个人listView适配器的问题

Question

我在使用自己的Adapter类创建带分隔符的ListView时遇到了一些麻烦。我是Android开发的初学者，所以我真的不能单独修复它。

我想用same layout as seen on this web site创建一个列表视图，我也希望我的项目按字母顺序排列。

所以我创建了两个Adapter，一个用于添加分隔符，另一个用于处理每个项目的特定布局。

类ListeMusicContainer是按名称按字母顺序排序的ArrayList。

每个人分别完美地工作，但是当我尝试两者时，我得到一个运行时错误。

当应用程序启动时，只有当我尝试滚动时才会出现错误（所以我猜我几乎不错）。

我真的不知道滚动时出现此错误的原因。怎么解决这个问题？

这是我用来创建带分隔符的ListView的适配器

abstract public class MusicAdapter extends BaseAdapter{

abstract protected View getHeaderView(String caption, int index,
        View convertView, ViewGroup parent);
private List<Section> sections = new ArrayList<Section>();

private static int TYPE_SECTION_HEADER = 0;

public MusicAdapter() {
    super();
}

public void addSection(String caption, ItemAdapter adapter){
    sections.add(new Section(caption, adapter));
}

public Object getItem(int position){
    for (Section section : this.sections){
        if (position == 0){
            return section;
        }

        int size = section.adapter.getCount() + 1;
        if (position < size){
            return section.adapter.getItem(position - 1);
        }
        position -= size;
    }
    return null;
}

public int getCount(){
    int total = 0;

    for (Section section : this.sections){
        total += section.adapter.getCount() + 1;
    }
    return total;
}

public int getItemViewType(int position){
    int typeOffset = TYPE_SECTION_HEADER + 1;

    for (Section section : this.sections) {
        if (position == 0) {
            return (TYPE_SECTION_HEADER);
        }

        int size = section.adapter.getCount() + 1;

        if (position < size) {
            return (typeOffset + section.adapter
                    .getItemViewType(position - 1));
        }

        position -= size;
        typeOffset += section.adapter.getViewTypeCount();
    }

    return -1;
}

public boolean areAllItemsSelectable(){
    return false;
}

public boolean isEnabled(int position) {
    return (getItemViewType(position) != TYPE_SECTION_HEADER);
}

@Override
public View getView(int position, View convertView, ViewGroup parent){
    int sectionIndex = 0;

    for (Section section : this.sections){
        if (position == 0){
            return (getHeaderView(section.caption, sectionIndex, convertView, parent));
        }
        int size = section.adapter.getCount() + 1;

        if (position < size){
            return (section.adapter.getView(position - 1, convertView,
                    parent));
        }
        position -= size;
        sectionIndex++;
    }
    return null;
}

@Override
public long getItemId(int position){
    return position;        
}

class Section {
    String caption;
    ItemAdapter adapter;

    Section(String caption, ItemAdapter adapter) {
        this.caption = caption;
        this.adapter = adapter;
    }
}
}

这是我用于每个项目的那个：

public class ItemAdapter extends BaseAdapter{

private ListeMusicContainer<Music> mList;
private LayoutInflater mInflater;

public ItemAdapter(Context context, ListeMusicContainer<Music> musics){
    mInflater = LayoutInflater.from(context);
    mList = musics;
}

@Override
public int getCount() {
    return mList.size();
}

@Override
public Object getItem(int position) {
    return position;
}

@Override
public long getItemId(int position) {
    return position;
}

@Override
public View getView(int position, View convertView, ViewGroup parent) {
    ViewHolder holder;

    if (convertView == null){
        convertView = mInflater.inflate(R.layout.list_item, null);

        holder = new ViewHolder();
        holder.nom = (TextView) convertView.findViewById(R.id.nomAlbum);
        holder.genre = (TextView) convertView.findViewById(R.id.genreAlbum);

        convertView.setTag(holder);
    }
    else{
        holder = (ViewHolder) convertView.getTag();
    }
    holder.nom.setText(mList.getItem(position).getNom());
    holder.genre.setText(mList.getItem(position).getGenre());

    return convertView;
}

static class ViewHolder{
    TextView nom;
    TextView genre;
}

}

以下是我初始化布局的方法：

public class TestView extends ListActivity {
/** Called when the activity is first created. */

private ListView mListView;
private static String[] items;
private XmlDataParser mParser;
private ListeMusicContainer<Music> mList;


private MusicAdapter mAdapter = new MusicAdapter() {
    protected View getHeaderView(String caption, int index,
            View convertView, ViewGroup parent) {
        TextView result = (TextView) convertView;

        if (convertView == null) {
            result = (TextView) getLayoutInflater().inflate(
                    R.layout.header, null);
        }

        result.setText(caption);

        return (result);
    }
};

@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);

    mParser = new XmlDataParser();
    mList = mParser.parseXml(this);

    ListeMusicContainer<Music> groupe = new ListeMusicContainer<Music>();
    String currLetter = null;

    for (int i = 0; i < mList.size(); i++){
        if (!mList.getItem(i).getLabel().equalsIgnoreCase(currLetter) && currLetter != null){
            mAdapter.addSection(mList.getItem(i).getLabel().toUpperCase(), new ItemAdapter(this, groupe));
            groupe = new ListeMusicContainer<Music>();
            currLetter = mList.getItem(i).getLabel();
        }
        if (currLetter == null){
            currLetter = mList.getItem(i).getLabel();
        }

        groupe.addData(mList.getItem(i));
    }

    setListAdapter(mAdapter);

}
}

编辑：在logcat中，这是我在运行应用程序时在logcat中得到的：

I/ActivityManager(   42): Displayed activity com.view/.TestView: 1480 ms (total
1480 ms)
D/dalvikvm(  975): GC_EXTERNAL_ALLOC freed 1214 objects / 78504 bytes in 96ms
D/AndroidRuntime(  975): Shutting down VM
W/dalvikvm(  975): threadid=1: thread exiting with uncaught exception (group=0x4
001d800)
E/AndroidRuntime(  975): FATAL EXCEPTION: main
E/AndroidRuntime(  975): java.lang.NullPointerException
E/AndroidRuntime(  975):        at com.view.ItemAdapter.getView(ItemAdapter.java
:51)
E/AndroidRuntime(  975):        at com.view.MusicAdapter.getView(Music
Adapter.java:91)
E/AndroidRuntime(  975):        at android.widget.AbsListView.obtainView(AbsList
View.java:1294)
E/AndroidRuntime(  975):        at android.widget.ListView.makeAndAddView(ListVi
ew.java:1727)
E/AndroidRuntime(  975):        at android.widget.ListView.fillDown(ListView.jav
a:652)
E/AndroidRuntime(  975):        at android.widget.ListView.fillGap(ListView.java
:623)
E/AndroidRuntime(  975):        at android.widget.AbsListView.trackMotionScroll(
AbsListView.java:2944)
E/AndroidRuntime(  975):        at android.widget.AbsListView.onTouchEvent(AbsLi
stView.java:2065)
E/AndroidRuntime(  975):        at android.widget.ListView.onTouchEvent(ListView
.java:3315)
E/AndroidRuntime(  975):        at android.view.View.dispatchTouchEvent(View.jav
a:3766)
E/AndroidRuntime(  975):        at android.view.ViewGroup.dispatchTouchEvent(Vie
wGroup.java:897)
E/AndroidRuntime(  975):        at android.view.ViewGroup.dispatchTouchEvent(Vie
wGroup.java:936)
E/AndroidRuntime(  975):        at android.view.ViewGroup.dispatchTouchEvent(Vie
wGroup.java:936)
E/AndroidRuntime(  975):        at android.view.ViewGroup.dispatchTouchEvent(Vie
wGroup.java:936)
E/AndroidRuntime(  975):        at com.android.internal.policy.impl.PhoneWindow$
DecorView.superDispatchTouchEvent(PhoneWindow.java:1671)
E/AndroidRuntime(  975):        at com.android.internal.policy.impl.PhoneWindow.
superDispatchTouchEvent(PhoneWindow.java:1107)
E/AndroidRuntime(  975):        at android.app.Activity.dispatchTouchEvent(Activ
ity.java:2086)
E/AndroidRuntime(  975):        at com.android.internal.policy.impl.PhoneWindow$
DecorView.dispatchTouchEvent(PhoneWindow.java:1655)
E/AndroidRuntime(  975):        at android.view.ViewRoot.handleMessage(ViewRoot.
java:1785)
E/AndroidRuntime(  975):        at android.os.Handler.dispatchMessage(Handler.ja
va:99)
E/AndroidRuntime(  975):        at android.os.Looper.loop(Looper.java:123)
E/AndroidRuntime(  975):        at android.app.ActivityThread.main(ActivityThrea
d.java:4627)
E/AndroidRuntime(  975):        at java.lang.reflect.Method.invokeNative(Native
Method)
E/AndroidRuntime(  975):        at java.lang.reflect.Method.invoke(Method.java:5
21)
E/AndroidRuntime(  975):        at com.android.internal.os.ZygoteInit$MethodAndA
rgsCaller.run(ZygoteInit.java:868)
E/AndroidRuntime(  975):        at com.android.internal.os.ZygoteInit.main(Zygot
eInit.java:626)
E/AndroidRuntime(  975):        at dalvik.system.NativeStart.main(Native Method)

W/ActivityManager(   42):   Force finishing activity com.view/.TestView