blocks|key|553563|text|没有完全理解这个问题，因为它太简单了：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|553564|ExampleFragment+fragment+=+(ExampleFragment)+getFragmentManager().findFragmentById(R.id.example_fragment);
fragment.<specific_function_name>();+|code-block|syntax|javascript|553565|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|$]]

not get the question exactly as it is too simple :
<pre><code>ExampleFragment fragment = (ExampleFragment) getFragmentManager().findFragmentById(R.id.example_fragment);
fragment.&lt;specific_function_name&gt;(); 
</code></pre>

blocks|key|553614|text|如果你正在使用一个支持库，你会想要这样做：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|553615|FragmentManager+manager+=+getSupportFragmentManager();
Fragment+fragment+=+manager.findFragmentById(R.id.my_fragment);
fragment.myMethod();|code-block|syntax|javascript|553616|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|$]]

If you're using a support library, you'll want to do something like this:

<pre><code>FragmentManager manager = getSupportFragmentManager();
Fragment fragment = manager.findFragmentById(R.id.my_fragment);
fragment.myMethod();
</code></pre>

blocks|key|337294|text|我认为最好的方法是在调用fragment中的方法之前检查是否添加了fragment。这样做可以避免空异常。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|337295|ExampleFragment+fragment+=+(ExampleFragment)+getFragmentManager().findFragmentById(R.id.example_fragment);
if(fragment.isAdded()){
++fragment.<specific_function_name>();+
}|code-block|syntax|javascript|337296|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|$]]

I think the best is to check if fragment is added before calling method in fragment. Do something like this to avoid null exception. 

<pre><code>ExampleFragment fragment = (ExampleFragment) getFragmentManager().findFragmentById(R.id.example_fragment);
if(fragment.isAdded()){
 fragment.&lt;specific_function_name&gt;(); 
}
</code></pre>

blocks|key|553755|text|您还可以使用如下接口调用片段方法|type|unstyled|depth|inlineStyleRanges|entityRanges|data|553756|首先创建接口|553757|public+interface+InterfaceName+{
++++void+methodName();
}|code-block|syntax|javascript|553758|创建接口后，在片段中实现接口|553759|MyFragment+extends+Fragment+implements+InterfaceName+{
++++@overide
++++void+methodName()+{

++++}
}|553760|并在活动中创建接口的引用|553761|class+Activityname+extends+AppCompatActivity+{
++++Button+click;
++++MyFragment+fragment;

++++protected+void+onCreate(Bundle+savedInstanceState)+{
++++++++super.onCreate(savedInstanceState);
++++++++setContentView(R.layout.activity);

++++++++click+=+findViewById(R.id.button);

++++++++fragment+=+new+MyFragment();

++++++++click.setOnClickListener(new+View.OnClickListener()+{
++++++++++++@Override
++++++++++++public+void+onClick(View+v)+{
+++++++++++++++fragment.methodName();
++++++++++++}
++++++++});
++++}
}|553762|entityMap^0|0|0|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|S|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|T|8|@]|9|@]|A|$]]|$1|D|3|E|5|F|7|U|8|@]|9|@]|A|$G|H]]|$1|I|3|J|5|6|7|V|8|@]|9|@]|A|$]]|$1|K|3|L|5|F|7|W|8|@]|9|@]|A|$G|H]]|$1|M|3|N|5|6|7|X|8|@]|9|@]|A|$]]|$1|O|3|P|5|F|7|Y|8|@]|9|@]|A|$G|H]]|$1|Q|3|-4|5|6|7|Z|8|@]|9|@]|A|$]]]|R|$]]

you also call fragment method using interface like 

first you create interface 

<pre><code>public interface InterfaceName {
 void methodName();
}
</code></pre>

after creating interface you implement interface in your fragment 

<pre><code>MyFragment extends Fragment implements InterfaceName {
 @overide
 void methodName() {

 }
}
</code></pre>

and you create the reference of interface in your activity 

<pre><code>class Activityname extends AppCompatActivity {
 Button click;
 MyFragment fragment;

 protected void onCreate(Bundle savedInstanceState) {
 super.onCreate(savedInstanceState);
 setContentView(R.layout.activity);

 click = findViewById(R.id.button);

 fragment = new MyFragment();

 click.setOnClickListener(new View.OnClickListener() {
 @Override
 public void onClick(View v) {
 fragment.methodName();
 }
 });
 }
}
</code></pre>

blocks|key|337668|text|这个问题太晚了，但这是一种获取片段实例并调用片段中方法的简单方法；您必须获取片段的实例，然后调用公共方法：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|337669|在您的片段中：|337670|+private+static+yourFragment+instance;|code-block|syntax|javascript|337671|然后在片段的onCreateView中：|offset|length|style|CODE|337672|++@Override
++++public+View+onCreateView(LayoutInflater+inflater,+ViewGroup+container,+
+++Bundle+savedInstanceState)+{

++++++++instance=+this;

++++++++View+v+=+inflater.inflate(R.layout.fragment_tools,+container,+false);
++++++++binding+=+FragmentToolsBinding.inflate(inflater,+container,+false);

++++++++return+v;
++++}|337673|此外，在您的片段中，还必须有一个返回实例的静态方法：|337674|public+static+yourFragment+GetInstance()
{
++++return+instance;
}|337675|然后在您的片段中有一个公共方法，您希望这样调用它：|337676|public++void++theMethod()
{
++++Toast.makeText(getActivity(),+"Test",+Toast.LENGTH_SHORT).show();
}|337677|然后，您可以获取片段实例并调用非静态公共方法，如下所示：|337678|+++yourFragment+frag+=+yourFragment.GetInstance();
+++frag.theMethod();|337679|entityMap^0|0|0|0|6|C|0|0|0|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|14|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|15|8|@]|9|@]|A|$]]|$1|D|3|E|5|F|7|16|8|@]|9|@]|A|$G|H]]|$1|I|3|J|5|6|7|17|8|@$K|18|L|19|M|N]]|9|@]|A|$]]|$1|O|3|P|5|F|7|1A|8|@]|9|@]|A|$G|H]]|$1|Q|3|R|5|6|7|1B|8|@]|9|@]|A|$]]|$1|S|3|T|5|F|7|1C|8|@]|9|@]|A|$G|H]]|$1|U|3|V|5|6|7|1D|8|@]|9|@]|A|$]]|$1|W|3|X|5|F|7|1E|8|@]|9|@]|A|$G|H]]|$1|Y|3|Z|5|6|7|1F|8|@]|9|@]|A|$]]|$1|10|3|11|5|F|7|1G|8|@]|9|@]|A|$G|H]]|$1|12|3|-4|5|6|7|1H|8|@]|9|@]|A|$]]]|13|$]]

Too late for the question but this is a easy way to get fragment instance and call methods in a fragment; you have to get instance of your fragment then call your public method:
In your fragment :
<pre><code> private static yourFragment instance;
</code></pre>
then in <code>onCreateView</code> of your fragment :
<pre><code> @Override
 public View onCreateView(LayoutInflater inflater, ViewGroup container, 
 Bundle savedInstanceState) {

 instance= this;

 View v = inflater.inflate(R.layout.fragment_tools, container, false);
 binding = FragmentToolsBinding.inflate(inflater, container, false);

 return v;
 }
</code></pre>
and also in your fragment you have to have a static method that returns the instance:
<pre><code>public static yourFragment GetInstance()
{
 return instance;
}
</code></pre>
then you have a public method in in your fragment that you want to call it like this:
<pre><code>public void theMethod()
{
 Toast.makeText(getActivity(), &quot;Test&quot;, Toast.LENGTH_SHORT).show();
}
</code></pre>
then you can get fragment instance and call your non static public method like this:
<pre><code> yourFragment frag = yourFragment.GetInstance();
 frag.theMethod();
 
</code></pre>

blocks|key|553725|text|首先，在fragment中创建方法，如下所示|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|553726|public+void+name()
{


}|code-block|syntax|javascript|553727|在您的activity中添加以下内容|553728|添加onCreate()方法|553729|myfragment+fragment=new+myfragment()|553730|最后，在想要调用add+this的地方调用方法|553731|fragment.method_name();|553732|试试这段代码|553733|entityMap^0|4|8|0|0|3|8|0|2|A|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|Y|8|@$9|Z|A|10|B|C]]|D|@]|E|$]]|$1|F|3|G|5|H|7|11|8|@]|D|@]|E|$I|J]]|$1|K|3|L|5|6|7|12|8|@$9|13|A|14|B|C]]|D|@]|E|$]]|$1|M|3|N|5|6|7|15|8|@$9|16|A|17|B|C]]|D|@]|E|$]]|$1|O|3|P|5|H|7|18|8|@]|D|@]|E|$I|J]]|$1|Q|3|R|5|6|7|19|8|@]|D|@]|E|$]]|$1|S|3|T|5|H|7|1A|8|@]|D|@]|E|$I|J]]|$1|U|3|V|5|6|7|1B|8|@]|D|@]|E|$]]|$1|W|3|-4|5|6|7|1C|8|@]|D|@]|E|$]]]|X|$]]

First you create method in your <code>fragment</code> like

<pre><code>public void name()
{


}
</code></pre>

in your <code>activity</code> you add this 

add <code>onCreate()</code> method 

<pre><code>myfragment fragment=new myfragment()
</code></pre>

finally call the method where you want to call add this

<pre><code>fragment.method_name();
</code></pre>

try this code

blocks|key|337399|text|FragmentManager+fm+=+getFragmentManager();+
MainFragment+frag+=+(MainFragment)fm.findFragmentById(R.id.main_fragment);+
frag.<specific_function_name>();+|type|code-block|depth|inlineStyleRanges|entityRanges|data|syntax|javascript|337400|unstyled|entityMap^0|0^^$0|@$1|2|3|4|5|6|7|G|8|@]|9|@]|A|$B|C]]|$1|D|3|-4|5|E|7|H|8|@]|9|@]|A|$]]]|F|$]]

<pre><code>FragmentManager fm = getFragmentManager(); 
MainFragment frag = (MainFragment)fm.findFragmentById(R.id.main_fragment); 
frag.&lt;specific_function_name&gt;(); 
</code></pre>

blocks|key|553829|text|我不知道Java，但在C#+(Xamarin.Android)中，不需要在每次需要调用方法时都查找片段，如下所示：|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|553830|public+class+BrandActivity+:+Activity
{
++++MyFragment+myFragment;

++++protected+override+void+OnCreate(Bundle+bundle)
++++{+++++++
++++++++//+...
++++++++myFragment+=+new+MyFragment();++++++
++++++++//+...
++++}

++++void+someMethod()
++++{
++++++++myFragment.MyPublicMethod();
++++}
}

public+class+MyFragment+:+Android.Support.V4.App.Fragment
{
++++public+override+void+OnCreate(Bundle+bundle)
++++{
++++++++//+...
++++}

++++public+override+View+OnCreateView(LayoutInflater+inflater,+ViewGroup+container,+Bundle+bundle)
++++{
++++++++//+...
++++}

++++public+void+MyPublicMethod()
++++{
++++++++//+...
++++}+++
}|code-block|syntax|javascript|553831|我认为在Java中也可以做到这一点。|553832|entityMap^0|4|4|B|2|0|0|4|4|0^^$0|@$1|2|3|4|5|6|7|O|8|@$9|P|A|Q|B|C]|$9|R|A|S|B|C]]|D|@]|E|$]]|$1|F|3|G|5|H|7|T|8|@]|D|@]|E|$I|J]]|$1|K|3|L|5|6|7|U|8|@$9|V|A|W|B|C]]|D|@]|E|$]]|$1|M|3|-4|5|6|7|X|8|@]|D|@]|E|$]]]|N|$]]

I don't know about <code>Java</code>, but in <code>C#</code> (Xamarin.Android) there is no need to look up the fragment everytime you need to call the method, see below:

<pre><code>public class BrandActivity : Activity
{
 MyFragment myFragment;

 protected override void OnCreate(Bundle bundle)
 { 
 // ...
 myFragment = new MyFragment(); 
 // ...
 }

 void someMethod()
 {
 myFragment.MyPublicMethod();
 }
}

public class MyFragment : Android.Support.V4.App.Fragment
{
 public override void OnCreate(Bundle bundle)
 {
 // ...
 }

 public override View OnCreateView(LayoutInflater inflater, ViewGroup container, Bundle bundle)
 {
 // ...
 }

 public void MyPublicMethod()
 {
 // ...
 } 
}
</code></pre>

I think in <code>Java</code> you can do the same.

blocks|key|553834|text|((HomesFragment)getSupportFragmentManager().findFragmentById(R.id.fragment_container)).filterValidation();|type|code-block|depth|inlineStyleRanges|entityRanges|data|syntax|javascript|553835|unstyled|entityMap^0|0^^$0|@$1|2|3|4|5|6|7|G|8|@]|9|@]|A|$B|C]]|$1|D|3|-4|5|E|7|H|8|@]|9|@]|A|$]]]|F|$]]

<pre><code>((HomesFragment)getSupportFragmentManager().findFragmentById(R.id.fragment_container)).filterValidation();
</code></pre>

I see in the <a href="http://developer.android.com/guide/topics/fundamentals/fragments.html" rel="noreferrer">Android Fragments Dev Guide</a> that an "activity can call methods in a fragment by acquiring a reference to the Fragment from FragmentManager, using <code>findFragmentById()</code> or <code>findFragmentByTag()</code>."

The example that follows shows how to get a fragment reference, but not how to call specific methods in the fragment.

Can anyone give an example of how to do this? I would like to call a specific method in a Fragment from the parent Activity. Thanks.

Calling a Fragment method from a parent Activity

我在中看到，“活动可以通过使用findFragmentById()或findFragmentByTag()从FragmentManager获取对片段的引用来调用片段中的方法”。下面的示例显示如何获取片段引用，但不显示如何调用片段中的特定方法。有没有人能举例说明如何做到这一点？我想从父活动中调用片段中的特定方法。谢谢。

问从父活动调用片段方法
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