Android基础-----Fragment与Activity之间的通讯

Fragment与Activity之间的通讯

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提示：本博客案例的创建部分在我的上一篇博客中
https://blog.csdn.net/weixin_38423829/article/details/80603782

1.从Fragment向Activity中传递数据

• 1.首先我们在我们在activity_main.xml中添加一个TextView控件放置在顶部

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

    <LinearLayout
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_gravity="center"
        >
        <TextView
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="请点击下方的文字"
            android:id="@+id/tv_top"
            android:gravity="center"
            android:textSize="20sp"
            />

    </LinearLayout>
    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="0px"
        android:layout_weight="1"
        >
        <TextView
            android:layout_width="0px"
            android:layout_height="match_parent"
            android:layout_weight="1"
            android:text="聊天"
            android:gravity="center"
            android:id="@+id/lay_charTop"
            />
        <TextView
            android:layout_width="0px"
            android:layout_height="match_parent"
            android:layout_weight="1"
            android:text="主页"
            android:gravity="center"
            android:id="@+id/lay_contentTop"
            />

        <TextView
            android:layout_width="0px"
            android:layout_height="match_parent"
            android:layout_weight="1"
            android:text="朋友圈"
            android:gravity="center"
            android:id="@+id/lay_friendsTop"
            />


    </LinearLayout>
    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="5px"
        >
        <View
            android:layout_width="0px"
            android:layout_height="match_parent"
            android:layout_weight="1"
            android:id="@+id/chars_bom"
            />
        <View
            android:layout_width="0px"
            android:layout_height="match_parent"
            android:layout_weight="1"
            android:id="@+id/content_bom"
            />
        <View
            android:layout_width="0px"
            android:layout_height="match_parent"
            android:layout_weight="1"
            android:id="@+id/frident_bom"
            />

    </LinearLayout>

    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="0px"
        android:layout_weight="7"
        >
        <android.support.v4.view.ViewPager
            android:layout_width="match_parent"
            android:layout_height="match_parent"
            android:id="@+id/lay_vp"
            ></android.support.v4.view.ViewPager>


    </LinearLayout>

</LinearLayout>

• 2.接着我们修改fone.java里的代码(在这之前，记得给fragment_one.xml中添加id)

package com.example.xiao.fragmentdemo2;


import android.os.Bundle;
import android.support.v4.app.Fragment;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.TextView;


/**
 * A simple {@link Fragment} subclass.
 */
public class Fone extends Fragment {


    public Fone() {
        // Required empty public constructor
    }


    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
                             Bundle savedInstanceState) {
        // Inflate the layout for this fragment

        //修改部分从这里开始
       //这里的view是为了实例化TextView作准备
        View view = inflater.inflate(R.layout.fragment_fone, container, false);
       TextView fone = view.findViewById(R.id.fone);  //记得给fragment_fone.xml中的文字添加一个id值哦



       fone.setOnClickListener(new View.OnClickListener() {
           @Override
           public void onClick(View v) {

               MainActivity mainActivity = (MainActivity) getActivity();  //实例化主类
               mainActivity.setToptv("这里是聊天窗口");  //调用主类里新建的setToptv方法
           }
       });

        return view;

    }

}

• 3.我们发现上面的代码中有一个setToptv方法我们没有创建过,那么我们就在主类里创建把，它的功能是点击fragment文字的时候，替换activity中的文字

MainActivity.java的代码如下：

package com.example.xiao.fragmentdemo2;

import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.graphics.Color;
import android.support.v4.app.Fragment;
import android.support.v4.view.ViewPager;
import android.view.View;
import android.widget.TextView;

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

public class MainActivity extends AppCompatActivity implements View.OnClickListener{

    private ViewPager viewPager;
    List<Fragment> fragmentList;
    Fone fragmentOne;
    Ftwo fargmentTwo;
    Fthree fragmentThree;
    TextView chars, contents, friends,top_tv;
    View chars_bom, content_bom, friend_bom;

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

         //实例化fragment对象并将加到fragmentlist对象里面
        fragmentList = new ArrayList<>();
        fragmentOne = new Fone();
        fargmentTwo = new Ftwo();
        fragmentThree=new Fthree();
        fragmentList.add(fragmentOne);
        fragmentList.add(fargmentTwo);
        fragmentList.add(fragmentThree);


        chars_bom.setBackgroundColor(Color.BLUE);//给聊天文字下的view标签添加下划线

        Adapter adapter = new Adapter(getSupportFragmentManager(), fragmentList);  //实例化适配器对象，将fragmentlist传入
        viewPager.setAdapter(adapter);  //将适配器对象设置到viewPager

        //设置viewpage的监听事件
        viewPager.setOnPageChangeListener(new ViewPager.OnPageChangeListener() {
            @Override
            public void onPageScrolled(int position, float positionOffset, int positionOffsetPixels) {

            }

            //滑动后产生的变化
            @Override
            public void onPageSelected(int position) {
                chars_bom.setBackgroundColor(Color.GRAY);
                content_bom.setBackgroundColor(Color.GRAY);
                friend_bom.setBackgroundColor(Color.GRAY);
                switch (position) {
                    case 0:
                        chars_bom.setBackgroundColor(Color.BLUE);
                        break;
                    case 1:
                        content_bom.setBackgroundColor(Color.BLUE);
                        break;
                    case 2:
                        friend_bom.setBackgroundColor(Color.BLUE);
                        break;
                    default:
                        break;
                }
            }

            @Override
            public void onPageScrollStateChanged(int state) {

            }
        });
    }

    private void init() {
        //初始化数据
        viewPager = findViewById(R.id.lay_vp);
        chars = findViewById(R.id.lay_charTop);
        friends = findViewById(R.id.lay_friendsTop);
        contents = findViewById(R.id.lay_contentTop);
        top_tv=findViewById(R.id.tv_top);
        chars_bom = findViewById(R.id.chars_bom);
        content_bom = findViewById(R.id.content_bom);
        friend_bom = findViewById(R.id.frident_bom);
        chars.setOnClickListener(this);
        friends.setOnClickListener(this);
        contents.setOnClickListener(this);
    }


    //点击上方的按钮也会实现跳转功能
    @Override
    public void onClick(View view) {
        switch (view.getId()){
            case R.id.lay_charTop:
                viewPager.setCurrentItem(0);
                break;
            case R.id.lay_contentTop:
                viewPager.setCurrentItem(1);
                break;
            case R.id.lay_friendsTop:
                viewPager.setCurrentItem(2);
                break;
            default:
                break;
        }

    }

   //用于替换top_tv里的文字
    public void setToptv(String s){
       top_tv.setText(s);
    }
}

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2. 从Activity向Fragment中传递数据

• 1.首先我们在activity中设置用于传送到Fragment当中的数据

在MainActivity中书写的代码如下

       Bundle bundle = new Bundle();   //创建打包对象
        bundle.putString("name","我是从Activity中来的");  //放入数据
        fargmentTwo.setArguments(bundle);   //将数据发送到Ftwo

• 2.接着我们在Ftwo.java里面接收数据并通过点击设置

代码如下

public class Ftwo extends Fragment {


    public Ftwo() {
        // Required empty public constructor
    }


    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
                             Bundle savedInstanceState) {
        // Inflate the layout for this fragment
       View view = inflater.inflate(R.layout.fragment_ftwo, container, false);



      final  TextView ftwo = view.findViewById(R.id.ftwo);  //记得给响应的textview添加id值

        ftwo.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                Bundle bundle = getArguments();
                String name = bundle.getString("name");
                ftwo.setText(name);
            }
        });

       return  view;
    }

}

效果