Question

我的应用程序基于互联网。当我的应用程序运行时没有互联网时，我需要显示一个警报对话框。因此，我创建了一个BroadcastReceiver并将其注册到MainActivity中。在每个活动或片段的顶部，我都无法显示带有烤面包的互联网，但是警报对话框仅在MainActivity中显示。当我处于另一个活动或片段中并且网络断开连接时，它在我当前的活动中不显示警报对话框，但在MainActivity中显示一个警报对话框，似乎上下文是MainActivity的上下文。我的代码在这里NetworkUtil.java作为实用程序类。

//NetworkUtil.java
public class NetworkUtil {
    public static final int TYPE_WIFI = 1;
    public static final int TYPE_MOBILE = 2;
    public static final int TYPE_NOT_CONNECTED = 0;
    public static final int NETWORK_STATUS_NOT_CONNECTED = 0;
    public static final int NETWORK_STATUS_WIFI = 1;
    public static final int NETWORK_STATUS_MOBILE = 2;

    public static int getConnectivityStatus(Context context) {
        ConnectivityManager cm = (ConnectivityManager) context.getSystemService(Context.CONNECTIVITY_SERVICE);

        NetworkInfo activeNetwork = cm.getActiveNetworkInfo();
        if (null != activeNetwork) {
            if(activeNetwork.getType() == ConnectivityManager.TYPE_WIFI)
                return TYPE_WIFI;

            if(activeNetwork.getType() == ConnectivityManager.TYPE_MOBILE)
                return TYPE_MOBILE;
        }
        return TYPE_NOT_CONNECTED;
    }

    public static int getConnectivityStatusString(Context context) {
        int conn = NetworkUtil.getConnectivityStatus(context);
        int status = 0;
        if (conn == NetworkUtil.TYPE_WIFI) {
            status = NETWORK_STATUS_WIFI;
        } else if (conn == NetworkUtil.TYPE_MOBILE) {
            status = NETWORK_STATUS_MOBILE;
        } else if (conn == NetworkUtil.TYPE_NOT_CONNECTED) {
            status = NETWORK_STATUS_NOT_CONNECTED;
        }
        return status;
    }
}

我的BroadcastReceiver CheckConnectivity

public class CheckConnectivity extends BroadcastReceiver{
@Override
    public void onReceive(final Context context, final Intent intent) {

        int status = NetworkUtil.getConnectivityStatusString(context);
        if ("android.net.conn.CONNECTIVITY_CHANGE".equals(intent.getAction())) {
            if (status == NetworkUtil.NETWORK_STATUS_NOT_CONNECTED) {
                new SweetAlertDialog(context, SweetAlertDialog.ERROR_TYPE)
                        .setTitleText("Oops...")
                        .setContentText("No internet! Check your network connection")
                        .show();
            Toast.makeText(context, "Internet Connection Lost", Toast.LENGTH_LONG).show();
            } else {
                Toast.makeText(context, "Internet Connected", Toast.LENGTH_LONG).show();
            }
        }
    }
}

MainActivity，其中已注册BroadcastReceiver。

public class MainActivity extends AppCompatActivity {

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

        BroadcastReceiver networkChangeReceiver=new CheckConnectivity();
        IntentFilter intentFilter = new IntentFilter();
        intentFilter.addAction(ConnectivityManager.CONNECTIVITY_ACTION);
        registerReceiver(networkChangeReceiver, intentFilter);
   }
}

Answer 1

面向Android 7.0（API级别24）及更高版本的应用程序如果在清单中声明了广播接收器，则不会收到CONNECTIVITY_ACTION广播。如果应用向Context.registerReceiver（）注册了自己的BroadcastReceiver，并且该上下文仍然有效，则它们仍将接收CONNECTIVITY_ACTION广播。

因此，以下是所有设备的完整解决方案。

创建一个通用类来检查设备是否连接到网络状态。

class ConnectivityHelper() {
    companion object {
        fun isConnectedToNetwork(): Boolean {
            val connectivityManager: ConnectivityManager =
                CenceApplication.cenceAppContext.getSystemService(Context.CONNECTIVITY_SERVICE) as ConnectivityManager
            val networkInfo = connectivityManager.activeNetworkInfo
            if (networkInfo != null) {
                return networkInfo.isConnected
            }
            return false
        }
    }
}

现在要检查牛轧糖以下的设备： 1.您需要在清单中设置广播接收器 2.倾听变化 3.通知您的基本活动。

注意：基本活动是普通活动，它由应用程序中的所有其他活动扩展，而基本活动由AppCompatActivity（）扩展

在清单中：

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

广播接收器类别：

class NetworkChangeReceiver : BroadcastReceiver() {

    companion object {
        lateinit var networkChangeListener: NetworkChangeListener
    }

    override fun onReceive(context: Context?, intent: Intent?) {
        networkChangeListener.networkStateChanged(ConnectivityHelper.isConnectedToNetwork())
    }
}

创建一个界面以在基本活动中进行通知：

interface NetworkChangeListener {
    fun networkStateChanged(boolean: Boolean)
}

应用程序中的初始化界面：

class YourApplication:Application() {

    companion object {
        lateinit var appContext: Context
    }

    override fun onCreate() {
        super.onCreate()
        appContext = this
    }


    fun initializeNetworkListener(listener:NetworkChangeListener){
        NetworkChangeReceiver.networkChangeListener = listener
    }
}

BasActivity，它实现了接口并在MutableLivedata的帮助下在网络中断时通知任何活动/碎片：

class BaseActivity : AppCompatActivity(), NetworkChangeListener {


    private var networkLiveData: MutableLiveData<Boolean> = MutableLiveData()
    private lateinit var snackbar: Snackbar

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setupNetworkState()
    }

    private fun setupNetworkState() {
        networkLiveData.postValue(checkNetworkState())

        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.N) {

            val connectivityManager: ConnectivityManager =
                this.getSystemService(Context.CONNECTIVITY_SERVICE) as ConnectivityManager

            connectivityManager.registerDefaultNetworkCallback(object : ConnectivityManager.NetworkCallback() {
                override fun onAvailable(network: Network?) {
                    super.onAvailable(network)
                    networkLiveData.postValue(checkNetworkState())
                }

                override fun onLost(network: Network?) {
                    super.onLost(network)
                    networkLiveData.postValue(checkNetworkState())
                }
            })


        } else {
            (application as YourApplication).initializeNetworkListener(this@BaseActivity)
        }
    }

    override fun networkStateChanged(boolean: Boolean) {
        networkLiveData.postValue(boolean)
    }


    fun getNetworkStateUpdate(): MutableLiveData<Boolean> {
        return networkLiveData
    }

    fun checkNetworkState(): Boolean {
        return ConnectivityHelper.isConnectedToNetwork()
    }

现在进入**您的任何活动/片段的最后一步****：在** onCreate（）方法中，

getNetworkStateUpdate().observe(this, object : Observer<Boolean> {
            val snackbar = Snackbar
                .make(
                    mIndMainParentLayout, "You're Offline",
                    Snackbar.LENGTH_INDEFINITE
                )

            override fun onChanged(t: Boolean?) {
                if (!t!!) {
                    snackbar.show()
                } else {
                    snackbar.dismiss()
                }
            }

        })

Answer 2

尝试以下代码：

public static boolean isConnectedToInternet(Context context){
    ConnectivityManager connectivityManager = (ConnectivityManager)context.getSystemService(Context.CONNECTIVITY_SERVICE);
    if (connectivityManager != null){
        NetworkInfo info = connectivityManager.getActiveNetworkInfo();
        if (info != null){
            if (info.getType() == ConnectivityManager.TYPE_WIFI){
                return true;
            }else if (info.getType() == ConnectivityManager.TYPE_MOBILE){
                return true;
            }
        }
    }
    return false;
}

if (isConnectedToInternet() {
        Toast.makeText(context, "Internet Connected", Toast.LENGTH_LONG).show();
    }else {
        new SweetAlertDialog(MainActivity.this, SweetAlertDialog.ERROR_TYPE)
                .setTitleText("Oops...")
                .setContentText("No internet! Check your network connection")
                .show();
        Toast.makeText(context, "Internet Connection Lost", Toast.LENGTH_LONG).show();
    }

Answer 3

在每种活动的BroadcastReceiver方法中注册onResume，然后在onPause中注销。现在，您仅在MainActivity中注册，但是MainActivity如果在后台，则无法显示AlertDialog。

没有互联网时如何显示警报对话框？

3 个答案: