我正在尝试使用自定义适配器来设置ListAdapter。我有一个所有者，一个OnwerAdapter，一个OnwerDetail和一个OnwerAsyncTask。我打电话给OwnerAsyncTask获取所有者列表;但是，当我设置列表适配器时，它会抛出异常。尝试设置textView时，将在OwnerAdapter类中抛出该execption。以下是一些示例代码：
//OwnerAdapter
package com.mb.carlovers.adapter;
import com.mb.carlovers.Owner;
import com.mb.carlovers.R;
import android.app.Activity;
import android.content.Context;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.ArrayAdapter;
import android.widget.TextView;
public class OwnerAdapter extends ArrayAdapter<Owner> {
private Context context;
private int layoutResourceId;
private Owner data[] = null;
public OwnerAdapter(Context context, int textViewResourceId,Owner[] data) {
super(context, textViewResourceId, data);
this.context = context;
this.layoutResourceId = textViewResourceId;
this.data = data;
}
@Override
public View getView(int position, View convertView, ViewGroup parent) {
View row = convertView;
OwnerHolder holder = null;
if(row == null)
{
LayoutInflater inflater = ((Activity)context).getLayoutInflater();
row = inflater.inflate(layoutResourceId, parent, false);
holder = new OwnerHolder();
holder.tvFName = (TextView) row.findViewById(R.id.tvFirstName);
holder.tvLName = (TextView) row.findViewById(R.id.tvLastName);
holder.tvCId = (TextView) row.findViewById(R.id.tvCarID);
row.setTag(holder);
} else
{
holder = (OwnerHolder) row.getTag();
}
Owner item = data[position];
String fName = item.getFirstName();
**//The exception is thrown here.**
// holder.tvFName.setText(item.setFirstName.toString()); //This was throwing an error.
holder.tvFName.setText("Tester") //This is still throwing an exception
holder.tvLName.setText("Example");
holder.tvCId.setText("1");
return row;
}
static class OwnerHolder
{
TextView tvFName;
TextView tvLName;
TextView tvCId;
}
}
// Here is the owner's class
package com.mb.carlovers;
public class Owner {
private String _firstName;
private String _lastName;
private String _carId;
private Car _car;
public Owner()
{
this._firstName = "";
this._lastName = "";
this._carId = "";
}
public Owner(String lName)
{
this._lastName = lName;
}
public Owner(String lName, String cId)
{
this._lastName = lName;
this._carId = cId;
}
public Owner(String lName, String fName, String cId)
{
this._lastName = lName;
this._firstName = fName;
this._carId = cId;
}
public Owner(String lName, String fName, String cId, Car car)
{
this._lastName = lName;
this._firstName = fName;
this._carId = cId;
this._car = car;
}
//Getters
public String getFirstName()
{
return _firstName;
}
public String getLastName()
{
return _lastName;
}
public String getCarId()
{
return _carId;
}
public Car getCar()
{
return _car;
}
//Setters
public void setFirstName(String fName)
{
_firstName = fName;
}
public void setLastName(String lName)
{
_lastName = lName;
}
public void setCarId(String cId)
{
_carId = cId;
}
public void setCar(Car car)
{
_car = car;
}
}
//Here is the owner AsyncTask
package com.mb.carlovers.asynctask;
import java.util.ArrayList;
import java.util.List;
import com.mb.carlovers.Owner;
import android.os.AsyncTask;
public class OnwerAsyncTask extends AsyncTask<String, Void, List<Owner>> {
private List<Owner> items = null;
@Override
protected List<Owner> doInBackground(String... params) {
try
{
items = new ArrayList<Owner>();
Owner own = new Owner();
own.setFirstName("John");
own.setLastName("Smith");
own.setCarId("1");
items.add(own);
Owner own1 = new Owner();
own1.setFirstName("Samantha");
own1.setLastName("Right");
own1.setCarId("2");
items.add(own1);
Owner own2 = new Owner();
own2.setFirstName("Regie");
own2.setLastName("Miller");
own2.setCarId("3");
items.add(own2);
Owner own3 = new Owner();
own3.setFirstName("Mark");
own3.setLastName("Adam");
own3.setCarId("4");
items.add(own3);
} catch(Exception ex)
{
ex.toString();
}
return items;
}
@Override
protected void onPostExecute(List<Owner> result) {
// TODO Auto-generated method stub
super.onPostExecute(result);
}
}
//Here is the OnwerDetailList whenre the AsyncTask is being called
package com.mb.carlovers;
import java.util.List;
import java.util.concurrent.ExecutionException;
import com.mb.carlovers.adapter.OwnerAdapter;
import com.mb.carlovers.asynctask.OnwerAsyncTask;
import android.os.AsyncTask;
import android.os.Bundle;
import android.support.v4.app.ListFragment;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.ArrayAdapter;
public class OwnerDetail extends ListFragment {
OwnerAdapter ownerAdapter = null;
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
return inflater.inflate(R.layout.customize_layout,container, false);
}
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
OnwerAsyncTask asynTask = new OnwerAsyncTask();
List<Owner> lt = null;
try {
lt = asynTask.execute("").get();
} catch (InterruptedException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (ExecutionException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
Owner myOwners[] = lt.toArray(new Owner[lt.size()]);
super.onActivityCreated(savedInstanceState);
ownerAdapter = new OwnerAdapter(getActivity(),android.R.layout.simple_list_item_activated_1 , myOwners);
}
@Override
public void onActivityCreated(Bundle savedInstanceState) {
super.onActivityCreated(savedInstanceState);
setListAdapter(ownerAdapter);
}
}
这是例外
07-30 14:18:15.155: E/AndroidRuntime(864): FATAL EXCEPTION: main
07-30 14:18:15.155: E/AndroidRuntime(864): java.lang.NullPointerException
07-30 14:18:15.155: E/AndroidRuntime(864): at com.mb.carlovers.adapter.OwnerAdapter.getView(OwnerAdapter.java:48)
07-30 14:18:15.155: E/AndroidRuntime(864): at android.widget.AbsListView.obtainView(AbsListView.java:2033)
07-30 14:18:15.155: E/AndroidRuntime(864): at android.widget.ListView.onMeasure(ListView.java:1127)
07-30 14:18:15.155: E/AndroidRuntime(864): at android.view.View.measure(View.java:12603)
07-30 14:18:15.155: E/AndroidRuntime(864): at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:4677)
07-30 14:18:15.155: E/AndroidRuntime(864): at android.widget.LinearLayout.measureChildBeforeLayout(LinearLayout.java:1369)
07-30 14:18:15.155: E/AndroidRuntime(864): at android.widget.LinearLayout.measureVertical(LinearLayout.java:660)
07-30 14:18:15.155: E/AndroidRuntime(864): at android.widget.LinearLayout.onMeasure(LinearLayout.java:553)
07-30 14:18:15.155: E/AndroidRuntime(864): at android.view.View.measure(View.java:12603)
07-30 14:18:15.155: E/AndroidRuntime(864): at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:4677)
07-30 14:18:15.155: E/AndroidRuntime(864): at android.widget.FrameLayout.onMeasure(FrameLayout.java:293)
07-30 14:18:15.155: E/AndroidRuntime(864): at android.view.View.measure(View.java:12603)
07-30 14:18:15.155: E/AndroidRuntime(864): at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:4677)
07-30 14:18:15.155: E/AndroidRuntime(864): at android.widget.LinearLayout.measureChildBeforeLayout(LinearLayout.java:1369)
答案 0 :(得分：0)
问题是你使用的simple_list_item_activated_1只包含一个字段：android.R.id.text1。
由于该布局中不存在R.id.tvFirstName，因此findViewById（）返回null，并且ViewHolder的属性为null，这就是它抛出空指针异常的原因。
为了使其正常工作，您将不得不使用这些字段创建自定义视图，并将其ID传递给您的适配器。
使用simple_list_item_activated_1可以做的最好的事情就是显示一个字段。使用simple_list_item_activated_2，您可以显示两个字段。对于任何自定义，您必须创建自己的视图。
为了使这个工作与simple_list_item_activated_1一致，你应该注释掉以下几行：
holder.tvLName.setText("Example");
holder.tvCId.setText("1");
并更改此行：
holder.tvFName = (TextView) row.findViewById(R.id.tvFirstName);
为：
holder.tvFName = (TextView) row.findViewById(android.R.id.text1);