判断网络是否可用

public class ClassTestDemoActivity extends Activity
{
    @Override
    public void onCreate(Bundle savedInstanceState)
    {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);
        if (isNetworkAvailable(ClassTestDemoActivity.this))
        {
            Toast.makeText(getApplicationContext(), "当前有可用网络！", Toast.LENGTH_LONG).show();
        }
        else
        {
            Toast.makeText(getApplicationContext(), "当前没有可用网络！", Toast.LENGTH_LONG).show();
        }
    }
    
    /**
     * 检查当前网络是否可用
     * 
     * @param context
     * @return
     */
    
    public boolean isNetworkAvailable(Activity activity)
    {
        Context context = activity.getApplicationContext();
        // 获取手机所有连接管理对象（包括对wi-fi,net等连接的管理）
        ConnectivityManager connectivityManager = (ConnectivityManager) context.getSystemService(Context.CONNECTIVITY_SERVICE);
        
        if (connectivityManager == null)
        {
            return false;
        }
        else
        {
            // 获取NetworkInfo对象
            NetworkInfo[] networkInfo = connectivityManager.getAllNetworkInfo();
            
            if (networkInfo != null && networkInfo.length > 0)
            {
                for (int i = 0; i < networkInfo.length; i++)
                {
                    System.out.println(i + "===状态===" + networkInfo[i].getState());
                    System.out.println(i + "===类型===" + networkInfo[i].getTypeName());
                    // 判断当前网络状态是否为连接状态
                    if (networkInfo[i].getState() == NetworkInfo.State.CONNECTED)
                    {
                        return true;
                    }
                }
            }
        }
        return false;
    }
}