android 检查可用网络

   在手机应用与网络交互数据的时候,我们首先要判断有没有可用的网络，如果没有则跳到相应的网络设置页面，方法详见代码：

private boolean CheckNetwork() {
       boolean flag = false;
       ConnectivityManager cwjManager = (ConnectivityManager) getSystemService(Context.CONNECTIVITY_SERVICE);
       if (cwjManager.getActiveNetworkInfo() != null)
           flag = cwjManager.getActiveNetworkInfo().isAvailable();
       if (!flag) {
           Builder b = new AlertDialog.Builder(this).setTitle("没有可用的网络").setMessage("请开启GPRS或WIFI网络连接");
           b.setPositiveButton("确定", new DialogInterface.OnClickListener() {
               public void onClick(DialogInterface dialog, int whichButton) {
                   Intent mIntent = new Intent("/");
                   ComponentName comp = new ComponentName("com.android.settings", "com.android.settings.WirelessSettings");
                   mIntent.setComponent(comp);
                   mIntent.setAction("android.intent.action.VIEW");
                   startActivity(mIntent);
               }
           }).setNeutralButton("取消", new DialogInterface.OnClickListener() {
               public void onClick(DialogInterface dialog, int whichButton) {
                   dialog.cancel();
               }
           }).create();
           b.show();
       }

       return flag;
   }