在android L（API 21）中，当设备失去网络连接时，我如何接收通知

我使用这段代码是为了在API 20及以下版本中连接丢失时得到通知

registerReceiver(getConnectivityStateBroadcastReceiver(), new IntentFilter(ConnectivityManager.CONNECTIVITY_ACTION));

private class ConnectivityStateBroadcastReceiver extends BaseBroadcastReceiver {

    /**
     * @param userLoggedIn
     * @param context
     * @param intent
     */
    @Override
    protected void onReceive(Boolean userLoggedIn, Context context, Intent intent) {

        Bundle extras = intent.getExtras();
        boolean notConnected = extras.getBoolean(ConnectivityManager.EXTRA_NO_CONNECTIVITY, false);

        // DO something
    }
}

但它在API 21中不起作用

---

我怎样才能解决这个问题？也许这和我的工作有关，但我没有找到任何使用它的例子。谢谢。

好的，我想知道怎么做，但如果能确认此解决方案是正确的，我将不胜感激

我所做的只是在我的应用程序类的onCreate中添加对该代码的调用

/**
 *
 */
@SuppressLint("NewApi")
private void registerConnectivityNetworkMonitorForAPI21AndUp() {

    if (Build.VERSION.SDK_INT < Build.VERSION_CODES.LOLLIPOP) {
        return;
    }

    ConnectivityManager connectivityManager = (ConnectivityManager) getSystemService(Context.CONNECTIVITY_SERVICE);

    NetworkRequest.Builder builder = new NetworkRequest.Builder();

    connectivityManager.registerNetworkCallback(
            builder.build(),
            new ConnectivityManager.NetworkCallback() {
                /**
                 * @param network
                 */
                @Override
                public void onAvailable(Network network) {

                    sendBroadcast(
                            getConnectivityIntent(false)
                    );

                }

                /**
                 * @param network
                 */
                @Override
                public void onLost(Network network) {

                    sendBroadcast(
                            getConnectivityIntent(true)
                    );

                }
            }

    );

}

 /**
 * @param noConnection
 * @return
 */
private Intent getConnectivityIntent(boolean noConnection) {

    Intent intent = new Intent();

    intent.setAction("mypackage.CONNECTIVITY_CHANGE");
    intent.putExtra(ConnectivityManager.EXTRA_NO_CONNECTIVITY, noConnection);

    return intent;

}

---

现在，我已经在工作的广播接收器也会收到API 21中网络更改的通知。

我将粘贴我的完整解决方案，因为我需要查看许多地方才能使其工作：

应用类

public void onCreate(){
...

IntentFilter filter = new IntentFilter();
    if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.N) {
        Timber.d("using registerNetworkCallback");
        createChangeConnectivityMonitor();
        filter.addAction(MY_CONNECTIVITY_CHANGE);
    } else {
        Timber.d("using old broadcast receiver");
        filter.addAction(ConnectivityManager.CONNECTIVITY_ACTION);
    }

    registerReceiver(new SyncOnConnectivityReceiver(), filter);
 }

  @RequiresApi(Build.VERSION_CODES.N)
   private void createChangeConnectivityMonitor() {
    final Intent intent = new Intent(MY_CONNECTIVITY_CHANGE);
    ConnectivityManager connectivityManager = (ConnectivityManager) 
  getSystemService(Context.CONNECTIVITY_SERVICE);
    if (connectivityManager != null) {
        connectivityManager.registerNetworkCallback(
               new NetworkRequest.Builder().build(), 
               new ConnectivityManager.NetworkCallback() {
                    /**
                     * @param network
                     */
                    @Override
                    public void onAvailable(Network network) {
                        Timber.d("On available network");
                        sendBroadcast(intent);
                    }

                    /**
                     * @param network
                     */
                    @Override
                    public void onLost(Network network) {
                        Timber.d("On not available network");
                        sendBroadcast(intent);
                    }
                });
    }

}

在我的听筒中：

public class SyncOnConnectivityReceiver extends BroadcastReceiver {

@Override
 public void onReceive(@Nullable final Context context, Intent intent) {
    Timber.d("triggering on connectivity change");
    if (context != null && isNetworkAvailable(context)) {
        Executors.newSingleThreadExecutor().submit(new Runnable() {
            @Override
            public void run() {
                syncBusData(context);
            }
        });
    }
}

private boolean isNetworkAvailable(Context context) {
    ConnectivityManager cm = (ConnectivityManager) context.getSystemService(Context.CONNECTIVITY_SERVICE);
    if (cm != null) {
        NetworkInfo networkInfo = cm.getActiveNetworkInfo();
        return networkInfo != null && networkInfo.isConnected();
    }
    return false;
}

private void syncData(Context context) {

}
}

在AndroidManifiest.xml中

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

<receiver android:name="com.innofied.viapool.location.SyncOnConnectivityReceiver"/>

如果需要，请尝试此方法

• 注册到网络状态更改
• 考虑所有网络接口
• 如果网络可用于任何接口，是否希望收到通知
• 该代码支持API>20（您也可以轻松添加遗留API支持）

在类中声明必要的变量：

private static final HashMap<Network, Boolean> mNetworkStates = new HashMap<>();
private final Object mSyncNetworkState = new Object();
private Boolean mNetworkState;

---

您可以创建一个线程，该线程在运行时递归运行，尝试连接到网络，当您从中捕获到NetworkException时，您就失去了连接。这听起来像是一种非常错误的方法。我在工作中使用了我自己的方法，没有错误，也没有过载，我宁愿使用内置功能我实现了这一点，并发现在Lolipop 5.0.1中，它没有捕捉到仅存在移动数据连接（无wifi）且连接经历信号丢失（即驶入隧道）的场景。使用飞行模式在设备上强制断开连接或关闭移动数据将触发此问题。我也有同样的问题，如果您发现一些值得关注的问题，请点击此处。但请记住，在某些情况下，当在lte上调用可用的wifi网络的交换网络（例如从lte到wifi）早于lte的onLost时，API级别28中不推荐使用此选项。在这种情况下，最后一次广播将告诉我们网络丢失的情况。但请记住，API级别28中不推荐使用此回调，但何时取消注册此回调？

private static final HashMap<Network, Boolean> mNetworkStates = new HashMap<>();
private final Object mSyncNetworkState = new Object();
private Boolean mNetworkState;

private void registerNetworkStateInfo(@NonNull final Context context) throws Exception {
    final ConnectivityManager connectivityManager = (ConnectivityManager) context.getSystemService(Context.CONNECTIVITY_SERVICE);
    NetworkRequest.Builder builder = new NetworkRequest.Builder();

    if (connectivityManager != null) {
        connectivityManager.registerNetworkCallback(
                builder.build(),
                new ConnectivityManager.NetworkCallback() {
                    @Override
                    public void onAvailable(@NonNull Network network) {
                        mNetworkStates.put(network, true);
                        synchronized (mSyncNetworkState){
                            mNetworkState = true;
                        }

                        Log.d("Network state", "Network state: true");
                    }

                    @Override
                    public void onLost(@NonNull Network network) {
                        mNetworkStates.put(network, false);
                        synchronized (mSyncNetworkState){
                            mNetworkState = false;
                            Log.d("Network state", "Network state: false");

                            mNetworkStates.forEach(new BiConsumer<Network, Boolean>() {
                                @Override
                                public void accept(Network nextNetwork, Boolean state) {
                                    if (state.equals(true)) {
                                        mNetworkState= true;
                                        Log.d("Network state", "Network state: but true");
                                    }
                                }
                            });
                        }
                    }
                }
        );
    } else {
        synchronized (mSyncNetworkState){
            mNetworkState = false;
        }
        throw new Exception("Connectivity Manager is not available");
    }
}

synchronized (mSyncNetworkState){
    if (!mNetworkState) {
        throw new Exception("No network available");
    }
}