CONNECTIVITY_ACTION文档:

针对Android 7.0 (API级别24)及以上的应用程序，如果它们在manifest中声明了广播接收器，则不会接收此广播。如果应用程序向context . registerreceiver()注册了BroadcastReceiver，并且该context仍然有效，那么应用程序仍然会接收广播。

回答第一个问题:您的广播接收器被调用了两次，因为

您已经添加了两个<intent-filter>

网络连接的改变: <action android:name="android.net.conn.CONNECTIVITY_CHANGE" /> WiFi状态变化: <action android:name="android.net.wifi.WIFI_STATE_CHANGED" />

就用一个: <action android:name="android.net.conn.CONNECTIVITY_CHANGE" />。

它将只响应一个操作而不是两个。更多信息请参见这里。

回答你的第二个问题(如果可以上网，你想让对方只打一次电话):

你的代码是完美的;只有在互联网可用时才通知。

更新

如果你只是想检查手机是否与互联网相连，你可以使用这种方法来检查你的连接。

public boolean isOnline(Context context) {

    ConnectivityManager cm = (ConnectivityManager) context.getSystemService(Context.CONNECTIVITY_SERVICE);
    NetworkInfo netInfo = cm.getActiveNetworkInfo();
    //should check null because in airplane mode it will be null
    return (netInfo != null && netInfo.isConnected());
}

到2022年，上述BroadcastReceiver方法都将失效。由于Android 7.0的限制，BroadcastReceiver方法将不再工作。检查互联网是否可用的最新和最简单的方法是使用以下代码。(Android 12测试)

val networkRequest = NetworkRequest.Builder()
        .addCapability(NetworkCapabilities.NET_CAPABILITY_INTERNET)
        .addTransportType(NetworkCapabilities.TRANSPORT_WIFI)
        .addTransportType(NetworkCapabilities.TRANSPORT_CELLULAR)
        .build()

private val networkCallback = object : ConnectivityManager.NetworkCallback() {
    // network is available for use
    override fun onAvailable(network: Network) {
        super.onAvailable(network)
    }

    // Network capabilities have changed for the network
    override fun onCapabilitiesChanged(
            network: Network,
            networkCapabilities: NetworkCapabilities
    ) {
        super.onCapabilitiesChanged(network, networkCapabilities)
        val unmetered = networkCapabilities.hasCapability(NetworkCapabilities.NET_CAPABILITY_NOT_METERED)
    }

    // lost network connection
    override fun onLost(network: Network) {
        super.onLost(network)
    }
}

val connectivityManager = getSystemService(ConnectivityManager::class.java) as ConnectivityManager
connectivityManager.requestNetwork(networkRequest, networkCallback

将这段代码放在一个函数中，并在activity/fragment的onCreate()中调用它。在onAvailable()和onLost()函数中，每当互联网连接或断开连接时，您都会收到通知。与此同时，您可以使用liveData或任何您喜欢的方式在其他活动/片段中广播这些更新。 官方文档链接:https://developer.android.com/training/monitoring-device-state/connectivity-status-type

每次使用广播接收器检查互联网状态:

谷歌驱动器上可用的完整源代码。

AndroidManifest.xml

<uses-permission android:name="android.permission.ACCESS_NETWORK_STATE"/>
<uses-permission android:name="android.permission.INTERNET"/>
<receiver android:name=".receivers.NetworkChangeReceiver">
            <intent-filter>
                <action android:name="android.net.conn.CONNECTIVITY_CHANGE" />
            </intent-filter>
</receiver>

BroadcastReciever

package com.keshav.networkchangereceiverexample.receivers;

import android.content.BroadcastReceiver;
import android.content.Context;
import android.content.Intent;
import android.net.ConnectivityManager;
import android.net.NetworkInfo;
import android.util.Log;

import static com.keshav.networkchangereceiverexample.MainActivity.dialog;

public class NetworkChangeReceiver extends BroadcastReceiver
{
    @Override
    public void onReceive(Context context, Intent intent)
    {
        try
        {
            if (isOnline(context)) {
                dialog(true);
                Log.e("keshav", "Online Connect Intenet ");
            } else {
                dialog(false);
                Log.e("keshav", "Conectivity Failure !!! ");
            }
        } catch (NullPointerException e) {
            e.printStackTrace();
        }
    }

    private boolean isOnline(Context context) {
        try {
            ConnectivityManager cm = (ConnectivityManager) context.getSystemService(Context.CONNECTIVITY_SERVICE);
            NetworkInfo netInfo = cm.getActiveNetworkInfo();
            //should check null because in airplane mode it will be null
            return (netInfo != null && netInfo.isConnected());
        } catch (NullPointerException e) {
            e.printStackTrace();
            return false;
        }
    }
}

MainActivity.java

package com.keshav.networkchangereceiverexample;

import android.content.BroadcastReceiver;
import android.content.Intent;
import android.content.IntentFilter;
import android.graphics.Color;
import android.net.ConnectivityManager;
import android.os.Build;
import android.os.Handler;
import android.os.Looper;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.util.Log;
import android.view.View;
import android.view.animation.Animation;
import android.view.animation.AnimationUtils;
import android.widget.TextView;

import com.keshav.networkchangereceiverexample.receivers.NetworkChangeReceiver;

public class MainActivity extends AppCompatActivity {

    private BroadcastReceiver mNetworkReceiver;
    static TextView tv_check_connection;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        tv_check_connection=(TextView) findViewById(R.id.tv_check_connection);
        mNetworkReceiver = new NetworkChangeReceiver();
        registerNetworkBroadcastForNougat();

    }

    public static void dialog(boolean value){

        if(value){
            tv_check_connection.setText("We are back !!!");
            tv_check_connection.setBackgroundColor(Color.GREEN);
            tv_check_connection.setTextColor(Color.WHITE);

            Handler handler = new Handler();
            Runnable delayrunnable = new Runnable() {
                @Override
                public void run() {
                    tv_check_connection.setVisibility(View.GONE);
                }
            };
            handler.postDelayed(delayrunnable, 3000);
        }else {
            tv_check_connection.setVisibility(View.VISIBLE);
            tv_check_connection.setText("Could not Connect to internet");
            tv_check_connection.setBackgroundColor(Color.RED);
            tv_check_connection.setTextColor(Color.WHITE);
        }
    }


    private void registerNetworkBroadcastForNougat() {
        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.N) {
            registerReceiver(mNetworkReceiver, new IntentFilter(ConnectivityManager.CONNECTIVITY_ACTION));
        }
        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.M) {
            registerReceiver(mNetworkReceiver, new IntentFilter(ConnectivityManager.CONNECTIVITY_ACTION));
        }
    }

    protected void unregisterNetworkChanges() {
        try {
            unregisterReceiver(mNetworkReceiver);
        } catch (IllegalArgumentException e) {
            e.printStackTrace();
        }
    }

    @Override
    public void onDestroy() {
        super.onDestroy();
        unregisterNetworkChanges();
    }
}

activity_main.xml

<?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="com.keshav.networkchangereceiverexample.MainActivity">

    <TextView
        android:id="@+id/tv_check_connection"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="Connection establised !"
        android:padding="25dp"
        app:layout_constraintBottom_toBottomOf="parent"
        android:gravity="center"
        app:layout_constraintLeft_toLeftOf="parent"
        app:layout_constraintRight_toRightOf="parent"
        app:layout_constraintTop_toTopOf="parent" />

</LinearLayout>

使用https://github.com/JobGetabu/DroidNet更容易

 @Override
    public void onInternetConnectivityChanged(boolean isConnected) {

        if (isConnected) {
            //do Stuff with internet
            netIsOn();
        } else {
            //no internet
            netIsOff();
        }
    }

    private void netIsOn(){...}

    private void netIsOff(){...}

首先，我们将创建一个类来检查网络状态的连通性。所以让我们创建一个类:

public class AppStatus {
    private static AppStatus instance = new AppStatus();
    static Context context;
    ConnectivityManager connectivityManager;
    NetworkInfo wifiInfo, mobileInfo;
    boolean connected = false;

    public static AppStatus getInstance(Context ctx) {
        context = ctx.getApplicationContext();
        return instance;
    }

    public boolean isOnline() {
        try {
            connectivityManager = (ConnectivityManager) context
                    .getSystemService(Context.CONNECTIVITY_SERVICE);

            NetworkInfo networkInfo = connectivityManager.getActiveNetworkInfo();
            connected = networkInfo != null && networkInfo.isAvailable() &&
                    networkInfo.isConnected();
            return connected;


        } catch (Exception e) {
            System.out.println("CheckConnectivity Exception: " + e.getMessage());
            Log.v("connectivity", e.toString());
        }
        return connected;
    }
}

现在创建一个新的Broadcast接收器类:

public class ConnectivityReceiver extends BroadcastReceiver {
    @Override
    public void onReceive(Context context, Intent intent) {
        if (AppStatus.getInstance(context).isOnline()) {

            Intent intent1=new Intent(context,DisplayAct.class);
            intent1.setFlags(Intent.FLAG_ACTIVITY_NEW_TASK);
            context.startActivity(intent1);




        } else {

            Toast.makeText(context, "Please !! Make your network ON", Toast.LENGTH_SHORT).show();

        }
    }
}

现在在清单上注册您的广播接收器:

<receiver android:name=".ConnectivityReceiver">
            <intent-filter>
                <action android:name="android.net.conn.CONNECTIVITY_CHANGE"/>
            </intent-filter>
        </receiver>