无法在 android 微调器中添加提示 [英] Unable to add hint in android spinner
问题描述
我有一个 spinner，它的行为类似于我的 android 应用程序 中的 dropdown.我正在 android studio 中开发应用程序.微调器从 api 获取数据.在运行时，它从 API 获取 usernames 并显示在 spinner 中.当应用程序运行时，它会显示所选用户的 username 和 ID，如下图所示
I have a spinner that behaves like a dropdown in my android application. I am developing the app in android studio. The spinner get data from the api. At run time it gets usernames from API and shows in the spinner. When app runs it shows the username and ID of the selected user like shown in below image
现在我想添加提示，所以我搜索了很多文章并找到了很多解决方案，我遵循了其中最简单的一个.更多理解请看下面代码
Now i want to add hint so i searched many articles and found many solutions and i follow the easiest of them. For more understanding please see the below code
try
{
JSONObject jobj = new JSONObject(jsonObject.toString());
// Locate the NodeList name
jsonArray = jobj.getJSONArray("users");
for(int i=0; i<jsonArray.length(); i++)
{
jsonObject = jsonArray.getJSONObject(i);
Users user = new Users();
user.setId(jsonObject.optString("Id"));
user.setName(jsonObject.optString("Name"));
users.add(user);
userList.add("Select a username");// i add this as a hint
userList.add(jsonObject.optString("Name"));
}
} catch (JSONException e) {
Log.e("Error", e.getMessage());
e.printStackTrace();
}
现在使用 onPostExecute() 方法
@Override
protected void onPostExecute(Void args)
{
// Locate the spinner in activity_main.xml
Spinner spinner = (Spinner)findViewById(R.id.spinner);
// Spinner adapter
spinner.setAdapter(new ArrayAdapter<String>(MainActivity.this, android.R.layout.simple_spinner_dropdown_item, userList));
// Spinner on item click listener
spinner.setOnItemSelectedListener(new AdapterView.OnItemSelectedListener() {
@Override
public void onItemSelected(AdapterView<?> parent, View view, int position, long id) {
textViewResult = (TextView)findViewById(R.id.textView);
// Set the text followed by the position
// Set the text followed by the position
if(!users.get(position).getName().equals("Select a username")) {
textViewResult.setText(" " + users.get(position - 1).getName() + " " + users.get(position - 1).getId());
}else {
textViewResult.setText("Hi " + users.get(position).getName() + " your ID is " + users.get(position).getId());
UserId = String.valueOf(users.get(position).getId());
progressDialog.dismiss();
_latitude.setText("");
_longitude.setText("");
Latitude = null;
Longitude = null;
}
}
@Override
public void onNothingSelected(AdapterView<?> parent) {
textViewResult.setText("");
}
});
}
当我运行应用程序时，应用程序崩溃，同时给我以下错误
When i run the application the app crashes while giving me the below error
Process: com.example.accurat.myapp, PID: 30382
java.lang.ArrayIndexOutOfBoundsException: length=12; index=-1
at java.util.ArrayList.get(ArrayList.java:310)
at com.example.accurat.myapp.MainActivity$DownloadJSON$1.onItemSelected(MainActivity.java:494)
at android.widget.AdapterView.fireOnSelected(AdapterView.java:931)
at android.widget.AdapterView.dispatchOnItemSelected(AdapterView.java:920)
at android.widget.AdapterView.-wrap1(AdapterView.java)
at android.widget.AdapterView$SelectionNotifier.run(AdapterView.java:890)
at android.os.Handler.handleCallback(Handler.java:746)
at android.os.Handler.dispatchMessage(Handler.java:95)
at android.os.Looper.loop(Looper.java:148)
at android.app.ActivityThread.main(ActivityThread.java:5491)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:728)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:618)
此错误发生在 textViewResult.setText(" " + users.get(position - 1).getName() + " " + users.get(position - 1).getId());
更新 1
按照Junaid Hafeez的回答我做了以下
for(int i=0; i<jsonArray.length(); i++)
{
jsonObject = jsonArray.getJSONObject(i);
Users user = new Users();
user.setId(jsonObject.optString("Id"));
user.setName(jsonObject.optString("Name"));
users.add(user);
userList.add(jsonObject.optString("Name"));
}
userList.add(0, "Select a username"); // after for loop ended i add `select a username` at `0` index
之后在 postExecute() 方法中我做了以下操作
after that in postExecute() method i have done the following
@Override
public void onItemSelected(AdapterView<?> parent, View view, int position, long id) {
textViewResult = (TextView)findViewById(R.id.textView);
// Set the text followed by the position
// Set the text followed by the position
if(position>0)
{
textViewResult.setText("Hi " + users.get(position).getName() + " your ID is " + users.get(position).getId());
UserId = String.valueOf(users.get(position).getId());
_latitude.setText("");
_longitude.setText("");
Latitude = null;
Longitude = null;
}
else {
}
progressDialog.dismiss();
}
我得到的结果低于
它确实向我显示了提示，但是当我选择任何用户名时，它向我显示下一个用户名的 name 和 id，如下图所示
It does show me the hint, but when i select any username it shows me the name and id of the next username as shown in below image
我坚持下去，找不到任何解决方案
I am stuck to it and couldn't find any solution
任何帮助将不胜感激.
推荐答案
可能你正在做的是，你正在点击微调器的第一项，其中 position = 0 并执行此 position - 1 在您的 setText 中，这使得实际上不存在的索引 -1 崩溃.其次你正在这样做
probably what you are doing is, you are clicking on first item of you spinner, where the position = 0 and doing this position - 1 in your setText which makes the index -1 that is actually not exists and crashes.
Secondly you are doing this
userList.add("Select a username");// i add this as a hint
在您的循环中，在每次迭代中添加新项目.你需要做的是
in your loop, which is adding new item on each iteration. what you need to do is
一旦您拥有完整的数据列表，只需像这样在其 0 索引上添加提示
once you have complete list of your data, just add hint on its 0 index like this
userList.add(0, "Select a username");
并在您的 onClick 中，检查天气 position >0 然后做你的工作，否则当用户点击提示时忽略.
and in your onClick, check weather position > 0 then do your work otherwise ignore as user clicked on hint.
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