Activity 与 Fragment通信方式-Android

Posted 2022-05-25 hequnwang10

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Fragment 与 Activity 通信存在三种情形：

Activity 操作内嵌的 Fragment
Fragment 操作宿主 Activity
Fragment 操作同属 Activity中的其他 Fragment

Fragment 与 Activity 通信方式：

Bundle
接口回调
广播
EventBus
Handler
ViewModel

一、Bundle

1、Activity 传递数据到 Fragment

activity_main.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:orientation="vertical"
    android:layout_width="match_parent"
    android:layout_height="match_parent">

    <Button
        android:id="@+id/button"
        android:layout_gravity="center"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:textSize="20dp"
        android:text="Activity" />

    <FrameLayout
        android:layout_below="@+id/button"
        android:id="@+id/fragment_container"
        android:layout_width="match_parent"
        android:layout_height="match_parent"/>
</LinearLayout>

activity_my_fragment.xml

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:orientation="vertical"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    >
    <Button
        android:id="@+id/change"
        android:layout_gravity="center"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:textSize="20dp"
        android:text="change消息" />

    <Button
        android:id="@+id/get"
        android:layout_gravity="center"
        android:text="get消息"
        android:layout_centerInParent="true"
        android:textSize="20dp"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content" />
</LinearLayout>

MainActivity.java

public class MainActivity extends AppCompatActivity 

    Button button;

    @Override
    protected void onCreate(Bundle savedInstanceState) 
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        button = (Button) findViewById(R.id.button);

        // 步骤1：获取FragmentManager
        FragmentManager fragmentManager = getFragmentManager();

        // 步骤2：获取FragmentTransaction
        FragmentTransaction fragmentTransaction = fragmentManager.beginTransaction();

        // 步骤3：创建需要添加的Fragment
        final MyFragment fragment = new MyFragment();

        // 步骤4:创建Bundle对象
        // 作用:存储数据，并传递到Fragment中
        Bundle bundle = new Bundle();

        // 步骤5:往bundle中添加数据
        bundle.putString("msg", "change成功");

        // 步骤6:把数据设置到Fragment中
        fragment.setArguments(bundle);

        // 步骤7：动态添加fragment
        // 即将创建的fragment添加到Activity布局文件中定义的占位符中（FrameLayout）
        fragmentTransaction.add(R.id.fragment_container,fragment);
        fragmentTransaction.commit();

MyFragment.java

public class MyFragment extends Fragment 

    Button change;
    Button get;
    Bundle bundle;
    String message;

    @Nullable
    @Override
    public View onCreateView(LayoutInflater inflater, @Nullable ViewGroup container, Bundle savedInstanceState) 
        View contentView = inflater.inflate(R.layout.activity_my_fragment, container, false);
        // 设置布局文件

        change = (Button) contentView.findViewById(R.id.change);
        get = (Button) contentView.findViewById(R.id.get);

        // 步骤1:通过getArgments()获取从Activity传过来的全部值
        bundle = this.getArguments();

        // 步骤2:获取某一值
        message = bundle.getString("msg");

        // 步骤3:设置按钮,将设置的值显示出来
        get.setOnClickListener(new View.OnClickListener() 
            @Override
            public void onClick(View v) 
                // 显示传递过来的值
                change.setText(message);
            
        );
        return contentView;

二、接口回调

1、Fragment 传递数据到 Activity

方法一：

接口用于Activity与Fragment通信
ICallBack.java

public interface ICallBack 
    void get_message_from_Fragment(String string);

activity_main.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:orientation="vertical"
    android:layout_width="match_parent"
    android:layout_height="match_parent">

    <Button
        android:id="@+id/button"
        android:layout_gravity="center"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:textSize="20dp"
        android:text="Activity接受消息前" />

    <Button
        android:id="@+id/get"
        android:layout_gravity="center"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:textSize="20dp"
        android:text="get消息" />

    <FrameLayout
        android:layout_below="@+id/button"
        android:id="@+id/fragment_container"
        android:layout_width="match_parent"
        android:layout_height="match_parent"/>
</LinearLayout>

activity_my_fragment.xml

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:orientation="vertical"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    >

    <Button
        android:id="@+id/fragment"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:gravity="center"
        android:text="fragment消息:发送成功"
        />
</LinearLayout>

MainActivity.java

public class MainActivity extends AppCompatActivity 
    Button button;
    Button get;

    @Override
    protected void onCreate(Bundle savedInstanceState) 
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        button = (Button) findViewById(R.id.button);
        get = (Button) findViewById(R.id.get);

        // 步骤1：获取FragmentManager
        FragmentManager fragmentManager = getFragmentManager();

        // 步骤2：获取FragmentTransaction
        FragmentTransaction fragmentTransaction = fragmentManager.beginTransaction();

        // 步骤3：创建需要添加的Fragment
        final MyFragment fragment = new MyFragment();

        // 步骤4：动态添加fragment
        // 即将创建的fragment添加到Activity布局文件中定义的占位符中（FrameLayout）
        fragmentTransaction.add(R.id.fragment_container, fragment);
        fragmentTransaction.commit();
        get.setOnClickListener(new View.OnClickListener() 
            @Override
            public void onClick(View v) 
                fragment.sendMessage(new ICallBack() 
                    @Override
                    public void get_message_from_Fragment(String string) 
                        button.setText(string);
                    
                );
            
        );

MyFragment.java

public class MyFragment extends Fragment 


    @Nullable
    @Override
    public View onCreateView(LayoutInflater inflater, @Nullable ViewGroup container, Bundle savedInstanceState) 
        View contentView = inflater.inflate(R.layout.activity_my_fragment, container, false);
        return contentView;
    
    public void sendMessage(ICallBack iCallBack)
        iCallBack.get_message_from_Fragment("发送成功");

方法二：

FragmentListener.java

public interface FragmentListener 
    void process(String str);

activity_main.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:orientation="vertical"
    android:layout_width="match_parent"
    android:layout_height="match_parent">

    <Button
        android:id="@+id/button"
        android:layout_gravity="center"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:textSize="20dp"
        android:text="Activity接受消息前" />

    <Button
        android:id="@+id/get"
        android:layout_gravity="center"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:textSize="20dp"
        android:text="get消息" />

    <FrameLayout
        android:layout_below="@+id/button"
        android:id="@+id/fragment_container"
        android:layout_width="match_parent"
        android:layout_height="match_parent"/>
</LinearLayout>

activity_my_fragment.xml

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:orientation="vertical"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    >

    <Button
        android:id="@+id/fragment2"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:gravity="center"
        android:text="fragment发送消息"
        />
</LinearLayout>

MainActivity.java

public class MainActivity extends AppCompatActivity implements FragmentListener
    Button button;
    Button get;
    String getstring;

    @Override
    protected void onCreate(Bundle savedInstanceState) 
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        button = (Button) findViewById(R.id.button);
        get = (Button) findViewById(R.id.get);
        // 步骤1：获取FragmentManager
        FragmentManager fragmentManager = getFragmentManager();
        // 步骤2：获取FragmentTransaction
        FragmentTransaction fragmentTransaction = fragmentManager.beginTransaction();
        final MyFragment2 myFragment2 = new MyFragment2();
        fragmentTransaction.add(R.id.fragment_container,myFragment2);
        fragmentTransaction.commit();
        get.setOnClickListener(new View.OnClickListener() 
            @Override
            public void onClick(View v) 
                button.setText(getstring);
            
        );
    

    @Override
    public void process(String str) 
        getstring = str;

MyFragment2.java

public class MyFragment2 extends Fragment 
    Button button;
    private FragmentListener listener;
    @Override
    public void onAttach(Activity activity) 
        super.onAttach(activity);
        if(activity instanceof FragmentListener)
            listener = (FragmentListener) activity;
        else
            throw new IllegalArgumentException("activity must implements Fragment interface");
        

    

    @Nullable
    @Override
    public View onCreateView(LayoutInflater inflater, @Nullable ViewGroup container, Bundle savedInstanceState) 
        View view = inflater.inflate(R.layout.activity_my_fragment2, container, false);
        button = (Button) view.findViewById(R.id.fragment2);
        listener.process("发送消息：我是接口");
        return view;
    

    @Override
    public void onDetach() 
        super.onDetach();
        listener = null;

三、EventBus

正常发送消息

简化组件之间的通信
解耦事件发送者和接收者
在活动、片段和后台线程中表现良好
避免复杂且容易出错的依赖关系和生命周期问题
让你的代码更简单

使用

1、添加依赖

implementation("org.greenrobot:eventbus:3.3.1")

2、EventBus 五步走

注册：EventBus.getDefault().register(this);
解注册：EventBus.getDefault().unregister(this);
构造发送消息类：public class MessageEvent
发布消息：EventBus.getDefault().post(new MessageEvent(“Fragment发送成功”));
接受消息：显示接受消息
activity_main.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:orientation="vertical"
    android:layout_width="match_parent"
    android:layout_height="match_parent">

    <Button
        android:id="@+id/button"
        android:layout_gravity="center"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:textSize="20dp"
        android:text="Activity接受消息前" />

    <Button
        android:id="@+id/get"
        android:layout_gravity="center"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:textSize="20dp"
        android:text="get消息" />

    <FrameLayout
        android:id="@+id/fragment_container"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:layout_below="@+id/button" />
</LinearLayout>

activity_event_bus_fragment.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:orientation="vertical"
    android:layout_width="match_parent"
    android:layout_height="match_parent">

    <Button
        android:id="@+id/bt_send"
        android:layout_gravity="center"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:textSize="20dp"
        android:text="Fragment发送数据" />

    <Button
        android:id="@+id/bt_get"
        android:layout_gravity="center"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:textSize="20dp"
        android:text="Fragment接受数据" />

    <Button
        android:id="@+id/msg"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_gravity="center"
        android:textSize="20dp"
        android:text="显示数据"/>
</LinearLayout>

MainActivity.java

public class MainActivity extends AppCompatActivity 
    Button button;
    Button get;

    @Override
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