嗨，我是android studio的新手，当我尝试放置Spinner并尝试按片段与MySQL数据库连接时，在这里选择Spinner的某些项目并将其显示在片段活动中。
公共类BusscheduleFragment扩展Fragment实现 Spinner.OnItemSelectedListener { 公共静态最终字符串DATA_URL = “”;
//Tags used in the JSON String
public static final String TAG_USERNAME = "username";
public static final String TAG_NAME = "name";
public static final String TAG_COURSE = "course";
public static final String TAG_SESSION = "session";
//JSON array name
public static final String JSON_ARRAY = "result";
View view;
private Spinner spinner;
private ArrayList<String> students;
private JSONArray result;
private TextView textViewName;
private TextView textViewCourse;
private TextView textViewSession;
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
view = inflater.inflate(R.layout.fragment_busschedule, container, false);
spinner = view.findViewById(R.id.spinner);
students = new ArrayList<String>();
spinner.setOnItemSelectedListener(this);
textViewName = view.findViewById(R.id.textViewName);
textViewCourse = view.findViewById(R.id.textViewCourse);
textViewSession = view.findViewById(R.id.textViewSession);
getData();
return view;
}
private void getData(){
//Creating a string request
StringRequest stringRequest = new StringRequest(DATA_URL,
new Response.Listener<String>() {
@Override
public void onResponse(String response) {
JSONObject j = null;
try {
//Parsing the fetched Json String to JSON Object
j = new JSONObject(response);
//Storing the Array of JSON String to our JSON Array
result = j.getJSONArray(JSON_ARRAY);
//Calling method getStudents to get the students from the JSON Array
getStudents(result);
} catch (JSONException e) {
e.printStackTrace();
}
}
},
new Response.ErrorListener() {
@Override
public void onErrorResponse(VolleyError error) {
}
});
//Creating a request queue
RequestQueue requestQueue = Volley.newRequestQueue(mCtx.getApplicationContext());
//Adding request to the queue
requestQueue.add(stringRequest);
}
private void getStudents(JSONArray j){
//Traversing through all the items in the json array
for(int i=0;i<j.length();i++){
try {
//Getting json object
JSONObject json = j.getJSONObject(i);
//Adding the name of the student to array list
students.add(json.getString(TAG_USERNAME));
} catch (JSONException e) {
e.printStackTrace();
}
}
//Setting adapter to show the items in the spinner
spinner.setAdapter(new ArrayAdapter<String>(getActivity(), android.R.layout.simple_spinner_dropdown_item, students));
}
//Method to get student name of a particular position
private String getName(int position){
String name="";
try {
//Getting object of given index
JSONObject json = result.getJSONObject(position);
//Fetching name from that object
name = json.getString(TAG_NAME);
} catch (JSONException e) {
e.printStackTrace();
}
//Returning the name
return name;
}
//Doing the same with this method as we did with getName()
private String getCourse(int position){
String course="";
try {
JSONObject json = result.getJSONObject(position);
course = json.getString(TAG_COURSE);
} catch (JSONException e) {
e.printStackTrace();
}
return course;
}
//Doing the same with this method as we did with getName()
private String getSession(int position){
String session="";
try {
JSONObject json = result.getJSONObject(position);
session = json.getString(TAG_SESSION);
} catch (JSONException e) {
e.printStackTrace();
}
return session;
}
//this method will execute when we pic an item from the spinner
@Override
public void onItemSelected(AdapterView<?> parent, View view, int position, long id) {
//Setting the values to textviews for a selected item
textViewName.setText(getName(position));
textViewCourse.setText(getCourse(position));
textViewSession.setText(getSession(position));
}
//When no item is selected this method would execute
@Override
public void onNothingSelected(AdapterView<?> parent) {
textViewName.setText("");
textViewCourse.setText("");
textViewSession.setText("");
}
}
这是工作的xml文件
<?xml version="1.0" encoding="utf-8"?>
<LinearLayoutLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical"
android:paddingLeft="@dimen/activity_horizontal_margin"
android:paddingRight="@dimen/activity_horizontal_margin"
android:paddingTop="@dimen/activity_vertical_margin"
android:paddingBottom="@dimen/activity_vertical_margin"
tools:context=".BusscheduleFragment"
>
<Spinner
android:id="@+id/spinner"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_alignParentStart="true"
/>
<TableLayout
android:layout_width="match_parent"
android:layout_height="wrap_content">
<TableRow>
<TextView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:textStyle="bold"
android:layout_marginRight="20dp"
android:layout_marginLeft="10dp"
android:text="Name"
/>
<TextView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:textStyle="bold"
android:layout_marginRight="20dp"
android:text="Course"
/>
<TextView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:textStyle="bold"
android:layout_marginRight="20dp"
android:text="Session"
/>
</TableRow>
<TableRow>
<TextView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_marginRight="20dp"
android:layout_marginLeft="10dp"
android:id="@+id/textViewName"
/>
<TextView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_marginRight="20dp"
android:id="@+id/textViewCourse"
/>
<TextView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_marginRight="20dp"
android:id="@+id/textViewSession"
/>
</TableRow>
</TableLayout>