add()、replace()和addToBackStack()的区别

调用这些方法的主要区别是什么:

fragmentTransaction.addToBackStack(name);
fragmentTransaction.replace(containerViewId, fragment, tag);
fragmentTransaction.add(containerViewId, fragment, tag);

替换一个已经存在的片段，并将一个片段添加到活动状态，并将一个活动添加到后台堆栈，这意味着什么?

其次，使用findFragmentByTag()，是否搜索由add()/replace()方法或addToBackStack()方法添加的标记?

当前回答

下面的图片显示了add()和replace()之间的区别

因此add()方法继续在FragmentContainer中的前一个片段之上添加片段。

replace()方法清除容器中所有之前的Fragment，然后将其添加到FragmentContainer中。

什么是addToBackStack

addtoBackStack方法可以与add()和replace方法一起使用。它在Fragment API中有不同的用途。

目的是什么?

片段API与活动API不同，默认情况下没有返回按钮导航。如果你想回到之前的Fragment，那么我们在Fragment中使用addToBackStack()方法。我们来理解一下

案例1:

getSupportFragmentManager()
            .beginTransaction()
            .add(R.id.fragmentContainer, fragment, "TAG")
            .addToBackStack("TAG")
            .commit();

案例2:

getSupportFragmentManager()
            .beginTransaction()
            .add(R.id.fragmentContainer, fragment, "TAG")
            .commit();

2020-06-13 01:25:48

其他回答

1） fragmentTransaction.addToBackStack（str）;

描述-将此事务添加到back堆栈。这意味着事务在提交后将被记住，并且在随后从堆栈弹出时将反转其操作。

2) fragmentTransaction。替换(int containerViewId, Fragment片段，String标签)

描述-替换已添加到容器中的现有片段。这本质上与调用remove(Fragment)为所有当前添加的片段，这些片段是用相同的containerViewId添加的，然后用这里给出的相同参数添加(int, Fragment, String)相同。

3) fragmentTransaction。add(int containerViewId, Fragment片段，String标签)

描述-为活动状态添加一个片段。这个片段也可以有它的视图(如果片段。onCreateView返回非空)到活动的容器视图中。

替换已经存在的片段和添加是什么意思一个活动状态的片段，并将一个活动添加到后面栈?

有一个堆栈，所有处于运行状态的活动都保存在其中。片段属于活动。所以你可以添加它们来嵌入到一个活动中。

您可以在单个活动中组合多个片段来构建多窗格UI，并在多个活动中重用片段。当你在不同的布局下定义片段容器时，这是非常有用的。你只需要在任何布局中替换任何其他片段。

当您导航到当前布局时，您有该容器的id，可以将其替换为所需的片段。

您还可以使用popBackStack()方法返回到backStack中的前一个片段。为此，您需要使用addToBackStack()将该片段添加到堆栈中，然后使用commit()进行反射。这是相反的顺序，电流在上面。

findFragmentByTag搜索由add/replace添加的标签方法或addToBackStack方法?

If取决于您如何添加标签。然后，它仅通过您之前定义的标记(在从XML膨胀时或在添加到事务时提供的标记)找到一个片段。

引用:FragmentTransaction

2013-09-05 10:51:50

使用Add()方法添加第一个片段—>第二个片段

 btn_one.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                Toast.makeText(getActivity(),"Click First 
Fragment",Toast.LENGTH_LONG).show();

                Fragment fragment = new SecondFragment();
                getActivity().getSupportFragmentManager().beginTransaction()
                        .add(R.id.fragment_frame, fragment, fragment.getClass().getSimpleName()).addToBackStack(null).commit();
//                        .replace(R.id.fragment_frame, fragment, fragment.getClass().getSimpleName()).addToBackStack(null).commit();

            }
        });

当我们在fragment中使用add()

E/Keshav SecondFragment: onAttach
E/Keshav SecondFragment: onCreate
E/Keshav SecondFragment: onCreateView
E/Keshav SecondFragment: onActivityCreated
E/Keshav SecondFragment: onStart
E/Keshav SecondFragment: onResume

当在fragment中使用replace()时

使用replace()方法将第一个片段转换到first中的第二个片段

 btn_one.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                Toast.makeText(getActivity(),"Click First Fragment",Toast.LENGTH_LONG).show();

                Fragment fragment = new SecondFragment();
                getActivity().getSupportFragmentManager().beginTransaction()
//                        .add(R.id.fragment_frame, fragment, fragment.getClass().getSimpleName()).addToBackStack(null).commit();
                        .replace(R.id.fragment_frame, fragment, fragment.getClass().getSimpleName()).addToBackStack(null).commit();

            }
        });

E/Keshav SecondFragment: onAttach
E/Keshav SecondFragment: onCreate

E/Keshav FirstFragment: onPause -------------------------- FirstFragment
E/Keshav FirstFragment: onStop --------------------------- FirstFragment
E/Keshav FirstFragment: onDestroyView -------------------- FirstFragment

E/Keshav SecondFragment: onCreateView
E/Keshav SecondFragment: onActivityCreated
E/Keshav SecondFragment: onStart
E/Keshav SecondFragment: onResume

在Replace First Fragment的情况下，这些方法是额外调用的(onPause,onStop,onDestroyView是额外调用的)

S / o

我/你

2019-06-24 10:01:22

需要注意的重要事项:

Replace和backstack Replace之间的区别是，当我们只使用Replace时，片段就会被销毁(ondestroy()被调用)，而当我们使用backstack时，片段ondestroy()不会被调用(即当返回按钮被按下时，片段会被其onCreateView()调用)

2020-03-21 06:28:54

虽然这是一个已经回答过的老问题，但也许下面的例子可以补充这个公认的答案，它们可以对像我这样的Android新程序员有用。

选项1 - "addToBackStack()"从未使用

案例1A -添加、删除和单击后退按钮

Activity :      onCreate() - onStart() - onResume()                             Activity is visible
add Fragment A :    onAttach() - onCreate() - onCreateView() - onActivityCreated() - onStart() - onResume()     Fragment A is visible
add Fragment B :    onAttach() - onCreate() - onCreateView() - onActivityCreated() - onStart() - onResume()     Fragment B is visible
add Fragment C :    onAttach() - onCreate() - onCreateView() - onActivityCreated() - onStart() - onResume()     Fragment C is visible
remove Fragment C :     onPause() - onStop() - onDestroyView() - onDestroy() - onDetach()               Fragment B is visible
(Back button clicked)
Activity :      onPause() - onStop() - onDestroy()
Fragment A :        onPause() - onStop() - onDestroyView() - onDestroy() - onDetach()
Fragment B :        onPause() - onStop() - onDestroyView() - onDestroy() - onDetach()               App is closed, nothing is visible

案例1B -添加、替换和单击返回按钮

Activity :      onCreate() - onStart() - onResume()                             Activity is visible
add Fragment A :    onAttach() - onCreate() - onCreateView() - onActivityCreated() - onStart() - onResume()     Fragment A is visible
add Fragment B :    onAttach() - onCreate() - onCreateView() - onActivityCreated() - onStart() - onResume()     Fragment B is visible
(replace Fragment C)    
Fragment B :        onPause() - onStop() - onDestroyView() - onDestroy() - onDetach()               
Fragment A :        onPause() - onStop() - onDestroyView() - onDestroy() - onDetach()
Fragment C :        onAttach() - onCreate() - onCreateView() - onActivityCreated() - onStart() - onResume()     Fragment C is visible
(Back button clicked)
Activity :      onPause() - onStop() - onDestroy()
Fragment C :        onPause() - onStop() - onDestroyView() - onDestroy() - onDetach()               App is closed, nothing is visible

选项2 - "addToBackStack()"总是被使用

案例2A -添加、删除和单击后退按钮

Activity :      onCreate() - onStart() - onResume()                             Activity is visible
add Fragment A :    onAttach() - onCreate() - onCreateView() - onActivityCreated() - onStart() - onResume()     Fragment A is visible
add Fragment B :    onAttach() - onCreate() - onCreateView() - onActivityCreated() - onStart() - onResume()     Fragment B is visible
add Fragment C :    onAttach() - onCreate() - onCreateView() - onActivityCreated() - onStart() - onResume()     Fragment C is visible
remove Fragment C :     onPause() - onStop() - onDestroyView()                              Fragment B is visible
(Back button clicked)
Fragment C :        onCreateView() - onActivityCreated() - onStart() - onResume()                   Fragment C is visible
(Back button clicked)
Fragment C :        onPause() - onStop() - onDestroyView() - onDestroy() - onDetach()               Fragment B is visible
(Back button clicked)
Fragment B :        onPause() - onStop() - onDestroyView() - onDestroy() - onDetach()               Fragment A is visible
(Back button clicked)
Fragment A :        onPause() - onStop() - onDestroyView() - onDestroy() - onDetach()               Activity is visible
(Back button clicked)
Activity :      onPause() - onStop() - onDestroy()                              App is closed, nothing is visible

案例2B -添加、替换、删除和单击返回按钮

Activity :      onCreate() - onStart() - onResume()                             Activity is visible
add Fragment A :    onAttach() - onCreate() - onCreateView() - onActivityCreated() - onStart() - onResume()     Fragment A is visible
add Fragment B :    onAttach() - onCreate() - onCreateView() - onActivityCreated() - onStart() - onResume()     Fragment B is visible
(replace Fragment C)    
Fragment B :        onPause() - onStop() - onDestroyView()  
Fragment A :        onPause() - onStop() - onDestroyView() 
Fragment C :        onAttach() - onCreate() - onCreateView() - onActivityCreated() - onStart() - onResume()     Fragment C is visible
remove Fragment C :     onPause() - onStop() - onDestroyView()                              Activity is visible
(Back button clicked)
Fragment C :        onCreateView() - onActivityCreated() - onStart() - onResume()                   Fragment C is visible
(Back button clicked)
Fragment C :        onPause() - onStop() - onDestroyView() - onDestroy() - onDetach()               
Fragment A :        onCreateView() - onActivityCreated() - onStart() - onResume()   
Fragment B :        onCreateView() - onActivityCreated() - onStart() - onResume()                   Fragment B is visible
(Back button clicked)
Fragment B :        onPause() - onStop() - onDestroyView() - onDestroy() - onDetach()               Fragment A is visible
(Back button clicked)
Fragment A :        onPause() - onStop() - onDestroyView() - onDestroy() - onDetach()               Activity is visible
(Back button clicked)
Activity :      onPause() - onStop() - onDestroy()                              App is closed, nothing is visible

选项3 - "addToBackStack()"不总是被使用(在下面的例子中，w/o表示它不被使用)

案例3A -添加、删除和单击后退按钮

Activity :      onCreate() - onStart() - onResume()                             Activity is visible
add Fragment A :    onAttach() - onCreate() - onCreateView() - onActivityCreated() - onStart() - onResume()     Fragment A is visible
add Fragment B w/o:     onAttach() - onCreate() - onCreateView() - onActivityCreated() - onStart() - onResume()     Fragment B is visible
add Fragment C w/o:     onAttach() - onCreate() - onCreateView() - onActivityCreated() - onStart() - onResume()     Fragment C is visible
remove Fragment C :     onPause() - onStop() - onDestroyView() - onDestroy() - onDetach()               Fragment B is visible
(Back button clicked)
Fragment B :        onPause() - onStop() - onDestroyView() - onDestroy() - onDetach()               
Fragment A :        onPause() - onStop() - onDestroyView() - onDestroy() - onDetach()               Activity is visible
(Back button clicked)
Activity :      onPause() - onStop() - onDestroy()                              App is closed, nothing is visible

案例3B -添加、替换、删除和单击返回按钮

Activity :      onCreate() - onStart() - onResume()                             Activity is visible
add Fragment A :    onAttach() - onCreate() - onCreateView() - onActivityCreated() - onStart() - onResume()     Fragment A is visible
add Fragment B w/o:     onAttach() - onCreate() - onCreateView() - onActivityCreated() - onStart() - onResume()     Fragment B is visible
(replace Fragment C)    
Fragment B :        onPause() - onStop() - onDestroyView() - onDestroy() - onDetach()   
Fragment A :        onPause() - onStop() - onDestroyView() 
Fragment C :        onAttach() - onCreate() - onCreateView() - onActivityCreated() - onStart() - onResume()     Fragment C is visible
remove Fragment C :     onPause() - onStop() - onDestroyView()                              Activity is visible
(Back button clicked)
Fragment C :        onCreateView() - onActivityCreated() - onStart() - onResume()                   Fragment C is visible
(Back button clicked)
Fragment C :        onPause() - onStop() - onDestroyView() - onDestroy() - onDetach()               
Fragment A :        onCreateView() - onActivityCreated() - onStart() - onResume()                   Fragment A is visible
(Back button clicked)
Fragment A :        onPause() - onStop() - onDestroyView() - onDestroy() - onDetach()               Activity is visible
(Back button clicked)
Activity :      onPause() - onStop() - onDestroy()                              App is closed, nothing is visible

2019-03-27 19:14:06