Android Helper类->空指针异常 [英] Android Helper class -> null pointer exception

问题描述

我想问:

在我的AppHelper类中，有以下方法可以检查互联网连接的可用性.

I have in my AppHelper class following method which check availability of internet connection.

public boolean checkInternetConnection(Context ctx) {
    ConnectivityManager cm = (ConnectivityManager) getSystemService(Context.CONNECTIVITY_SERVICE);
    // test for connection
    if (cm.getActiveNetworkInfo() != null
            && cm.getActiveNetworkInfo().isAvailable()
            && cm.getActiveNetworkInfo().isConnected()) {
        return true;
    } else {
        Log.i(GlobalApplication.APP_LOG_NAMESPACE, "Internet Connection Not Present");
        return false;
    }
}

我正在尝试通过以下方式获取布尔值:

Im trying to get Boolean value by using:

// check internet connection and availability
        Boolean isConnectionAvailable = appHelper.checkInternetConnection(getBaseContext());

但是不幸的是，我总是得到空指针异常.传递的应用程序上下文有关系吗?我该如何解决这个问题?

But unfortunately i get always null pointer exception. Is it matter of passed application context? And how should i solve that issue?

谢谢您的任何建议.

推荐答案

我要在黑暗中a一口，说AppHelper类是一个单独的Activity，永远不会从意图上正确启动.

I'm going to take a stab in the dark and say that AppHelper class is a seperate Activity that is never properly started with an intent.

如果是这样，我会改为将AppHelper作为服务而不是Activity来实现，因为"checkInternetConnection"方法更适合此类任务.

If this is so, I would instead implement AppHelper as a Service instead of an Activity, as the method "checkInternetConnection" is better suited for this type of task.

该服务是否在其自身的进程中运行或不运行，取决于我眼前的具体问题.

Weather or not the service runs in its own process or not I suppose would depend on the particular problem at hand.

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