public void directionSpinner (String directions []) {
//Does some stuff to assign namedDirections [0] and namedDirections[1] a value.
dirSpinner = (Spinner) findViewById(R.id.route_direction_spinner); //THIS IS LINE 87
dirSpinner.setOnItemSelectedListener(this);
ArrayAdapter<CharSequence> adapter = new ArrayAdapter(this, android.R.layout.simple_spinner_item);
adapter.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item);
adapter.add(namedDirections[0]);
adapter.add(namedDirections[1]);
dirSpinner.setAdapter(adapter);
Log.i(TAG, "spinner populated");
}
logcat的：
12-09 20:50:13.497: E/AndroidRuntime(857): FATAL EXCEPTION: main
12-09 20:50:13.497: E/AndroidRuntime(857): java.lang.NullPointerException
12-09 20:50:13.497: E/AndroidRuntime(857): at android.app.Activity.findViewById(Activity.java:1839)
12-09 20:50:13.497: E/AndroidRuntime(857): at com.nicotera.colton.londontransitguide.RoutesActivity.directionSpinner(RoutesActivity.java:87)
12-09 20:50:13.497: E/AndroidRuntime(857): at com.nicotera.colton.londontransitguide.MyInnerClass.onPostExecute(RoutesActivity.java:142)
12-09 20:50:13.497: E/AndroidRuntime(857): at com.nicotera.colton.londontransitguide.MyInnerClass.onPostExecute(RoutesActivity.java:1)
无论如何，route_direction_spinner是正确定义的。 directionSpinner（）在AsyncTask完成后运行。
整个代码：
package com.nicotera.colton.londontransitguide;
import java.io.IOException;
import java.text.DecimalFormat;
import java.util.regex.Matcher;
import java.util.regex.Pattern;
import org.jsoup.*;
import org.jsoup.nodes.Attributes;
import org.jsoup.nodes.Document;
import org.jsoup.nodes.Element;
import org.jsoup.select.Elements;
import android.app.Activity;
import android.os.AsyncTask;
import android.os.Bundle;
import android.os.Handler;
import android.util.Log;
import android.view.View;
import android.widget.AdapterView;
import android.widget.AdapterView.OnItemSelectedListener;
import android.widget.ArrayAdapter;
import android.widget.Spinner;
import android.widget.TextView;
public class RoutesActivity extends Activity implements OnItemSelectedListener {
Spinner dirSpinner;
Spinner routeSpinner;
static String [] namedDirections = new String [2];
private static final String TAG = "RoutesActivity";
/** Called when the activity is first created. */
@Override
public void onCreate(Bundle savedInstanceState){
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_routes);
dirSpinner = (Spinner) findViewById(R.id.route_direction_spinner); // Create an ArrayAdapter using the string array and a default spinner layout
routeSpinner = (Spinner) findViewById(R.id.route_name_spinner); // Create an ArrayAdapter using the string array and a default spinner layout
routeSpinner.setOnItemSelectedListener(this);
ArrayAdapter<CharSequence> adapter = ArrayAdapter.createFromResource(this, R.array.routes_array, android.R.layout.simple_spinner_item);
// Specify the layout to use when the list of choices appears
adapter.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item); // Apply the adapter to the spinner
routeSpinner.setAdapter(adapter);
Log.i(TAG, "second spinner populated");
}
public void onItemSelected(AdapterView<?> parent, View view,
int pos, long id) {
Log.i(TAG, "Item selected");
//DecimalFormat df = new DecimalFormat("00##");
int tempPos = pos;
Log.i(TAG, ("Position of selected item: " + tempPos));
int routeSelected;
if (tempPos < 17)
routeSelected = (tempPos + 1);
else if (tempPos >= 17 && tempPos < 29)
routeSelected = (tempPos + 2);
else
routeSelected = (tempPos + 3);
String temp;
if (routeSelected < 10)
temp = ("0") + routeSelected;
else
temp = ("") + routeSelected;
String url = "http://www.ltconline.ca/WebWatch/MobileAda.aspx?r=" + temp;
new MyInnerClass().execute(url);
}
public void directionSpinner (String directions []) {
int temp;
for (int i = 1; i <=2; i++)
{
temp = Integer.parseInt(directions[i]);
if (temp == 1)
namedDirections[(i-1)] = "Eastbound";
else if (temp == 2)
namedDirections[(i-1)] = "Northbound";
else if (temp == 3)
namedDirections[(i-1)] = "Southbound";
else if (temp == 4)
namedDirections[(i-1)] = "Westbound";
}
//setContentView(R.layout.activity_routes);
dirSpinner.setOnItemSelectedListener(this);
ArrayAdapter<CharSequence> adapter = new ArrayAdapter(this, android.R.layout.simple_spinner_item);
adapter.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item);
adapter.add(namedDirections[0]);
adapter.add(namedDirections[1]);
dirSpinner.setAdapter(adapter);
Log.i(TAG, "spinner populated");
}
public void onNothingSelected(AdapterView<?> parent) {
// Another interface callback
}
}
class MyInnerClass extends AsyncTask<String, Void, String> {
String [] directions = new String [3];
String [] directionNames = new String [3];
private static final String TAG = "RoutesActivity";
@Override
protected void onPreExecute() {
super.onPreExecute();
}
@Override
protected void onPostExecute(String result) {
super.onPostExecute(result);
RoutesActivity tc = new RoutesActivity();
tc.directionSpinner(directions);
}
@Override
protected String doInBackground(String... params) {
try{
Pattern routeDirPattern = Pattern.compile("\\&d=(\\d{1,2})");
Connection conn = Jsoup.connect(params[0]);
Document doc = conn.get();
int i = 0;
Elements routeLinks = doc.select("a[href]");
for (Element routeLink : routeLinks) {
i = (i + 1);
String name = routeLink.text();
Attributes attrs = routeLink.attributes();
String href = attrs.get("href");
Matcher m = routeDirPattern.matcher(href);
if (m.find()) {
String number = m.group(1);
directions [i] = number;
directionNames [i] = name;
Log.i(TAG, directionNames [i]);
}
}
}catch(Exception e){Log.d("doinbackground exception", e.toString());}
return ("Done");
}
}
基本上，这会从公交网站上获取一些值。到目前为止，这段代码只是根据所选路线得到路线的方向。
答案 0 :(得分：1)
（您的directionSpinner()方法在您发布的两个代码段中有所不同，我使用稍后添加的代码段，但此解决方案适用于两个代码段，假设问题是同样的）
您的问题是您没有正确遵循活动生命周期。
致电时：
RoutesActivity tc = new RoutesActivity();
tc.directionSpinner(directions);
您实际上正在创建RoutesActivity的全新实例。因为您将其称为标准Java类，所以它永远不会遵循Activity生命周期，这意味着永远不会调用onCreate()，这反过来意味着您的两个微调器对象保持为null（因为您指定了值）他们在onCreate()）。
因此，当你使用：
dirSpinner.setOnItemSelectedListener(this);
dirSpinner实际上是null，导致NullPointerException。
相反，请尝试使用：
RoutesActivity.this.directionSpinner(directions);
而不是：
RoutesActivity tc = new RoutesActivity();
tc.directionSpinner(directions);