二十六、从acticity发送信息到FragMnet

一、使用 Bundle 对象进行传递

1. activity 段中的代码

@Override
   public void onClick(View view) {
       switch (view.getId()){
           case R.id.btn:
               Bundle bundle = new Bundle();
               bundle.putString("message","使用Bundle传递");
               BlankFragment1 bf = new BlankFragment1();
               bf.setArguments(bundle);
               replaceFragment(bf);
               break;
           case R.id.btn2:
               replaceFragment(new ItemFragment());
               break;
       }
   }

2. FragMent中的代码

@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
 
    Bundle bundle = this.getArguments();
    String str = bundle.getString("message");
    Log.e("TAG", "onCreate: "+ str);
 
    if (getArguments() != null) {
        mParam1 = getArguments().getString(ARG_PARAM1);
        mParam2 = getArguments().getString(ARG_PARAM2);
    }
}

二、Java语言中类与类字迹通信常用方案：接口

1. 创建接口

package com.example.dongtaifragment;
 
public interface IfragmentCallback {
    void sendMsgToActivity(String string);
    String getMsgFromActivity(String msg);
}

2. 页面代码

<?xml version="1.0" encoding="utf-8"?>
<FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical"
    tools:context=".BlankFragment1">
 
    <!-- TODO: Update blank fragment layout -->
    <TextView
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:text="@string/hello_blank_fragment" />
    <Button
        android:layout_marginTop="100dp"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:id="@+id/btn_3"
        android:text="数据传递ToActivity"/>
    <Button
        android:layout_marginTop="200dp"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:id="@+id/btn_4"
        android:text="数据传递FromActivity"/>
</FrameLayout>

3. activity 段中的代码

package com.example.dongtaifragment;
 
import androidx.appcompat.app.AppCompatActivity;
import androidx.fragment.app.Fragment;
import androidx.fragment.app.FragmentManager;
import androidx.fragment.app.FragmentTransaction;
 
import android.os.Binder;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.Toast;
 
//动态添加 fragment
public class MainActivity extends AppCompatActivity implements View.OnClickListener {
 
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
 
        Button btn = findViewById(R.id.btn);
        btn.setOnClickListener(this);
        Button btn2 = findViewById(R.id.btn2);
        btn2.setOnClickListener(this);
    }
 
    @Override
    public void onClick(View view) {
        switch (view.getId()){
            case R.id.btn:
                Bundle bundle = new Bundle();
                bundle.putString("message","使用Bundle传递");
                BlankFragment1 bf = new BlankFragment1();
                bf.setArguments(bundle);
 
                bf.setifragmentCallback(new IfragmentCallback() {
                    @Override
                    public void sendMsgToActivity(String string) {
                        Toast.makeText(MainActivity.this,string,Toast.LENGTH_SHORT).show();
                    }
 
                    @Override
                    public String getMsgFromActivity(String msg) {
                        String msgs = msg;
                        if (msg =="null"){
                            msgs = "Hellow,调用了MainActivity的方法 ";
                        }
                        return msgs;
                    }
                });
 
                replaceFragment(bf);
                break;
            case R.id.btn2:
                replaceFragment(new ItemFragment());
                break;
        }
    }
 
    //同台切换Fragment
    private void replaceFragment(Fragment fragment){
        FragmentManager fragmentManager = getSupportFragmentManager();
        //创建一个事件
        FragmentTransaction transaction = fragmentManager.beginTransaction();
        //替换一个
        transaction.replace(R.id.framelayouts,fragment);
        //将fragment添加到站中，当点击手机返回时，会返回到上一个的页面，
        //以值持续到回到最开始的页面，然后返回桌面
        transaction.addToBackStack(null);
        //提交
        transaction.commit();
    }
 
}

4. FragMent中的代码

package com.example.dongtaifragment;
 
import android.os.Bundle;
 
import androidx.fragment.app.Fragment;
 
import android.util.Log;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.Button;
import android.widget.Toast;
 
import java.net.IDN;
 
 
public class BlankFragment1 extends Fragment {
 
    private  View views;
    private  IfragmentCallback ifragmentCallback;
    public void setifragmentCallback( IfragmentCallback callbanck){
        ifragmentCallback = callbanck;
    }
 
 
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
 
        Bundle bundle = this.getArguments();
        String str = bundle.getString("message");
        Log.e("TAG", "onCreate: "+ str);
 
    }
 
    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
                             Bundle savedInstanceState) {
        if (views==null){
            views = inflater.inflate(R.layout.fragment_blank1, container, false);
        }
        Button btn=views.findViewById(R.id.btn_3);
        btn.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                ifragmentCallback.sendMsgToActivity("Hellow,调用了BlankFragment1的方法 ");
            }
        });
 
        Button btn2=views.findViewById(R.id.btn_4);
        btn2.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                String msg = ifragmentCallback.getMsgFromActivity("null");
                Toast.makeText(BlankFragment1.this.getContext(),msg,Toast.LENGTH_SHORT).show();
            }
        });
 
        return views;
    }
 
    @Override
    public void onResume() {
        super.onResume();
    }
}