[英]Return ArrayList from async task
1) I already read all questions about that here, so please tell me more, than just url from SO... 1)我已经在这里阅读了有关此问题的所有问题,因此,请告诉我更多信息,而不仅仅是SO的网址...
2) I want to return only ONE variable from asynctask, but it can be message error or user details. 2)我只想从asynctask返回一个变量,但是它可能是消息错误或用户详细信息。 So I decided to return ArrayList with indexes 0 (for error messages) and 1 (for success).
因此,我决定返回索引为0(错误消息)和1(成功)的ArrayList。
AsyncTask 异步任务
public class LoginGet extends AsyncTask<String, ProgressBar, ArrayList<String>> {
...
public ArrayList<String> result = new ArrayList<String>();
public LoginGet(Context mContext, String loginText, String passwordText) {
//Get values form LoginActivity
}
protected void onPreExecute(){
super.onPreExecute();
// progressDialog
}
@Override
protected ArrayList doInBackground(String... arg0){
try {
// Making HTTP Request
try {
// Creating HTTP client
...
...
JSONObject jObject = new JSONObject(json);
success = jObject.getString("success");
result.add(0, "");
result.add(1, "");
if (success != null) {
if (success == "1") {
result.add(1, jObject.getString("hash"));
return result;
} else if (success == "0") {
result.add(0, jObject.getString("error"));
return result;
}
} else {
result.add(0, "Error while logging.");
return result;
}
// writing response to log
Log.d("Http Response:", response.toString());
} catch (UnsupportedEncodingException e) {
e.printStackTrace();
} catch (ClientProtocolException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}
}catch (Exception e) {
}
return result;
}
@Override
protected void onPostExecute(ArrayList<String> result) {
((LoginActivity)context).getResult(result);
progressDialog.dismiss();
}
}
LoginActivity 登录活动
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
...
loginButton.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
...
if (loginText.compareTo("") == 0 || passwordText.compareTo("") == 0) {
...
}else{
LoginGet loginPost = new LoginGet(LoginActivity.this,loginText,passwordText);
loginPost.execute();
}
}
});
}
// Get result from asynctask LoginGet
public void getResult(ArrayList<String> result){
if (result.get(0) != "") {
loginButton.setEnabled(true);
Toast.makeText(LoginActivity.this, result.get(0), Toast.LENGTH_SHORT).show();
} else if (result.get(1) != "") {
SharedPreferences preferences = PreferenceManager.getDefaultSharedPreferences(LoginActivity.this);
SharedPreferences.Editor editor = preferences.edit();
editor.putString("Login", result.get(1));
editor.commit();
Intent intent = new Intent(LoginActivity.this, MainActivity.class);
startActivity(intent);
}
}
Error: 错误:
java.lang.IndexOutOfBoundsException: Invalid index 0, size is 0
at java.util.ArrayList.throwIndexOutOfBoundsException(ArrayList.java:255)
at java.util.ArrayList.get(ArrayList.java:308)
at cz.jacon.smsapp.LoginActivity.getResult(LoginActivity.java:57)
at cz.jacon.smsapp.background.LoginGet.onPostExecute(LoginGet.java:121)
at cz.jacon.smsapp.background.LoginGet.onPostExecute(LoginGet.java:30)
3) In my AsyncTask I have result.add(0, "");
3)在我的AsyncTask中,我有
result.add(0, "");
and result.add(1, "");
和
result.add(1, "");
, so why is the ArrayList size 0? ,为什么ArrayList的大小为0?
In my opinion result.add(0, "");
我认为
result.add(0, "");
isn't even reached, since the try block might be failing. 甚至没有达到,因为try块可能失败了。
And sadly you have an empty catch block, just waiting to skip them errors: 不幸的是,您有一个空的catch块,只是在等待跳过它们的错误:
catch (Exception e) {
}
Your solution would be to add these 您的解决方案是添加这些
result.add(0, "");
result.add(1, "");
to the very beginning of the doInBackground
or even to the constructor and you should be fine. 到
doInBackground
的最开始甚至是构造函数,您都应该可以。
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