我得到了一个AsyncTask，应该检查对主机名的网络访问。但是doInBackground()永远不会超时。有人知道吗?
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();
}
}
这个线程中的大多数答案只检查是否有可用的连接，但不检查该连接是否工作，其他答案不是设备范围，我的解决方案应该在每个设备上工作。
你可以在启动应用程序之前在你的主要活动中删除我的代码，它会快速确定是否有实际的互联网连接，如果有对话框将立即删除，应用程序将被启动，如果没有警报会弹出说应用程序需要互联网连接才能工作。
final AlertDialog alertDialog = new AlertDialog.Builder(this).create();
alertDialog.setTitle("Checking Connection");
alertDialog.setMessage("Checking...");
alertDialog.show();
new CountDownTimer(5000, 1000) {
@Override
public void onTick(long millisUntilFinished) {
new Thread(new Runnable() {
public void run() {
try {
URL url = new URL("http://web.mit.edu/");
HttpURLConnection connection = (HttpURLConnection) url.openConnection();
connection.setRequestMethod("GET");
connection.setConnectTimeout(5000);
isConnected = connection.getResponseCode() == HttpURLConnection.HTTP_OK;
} catch (Exception e) {
e.printStackTrace();
}
}
}).start();
if (isConnected == false){
alertDialog.setMessage("Try " + (5 - millisUntilFinished/1000) + " of 5.");
} else {
alertDialog.dismiss();
}
}
@Override
public void onFinish() {
if (isConnected == false) {
alertDialog.dismiss();
new AlertDialog.Builder(activity)
.setTitle("No Internet")
.setMessage("Please connect to Internet first.")
.setPositiveButton(android.R.string.yes, new DialogInterface.OnClickListener() {
public void onClick(DialogInterface dialog, int which) {
// kill the app?
}
})
.setIcon(android.R.drawable.ic_dialog_alert)
.show();
} else {
// Launch the app
}
}
}.start();
我已经经历了所有的答案，我想出了我自己的答案，首先检查互联网是否可用，如果互联网可用，然后检查它是否活跃。
我已经包括了所有必要的方法和类来检查活跃的Internet连接。
NetworkUtils.class
public class NetworkUtils {
public static final int STATUS_CONNECTED = 0 ;
public static boolean isInternetAvailable(Context ctx){
ConnectivityManager cm = (ConnectivityManager)ctx.getSystemService(Context.CONNECTIVITY_SERVICE);
NetworkInfo activeNetwork = cm.getActiveNetworkInfo();
return activeNetwork != null && activeNetwork.isConnectedOrConnecting();
}
public static int isInternetActiveWithPing() {
try {
Runtime runtime = Runtime.getRuntime();
Process process = runtime.exec("/system/bin/ping -c 1 8.8.8.8");
int exitValue = process.waitFor();
return exitValue;
} catch (Exception ex) {
return -1;
}
}
public static boolean isInternetActiveWithInetAddress() {
try {
InetAddress inetAddress = InetAddress.getByName("www.google.com");
return inetAddress != null && !inetAddress.toString().equals("");
} catch (Exception ex) {
return false;
}
}
public static void displayInternetConnectionMessage(Context ctx){
Toast.makeText(ctx, "Check Internet Connection", Toast.LENGTH_SHORT).show();
}
}
你可以使用下面的代码检查互联网是否活跃:
private void checkInternetConnection() {
if (NetworkUtils.isInternetAvailable(this)) {
new Thread(new Runnable() {
@Override
public void run() {
if (NetworkUtils.isInternetActiveWithPing() == NetworkUtils.STATUS_CONNECTED) {
performNetworkingOperations();
} else {
if (NetworkUtils.isInternetActiveWithInetAddress()) {
performNetworkingOperations();
} else {
displayConnectionMessage();
}
}
}
}).start();
} else {
displayConnectionMessage();
}
}
private void performNetworkingOperations() {
runOnUiThread(new Runnable() {
@Override
public void run() {
Toast.makeText(MainActivity.this, "Internet is Available", Toast.LENGTH_SHORT).show();
}
});
}
private void displayConnectionMessage() {
runOnUiThread(new Runnable() {
@Override
public void run() {
NetworkUtils.displayInternetConnectionMessage(MainActivity.this);
}
});
}
如果你需要检查网络连接，使用ping到服务器的方法:
public boolean checkIntCON() {
try {
Process ipProcess = Runtime.getRuntime().exec("/system/bin/ping -c 1 8.8.8.8");
return (ipProcess.waitFor() == 0);
}
catch (IOException e) { e.printStackTrace(); }
catch (InterruptedException e) { e.printStackTrace(); }
return false;
}
您可以使用端口进行检查
public boolean checkIntCON() {
try {
Socket sock = new Socket();
SocketAddress sockaddr = new InetSocketAddress("8.8.8.8", 80);
// port will change according to protocols
sock.connect(sockaddr, 1250);
sock.close();
return true;
} catch (IOException e) { return false; }
}
