如何检查在Android上网？ InetAddress类从不超时... [英] How to check internet access on Android? InetAddress never timeouts...

问题描述

我有一个的AsyncTask 是应该检查网络访问的主机名。但 doInBackground（）永不超时。任何人都有一个线索吗？

 公共类HostAvailabilityTask扩展的AsyncTask＆LT;字符串，太虚，布尔＆GT; {

    私营主为主;

    公共HostAvailabilityTask（主主）{
        this.main =为主;
    }

    保护布尔doInBackground（字符串... PARAMS）{
        Main.Log（doInBackground（）isHostAvailable（）：+参数[0]）;

        尝试 {
            返回InetAddress.getByName（PARAMS [0]）isReachable（30）。
        }赶上（UnknownHostException异常E）{
            e.printStackTrace（）;
        }赶上（IOException异常E）{
            e.printStackTrace（）;
        }
        返回false;
    }

    保护无效onPostExecute（布尔......结果）{
        Main.Log（onPostExecute（））;

        如果（结果[0] == FALSE）{
            main.setContentView（R.layout.splash）;
            返回;
        }

        main.continueAfterHostCheck（）;
    }
}
 

解决方案

@Eddie。只是一个小修改，以您的解决方案 - 如果设备处于飞行模式（或presumably在其他情况下，有无可用网络）， cm.getActiveNetworkInfo（）将空，所以你需要添加一个空检查。

以下修改方案：

 公共布尔isOnline（）{
    ConnectivityManager厘米=
        （ConnectivityManager）getSystemService（Context.CONNECTIVITY_SERVICE）;
    的NetworkInfo的NetInfo = cm.getActiveNetworkInfo（）;
    返回的NetInfo = NULL和放大器;！＆安培; netInfo.isConnectedOrConnecting（）;
}
 

另外添加以下权限到的Andr​​oidManifest.xml ：

 ＆LT;使用-权限的Andr​​oid：名称=android.permission.ACCESS_NETWORK_STATE/＆GT;
 

另外一个小点，如果你确实需要在给定时间点的网络连接，那么它可能是最好使用 netInfo.isConnected（）而不是 netInfo.isConnectedOrConnecting 。我想这是最多不过indivudal用例。

I got a AsyncTask that is supposed to check the network access to a host name. But the doInBackground() is never timed out. Anyone have a clue?

public class HostAvailabilityTask extends AsyncTask<String, Void, Boolean> {

    private Main main;

    public HostAvailabilityTask(Main main) {
        this.main = main;
    }

    protected Boolean doInBackground(String... params) {
        Main.Log("doInBackground() isHostAvailable():"+params[0]);

        try {
            return InetAddress.getByName(params[0]).isReachable(30); 
        } catch (UnknownHostException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        }
        return false;       
    }

    protected void onPostExecute(Boolean... result) {
        Main.Log("onPostExecute()");

        if(result[0] == false) {
            main.setContentView(R.layout.splash);
            return;
        }

        main.continueAfterHostCheck();
    }   
}

解决方案

@Eddie. Just a minor edit to your solution - if the device is in airplane mode (or presumably in other situations where there's no available network), cm.getActiveNetworkInfo() will be null, so you need to add a null check.

Modified solution below:

public boolean isOnline() {
    ConnectivityManager cm =
        (ConnectivityManager) getSystemService(Context.CONNECTIVITY_SERVICE);
    NetworkInfo netInfo = cm.getActiveNetworkInfo();
    return netInfo != null && netInfo.isConnectedOrConnecting();
}

Also add the following permission to the AndroidManifest.xml:

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

One other small point, if you absolutely need a network connection at the given point in time, then it might be better to use netInfo.isConnected() rather than netInfo.isConnectedOrConnecting. I guess this is up to the indivudal use-case however.

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