Question

这不是重复的

如果有可用连接，我想使用activity和AsyncTask检查Handler的实时互联网连接，以显示或隐藏TexView。但它不起作用。

我的代码即使使用AsyncTask
也会抛出NetworkOnMainThreadException

我正在使用此代码：

class  CheckNetWorkConnection  extends AsyncTask<String, Void,Boolean>{
MyActivity activity;
    public checkNetWorkConnection(MyActivity activity) {
        this.activity= activity;

    }

    @Override
    protected Boolean doInBackground(String... strings) {
        boolean networkAvalaible;

                try {
                    URL myUrl = new URL("https://www.stackoverflow.com");
                    URLConnection connection = myUrl.openConnection();
                    connection.setConnectTimeout(3000);
                    connection.connect();

                    networkAvalaible = true;
                } catch (Exception e) {
                  //I'm catching NetworkInMainThreadException here 
                    e.printStackTrace();
                    networkAvalaible = false;
                }
            }
        });

   // doInBackground always retun false
        return networkAvalaible;
    }

    @Override
    protected void onPostExecute(Boolean aBoolean) {

    // Using handler to repeat Task


        new Handler().postDelayed(new Runnable() {
            @Override
            public void run() {
                if (aBoolean){
                    activity.noConnection.setVisibility(View.GONE);
                }else {

                    activity.noConnection.setVisibility(View.VISIBLE);
                }
            }

        },3000);


        super.onPostExecute(aBoolean);
    }
}

Answer 1

使用它，你打电话

new CheckNetWorkConnection().execute();

您将希望您的异步任务无限期运行，直到互联网连接丢失。您当前的代码只会检查一次。

您需要更改代码以进行轮询以使其正常工作。

@Override
protected Boolean doInBackground(String... strings) {
    boolean networkAvalaible = false;

    do {
            try {
                URL myUrl = new URL("https://www.stackoverflow.com");
                URLConnection connection = myUrl.openConnection();
                connection.setConnectTimeout(3000);
                connection.connect();

                networkAvalaible = true;

                sleep(5000); //check connection every 5 seconds.

// you can call publish progress here to tell your process that 
// connection is available

            } catch (Exception e) {
              //I'm catching NetworkInMainThreadException here 
                e.printStackTrace();
                networkAvalaible = false;
            }
     } while (networkAvalaible); 

//you only exit and asyncTask when connection is lost.


    return networkAvalaible;
}

虽然AsyncTask不是正确的方法...但请看下面的以下文章。 https://www.grokkingandroid.com/android-getting-notified-of-connectivity-changes/

Answer 2

将此类放入 util 包中，以便在您项目的任何位置查看互联网连接。

<强> ConnectionDetector.java

package util;
import android.content.Context;
import android.net.ConnectivityManager;
import android.net.NetworkInfo;

/**
 * Created by Pranav on 29/08/16.
 */
public class ConnectionDetector {
    private Context _context;

    public ConnectionDetector(Context context) {
        this._context = context;
    }

    public boolean isConnectingToInternet() {
        ConnectivityManager connectivity = (ConnectivityManager) _context.getSystemService(Context.CONNECTIVITY_SERVICE);
        if (connectivity != null) {
            NetworkInfo[] info = connectivity.getAllNetworkInfo();
            if (info != null)
                for (int i = 0; i < info.length; i++)
                    if (info[i].getState() == NetworkInfo.State.CONNECTED) {
                        return true;
                    }
        }
        return false;
    }
}

以下是 MainActivity.java 检查互联网连接的代码段，如果互联网连接已开启，则调用asynctask，否则会提供Toast消息。

import android.app.Activity;
import android.content.Context;
import android.os.AsyncTask;
import android.os.Bundle;
import android.widget.Toast;

import java.net.URL;
import java.net.URLConnection;

import util.ConnectionDetector;

/**
 * Created by Pranav on 29/08/16.
 */


public class CaseDetaiksActivity extends Activity {

    public static Context context;
    ConnectionDetector mConnectionDetector;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        context = this;
        mConnectionDetector = new ConnectionDetector(context);
        setContentView(R.layout.activity_mail);

        if (mConnectionDetector.isConnectingToInternet()) {
            MyAyncTask MyTask = new MyAyncTask();
            MyTask.execute();
        } else {
            Toast.makeText(context, getString(R.string.please_check_internet), Toast.LENGTH_SHORT).show();
        }
    }

    public static class MyAyncTask extends AsyncTask<Void, Void, Void> {

        @Override
        protected void onPreExecute() {
            super.onPreExecute();
        }

        @Override
        protected void onPostExecute(Void aVoid) {
            super.onPostExecute(aVoid);
        }

        @Override
        protected void onProgressUpdate(Void... values) {
            super.onProgressUpdate(values);
            // You can track you progress update here
        }

        @Override
        protected Void doInBackground(Void... params) {
            try {
                URL myUrl = new URL("https://www.stackoverflow.com");
                URLConnection connection = myUrl.openConnection();
                connection.setConnectTimeout(3000);
                connection.connect();

            } catch (Exception e) {
                //I'm catching NetworkInMainThreadException here
                e.printStackTrace();
            }
            return null;
        }
    }
}

希望这有助于你

Answer 3

a。创建广播接收器类

  public class NetworkChangeReceiver extends BroadcastReceiver {

  @Override
  public void onReceive(final Context context, final Intent intent) {

  if(checkInternet(context)){
    Toast.makeText(context, "Network Available Do operations",Toast.LENGTH_LONG).show(); 
    }
  }

 public boolean checkInternet(Context context) {
    ServiceManager serviceManager = new ServiceManager(context);
    if (serviceManager.isNetworkAvailable()) {
    return true;
    } else {
    return false;
     }
   }
 }

湾创建服务管理器类

public class ServiceManager {
  Context context;

  public ServiceManager(Context base) {
      context = base;
   }

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

在Android清单中注册权限

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

在Android清单中声明广播接收器

  <receiver android:name=".receivers.NetworkChangeReceiver">
      <intent-filter>
          <action android:name="android.net.conn.CONNECTIVITY_CHANGE" />
      </intent-filter>
  </receiver>

在您的活动中：

一个。在onResume（）

中注册您的广播接收器

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

湾在onPause（）;

中取消注册您的广播接收器

    unregisterReceiver(new NetworkChangeReceiver());

从AsyncTask检查Internet连接

3 个答案: