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>

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());
}

public static boolean isNetworkAvailable(Context context) {
        boolean isMobile = false, isWifi = false;

        NetworkInfo[] infoAvailableNetworks = getConnectivityManagerInstance(
                context).getAllNetworkInfo();

        if (infoAvailableNetworks != null) {
            for (NetworkInfo network : infoAvailableNetworks) {

                if (network.getType() == ConnectivityManager.TYPE_WIFI) {
                    if (network.isConnected() && network.isAvailable())
                        isWifi = true;
                }
                if (network.getType() == ConnectivityManager.TYPE_MOBILE) {
                    if (network.isConnected() && network.isAvailable())
                        isMobile = true;
                }
            }
        }

        return isMobile || isWifi;
    }

/* You can write such method somewhere in utility class and call it NetworkChangeReceiver like below */
public class NetworkChangedReceiver extends BroadcastReceiver 
{
@Override
    public void onReceive(Context context, Intent intent) {

        if (isNetworkAvailable(context)) 
                {
             Toast.makeText(context, "Network Available Do operations",Toast.LENGTH_LONG).show(); 


    }
    }
}

只有当网络状态变为已连接而不是已断开时，才会调用上述广播接收器。

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

警告:为android.net.conn.CONNECTIVITY_CHANGE声明一个broadcastreceiver对于目标为N或更高的应用程序是不建议使用的。一般来说，应用程序不应该依赖于这个广播，而是使用JobScheduler或GCMNetworkManager。

由于CONNECTIVITY_CHANGE已弃用，那么我们应该使用另一种方式来做相同的事情

接下来的NetworkConnectionLiveData将处理所有的OS Version，直到现在，如果目标SDK小于Build.VERSION_CODES。棒棒糖，那么只有我们可以使用broadcastReceiver

最好的部分是这个类使用LiveData，所以不需要注册任何接收器使用LiveData，它将处理所有的事情

class NetworkConnectionLiveData(val context: Context) : LiveData<Boolean>() {

    private var connectivityManager: ConnectivityManager = context.getSystemService(CONNECTIVITY_SERVICE) as ConnectivityManager

    private lateinit var connectivityManagerCallback: ConnectivityManager.NetworkCallback

    override fun onActive() {
        super.onActive()
        updateConnection()
        when {
            Build.VERSION.SDK_INT >= Build.VERSION_CODES.N -> connectivityManager.registerDefaultNetworkCallback(getConnectivityManagerCallback())
            Build.VERSION.SDK_INT >= Build.VERSION_CODES.LOLLIPOP -> lollipopNetworkAvailableRequest()
            else -> {
                if (Build.VERSION.SDK_INT < Build.VERSION_CODES.LOLLIPOP) {
                    context.registerReceiver(networkReceiver, IntentFilter("android.net.conn.CONNECTIVITY_CHANGE"))
                }
            }
        }
    }

    override fun onInactive() {
        super.onInactive()
        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.LOLLIPOP) {
            connectivityManager.unregisterNetworkCallback(connectivityManagerCallback)
        } else {
            context.unregisterReceiver(networkReceiver)
        }
    }

    @TargetApi(Build.VERSION_CODES.LOLLIPOP)
    private fun lollipopNetworkAvailableRequest() {
        val builder = NetworkRequest.Builder()
                .addTransportType(android.net.NetworkCapabilities.TRANSPORT_CELLULAR)
                .addTransportType(android.net.NetworkCapabilities.TRANSPORT_WIFI)
        connectivityManager.registerNetworkCallback(builder.build(), getConnectivityManagerCallback())
    }

    private fun getConnectivityManagerCallback(): ConnectivityManager.NetworkCallback {
        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.LOLLIPOP) {

            connectivityManagerCallback = object : ConnectivityManager.NetworkCallback() {
                override fun onAvailable(network: Network?) {
                    postValue(true)
                }

                override fun onLost(network: Network?) {
                    postValue(false)
                }
            }
            return connectivityManagerCallback
        } else {
            throw IllegalAccessError("Should not happened")
        }
    }

    private val networkReceiver = object : BroadcastReceiver() {
        override fun onReceive(context: Context, intent: Intent) {
            updateConnection()
        }
    }

    private fun updateConnection() {
        val activeNetwork: NetworkInfo? = connectivityManager.activeNetworkInfo
        postValue(activeNetwork?.isConnected == true)
    }
} 

使用LiveData到任何类:

NetworkConnectionLiveData(context ?: return)
    .observe(viewLifecycleOwner, Observer { isConnected ->
        if (!isConnected) {
            // Internet Not Available
            return@Observer
        }
        // Internet Available
})

1)在manifest: -调用接收器如下代码

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    package="com.safal.checkinternet">

    <uses-permission android:name="android.permission.INTERNET" />
    <uses-permission android:name="android.permission.ACCESS_NETWORK_STATE" />

    <application
        android:allowBackup="true"
        android:icon="@mipmap/ic_launcher"
        android:label="@string/app_name"
        android:roundIcon="@mipmap/ic_launcher_round"
        android:supportsRtl="true"
        android:theme="@style/AppTheme"
        tools:ignore="AllowBackup,GoogleAppIndexingWarning">
        <receiver android:name=".NetworkChangeReceiver" >
            <intent-filter>
                <action android:name="android.net.conn.CONNECTIVITY_CHANGE" />
            </intent-filter>
        </receiver>
        <activity android:name=".MainActivity">
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />

                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>
    </application>

</manifest>

2)创建一个宽播接收器类:在这个类中添加网络检查的代码

package com.safal.checkinternet;

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 android.widget.Toast;

public class NetworkChangeReceiver extends BroadcastReceiver {

    @Override
    public void onReceive(final Context context, final Intent intent) {
        if (isOnline(context)){
            Toast.makeText(context, "Available", Toast.LENGTH_SHORT).show();
        }else {
            Toast.makeText(context, "Not Available", Toast.LENGTH_SHORT).show();
        }
    }
    public boolean isOnline(Context context) {

        ConnectivityManager cm = (ConnectivityManager) context.getSystemService(Context.CONNECTIVITY_SERVICE);
        assert cm != null;
        NetworkInfo netInfo = cm.getActiveNetworkInfo();
        return (netInfo != null && netInfo.isConnected());
    }    
} 

3)在您的活动中呼叫广播接收器:-

package com.safal.checkinternet;

import androidx.appcompat.app.AppCompatActivity;

import android.content.Intent;
import android.content.IntentFilter;
import android.os.Bundle;

public class MainActivity extends AppCompatActivity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
//Call Broad cast Receiver 
        IntentFilter filter = new IntentFilter();
        filter.addAction("android.net.conn.CONNECTIVITY_CHANGE");
        registerReceiver(new NetworkChangeReceiver(), filter);
    }
}