Android的意图中的AsyncTask类给错误 [英] Android Intent in AsyncTask class giving error
问题描述
我是新来的Android程序，并试图与我的同胞用户＃1的帮助下学习的概念，当然。
什么，我试图做：从登录页面，我试图从位于服务器上的JSON文件获取登录凭据。解析JSON文件，并验证登录凭据后，我开始一个新的意图我的应用程序（主页）的下一个页面。
问题：我已经成功做了所有networkings操作和分析使用的AsyncTask后台线程，通过计算器用户的建议。但是，验证登录凭据后，当我尝试启动的AsyncTask类的postExecute方法中一个新的意图，它给了我下面的错误。请建议什么是错的。
错误
构造意图（LoginActivity.RetreiveDataAsynctask，类＆LT; HomeActivity＆gt;）的不确定
错误行：
意向意图=新意图（这一点，HomeActivity.class）;
code
私有类RetreiveDataAsynctask扩展的AsyncTask＆LT;弦乐，无效的JSONObject＆GT; { @覆盖
受保护的JSONObject doInBackground（字符串... loginURL）{
的JSONObject物镜= getJSONfromURL（loginURL [0]）;
返回OBJ;
} @覆盖
保护无效onPostExecute（OBJ的JSONObject）{
//是否所有乌尔UI相关的东西，因为这将在UI线程执行 super.onPostExecute（OBJ）; TextView的loginStatus =（的TextView）findViewById（R.id.login）;
TextView的用户id =（的TextView）findViewById（R.id.userId）; //如果登录成功，然后进入下一个页面。 尝试{
loginStatus.setText（obj.getString（登录））;
userId.setText（obj.getString（用户id））; AlertDialog.Builder ADB =新AlertDialog.Builder（
LoginActivity.this）;
adb.setTitle（登录服务）;
adb.setPositiveButton（OK，NULL）; 如果（obj.getString（登录）equalsIgnoreCase（TRUE）及＆安培;！obj.getString（用户id）equalsIgnoreCase（））{
//调用下一页
adb.setMessage（登录成功......！）; 意向意图=新意图（这一点，HomeActivity.class）; ** //这条线显示错误**
startActivity（意向）; }其他{//登录不成功
adb.setMessage（登录失败... !!）; } adb.show（）;
}赶上（JSONException E）{
Log.e（log_tag，JSONException+ e.toString（））;
}
}
@覆盖
在preExecute保护无效（）{ TextView的loginStatus =（的TextView）findViewById（R.id.login）;
TextView的用户id =（的TextView）findViewById（R.id.userId）;
loginStatus.setText（未读取）;
userId.setText（未读取）; } @覆盖
保护无效onProgressUpdate（虚空......值）{
}
}
寻找一个解决方案。先谢谢了。
意向意图=新意图（这一点，HomeActivity.class）;
在上面的一行，这个指的AsyncTask的实例和意图使用应用程序或活动上下文作为构造函数的参数。
因此，它应该是这样的，
意向意图=新意图（小于Your_Calling_Activity_Name.this＆GT;，HomeActivity.class）;
在你的情况，
意向意图=新意图（LoginActivity.this，HomeActivity.class）;
或
意向意图=新意图（mContext，HomeActivity.class）;
下面 mContext 是呼吁的AsyncTask A活动上下文。你可以通过这方面的AsyncTask的构造函数。
I am new to Android programming and trying to learn the concepts, of course with the help from my fellow Stackoverflow user.
What i am trying to do: From the Login page, I am trying to fetch the login credentials from a json file located on a server. After parsing the json file and verifying the login credentials, i am starting a new intent to the next page of my app(Home).
Problem: I have successfully done all the networkings operations and parsing on a background thread using AsyncTask, as suggested by stackoverflow users. But, after verifying the login credentials, when i try to start a new intent inside the postExecute method of AsyncTask class, it gives me the following error. Please suggest what is wrong.
Error:
The constructor Intent(LoginActivity.RetreiveDataAsynctask, Class<HomeActivity>) is undefined
Error in line:
Intent intent = new Intent(this,HomeActivity.class);
code:
private class RetreiveDataAsynctask extends AsyncTask<String,Void,JSONObject> {
@Override
protected JSONObject doInBackground(String... loginURL) {
JSONObject obj = getJSONfromURL(loginURL[0]);
return obj;
}
@Override
protected void onPostExecute(JSONObject obj) {
//Do all ur UI related stuff as this will be executing in ui thread
super.onPostExecute(obj);
TextView loginStatus = (TextView) findViewById(R.id.login);
TextView userId = (TextView) findViewById(R.id.userId);
//if login successful, then go to the next page.
try {
loginStatus.setText(obj.getString("LOGIN"));
userId.setText(obj.getString("userId"));
AlertDialog.Builder adb = new AlertDialog.Builder(
LoginActivity.this);
adb.setTitle("Login Service");
adb.setPositiveButton("Ok", null);
if(obj.getString("LOGIN").equalsIgnoreCase("TRUE") && !obj.getString("userId").equalsIgnoreCase("")){
//call next page
adb.setMessage("Login Success...!!");
Intent intent = new Intent(this,HomeActivity.class); **//THIS LINE SHOWS ERROR**
startActivity(intent);
}else{//login unsuccessful
adb.setMessage("Login Failed...!!");
}
adb.show();
} catch (JSONException e) {
Log.e("log_tag", "JSONException "+e.toString());
}
}
@Override
protected void onPreExecute() {
TextView loginStatus = (TextView) findViewById(R.id.login);
TextView userId = (TextView) findViewById(R.id.userId);
loginStatus.setText("Not Fetched");
userId.setText("Not Fetched");
}
@Override
protected void onProgressUpdate(Void... values) {
}
}
Looking for a solution. Thanks in advance.
Intent intent = new Intent(this,HomeActivity.class);
In above line, this refers to AsyncTask's instance, and Intent use Application or Activity Context as a Constructor argument.
So it should be like,
Intent intent = new Intent(<Your_Calling_Activity_Name.this>,HomeActivity.class);
in your case,
Intent intent = new Intent(LoginActivity.this,HomeActivity.class);
or
Intent intent = new Intent(mContext,HomeActivity.class);
Here mContext is a Activity Context which is calling AsyncTask. You can pass this context to AsyncTask's Constructor.
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