在微调器中获取错误 mainActivity.java文件
package com.example.sachin.demodb;
import android.os.Bundle;
import android.support.design.widget.FloatingActionButton;
import android.support.design.widget.NavigationView;
import android.support.design.widget.Snackbar;
import android.support.v4.view.GravityCompat;
import android.support.v4.widget.DrawerLayout;
import android.support.v7.app.ActionBarDrawerToggle;
import android.support.v7.app.AppCompatActivity;
import android.support.v7.widget.Toolbar;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.widget.AdapterView;
import android.widget.ArrayAdapter;
import android.widget.Spinner;
import android.widget.TextView;
import com.android.volley.RequestQueue;
import com.android.volley.Response;
import com.android.volley.VolleyError;
import com.android.volley.toolbox.StringRequest;
import com.android.volley.toolbox.Volley;
import org.json.JSONArray;
import org.json.JSONException;
import org.json.JSONObject;
import java.util.ArrayList;
public class MainActivity extends AppCompatActivity
implements NavigationView.OnNavigationItemSelectedListener {
private Spinner spinner;
private ArrayList<String> students;
private JSONArray result;
private TextView textViewName;
private TextView textViewCourse;
private TextView textViewSession;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
students = new ArrayList<String>();
spinner = (Spinner) findViewById(R.id.spinner);
//spinner.setOnItemSelectedListener(this);
spinner.setOnItemSelectedListener(this);
textViewName = (TextView) findViewById(R.id.textViewName);
textViewCourse = (TextView) findViewById(R.id.textViewCourse);
textViewSession = (TextView) findViewById(R.id.textViewSession);
Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
setSupportActionBar(toolbar);
FloatingActionButton fab = (FloatingActionButton) findViewById(R.id.fab);
fab.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
Snackbar.make(view, "Replace with your own action", Snackbar.LENGTH_LONG)
.setAction("Action", null).show();
}
});
DrawerLayout drawer = (DrawerLayout) findViewById(R.id.drawer_layout);
ActionBarDrawerToggle toggle = new ActionBarDrawerToggle(
this, drawer, toolbar, R.string.navigation_drawer_open, R.string.navigation_drawer_close);
drawer.setDrawerListener(toggle);
toggle.syncState();
NavigationView navigationView = (NavigationView) findViewById(R.id.nav_view);
navigationView.setNavigationItemSelectedListener(this);
//This method will fetch the data from the URL
getData();
}
private void getData() {
//Creating a string request
StringRequest stringRequest = new StringRequest(com.example.sachin.demodb.Config.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(com.example.sachin.demodb.Config.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(this);
//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(com.example.sachin.demodb.Config.TAG_USERNAME));
} catch (JSONException e) {
e.printStackTrace();
}
}
//Setting adapter to show the items in the spinner
spinner.setAdapter(new ArrayAdapter<String>(MainActivity.this, 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(com.example.sachin.demodb.Config.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(com.example.sachin.demodb.Config.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(com.example.sachin.demodb.Config.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("");
}
@Override
public void onBackPressed() {
DrawerLayout drawer = (DrawerLayout) findViewById(R.id.drawer_layout);
if (drawer.isDrawerOpen(GravityCompat.START)) {
drawer.closeDrawer(GravityCompat.START);
} else {
super.onBackPressed();
}
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.main, menu);
return true;
}
@Override
public boolean onOptionsItemSelected(MenuItem item) {
// Handle action bar item clicks here. The action bar will
// automatically handle clicks on the Home/Up button, so long
// as you specify a parent activity in AndroidManifest.xml.
int id = item.getItemId();
//noinspection SimplifiableIfStatement
if (id == R.id.action_settings) {
return true;
}
return super.onOptionsItemSelected(item);
}
@SuppressWarnings("StatementWithEmptyBody")
@Override
public boolean onNavigationItemSelected(MenuItem item) {
// Handle navigation view item clicks here.
int id = item.getItemId();
if (id == R.id.nav_camera) {
// Handle the camera action
} else if (id == R.id.nav_gallery) {
} else if (id == R.id.nav_slideshow) {
} else if (id == R.id.nav_manage) {
} else if (id == R.id.nav_share) {
} else if (id == R.id.nav_send) {
}
DrawerLayout drawer = (DrawerLayout) findViewById(R.id.drawer_layout);
drawer.closeDrawer(GravityCompat.START);
return true;
}
}
在以下文件中我在微调器上出现错误，
spinner = (Spinner) findViewById(R.id.spinner);
spinner.setOnItemSelectedListener(this);
这是我的config.java文件
package com.example.sachin.demodb;
/**
* Created by sachin on 8/10/2016.
*/
public class Config {
//JSON URL
public static final String DATA_URL = "http://10.0.2.2/portal/fetchvisit.php";
//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";
}
现在这是my.xml文件..
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical"
android:paddingBottom="@dimen/activity_vertical_margin"
android:paddingLeft="@dimen/activity_horizontal_margin"
android:paddingRight="@dimen/activity_horizontal_margin"
android:paddingTop="@dimen/activity_vertical_margin"
app:layout_behavior="@string/appbar_scrolling_view_behavior"
tools:context="com.example.sachin.demodb.MainActivity"
tools:showIn="@layout/app_bar_main">
<Spinner
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:id="@+id/spinner" />
<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>
</LinearLayout>
获取错误
Error:(50, 43) error: incompatible types: MainActivity cannot be converted to OnItemSelectedListener
请帮我解决这个问题..
答案 0 :(得分：0)
由于您在spinner.setOnItemSelectedListener(this);传递了活动，因此您的活动（MainActivity）必须实施该界面。因此，您的MainActivity定义将如下所示：
public class MainActivity extends AppCompatActivity
implements OnItemSelectedListener , NavigationView.OnNavigationItemSelectedListener {
// Also implement the methods in OnItemSelectedListener interface
}
答案 1 :(得分：0)
Your Activity is not implementing OnItemSelectedListener interface then you can't pass context to spinner item click listener implement OnItemSelectedListener in MainActivity.
spinner1.setOnItemSelectedListener(this);
Otherwise, you can pass an anonymous class instance which implements OnItemSelectedListener interface.
spinner1.setOnItemSelectedListener(new AdapterView.OnItemSelectedListener() {
@Override
public void onItemSelected(AdapterView<?> parent, View view, int position, long id) {
}
@Override
public void onNothingSelected(AdapterView<?> parent) {
}
});