利用Broadcast实现Fragment向Activity传递消息

本文链接： https://blog.csdn.net/weixin_43219615/article/details/99675580

利用广播可以轻易实现Fragment向Activity传递消息。在Fragment通过广播发送消息，接收页面注册广播接收消息即可。下面是一个例子（当Fragment中的Spinner触发响应事件时，发送广播消息，整个页面的背景颜色改变）。
在这里插入图片描述

创建自己的Fragment，如MyFragment。代码如下（item_dropdown.xml和item_selected.xml比较简单就不贴了）。

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

    <TextView
        android:layout_width="0dp"
        android:layout_height="match_parent"
        android:layout_weight="1"
        android:gravity="center"
        android:text="改变页面颜色"
        android:textColor="#000000"
        android:textSize="17sp"/>

    <Spinner
        android:id="@+id/sp_background"
        android:layout_width="0dp"
        android:layout_height="match_parent"
        android:layout_weight="5"
        android:spinnerMode="dropdown"></Spinner>
</LinearLayout>

package xyz.strasae.androidlearn.myandroidapplication;

import android.content.Context;
import android.content.Intent;
import android.graphics.Color;
import android.os.Bundle;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.AdapterView;
import android.widget.ArrayAdapter;
import android.widget.Spinner;

import androidx.annotation.NonNull;
import androidx.annotation.Nullable;
import androidx.fragment.app.Fragment;
import androidx.localbroadcastmanager.content.LocalBroadcastManager;

public class MyFragment extends Fragment {
    protected View view;
    protected Context context;
    private Spinner sp_background;
    private int[] mColor = {Color.RED, Color.GREEN, Color.BLUE, Color.CYAN, Color.WHITE};
    private String[] sColor = {"红色", "绿色", "蓝色", "青色", "白色"};

    @Nullable
    @Override
    //创建Fragment视图
    public View onCreateView(@NonNull LayoutInflater inflater, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState) {
        context = this.getActivity();
        //从xml文件获取对象 以便代码操作
        view = inflater.inflate(R.layout.my_fragment, container, false);
        sp_background = view.findViewById(R.id.sp_background);
        ArrayAdapter<String> adapter = new ArrayAdapter<String>(context, R.layout.item_selected, sColor);
        adapter.setDropDownViewResource(R.layout.item_dropdown);
        sp_background.setAdapter(adapter);
        sp_background.setPrompt("请选择颜色");
        sp_background.setSelection(0);
        sp_background.setOnItemSelectedListener(new AdapterView.OnItemSelectedListener() {
            @Override
            public void onItemSelected(AdapterView<?> adapterView, View view, int i, long l) {
                Intent intent = new Intent("MY_EVENT");
                intent.putExtra("color", mColor[i]);
                //发送包裹
                LocalBroadcastManager.getInstance(context).sendBroadcast(intent);
            }

            @Override
            public void onNothingSelected(AdapterView<?> adapterView) {

            }
        });
        return view;
    }
}

创建接受的Activity。代码如下。

<?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"
    tools:context=".BroadcastDemoActivity"
    android:orientation="vertical"
    android:id="@+id/ll_broadcast_test">

    <fragment
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:name="xyz.strasae.androidlearn.myandroidapplication.MyFragment"/>
</LinearLayout>

package xyz.strasae.androidlearn.myandroidapplication;

import androidx.appcompat.app.AppCompatActivity;
import androidx.localbroadcastmanager.content.LocalBroadcastManager;

import android.content.BroadcastReceiver;
import android.content.Context;
import android.content.Intent;
import android.content.IntentFilter;
import android.os.Bundle;
import android.widget.LinearLayout;

public class BroadcastDemoActivity extends AppCompatActivity {
    private LinearLayout ll_test;
    private BgChangeReceiver bgChangeReceiver;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_broadcast_demo);
        ll_test = findViewById(R.id.ll_broadcast_test);
    }

    @Override
    protected void onStart() {
        super.onStart();
        bgChangeReceiver = new BgChangeReceiver();
        //过滤器
        IntentFilter intentFilter = new IntentFilter("MY_EVENT");
        //注册
        LocalBroadcastManager.getInstance(this).registerReceiver(bgChangeReceiver, intentFilter);
    }

    @Override
    protected void onStop() {
        //销毁注册
        LocalBroadcastManager.getInstance(this).unregisterReceiver(bgChangeReceiver);
        super.onStop();
    }

    private class BgChangeReceiver extends BroadcastReceiver {
        @Override
        public void onReceive(Context context, Intent intent) {
            if(intent != null) {
                ll_test.setBackgroundColor(intent.getIntExtra("color", 0));
            }
        }
    }
}

利用Broadcast实现Fragment向Activity传递消息

猜你喜欢