Broadcast组件——收发广播应用——监听系统广播——接收网络变更广播

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布局：

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:padding="5dp"
    android:orientation="vertical">

    <ScrollView
        android:layout_width="match_parent"
        android:layout_height="wrap_content">

        <LinearLayout
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:orientation="vertical">

            <TextView
                android:id="@+id/tv_network"
                android:layout_width="match_parent"
                android:layout_height="wrap_content"
                android:textColor="@color/black"
                android:textSize="17sp" />

        </LinearLayout>
    </ScrollView>

</LinearLayout>

 

代码：

package com.example.myapplication;

import android.content.BroadcastReceiver;
import android.content.Context;
import android.content.Intent;
import android.content.IntentFilter;
import android.net.NetworkInfo;
import android.os.Bundle;
import android.widget.TextView;

import androidx.appcompat.app.AppCompatActivity;

public class MainActivity extends AppCompatActivity
{

    private TextView tv_network; // 声明一个文本视图对象

    private String desc = "开始侦听网络变更广播，请开关WLAN或者数据连接，再观察广播结果";

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


        tv_network = findViewById(R.id.tv_network);
        tv_network.setText(desc);
    }

    @Override
    protected void onStart()
    {
        super.onStart();
        networkReceiver = new NetworkReceiver(); // 创建一个网络变更的广播接收器

        // 创建一个意图过滤器，只处理网络状态变化的广播
        IntentFilter filter = new IntentFilter("android.net.conn.CONNECTIVITY_CHANGE");

        registerReceiver(networkReceiver, filter); // 注册接收器，注册之后才能正常接收广播
    }

    @Override
    protected void onStop()
    {
        super.onStop();

        unregisterReceiver(networkReceiver); // 注销接收器，注销之后就不再接收广播
    }

    private NetworkReceiver networkReceiver; // 声明一个网络变更的广播接收器实例

    // 定义一个网络变更的广播接收器
    private class NetworkReceiver extends BroadcastReceiver
    {
        // 一旦接收到网络变更的广播，马上触发接收器的onReceive方法
        @Override
        public void onReceive(Context context, Intent intent)
        {
            if (intent != null)
            {
                NetworkInfo networkInfo = intent.getParcelableExtra("networkInfo");

                String networkClass = NetworkUtil.getNetworkClass(networkInfo.getSubtype());

                desc = String.format("%s\n%s 收到一个网络变更广播，网络大类为%s，" + "网络小类为%s，网络制式为%s，网络状态为%s", desc, DateUtil.getNowTime(), networkInfo.getTypeName(), networkInfo.getSubtypeName(), networkClass, networkInfo.getState().toString());

                tv_network.setText(desc);
            }
        }
    }

}

 

NetworkUtil：

package com.example.myapplication;

import android.telephony.TelephonyManager;

public class NetworkUtil
{
    // 获取数据连接的制式类型
    public static String getNetworkClass(int subType)
    {
        switch (subType)
        {
            case TelephonyManager.NETWORK_TYPE_GPRS:
            case TelephonyManager.NETWORK_TYPE_EDGE:
            case TelephonyManager.NETWORK_TYPE_CDMA:
            case TelephonyManager.NETWORK_TYPE_1xRTT:
            case TelephonyManager.NETWORK_TYPE_IDEN:
                return "2G";
            case TelephonyManager.NETWORK_TYPE_UMTS:
            case TelephonyManager.NETWORK_TYPE_EVDO_0:
            case TelephonyManager.NETWORK_TYPE_EVDO_A:
            case TelephonyManager.NETWORK_TYPE_HSDPA:
            case TelephonyManager.NETWORK_TYPE_HSUPA:
            case TelephonyManager.NETWORK_TYPE_HSPA:
            case TelephonyManager.NETWORK_TYPE_EVDO_B:
            case TelephonyManager.NETWORK_TYPE_EHRPD:
            case TelephonyManager.NETWORK_TYPE_HSPAP:
                return "3G";
            case TelephonyManager.NETWORK_TYPE_LTE:
                return "4G";
            case TelephonyManager.NETWORK_TYPE_NR:
                return "5G";
            default:
                return "未知";
        }
    }
}

DateUtil：

package com.example.myapplication;

import android.annotation.SuppressLint;
import android.text.TextUtils;

import java.text.SimpleDateFormat;
import java.util.Calendar;
import java.util.Date;

@SuppressLint("SimpleDateFormat")
public class DateUtil
{
    // 获取当前的日期时间
    public static String getNowDateTime(String formatStr)
    {
        String format = formatStr;
        if (TextUtils.isEmpty(format))
        {
            format = "yyyyMMddHHmmss";
        }

        SimpleDateFormat sdf = new SimpleDateFormat(format);
        return sdf.format(new Date());
    }

    // 获取当前的时间
    public static String getNowTime()
    {
        SimpleDateFormat sdf = new SimpleDateFormat("HH:mm:ss");
        return sdf.format(new Date());
    }

    // 获取当前的时间（精确到毫秒）
    public static String getNowTimeDetail()
    {
        SimpleDateFormat sdf = new SimpleDateFormat("HH:mm:ss.SSS");
        return sdf.format(new Date());
    }

    public static String getNowDate()
    {
        SimpleDateFormat sdf = new SimpleDateFormat("yyyyMMdd");
        return sdf.format(new Date());
    }

    public static String getDate(Calendar calendar)
    {
        Date date = calendar.getTime();
        // 创建一个日期格式化的工具
        SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd");
        // 将当前日期时间按照指定格式输出格式化后的日期时间字符串
        return sdf.format(date);
    }

    public static String getMonth(Calendar calendar)
    {
        Date date = calendar.getTime();
        // 创建一个日期格式化的工具
        SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM");
        // 将当前日期时间按照指定格式输出格式化后的日期时间字符串
        return sdf.format(date);
    }

    public static Date formatString(String strTime)
    {
        Date date = new Date();
        SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd");

        try {
            date = sdf.parse(strTime);
        } catch (Exception e) {
            e.printStackTrace();
        }

        return date;
    }

}