我得到一个空指针错误，我找不到它有什么问题。这是活动代码
package ie.gmit.gmitapp;
import android.os.Bundle;
import android.app.ListActivity;
import android.content.Context;
import android.view.View;
import android.view.ViewGroup;
import android.widget.BaseAdapter;
import android.widget.LinearLayout;
import android.widget.ListView;
import android.widget.TextView;
public class BusinessActivity extends ListActivity {
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
//setContentView(R.layout.activity_bussiness);
//use our own list adapter
setListAdapter(new BusinessListAdapter(this));
}
protected void onListItemClick(ListView l, View v, int position, long id)
{
((BusinessListAdapter)getListAdapter()).toggle(position);
}
/**
* A sample ListAdapter that presents content
* from arrays of text and titles.
*
*/
private class BusinessListAdapter extends BaseAdapter {
public BusinessListAdapter(Context context)
{
mContext = context;
}
/**
* The number of items in the list is determined by the number of speeches
* in our array.
*
* @see android.widget.ListAdapter#getCount()
*/
public int getCount() {
return mTitles.length;
}
/**
* Since the data comes from an array, just returning
* the index is sufficent to get at the data. If we
* were using a more complex data structure, we
* would return whatever object represents one
* row in the list.
*
* @see android.widget.ListAdapter#getItem(int)
*/
public Object getItem(int position) {
return position;
}
/**
* Use the array index as a unique id.
* @see android.widget.ListAdapter#getItemId(int)
*/
public long getItemId(int position) {
return position;
}
/**
* Make a DescriptionView to hold each row.
* @see android.widget.ListAdapter#getView(int, android.view.View, android.view.ViewGroup)
*/
public View getView(int position, View convertView, ViewGroup parent) {
DescriptionView dv;
if (convertView == null) {
dv = new DescriptionView(mContext, mTitles[position], mDescription[position], mExpanded[position]);
} else {
dv = (DescriptionView)convertView;
dv.setTitle(mTitles[position]);
dv.setDescription(mDescription[position]);
dv.setExpanded(mExpanded[position]);
}
return dv;
}
public void toggle(int position) {
mExpanded[position] = !mExpanded[position];
notifyDataSetChanged();
}
/**
* Remember our context so we can use it when constructing views.
*/
private Context mContext;
/**
* Our data, part 1.
*/
private String[] mTitles =
{
"Bachelor of Business",
"Bachelor of Business (Honours)"
};
private String[] mDescription =
{
"This programme provides you with a broadly-based business education" +
" to assist you to work successfully in business. You will study a variety " +
"of business subjects and develop a general understandng of the administrative, " +
"economics, legal, and social environment within which business operates. You will " +
"study the basics of business and get an insight into many business disciplines" +
" in years one and two. In year three you can specialise in Marketing, Human" +
" Resource Management, or Information Systems Management. There is a strong " +
"emphasis during the programme on practical business projects to develop the" +
"skills required by graduates in the workplace. (Students may apply to the" +
" Registrar for a Higher Certificate in Business after successfully completing " +
"two years of the programme.)",
"The School of Business offers a four-year honours degree (Level 8) in Business. " +
"This programme provides students with a broad-based business education to work" +
" successfully in business and offers students the opportunity to specialise in one " +
"of five streams. You will study a variety of business subjects and develop a general" +
" understanding of the administrative, economic, legal and social environment within" +
" which business operates. You will study the basics of business and get an insight" +
" into many business disciplines in years one and two. In year three you can specialise " +
"in marketing, human resource management or information systems management. In year four " +
"you can specialise in economics and finance, human resource management, management," +
" marketing or rural enterprise and agri-business. There is a strong emphasis on the" +
" current business environment and acquiring the skills and knowledge required for " +
"employment in business. Case studies and practical business projects are used to develop" +
" students' analysis, communication and professional business skills."
};
/**
* Our data, part 3.
*/
private boolean[] mExpanded =
{
false,
false,
};
}
/**
* We will use a DescriptionView to display each speech. It's just a LinearLayout
* with two text fields.
*
*/
private class DescriptionView extends LinearLayout {
private TextView mTitle;
private TextView mDescription;
public DescriptionView(Context context, String title, String desc, boolean expanded) {
super(context);
this.setOrientation(VERTICAL);
// Here we build the child views in code. They could also have
// been specified in an XML file.
mTitle = new TextView(context);
mTitle.setText(title);
addView(mTitle, new LinearLayout.LayoutParams(LayoutParams.MATCH_PARENT, LayoutParams.WRAP_CONTENT));
mDescription.setText(desc);
addView(mDescription, new LinearLayout.LayoutParams(LayoutParams.MATCH_PARENT, LayoutParams.WRAP_CONTENT));
mDescription.setVisibility(expanded ? VISIBLE : GONE);
}
/**
* Convenience method to set the title of a DescriptionView
*/
public void setTitle(String title) {
mTitle.setText(title);
}
/**
* Convenience method to set the description of a DescriptionView
*/
public void setDescription(String words) {
mDescription.setText(words);
}
/**
* Convenience method to expand or hide the description
*/
public void setExpanded(boolean expanded) {
mDescription.setVisibility(expanded ? VISIBLE : GONE);
}
}
}
这是日志猫：
03-25 13:34:07.753: E/AndroidRuntime(912): FATAL EXCEPTION: main
03-25 13:34:07.753: E/AndroidRuntime(912): java.lang.NullPointerException
03-25 13:34:07.753: E/AndroidRuntime(912): at ie.gmit.gmitapp.BusinessActivity$DescriptionView.<init>(BusinessActivity.java:174)
03-25 13:34:07.753: E/AndroidRuntime(912): at ie.gmit.gmitapp.BusinessActivity$BusinessListAdapter.getView(BusinessActivity.java:82)
03-25 13:34:07.753: E/AndroidRuntime(912): at android.widget.AbsListView.obtainView(AbsListView.java:2159)
03-25 13:34:07.753: E/AndroidRuntime(912): at android.widget.ListView.makeAndAddView(ListView.java:1831)
第 174 行是
mDescription.setText(desc)
第 82 行是
dv = new DescriptionView(mContext, mTitles[position], mDescription[position], mExpanded[position]);