blocks|key|409831|text|您可以使用getBackStackEntryAt()。为了了解活动在后台堆栈中有多少条目，您可以使用getBackStackEntryCount()|type|unstyled|depth|inlineStyleRanges|entityRanges|offset|length|data|409832|int+lastFragmentCount+=+getBackStackEntryCount()+-+1;|code-block|syntax|javascript|409833|entityMap|0|LINK|mutability|MUTABLE|url|http://developer.android.com/reference/android/app/FragmentManager.html#getBackStackEntryAt%2528int%2529|1|http://developer.android.com/reference/android/app/FragmentManager.html#getBackStackEntryCount%2528%2529^0|5|L|0|1E|O|1|0|0^^$0|@$1|2|3|4|5|6|7|S|8|@]|9|@$A|T|B|U|1|V]|$A|W|B|X|1|Y]]|C|$]]|$1|D|3|E|5|F|7|Z|8|@]|9|@]|C|$G|H]]|$1|I|3|-4|5|6|7|10|8|@]|9|@]|C|$]]]|J|$K|$5|L|M|N|C|$O|P]]|Q|$5|L|M|N|C|$O|R]]]]

you can use <a href="http://developer.android.com/reference/android/app/FragmentManager.html#getBackStackEntryAt%28int%29" rel="nofollow noreferrer">getBackStackEntryAt()</a>. In order to know how many entry the activity holds in the backstack you can use <a href="http://developer.android.com/reference/android/app/FragmentManager.html#getBackStackEntryCount%28%29" rel="nofollow noreferrer">getBackStackEntryCount()</a> 

<pre><code>int lastFragmentCount = getBackStackEntryCount() - 1;
</code></pre>

blocks|key|409913|text|您可以使用API级别14中引入的FragmentManager.BackStackEntry的getName()方法。此方法将返回一个标记，该标记是您使用addTobackStack(tag)将片段添加到后台堆栈时使用的标记。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|409914|int+index+=+getActivity().getFragmentManager().getBackStackEntryCount()+-+1
FragmentManager.BackStackEntry+backEntry+=+getFragmentManager().getBackStackEntryAt(index);
String+tag+=+backEntry.getName();
Fragment+fragment+=+getFragmentManager().findFragmentByTag(tag);|code-block|syntax|javascript|409915|您需要确保将片段添加到后台堆栈，如下所示：|409916|fragmentTransaction.addToBackStack(tag);|409917|entityMap^0|G|U|1B|9|25|J|0|0|0|0^^$0|@$1|2|3|4|5|6|7|Q|8|@$9|R|A|S|B|C]|$9|T|A|U|B|C]|$9|V|A|W|B|C]]|D|@]|E|$]]|$1|F|3|G|5|H|7|X|8|@]|D|@]|E|$I|J]]|$1|K|3|L|5|6|7|Y|8|@]|D|@]|E|$]]|$1|M|3|N|5|H|7|Z|8|@]|D|@]|E|$I|J]]|$1|O|3|-4|5|6|7|10|8|@]|D|@]|E|$]]]|P|$]]

You can use the <code>getName()</code> method of <code>FragmentManager.BackStackEntry</code> which was introduced in API level 14. This method will return a tag which was the one you used when you added the Fragment to the backstack with <code>addTobackStack(tag)</code>.

<pre><code>int index = getActivity().getFragmentManager().getBackStackEntryCount() - 1
FragmentManager.BackStackEntry backEntry = getFragmentManager().getBackStackEntryAt(index);
String tag = backEntry.getName();
Fragment fragment = getFragmentManager().findFragmentByTag(tag);
</code></pre>

You need to make sure that you added the fragment to the backstack like this:

<pre><code>fragmentTransaction.addToBackStack(tag);
</code></pre>

blocks|key|409970|text|deepak+goel给出的答案对我不起作用，因为我总是从entry.getName()得到null；|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|409971|我所做的是以这种方式为片段设置一个标记：|409972|ft.add(R.id.fragment_container,+fragmentIn,+FRAGMENT_TAG);|code-block|syntax|javascript|409973|其中ft是我的片段事务，FRAGMENT_TAG是标记。然后我使用下面的代码来获取片段：|409974|Fragment+prev_fragment+=+fragmentManager.findFragmentByTag(FRAGMENT_TAG);|409975|entityMap^0|T|F|0|0|0|C|C|0|0^^$0|@$1|2|3|4|5|6|7|S|8|@$9|T|A|U|B|C]]|D|@]|E|$]]|$1|F|3|G|5|6|7|V|8|@]|D|@]|E|$]]|$1|H|3|I|5|J|7|W|8|@]|D|@]|E|$K|L]]|$1|M|3|N|5|6|7|X|8|@$9|Y|A|Z|B|C]]|D|@]|E|$]]|$1|O|3|P|5|J|7|10|8|@]|D|@]|E|$K|L]]|$1|Q|3|-4|5|6|7|11|8|@]|D|@]|E|$]]]|R|$]]

The answer given by deepak goel does not work for me because I always get null from <code>entry.getName()</code>;

What I do is to set a Tag to the fragment this way:

<pre><code>ft.add(R.id.fragment_container, fragmentIn, FRAGMENT_TAG);
</code></pre>

Where ft is my fragment transaction and <code>FRAGMENT_TAG</code> is the tag. Then I use this code to get the fragment:

<pre><code>Fragment prev_fragment = fragmentManager.findFragmentByTag(FRAGMENT_TAG);
</code></pre>

blocks|key|625053|text|FragmentManager.findFragmentById(fragmentsContainerId)+|type|code-block|depth|inlineStyleRanges|entityRanges|data|syntax|javascript|625054|function返回到backstack中顶部Fragment的链接。使用示例：|unstyled|offset|length|style|CODE|625055|++++fragmentManager.addOnBackStackChangedListener(new+OnBackStackChangedListener()+{
++++++++@Override
++++++++public+void+onBackStackChanged()+{
++++++++++++Fragment+fr+=+fragmentManager.findFragmentById(R.id.fragmentsContainer);
++++++++++++if(fr!=null){
++++++++++++++++Log.e("fragment=",+fr.getClass().getSimpleName());
++++++++++++}
++++++++}
++++});|625056|entityMap|0|LINK|mutability|MUTABLE|url|http://developer.android.com/reference/android/app/FragmentManager.html#findFragmentById%2528int%2529^0|0|N|8|0|8|0|0|0^^$0|@$1|2|3|4|5|6|7|U|8|@]|9|@]|A|$B|C]]|$1|D|3|E|5|F|7|V|8|@$G|W|H|X|I|J]]|9|@$G|Y|H|Z|1|10]]|A|$]]|$1|K|3|L|5|6|7|11|8|@]|9|@]|A|$B|C]]|$1|M|3|-4|5|F|7|12|8|@]|9|@]|A|$]]]|N|$O|$5|P|Q|R|A|$S|T]]]]

<pre><code>FragmentManager.findFragmentById(fragmentsContainerId) 
</code></pre>

<a href="http://developer.android.com/reference/android/app/FragmentManager.html#findFragmentById%28int%29">function</a> returns link to top <code>Fragment</code> in backstack. Usage example:

<pre><code> fragmentManager.addOnBackStackChangedListener(new OnBackStackChangedListener() {
 @Override
 public void onBackStackChanged() {
 Fragment fr = fragmentManager.findFragmentById(R.id.fragmentsContainer);
 if(fr!=null){
 Log.e("fragment=", fr.getClass().getSimpleName());
 }
 }
 });
</code></pre>

blocks|key|410049|text|保留自己的后端堆栈：myBackStack。在将片段Add到FragmentManager时，还要将其添加到myBackStack。在onBackStackChanged()中，当其长度大于getBackStackEntryCount时从myBackStack中弹出。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|410050|entityMap^0|A|B|Q|3|U|F|1I|B|1V|K|2N|M|3B|B|0^^$0|@$1|2|3|4|5|6|7|H|8|@$9|I|A|J|B|C]|$9|K|A|L|B|C]|$9|M|A|N|B|C]|$9|O|A|P|B|C]|$9|Q|A|R|B|C]|$9|S|A|T|B|C]|$9|U|A|V|B|C]]|D|@]|E|$]]|$1|F|3|-4|5|6|7|W|8|@]|D|@]|E|$]]]|G|$]]

Keep your own back stack: <code>myBackStack</code>. As you <code>Add</code> a fragment to the <code>FragmentManager</code>, also add it to <code>myBackStack</code>. In <code>onBackStackChanged()</code> pop from <code>myBackStack</code> when its length is greater than <code>getBackStackEntryCount</code>.

blocks|key|410122|text|或者，您可以在添加与其内容相对应的片段时添加一个标记，并使用简单的静态字符串字段(也可以将其保存在onSaveInstanceState(捆绑)方法中的活动实例包中)来保存最后添加的片段标记，并在需要的任何时候获取此片段byTag()……|type|unstyled|depth|inlineStyleRanges|entityRanges|data|410123|entityMap^0|0^^$0|@$1|2|3|4|5|6|7|D|8|@]|9|@]|A|$]]|$1|B|3|-4|5|6|7|E|8|@]|9|@]|A|$]]]|C|$]]

Or you may just add a tag when adding fragments corresponding to their content and use simple static String field (also you may save it in activity instance bundle in onSaveInstanceState(Bundle) method) to hold last added fragment tag and get this fragment byTag() at any time you need...

blocks|key|410177|text|我亲自尝试了其中的许多解决方案，最终得到了这个有效的解决方案：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|410178|添加下面将多次使用的这个实用程序方法，以获取backstack中的碎片数量：|410179|protected+int+getFragmentCount()+{
++++return+getSupportFragmentManager().getBackStackEntryCount();
}|code-block|syntax|javascript|410180|然后，当您使用FragmentTransaction方法添加/替换您的片段时，为您的片段生成一个唯一的标记(例如:使用堆栈中的片段数量)：|410181|getSupportFragmentManager().beginTransaction().add(yourContainerId,+yourFragment,+Integer.toString(getFragmentCount()));|410182|最后，您可以使用此方法在后台堆栈中找到任何片段：|410183|private+Fragment+getFragmentAt(int+index)+{
++++return+getFragmentCount()+>+0+?+getSupportFragmentManager().findFragmentByTag(Integer.toString(index))+:+null;
}|410184|因此，在后栈中获取顶部片段可以通过调用以下命令轻松实现：|410185|protected+Fragment+getCurrentFragment()+{
++++return+getFragmentAt(getFragmentCount()+-+1);
}|410186|希望这能有所帮助！|410187|entityMap^0|0|0|0|0|0|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|Y|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|Z|8|@]|9|@]|A|$]]|$1|D|3|E|5|F|7|10|8|@]|9|@]|A|$G|H]]|$1|I|3|J|5|6|7|11|8|@]|9|@]|A|$]]|$1|K|3|L|5|F|7|12|8|@]|9|@]|A|$G|H]]|$1|M|3|N|5|6|7|13|8|@]|9|@]|A|$]]|$1|O|3|P|5|F|7|14|8|@]|9|@]|A|$G|H]]|$1|Q|3|R|5|6|7|15|8|@]|9|@]|A|$]]|$1|S|3|T|5|F|7|16|8|@]|9|@]|A|$G|H]]|$1|U|3|V|5|6|7|17|8|@]|9|@]|A|$]]|$1|W|3|-4|5|6|7|18|8|@]|9|@]|A|$]]]|X|$]]

I personnaly tried many of those solutions and ended up with this working solution:

Add this utility method that will be used several times below to get the number of fragments in your backstack:

<pre><code>protected int getFragmentCount() {
 return getSupportFragmentManager().getBackStackEntryCount();
}
</code></pre>

Then, when you add/replace your fragment using FragmentTransaction method, generate a unique tag to your fragment (e.g.: by using the number of fragments in your stack):

<pre><code>getSupportFragmentManager().beginTransaction().add(yourContainerId, yourFragment, Integer.toString(getFragmentCount()));
</code></pre>

Finally, you can find any of your fragments in your backstack with this method:

<pre><code>private Fragment getFragmentAt(int index) {
 return getFragmentCount() &gt; 0 ? getSupportFragmentManager().findFragmentByTag(Integer.toString(index)) : null;
}
</code></pre>

Therefore, fetching the top fragment in your backstack can be easily achieved by calling:

<pre><code>protected Fragment getCurrentFragment() {
 return getFragmentAt(getFragmentCount() - 1);
}
</code></pre>

Hope this helps!

blocks|key|625327|text|在fragmentMananger中有一个片段列表。请注意，删除片段并不会使列表大小减小(片段条目只会变为null)。因此，有效的解决方案是：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|625328|public+Fragment+getTopFragment()+{
+List<Fragment>+fragentList+=+fragmentManager.getFragments();
+Fragment+top+=+null;
++for+(int+i+=+fragentList.size()+-1;+i>=0+;+i--)+{
+++top+=+(Fragment)+fragentList.get(i);
+++++if+(top+!=+null)+{
+++++++return+top;
+++++}
+++}
+return+top;
}|code-block|syntax|javascript|625329|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|J|8|@]|9|@]|A|$E|F]]|$1|G|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|H|$]]

There is a list of fragments in the fragmentMananger. Be aware that removing a fragment, does not make the list size decrease (the fragment entry just turn to null). Therefore, a valid solution would be:

<pre><code>public Fragment getTopFragment() {
 List&lt;Fragment&gt; fragentList = fragmentManager.getFragments();
 Fragment top = null;
 for (int i = fragentList.size() -1; i&gt;=0 ; i--) {
 top = (Fragment) fragentList.get(i);
 if (top != null) {
 return top;
 }
 }
 return top;
}
</code></pre>

blocks|key|625417|text|实际上，没有最新的片段添加到堆栈中，因为您可以在单个事务中向堆栈添加几个或多个片段，或者只删除片段而不添加新的片段。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|625418|如果您真的想要有一个片段堆栈，并且能够通过它在堆栈中的索引来访问一个片段，那么您最好在FragmentManager及其后栈上有一个抽象层。下面是你怎么做的：|offset|length|style|CODE|625419|public+class+FragmentStackManager+{
++private+final+FragmentManager+fragmentManager;
++private+final+int+containerId;

++private+final+List<Fragment>+fragments+=+new+ArrayList<>();

++public+FragmentStackManager(final+FragmentManager+fragmentManager,
++++++final+int+containerId)+{
++++this.fragmentManager+=+fragmentManager;
++++this.containerId+=+containerId;
++}

++public+Parcelable+saveState()+{
++++final+Bundle+state+=+new+Bundle(fragments.size());
++++for+(int+i+=+0,+count+=+fragments.size();+i+<+count;+%2B%2Bi)+{
++++++fragmentManager.putFragment(state,+Integer.toString(i),+fragments.get(i));
++++}
++++return+state;
++}

++public+void+restoreState(final+Parcelable+state)+{
++++if+(state+instanceof+Bundle)+{
++++++final+Bundle+bundle+=+(Bundle)+state;
++++++int+index+=+0;
++++++while+(true)+{
++++++++final+Fragment+fragment+=
++++++++++++fragmentManager.getFragment(bundle,+Integer.toString(index));
++++++++if+(fragment+==+null)+{
++++++++++break;
++++++++}

++++++++fragments.add(fragment);
++++++++index+%2B=+1;
++++++}
++++}
++}

++public+void+replace(final+Fragment+fragment)+{
++++fragmentManager.popBackStackImmediate(
++++++++null,+FragmentManager.POP_BACK_STACK_INCLUSIVE);
++++fragmentManager.beginTransaction()
++++++++.replace(containerId,+fragment)
++++++++.addToBackStack(null)
++++++++.commit();
++++fragmentManager.executePendingTransactions();

++++fragments.clear();
++++fragments.add(fragment);
++}

++public+void+push(final+Fragment+fragment)+{
++++fragmentManager
++++++++.beginTransaction()
++++++++.replace(containerId,+fragment)
++++++++.addToBackStack(null)
++++++++.commit();
++++fragmentManager.executePendingTransactions();

++++fragments.add(fragment);
++}

++public+boolean+pop()+{
++++if+(isEmpty())+{
++++++return+false;
++++}

++++fragmentManager.popBackStackImmediate();

++++fragments.remove(fragments.size()+-+1);
++++return+true;
++}

++public+boolean+isEmpty()+{
++++return+fragments.isEmpty();
++}

++public+int+size()+{
++++return+fragments.size();
++}

++public+Fragment+getFragment(final+int+index)+{
++++return+fragments.get(index);
++}
}|code-block|syntax|javascript|625420|现在，您应该使用FragmentStackManager的push()、replace()和pop()方法，而不是通过直接调用FragmentManager来添加和删除片段。您只需调用stack.get(stack.size()+-+1)即可访问最上面的片段。|625421|但如果你喜欢黑客，我不得不用其他方式来做类似的事情。我必须提到的唯一一件事是，这些hack只能与支持片段一起工作。|625422|第一个技巧是将所有活动片段添加到片段管理器中。如果你只是一个接一个地替换片段，并从堆栈中弹出，这个方法将返回最上面的片段：|625423|public+class+BackStackHelper+{
++public+static+List<Fragment>+getTopFragments(
++++++final+FragmentManager+fragmentManager)+{
++++final+List<Fragment>+fragments+=+fragmentManager.getFragments();
++++final+List<Fragment>+topFragments+=+new+ArrayList<>();

++++for+(final+Fragment+fragment+:+fragments)+{
++++++if+(fragment+!=+null+&&+fragment.isResumed())+{
++++++++topFragments.add(fragment);
++++++}
++++}

++++return+topFragments;
++}
}|625424|第二种方法是更加复杂的event，它允许您获取在调用addToBackStack的最后一个事务中添加的所有片段：|625425|package+android.support.v4.app;

import+java.util.ArrayList;
import+java.util.Collections;
import+java.util.List;

public+class+BackStackHelper+{
++public+static+List<Fragment>+getTopFragments(
++++++final+FragmentManager+fragmentManager)+{
++++if+(fragmentManager.getBackStackEntryCount()+==+0)+{
++++++return+Collections.emptyList();
++++}

++++final+List<Fragment>+fragments+=+new+ArrayList<>();

++++final+int+count+=+fragmentManager.getBackStackEntryCount();
++++final+BackStackRecord+record+=
++++++++(BackStackRecord)+fragmentManager.getBackStackEntryAt(count+-+1);
++++BackStackRecord.Op+op+=+record.mHead;
++++while+(op+!=+null)+{
++++++switch+(op.cmd)+{
++++++++case+BackStackRecord.OP_ADD:
++++++++case+BackStackRecord.OP_REPLACE:
++++++++case+BackStackRecord.OP_SHOW:
++++++++case+BackStackRecord.OP_ATTACH:
++++++++++fragments.add(op.fragment);
++++++}
++++++op+=+op.next;
++++}

++++return+fragments;
++}
}|625426|请注意，在这种情况下，您必须将此类放入android.support.v4.app包中。|625427|entityMap^0|0|17|F|0|0|8|K|T|6|10|9|1A|5|1R|F|2K|R|0|0|0|0|Q|E|0|0|J|M|0^^$0|@$1|2|3|4|5|6|7|12|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|13|8|@$D|14|E|15|F|G]]|9|@]|A|$]]|$1|H|3|I|5|J|7|16|8|@]|9|@]|A|$K|L]]|$1|M|3|N|5|6|7|17|8|@$D|18|E|19|F|G]|$D|1A|E|1B|F|G]|$D|1C|E|1D|F|G]|$D|1E|E|1F|F|G]|$D|1G|E|1H|F|G]|$D|1I|E|1J|F|G]]|9|@]|A|$]]|$1|O|3|P|5|6|7|1K|8|@]|9|@]|A|$]]|$1|Q|3|R|5|6|7|1L|8|@]|9|@]|A|$]]|$1|S|3|T|5|J|7|1M|8|@]|9|@]|A|$K|L]]|$1|U|3|V|5|6|7|1N|8|@$D|1O|E|1P|F|G]]|9|@]|A|$]]|$1|W|3|X|5|J|7|1Q|8|@]|9|@]|A|$K|L]]|$1|Y|3|Z|5|6|7|1R|8|@$D|1S|E|1T|F|G]]|9|@]|A|$]]|$1|10|3|-4|5|6|7|1U|8|@]|9|@]|A|$]]]|11|$]]

Actually there's no latest fragment added to the stack because you can add several or fragments to the stack in a single transaction or just remove fragments without adding a new one.

If you really want to have a stack of fragments and to be able to access a fragment by its index in the stack, you'd better have an abstraction layer over the <code>FragmentManager</code> and its backstack. Here's how you can do it:

<pre><code>public class FragmentStackManager {
 private final FragmentManager fragmentManager;
 private final int containerId;

 private final List&lt;Fragment&gt; fragments = new ArrayList&lt;&gt;();

 public FragmentStackManager(final FragmentManager fragmentManager,
 final int containerId) {
 this.fragmentManager = fragmentManager;
 this.containerId = containerId;
 }

 public Parcelable saveState() {
 final Bundle state = new Bundle(fragments.size());
 for (int i = 0, count = fragments.size(); i &lt; count; ++i) {
 fragmentManager.putFragment(state, Integer.toString(i), fragments.get(i));
 }
 return state;
 }

 public void restoreState(final Parcelable state) {
 if (state instanceof Bundle) {
 final Bundle bundle = (Bundle) state;
 int index = 0;
 while (true) {
 final Fragment fragment =
 fragmentManager.getFragment(bundle, Integer.toString(index));
 if (fragment == null) {
 break;
 }

 fragments.add(fragment);
 index += 1;
 }
 }
 }

 public void replace(final Fragment fragment) {
 fragmentManager.popBackStackImmediate(
 null, FragmentManager.POP_BACK_STACK_INCLUSIVE);
 fragmentManager.beginTransaction()
 .replace(containerId, fragment)
 .addToBackStack(null)
 .commit();
 fragmentManager.executePendingTransactions();

 fragments.clear();
 fragments.add(fragment);
 }

 public void push(final Fragment fragment) {
 fragmentManager
 .beginTransaction()
 .replace(containerId, fragment)
 .addToBackStack(null)
 .commit();
 fragmentManager.executePendingTransactions();

 fragments.add(fragment);
 }

 public boolean pop() {
 if (isEmpty()) {
 return false;
 }

 fragmentManager.popBackStackImmediate();

 fragments.remove(fragments.size() - 1);
 return true;
 }

 public boolean isEmpty() {
 return fragments.isEmpty();
 }

 public int size() {
 return fragments.size();
 }

 public Fragment getFragment(final int index) {
 return fragments.get(index);
 }
}
</code></pre>

Now instead of adding and removing fragments by calling <code>FragmentManager</code> directly, you should use <code>push()</code>, <code>replace()</code>, and <code>pop()</code> methods of <code>FragmentStackManager</code>. And you will be able to access the topmost fragment by just calling <code>stack.get(stack.size() - 1)</code>.

But if you like hacks, I have to other ways of doing similar things. The only thing I have to mention is that these hacks will work only with support fragments.

The first hack is just to get all active fragments added to the fragment manager. If you just replace fragments one by one and pop the from the stack this method will return the topmost fragment:

<pre><code>public class BackStackHelper {
 public static List&lt;Fragment&gt; getTopFragments(
 final FragmentManager fragmentManager) {
 final List&lt;Fragment&gt; fragments = fragmentManager.getFragments();
 final List&lt;Fragment&gt; topFragments = new ArrayList&lt;&gt;();

 for (final Fragment fragment : fragments) {
 if (fragment != null &amp;&amp; fragment.isResumed()) {
 topFragments.add(fragment);
 }
 }

 return topFragments;
 }
}
</code></pre>

The second approach is event more hacky and allows you to get all fragments added in the last transaction for which <code>addToBackStack</code> has been called:

<pre><code>package android.support.v4.app;

import java.util.ArrayList;
import java.util.Collections;
import java.util.List;

public class BackStackHelper {
 public static List&lt;Fragment&gt; getTopFragments(
 final FragmentManager fragmentManager) {
 if (fragmentManager.getBackStackEntryCount() == 0) {
 return Collections.emptyList();
 }

 final List&lt;Fragment&gt; fragments = new ArrayList&lt;&gt;();

 final int count = fragmentManager.getBackStackEntryCount();
 final BackStackRecord record =
 (BackStackRecord) fragmentManager.getBackStackEntryAt(count - 1);
 BackStackRecord.Op op = record.mHead;
 while (op != null) {
 switch (op.cmd) {
 case BackStackRecord.OP_ADD:
 case BackStackRecord.OP_REPLACE:
 case BackStackRecord.OP_SHOW:
 case BackStackRecord.OP_ATTACH:
 fragments.add(op.fragment);
 }
 op = op.next;
 }

 return fragments;
 }
}
</code></pre>

Please notice that in this case you have to put this class into <code>android.support.v4.app</code> package.

blocks|key|625533|text|最高的答案(Deepak+Goel)对我来说效果不好。不知何故，标签没有正确添加。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|625534|我最终只是通过流发送了片段的ID+(使用意图)，并直接从片段管理器中检索它。|625535|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|F|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|G|8|@]|9|@]|A|$]]|$1|D|3|-4|5|6|7|H|8|@]|9|@]|A|$]]]|E|$]]

The highest (Deepak Goel) answer didn't work well for me. Somehow the tag wasn't added properly.

I ended up just sending the ID of the fragment through the flow (using intents) and retrieving it directly from fragment manager.

blocks|key|410469|text|这个帮助器方法从堆栈顶部获取片段：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|410470|public+Fragment+getTopFragment()+{
++++if+(getSupportFragmentManager().getBackStackEntryCount()+==+0)+{
++++++++return+null;
++++}
++++String+fragmentTag+=+getSupportFragmentManager().getBackStackEntryAt(getSupportFragmentManager().getBackStackEntryCount()+-+1).getName();
++++return+getSupportFragmentManager().findFragmentByTag(fragmentTag);
}|code-block|syntax|javascript|410471|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|J|8|@]|9|@]|A|$E|F]]|$1|G|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|H|$]]

this helper method get fragment from top of stack:

<pre><code>public Fragment getTopFragment() {
 if (getSupportFragmentManager().getBackStackEntryCount() == 0) {
 return null;
 }
 String fragmentTag = getSupportFragmentManager().getBackStackEntryAt(getSupportFragmentManager().getBackStackEntryCount() - 1).getName();
 return getSupportFragmentManager().findFragmentByTag(fragmentTag);
}
</code></pre>

blocks|key|410530|text|刚刚接受了@roghayeh+hosseini+(正确)的答案，并在Kotlin为2017年这里的人做了它:)|type|unstyled|depth|inlineStyleRanges|entityRanges|data|410531|fun+getTopFragment():+Fragment?+{
++++supportFragmentManager.run+{
++++++++return+when+(backStackEntryCount)+{
++++++++++++0+->+null
++++++++++++else+->+findFragmentByTag(getBackStackEntryAt(backStackEntryCount+-+1).name)
++++++++}
++++}
}|code-block|syntax|javascript|410532|*应从Activity内部调用。|410533|享受:)|410534|entityMap^0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|M|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|N|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|O|8|@]|9|@]|A|$]]|$1|I|3|J|5|6|7|P|8|@]|9|@]|A|$]]|$1|K|3|-4|5|6|7|Q|8|@]|9|@]|A|$]]]|L|$]]

Just took @roghayeh hosseini (correct) answer and made it in Kotlin for those here in 2017 :)

<pre><code>fun getTopFragment(): Fragment? {
 supportFragmentManager.run {
 return when (backStackEntryCount) {
 0 -&gt; null
 else -&gt; findFragmentByTag(getBackStackEntryAt(backStackEntryCount - 1).name)
 }
 }
}
</code></pre>

*This should be called from inside an Activity.

Enjoy :)

blocks|key|410574|text|看起来有些东西已经变得更好了，因为下面的代码对我来说工作得很好，但我在已经提供的答案中找不到它。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|410575|Kotlin：|410576|supportFragmentManager.fragments[supportFragmentManager.fragments.size+-+1]|code-block|syntax|javascript|410577|Java：|410578|getSupportFragmentManager().getFragments()
.get(getSupportFragmentManager().getFragments().size()+-+1)|410579|entityMap^0|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|O|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|P|8|@]|9|@]|A|$]]|$1|D|3|E|5|F|7|Q|8|@]|9|@]|A|$G|H]]|$1|I|3|J|5|6|7|R|8|@]|9|@]|A|$]]|$1|K|3|L|5|F|7|S|8|@]|9|@]|A|$G|H]]|$1|M|3|-4|5|6|7|T|8|@]|9|@]|A|$]]]|N|$]]

Looks like something has changed for the better, because code below works perfectly for me, but I didn't find it in already provided answers.

Kotlin:

<pre><code>supportFragmentManager.fragments[supportFragmentManager.fragments.size - 1]
</code></pre>

Java:

<pre><code>getSupportFragmentManager().getFragments()
.get(getSupportFragmentManager().getFragments().size() - 1)
</code></pre>

blocks|key|625698|text|Kotlin|type|unstyled|depth|inlineStyleRanges|entityRanges|data|625699|//+In+activities
activity.supportFragmentManager.fragments.lastOrNull()

//+In+fragments
fragment.childFragmentManager.fragments.lastOrNull()|code-block|syntax|javascript|625700|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|J|8|@]|9|@]|A|$E|F]]|$1|G|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|H|$]]

Kotlin
<pre><code>// In activities
activity.supportFragmentManager.fragments.lastOrNull()

// In fragments
fragment.childFragmentManager.fragments.lastOrNull()
</code></pre>

blocks|key|625723|text|如果您使用addToBackStack()，则可以使用以下代码。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|625724|List<Fragment>+fragments+=+fragmentManager.getFragments();+activeFragment+=+fragments.get(fragments.size()+-+1);|625725|entityMap^0|5|G|0|0|34|0^^$0|@$1|2|3|4|5|6|7|J|8|@$9|K|A|L|B|C]]|D|@]|E|$]]|$1|F|3|G|5|6|7|M|8|@$9|N|A|O|B|C]]|D|@]|E|$]]|$1|H|3|-4|5|6|7|P|8|@]|D|@]|E|$]]]|I|$]]

If you use <code>addToBackStack()</code>, you can use following code.

<code>List&lt;Fragment&gt; fragments = fragmentManager.getFragments();
activeFragment = fragments.get(fragments.size() - 1);</code>

blocks|key|625750|text|我将在Deepak+Goel's+answer中添加一些东西，因为很多人，包括我，通过使用他的方法得到了一个null。显然，当您将片段添加到backstack时，为了使标记工作，您应该这样做：|type|unstyled|depth|inlineStyleRanges|entityRanges|offset|length|data|625751|getSupportFragmentManager.beginTransaction().replace(R.id.container_id,FragmentName,TAG_NAME).addToBackStack(TAG_NAME).commit();|code-block|syntax|javascript|625752|您需要添加两次相同的标签。|625753|我本想发表评论，但我没有50个名气。|625754|entityMap|0|LINK|mutability|MUTABLE|url|https://stackoverflow.com/a/9787891/11731416^0|3|K|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|U|8|@]|9|@$A|V|B|W|1|X]]|C|$]]|$1|D|3|E|5|F|7|Y|8|@]|9|@]|C|$G|H]]|$1|I|3|J|5|6|7|Z|8|@]|9|@]|C|$]]|$1|K|3|L|5|6|7|10|8|@]|9|@]|C|$]]|$1|M|3|-4|5|6|7|11|8|@]|9|@]|C|$]]]|N|$O|$5|P|Q|R|C|$S|T]]]]

I will add something to <a href="https://stackoverflow.com/a/9787891/11731416">Deepak Goel's answer</a> since a lot of people, me included, were getting a null by using his method. Apparently to make the tag work when you add a fragment to the backstack you should be doing it like this:

<pre><code>getSupportFragmentManager.beginTransaction().replace(R.id.container_id,FragmentName,TAG_NAME).addToBackStack(TAG_NAME).commit();
</code></pre>

You need to add the same tag twice.

I would have commented but i don't have 50 reputation.

How can I get the latest fragment instance added in backstack (if I do not know the fragment tag &amp; id)?

<pre><code>FragmentManager fragManager = activity.getSupportFragmentManager();
FragmentTransaction fragTransacion = fragMgr.beginTransaction();

/****After add , replace fragments 
 (some of the fragments are add to backstack , some are not)***/

//HERE, How can I get the latest added fragment from backstack ??
</code></pre>

get the latest fragment in backstack

Kotlin

Java

如何在后台堆栈中添加最新的分片实例(如果我不知道分片标签& id)？FragmentManager fragManager = activity.getSupportFragmentManager();FragmentTransaction fragTransacion = fragMgr.beginTransacti...

问获取backstack中的最新片段
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