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
add()和replace()之间的基本区别可以描述为:
Add()用于简单地向某个根元素添加片段。 Replace()的行为类似，但首先它删除之前的片段，然后添加下一个片段。
当我们将addToBackStack()与add()或replace()一起使用时，我们可以看到确切的区别。
当我们按下返回按钮后，如果add()…onCreateView从未被调用，但在replace()的情况下，当我们按下返回按钮…每次都调用oncreateView。
其他回答
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();
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)
例如，一个活动有2个片段，我们使用FragmentManager替换/添加addToBackstack每个片段到活动的布局中
使用替换
去Fragment1
Fragment1: onAttach
Fragment1: onCreate
Fragment1: onCreateView
Fragment1: onActivityCreated
Fragment1: onStart
Fragment1: onResume
去Fragment2
Fragment2: onAttach
Fragment2: onCreate
Fragment1: onPause
Fragment1: onStop
Fragment1: onDestroyView
Fragment2: onCreateView
Fragment2: onActivityCreated
Fragment2: onStart
Fragment2: onResume
流行Fragment2
Fragment2: onPause
Fragment2: onStop
Fragment2: onDestroyView
Fragment2: onDestroy
Fragment2: onDetach
Fragment1: onCreateView
Fragment1: onStart
Fragment1: onResume
流行Fragment1
Fragment1: onPause
Fragment1: onStop
Fragment1: onDestroyView
Fragment1: onDestroy
Fragment1: onDetach
使用添加
去Fragment1
Fragment1: onAttach
Fragment1: onCreate
Fragment1: onCreateView
Fragment1: onActivityCreated
Fragment1: onStart
Fragment1: onResume
去Fragment2
Fragment2: onAttach
Fragment2: onCreate
Fragment2: onCreateView
Fragment2: onActivityCreated
Fragment2: onStart
Fragment2: onResume
流行Fragment2
Fragment2: onPause
Fragment2: onStop
Fragment2: onDestroyView
Fragment2: onDestroy
Fragment2: onDetach
流行Fragment1
Fragment1: onPause
Fragment1: onStop
Fragment1: onDestroyView
Fragment1: onDestroy
Fragment1: onDetach
示例项目
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
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
我/你
