Android在Android中检查null或空字符串 [英] Android check null or empty string in Android
本文介绍了Android在Android中检查null或空字符串的处理方法,对大家解决问题具有一定的参考价值,需要的朋友们下面随着小编来一起学习吧!
问题描述
在尝试AsyncTask
时,我从服务器获取电子邮件地址.在onPostExecute()
中,我必须检查电子邮件地址是empty
还是null
.我使用以下代码对其进行了检查:
In my trying AsyncTask
I get email address from my server. In onPostExecute()
I have to check is email address empty
or null
. I used following code to check it:
if (userEmail != null && !userEmail.isEmpty()) {
Toast.makeText(getActivity(), userEmail, Toast.LENGTH_LONG).show();
UserEmailLabel.setText(userEmail);
}
但是在我的Toast
中,我看到null
已打印.我的完整代码:
But in my Toast
I see null
is printed. My full code:
private class LoadPersonalData extends AsyncTask<String, Void, Void> {
@Override
protected void onPreExecute() {
super.onPreExecute();
}
protected Void doInBackground(String... res) {
List<NameValuePair> params = new ArrayList<NameValuePair>();
params.add(new BasicNameValuePair("user_id", PrefUserName));
params.add(new BasicNameValuePair("type", type_data));
JSONObject json = jsonParser.makeHttpRequest(Url, "POST", params);
String result = "";
try {
result = json.getString("message");
} catch (JSONException e) {
e.printStackTrace();
}
if (result.equals("success")) {
try {
userEmail = json.getString("email");
} catch (JSONException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
return null;
}
@Override
protected void onPostExecute(Void result) {
// TODO Auto-generated method stub
super.onPostExecute(result);
if (userEmail != null && !userEmail.isEmpty()) {
Toast.makeText(getActivity(), userEmail, Toast.LENGTH_LONG).show();
UserEmailLabel.setText(userEmail);
}
}
如何检查null
和empty
字符串?
推荐答案
@Jon Skeet注释中,实际上String
的值是"null"
.以下代码解决了它
From @Jon Skeet comment, really the String
value is "null"
. Following code solved it
if (userEmail != null && !userEmail.isEmpty() && !userEmail.equals("null"))
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