我是一个新的android程序员如何在getView方法中解决空指针异常。在sqlite值没有进入列表视图对象。
package com.example.extra;
import java.util.List;
import com.example.dto.DriverSelectedRouteArrayList;
import com.example.main.R;
import android.content.Context;
import android.util.Log;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.ArrayAdapter;
import android.widget.CheckBox;
import android.widget.CompoundButton;
import android.widget.TextView;
public class CustomerAdapter extends ArrayAdapter<DriverSelectedRouteArrayList>
{
DriverSelectedRouteArrayList driverSelectedRouteArrayList;
private List<DriverSelectedRouteArrayList> list;
private LayoutInflater layoutInflater;
Context context;
public CustomerAdapter(Context context, int resource,
List<DriverSelectedRouteArrayList> objects)
{
super(context, resource,objects);
layoutInflater = (LayoutInflater) context.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
}
@Override
public View getView(int position, View convertView, ViewGroup parent)
{
ViewHolder holder = null;
if(convertView == null)
{
convertView = layoutInflater.inflate(R.layout.student_list_view_itom, null);
holder = new ViewHolder();
holder.srNumberTextView = (TextView) convertView.findViewById(R.id.srNumberTextView);
holder.nameTextView = (TextView) convertView.findViewById(R.id.textViewStudentItem);
holder.phoneNumberTextView = (TextView) convertView.findViewById(R.id.textViewPhoneNumber);
holder.checkBox = (CheckBox) convertView.findViewById(R.id.checkBoxSelectForStudentList);
holder.checkBox
.setOnCheckedChangeListener(new CompoundButton.OnCheckedChangeListener() {
@Override
public void onCheckedChanged(CompoundButton buttonView, boolean isChecked)
{
int getPosition = (Integer) buttonView.getTag();
list.get(getPosition).setSelected(buttonView.isChecked());
}
});
convertView.setTag(holder);
convertView.setTag(R.id.srNumberTextView,holder.srNumberTextView);
convertView.setTag(R.id.textViewStudentItem, holder.nameTextView);
convertView.setTag(R.id.textViewPhoneNumber, holder.phoneNumberTextView);
}else{
holder = (ViewHolder) convertView.getTag();
}
holder.checkBox.setTag(position);
Log.e("get position=======>", ""+list.get(position));
holder.srNumberTextView.setText(list.get(position).get_id());
holder.nameTextView.setText(list.get(position).getFirst_name());
holder.phoneNumberTextView.setText(list.get(position).getPhone_number());
holder.checkBox.setChecked(list.get(position).isSelected());
return convertView;
}
static class ViewHolder
{
protected TextView srNumberTextView;
protected TextView nameTextView;
protected TextView phoneNumberTextView;
protected CheckBox checkBox;
}
}
package com.example.main;
import java.util.ArrayList;
import java.util.Collections;
import java.util.Comparator;
import java.util.List;
import org.apache.http.HttpResponse;
import org.apache.http.StatusLine;
import org.apache.http.client.HttpClient;
import org.apache.http.client.methods.HttpPost;
import org.apache.http.entity.StringEntity;
import org.apache.http.impl.client.DefaultHttpClient;
import com.example.dao.StudentListDatabaseHelper;
import com.example.dto.DriverSelectedRouteArrayList;
import com.example.extra.CustomerAdapter;
import com.example.input.DriverSelectedRouteinput;
import com.example.url.UrlAccess;
import com.example.webservcie.ParseDriverSelectedRouteId;
import android.app.Activity;
import android.app.ProgressDialog;
import android.content.res.Resources;
import android.os.AsyncTask;
import android.os.Bundle;
import android.util.Log;
import android.view.View;
import android.widget.AdapterView;
import android.widget.AdapterView.OnItemClickListener;
import android.widget.CheckBox;
import android.widget.ListView;
import android.widget.TextView;
import android.widget.Toast;
public class StudentCheckBoxAndListShow extends Activity implements OnItemClickListener
{
int layout = R.layout.student_list_view_itom;
//private String SERVICE_URL = "http://10.0.2.2:8080/SBTsystem/service/viewAllStudentlist";
UrlAccess urlAccess = new UrlAccess();
String urlAccessStringVariable = urlAccess.SERVICE_URL;
String SERVICE_URL = urlAccessStringVariable+"/viewAllStudentlist";
ProgressDialog progressDialog;
HttpPost httpPost;
HttpResponse httpResponse;
HttpClient httpclient ;
StatusLine statusLine;
TextView srNumberTextView;
ListView listView;
CustomerAdapter customerAdapter;
Resources resources;
List<DriverSelectedRouteArrayList> items;
DriverSelectedRouteArrayList driverSelectedRouteArrayList = new DriverSelectedRouteArrayList();
ParseDriverSelectedRouteId parseDriverSelectedRouteId = new ParseDriverSelectedRouteId();
public ArrayList<DriverSelectedRouteArrayList> studentsListContact = new ArrayList<DriverSelectedRouteArrayList>();
// CustomAdapter customAdapter;
StudentListDatabaseHelper studentListDatabaseHelper;
// oncreate method override
@Override
protected void onCreate(Bundle savedInstanceState)
{
// TODO Auto-generated method stub
super.onCreate(savedInstanceState);
setContentView(R.layout.student_list_view_show);
studentListDatabaseHelper = new StudentListDatabaseHelper(this);
resources = getResources();
srNumberTextView = (TextView) findViewById(R.id.srNumberTextView);
listView = (ListView) findViewById(R.id.studentlistView);
httpclient = new DefaultHttpClient();
// call async task class
new StudentListShowAsyncTask().execute();
}
private void populateListView(Resources resource,ListView listView)
{
}
private class StudentListShowAsyncTask extends AsyncTask<String, String, String>
{
//this.getIntent().getExtras();
@Override
protected void onPreExecute()
{
// TODO Auto-generated method stub
super.onPreExecute();
progressDialog = ProgressDialog.show(StudentCheckBoxAndListShow.this,""
,"Loading. Please wait...", true);
progressDialog.show();
Log.d("on pre execute method=====>", "on preexcute");
}
@Override
protected String doInBackground(String... params)
{
Bundle extras = getIntent().getExtras();
String routeIdFromDriverSelected = extras.getString("routeId");
try {
httpPost = new HttpPost(SERVICE_URL);
DriverSelectedRouteinput driverSelectedRouteinput = new DriverSelectedRouteinput();
String jsonRequest = driverSelectedRouteinput.createjsonRequestForDriverSelectedRoute(routeIdFromDriverSelected);
StringEntity stringEntety;
stringEntety = new StringEntity(jsonRequest);
stringEntety.setContentEncoding("UTF-8");
stringEntety.setContentType("application/json");
httpPost.setEntity(stringEntety);
httpResponse = httpclient.execute(httpPost);
statusLine = httpResponse.getStatusLine();
int statusCode = statusLine.getStatusCode();
if(statusCode == 200)
{
Log.d("status code", statusCode+"");
driverSelectedRouteArrayList = parseDriverSelectedRouteId.parseResponseForRouteIdResult(httpResponse);
/*int arrayListSize = parseDriverSelectedRouteId.studentList.size();
for(int i =0; i<arrayListSize; i++)
{
Log.d("response first name=-=-==-===-=-=-=-=>"+i, driverSelectedRouteArrayList.getFirst_name()+"");
}*/
//String routeId = driverSelectedRouteArrayList.getRoute_id();
//Log.d("route id------>", routeId);
StudentListDatabaseHelper studentListDatabaseHelper = new StudentListDatabaseHelper(getBaseContext());
//studentListDatabaseHelper.getWritableDatabase();
studentListDatabaseHelper.insertRecord( driverSelectedRouteArrayList);
//select sqlite database in android
items = studentListDatabaseHelper.selectRecord();
//int _id = driverSelectedRouteArrayList.get_id();
/*String _idString = ""+_id;
Log.d("id get from the sqlite database-==-=-=-=>",_idString);*/
Log.e("database created=========>>", items+"sqlite database created");
}
//Log.d("status code", statusCode+"");
} catch (Exception e)
{
e.printStackTrace();
}
return null;
}
@Override
protected void onPostExecute(String result)
{
progressDialog.dismiss();
super.onPostExecute(result);
setAdapterToListview();
}
}
// set setAdapterToListview
public void setAdapterToListview()
{
Log.e("set adpter items value====>", ""+items);
Collections.sort(items,new Comparator<DriverSelectedRouteArrayList>() {
@Override
public int compare(DriverSelectedRouteArrayList lhs,
DriverSelectedRouteArrayList rhs)
{
return lhs.getFirst_name().compareTo(rhs.getFirst_name());
}
});
customerAdapter = new CustomerAdapter(StudentCheckBoxAndListShow.this,MODE_MULTI_PROCESS, items);
Log.e("items==========>>>>>>>>>>>>>>", ""+items);
listView.setAdapter(customerAdapter);
listView.setOnItemClickListener(new OnItemClickListener()
{
@Override
public void onItemClick(AdapterView<?> parent, View view, int position,
long id)
{
CheckBox checkBox = (CheckBox) view.findViewById(R.id.checkBoxSelectForStudentList);
DriverSelectedRouteArrayList listViewStudent = items.get(position);
if(listViewStudent.isSelected())
{
listViewStudent.setSelected(false);
checkBox.setChecked(false);
}else
{
listViewStudent.setSelected(true);
checkBox.setChecked(true);
}
}
});
}
@Override
public void onItemClick(AdapterView<?> arg0, View arg1, int arg2, long arg3)
{
DriverSelectedRouteArrayList tempValues = studentsListContact.get(arg2);
Toast.makeText(this, ""+tempValues.getFirst_name()+"phone number"+tempValues.getPhone_number(), Toast.LENGTH_LONG).show();
}
}
package com.example.dto;
import java.util.ArrayList;
import java.util.List;
public class DriverSelectedRouteArrayList
{
// ArrayList arrayList = new ArrayList();
ArrayList<String> studentArrayList = new ArrayList<String>();
// create list view object
public List<DriverSelectedRouteArrayList> driverSelectedRouteArrayList;
public int _id;
public String first_name;
public String middle_name;
public String last_name;
public String route_id;
public String phone_number;
boolean selected;
public DriverSelectedRouteArrayList()
{
first_name = null;
middle_name = null;
last_name = null;
route_id = null;
phone_number = null;
}
public int get_id()
{
return _id;
}
public int set_id(int _id)
{
return this._id = _id;
}
public ArrayList<String> getStudentArrayList()
{
return studentArrayList;
}
public void setStudentArrayList(ArrayList<String> studentArrayList)
{
this.studentArrayList = studentArrayList;
}
public String getFirst_name() {
return first_name;
}
public String setFirst_name(String first_name) {
return this.first_name = first_name;
}
public String getMiddle_name()
{
return middle_name;
}
public String setMiddle_name(String middle_name)
{
return this.middle_name = middle_name;
}
public String getLast_name()
{
return last_name;
}
public String setLast_name(String last_name)
{
return this.last_name = last_name;
}
public String getRoute_id()
{
return route_id;
}
public String setRoute_id(String routeId)
{
return this.route_id = routeId;
}
public String getPhone_number()
{
return phone_number;
}
public String setPhone_number(String phone_number)
{
return this.phone_number = phone_number;
}
public boolean isSelected() {
return selected;
}
public void setSelected(boolean selected) {
this.selected = selected;
}
public List<DriverSelectedRouteArrayList> getDriverSelectedRouteArrayList()
{
return driverSelectedRouteArrayList;
}
public void setDriverSelectedRouteArrayList(
List<DriverSelectedRouteArrayList> driverSelectedRouteArrayList)
{
this.driverSelectedRouteArrayList = driverSelectedRouteArrayList;
}
}
01-03 18:30:07.862: E/AndroidRuntime(3989): FATAL EXCEPTION: main
01-03 18:30:07.862: E/AndroidRuntime(3989): java.lang.NullPointerException
01-03 18:30:07.862: E/AndroidRuntime(3989): at com.example.extra.CustomerAdapter.getView(CustomerAdapter.java:65)
01-03 18:30:07.862: E/AndroidRuntime(3989): at android.widget.AbsListView.obtainView(AbsListView.java:2452)
01-03 18:30:07.862: E/AndroidRuntime(3989): at android.widget.ListView.measureHeightOfChildren(ListView.java:1250)
01-03 18:30:07.862: E/AndroidRuntime(3989): at android.widget.ListView.onMeasure(ListView.java:1161)
01-03 18:30:07.862: E/AndroidRuntime(3989): at android.view.View.measure(View.java:12865)
01-03 18:30:07.862: E/AndroidRuntime(3989): at android.widget.RelativeLayout.measureChild(RelativeLayout.java:579)
01-03 18:30:07.862: E/AndroidRuntime(3989): at android.widget.RelativeLayout.onMeasure(RelativeLayout.java:392)
01-03 18:30:07.862: E/AndroidRuntime(3989): at android.view.View.measure(View.java:12865)
01-03 18:30:07.862: E/AndroidRuntime(3989): at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:4712)
01-03 18:30:07.862: E/AndroidRuntime(3989): at android.widget.FrameLayout.onMeasure(FrameLayout.java:293)
01-03 18:30:07.862: E/AndroidRuntime(3989): at android.view.View.measure(View.java:12865)
01-03 18:30:07.862: E/AndroidRuntime(3989): at android.widget.LinearLayout.measureVertical(LinearLayout.java:822)
01-03 18:30:07.862: E/AndroidRuntime(3989): at android.widget.LinearLayout.onMeasure(LinearLayout.java:563)
01-03 18:30:07.862: E/AndroidRuntime(3989): at android.view.View.measure(View.java:12865)
01-03 18:30:07.862: E/AndroidRuntime(3989): at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:4712)
01-03 18:30:07.862: E/AndroidRuntime(3989): at android.widget.FrameLayout.onMeasure(FrameLayout.java:293)
01-03 18:30:07.862: E/AndroidRuntime(3989): at com.android.internal.policy.impl.PhoneWindow$DecorView.onMeasure(PhoneWindow.java:2242)
01-03 18:30:07.862: E/AndroidRuntime(3989): at android.view.View.measure(View.java:12865)
01-03 18:30:07.862: E/AndroidRuntime(3989): at android.view.ViewRootImpl.performTraversals(ViewRootImpl.java:1240)
01-03 18:30:07.862: E/AndroidRuntime(3989): at android.view.ViewRootImpl.handleMessage(ViewRootImpl.java:2628)
01-03 18:30:07.862: E/AndroidRuntime(3989): at android.os.Handler.dispatchMessage(Handler.java:99)
01-03 18:30:07.862: E/AndroidRuntime(3989): at android.os.Looper.loop(Looper.java:137)
01-03 18:30:07.862: E/AndroidRuntime(3989): at android.app.ActivityThread.main(ActivityThread.java:4517)
01-03 18:30:07.862: E/AndroidRuntime(3989): at java.lang.reflect.Method.invokeNative(Native Method)
01-03 18:30:07.862: E/AndroidRuntime(3989): at java.lang.reflect.Method.invoke(Method.java:511)
01-03 18:30:07.862: E/AndroidRuntime(3989): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:993)
01-03 18:30:07.862: E/AndroidRuntime(3989): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:760)
01-03 18:30:07.862: E/AndroidRuntime(3989): at dalvik.system.NativeStart.main(Native Method)
01-03 18:51:17.792: E/AndroidRuntime(7628): FATAL EXCEPTION: main
01-03 18:51:17.792: E/AndroidRuntime(7628): java.lang.NullPointerException
01-03 18:51:17.792: E/AndroidRuntime(7628): at java.util.Collections.sort(Collections.java:1890)
01-03 18:51:17.792: E/AndroidRuntime(7628): at com.example.main.StudentCheckBoxAndListShow.setAdapterToListview(StudentCheckBoxAndListShow.java:188)
01-03 18:51:17.792: E/AndroidRuntime(7628): at com.example.main.StudentCheckBoxAndListShow$StudentListShowAsyncTask.onPostExecute(StudentCheckBoxAndListShow.java:179)
01-03 18:51:17.792: E/AndroidRuntime(7628): at com.example.main.StudentCheckBoxAndListShow$StudentListShowAsyncTask.onPostExecute(StudentCheckBoxAndListShow.java:1)
01-03 18:51:17.792: E/AndroidRuntime(7628): at android.os.AsyncTask.finish(AsyncTask.java:602)
01-03 18:51:17.792: E/AndroidRuntime(7628): at android.os.AsyncTask.access$600(AsyncTask.java:156)
01-03 18:51:17.792: E/AndroidRuntime(7628): at android.os.AsyncTask$InternalHandler.handleMessage(AsyncTask.java:615)
01-03 18:51:17.792: E/AndroidRuntime(7628): at android.os.Handler.dispatchMessage(Handler.java:99)
01-03 18:51:17.792: E/AndroidRuntime(7628): at android.os.Looper.loop(Looper.java:137)
01-03 18:51:17.792: E/AndroidRuntime(7628): at android.app.ActivityThread.main(ActivityThread.java:4517)
01-03 18:51:17.792: E/AndroidRuntime(7628): at java.lang.reflect.Method.invokeNative(Native Method)
01-03 18:51:17.792: E/AndroidRuntime(7628): at java.lang.reflect.Method.invoke(Method.java:511)
01-03 18:51:17.792: E/AndroidRuntime(7628): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:993)
01-03 18:51:17.792: E/AndroidRuntime(7628): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:760)
01-03 18:51:17.792: E/AndroidRuntime(7628): at dalvik.system.NativeStart.main(Native Method)
答案 0 :(得分：3)
您尚未初始化私人“列表”对象。
并试图在第65行使用
Log.e("get position=======>", ""+list.get(position));
解决方案
public CustomerAdapter(Context context, int resource,
List<DriverSelectedRouteArrayList> objects)
{
super(context, resource,objects);
layoutInflater = (LayoutInflater) context.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
list = objects;
}