移动开发----判断网络

  /**
     * 进入界面判断是否有网络存在
     *
     * @return
     */
    private boolean CheckNetwork() {
        boolean flag = false;
        ConnectivityManager cwjManager = (ConnectivityManager) getSystemService(CONNECTIVITY_SERVICE);
        if (cwjManager.getActiveNetworkInfo() != null)
            flag = cwjManager.getActiveNetworkInfo().isAvailable();
        if (!flag) {
            AlertDialog.Builder b = new AlertDialog.Builder(this);
            b.setTitle("没有可用的网络");
            b.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 intent = new Intent(Settings.ACTION_SETTINGS);
                    startActivity(intent);
                }
            }).setNeutralButton("取消", new DialogInterface.OnClickListener() {
                public void onClick(DialogInterface dialog, int whichButton) {
                    dialog.cancel();
                }
            }).create();
            b.show();
        }
        return flag;
    }