentInFragment--->onStart
BlankFragment1--->onStart
AddShowHideFragmentInFragmentActivity--->onStart
AddShowHideFragmentInFragmentActivity--->onResume
AddFragmentInFragment--->onResume
BlankFragment1--->onResume <<=================== 当前页
点击显示第二页
BlankFragment2--->onAttach
BlankFragment2--->onCreate
BlankFragment1--->onHiddenChanged=true
BlankFragment1--->onPause
BlankFragment1--->onStop
BlankFragment1--->onDestroyView
BlankFragment2--->onViewCreated
BlankFragment2--->onActivityCreated
BlankFragment2--->onStart
BlankFragment2--->onResume <<=================== 当前页
锁屏
AddFragmentInFragment--->onPause
BlankFragment2--->onPause
AddShowHideFragmentInFragmentActivity--->onPause
AddFragmentInFragment--->onStop
BlankFragment2--->onStop
AddShowHideFragmentInFragmentActivity--->onStop
AddShowHideFragmentInFragmentActivity--->onSaveInstanceState
解锁屏幕
AddShowHideFragmentInFragmentActivity--->onRestart
AddFragmentInFragment--->onStart
BlankFragment2--->onStart
AddShowHideFragmentInFragmentActivity--->onStart
AddShowHideFragmentInFragmentActivity--->onResume
AddFragmentInFragment--->onResume
BlankFragment2--->onResume <<=================== 当前页
HOME回到桌面
AddFragmentInFragment--->onPause
BlankFragment2--->onPause
AddShowHideFragmentInFragmentActivity--->onPause
AddFragmentInFragment--->onStop
BlankFragment2--->onStop
AddShowHideFragmentInFragmentActivity--->onStop
AddShowHideFragmentInFragmentActivity--->onSaveInstanceState
返回app页面
AddShowHideFragmentInFragmentActivity--->onRestart
AddFragmentInFragment--->onStart
BlankFragment2--->onStart
AddShowHideFragmentInFragmentActivity--->onStart
AddShowHideFragmentInFragmentActivity--->onResume
AddFragmentInFragment--->onResume
BlankFragment2--->onResume <<=================== 当前页
跳转新页面
AddFragmentInFragment--->onPause
BlankFragment2--->onPause
AddShowHideFragmentInFragmentActivity--->onPause
MMKVActivity--->onCreate
MMKVActivity--->onStart
MMKVActivity--->onResume
AddFragmentInFragment--->onStop
BlankFragment2--->onStop
AddShowHideFragmentInFragmentActivity--->onStop
AddShowHideFragmentInFragmentActivity--->onSaveInstanceState
返回当前页
MMKVActivity--->onPause
AddShowHideFragmentInFragmentActivity--->onRestart
AddFragmentInFragment--->onStart
BlankFragment2--->onStart
AddShowHideFragmentInFragmentActivity--->onStart
AddShowHideFragmentInFragmentActivity--->onResume
AddFragmentInFragment--->onResume
BlankFragment2--->onResume <<=================== 当前页
三、小结
上面列举了四种不同的使用场景,以及各种常见的操作逻辑,除了保证页面只有显示为当前页时才显示onResume生命周期函数外,也通过saveState方法解决了fragment销毁后,重叠显示的UI异常。
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