执行网络操作以检查用户是否具有与异步任务的互联网连接

Question

我低于异常

android.os.NetworkOnMainThreadException

因为我没有使用异步任务来进行特定的网络操作。我已经搜索过这个，但它让我很困惑。有人可以让它与异步任务和特定功能一起使用吗？

下面是我使用的两个函数：

1) isNetworkAvailable()

private boolean isNetworkAvailable() {

    ConnectivityManager connectivityManager
            = (ConnectivityManager) getSystemService(Context.CONNECTIVITY_SERVICE);
    NetworkInfo activeNetworkInfo = connectivityManager.getActiveNetworkInfo();
    return activeNetworkInfo != null;

}

2) hasInternetAccess(Boolean showMessage)

当我想显示吐司时，我调用这个函数，将参数设置为 true。

public boolean hasInternetAccess(Boolean showMessage) {

    if (isNetworkAvailable()) {
        try {
            HttpURLConnection urlc = (HttpURLConnection)
                    (new URL("http://clients3.google.com/generate_204")
                            .openConnection());
            urlc.setRequestProperty("User-Agent", "Android");
            urlc.setRequestProperty("Connection", "close");
            urlc.setConnectTimeout(1500);
            urlc.connect();
            return (urlc.getResponseCode() == 204 &&
                    urlc.getContentLength() == 0);
        } catch (IOException e) {
            Log.w("connection", "Error checking internet connection", e);
        }
    } else {
        if(showMessage) // If i want to show the toast, it's true
            showAToast("No Internet Connection", Toast.LENGTH_SHORT); // Just another function to show a toast
    }
    return false;
}

Answer 1

这是通过创建一个扩展 AsyncTask 的内部 class 来使用 AsyncTask 的方法。

private class NetworkInAsync extends AsyncTask<String, Void, Boolean> {

    private Context context;
    private Activity activity;

    NetworkInAsync(Activity activity) {
        this.context = activity.getApplicationContext();
        this.activity = activity;
    }


    @Override
    protected void onPreExecute() {
    }

    @Override
    protected void onPostExecute(Boolean result) {
        // Do something with the result here 
    }

    @Override
    protected Boolean doInBackground(String... params) {
        if (isNetworkAvailable()) {
            try {
                HttpURLConnection urlc = (HttpURLConnection)
                (new URL("http://clients3.google.com/generate_204")
                        .openConnection());
                urlc.setRequestProperty("User-Agent", "Android");
                urlc.setRequestProperty("Connection", "close");
                urlc.setConnectTimeout(1500);
                urlc.connect();
                return (urlc.getResponseCode() == 204 &&
                urlc.getContentLength() == 0);
            } catch (IOException e) {
                Log.w("connection", "Error checking internet connection", e);
            }
        } else {
            if(showMessage) // If i want to show the toast, it's true
            showAToast("No Internet Connection", Toast.LENGTH_SHORT); // Just another function to show a toast
        }
        return false;
    }
}

您可以按如下方式执行AsyncTask

new NetworkInAsync(this).execute();

我仍然建议您阅读文档 here 以弄清楚 AsyncTask 在 Android 中的工作原理。

Answer 2

当您从 AsyncTask 的 doInBackground 方法

调用代码时，代码应该可以工作

致电test();

private void test() {
HttpURLConnection urlc = (HttpURLConnection)
                    (new URL("http://clients3.google.com/generate_204")
                            .openConnection());

            urlc.setConnectTimeout(1500);
            urlc.connect();
}

你可以在调用之前检查网络连接，但是无论如何，你应该在TimeOut异常中捕获异常。所以我认为，在拨打电话之前检查连接性对您没有多大好处。

执行网络操作以检查用户是否具有与异步任务的互联网连接

Perform network operation to check if user has internet connection with async task

android

android-asynctask

internet-connection