判断网络是否连接的单例模式，

package com.zhoujh.appstore.network;

import android.app.Activity;
import android.app.AlertDialog;
import android.content.Context;
import android.content.DialogInterface;
import android.content.Intent;
import android.net.ConnectivityManager;
import android.net.NetworkInfo;
import android.provider.Settings;

public class ConnectionDetector {

public static ConnectionDetector m_connectionDetector;

public static ConnectionDetector getInstance(){

if( m_connectionDetector == null){

m_connectionDetector = new ConnectionDetector();
}

return m_connectionDetector;

}
private ConnectionDetector(){
}
/**
*
* @return
*/
public boolean isConnectingToInternet(Context _context){
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;
}

/**
* Function to display simple Alert Dialog
* @param context - application context
* @param title - alert dialog title
* @param message - alert message
* @param status - success/failure (used to set icon)
* */
public void showAlertDialog(final Activity ctx, String title, String message, Boolean status) {
AlertDialog alertDialog = new AlertDialog.Builder(ctx.getApplicationContext()).create();
// Setting Dialog Title
alertDialog.setTitle(title);
// Setting Dialog Message
alertDialog.setMessage(message);
// Setting alert dialog icon
// alertDialog.setIcon((status) ? R.drawable.icon_qq : R.drawable.icon_360);
// Setting OK Button
//跳转到系统网络设置界面。
alertDialog.setButton("Settings", new DialogInterface.OnClickListener() {
public void onClick(DialogInterface dialog, int which) {
Intent intent=new Intent(Settings.ACTION_WIRELESS_SETTINGS);
ctx.startActivity(intent);
ctx.finish();
}
});
// Showing Alert Message
alertDialog.show();
}
}