android - ArrayAdapter 数据集中的元素数为零

Question

我正在尝试构建一个包含行的自定义 View 的列表，每行将包含一个 ImageView 和两个 TextView 。

为此，我扩展了 ArrayAdapter 类(称为 PostersArrayAdapter)并覆盖了 getView() 方法，以便在数据和行布局之间建立正确的连接。

但是，当我尝试使用一些数据构造带有 PosterData 类数组(我的实现)的 PostersArrayAdapter 时，结果是适配器为空，这意味着 getCount() 返回零并且 listView 为空。

谁能告诉我我做错了什么？我依赖于我在这里找到的代码 - http://www.vogella.de/articles/AndroidListView/article.html

非常感谢!

这里是相关代码:(PosterData类只是一个有两个字符串字段的类)

public class PostersListActivity extends ListActivity {
final private int NUM_OF_PICS = 2;
private ContentGetter   cg;
private PosterData[]    posters;
private ListView        listView;

@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.main);
    cg = new ContentGetter(NUM_OF_PICS);
    try 
    {
        posters = cg.parseIndexFile();
        int res = cg.DownloadPosterPics(1);

    } 
    catch (ClientProtocolException e) 
    {
        e.printStackTrace();
    } 
    catch (IOException e) 
    {
        e.printStackTrace();
    }

    // Use our own list adapter
    listView = (ListView)findViewById(android.R.id.list);
    //listView.setAdapter((ListAdapter) new ArrayAdapter<String>(this,R.layout.list_item,R.id.title,titles));
    PostersArrayAdapter postersAdapter = new PostersArrayAdapter(this, posters);
    Log.d("PostersListActivity.onCreate()","Number of elementes in the data set of the adapter is " + postersAdapter.getCount());
    listView.setAdapter(postersAdapter);
}


public class PostersArrayAdapter extends ArrayAdapter<PosterData> {
    private final Activity context;
    private final PosterData[] posters;

    public PostersArrayAdapter(Activity context, PosterData[] posters) {
        super(context, R.layout.list_item);
        this.context = context;
        this.posters = posters;
    }

    // static to save the reference to the outer class and to avoid access to
    // any members of the containing class
    class ViewHolder {
        public ImageView logo;
        public TextView  title;
        public TextView  names;
    }

    @Override
    public View getView(int position, View convertView, ViewGroup parent) {
        // ViewHolder will buffer the assess to the individual fields of the row
        // layout

        ViewHolder holder;
        // Recycle existing view if passed as parameter
        // This will save memory and time on Android
        // This only works if the base layout for all classes are the same
        View rowView = convertView;
        if (rowView == null) 
        {
            LayoutInflater inflater = context.getLayoutInflater();
            rowView = inflater.inflate(R.layout.list_item, null, true);
            holder = new ViewHolder();
            holder.title = (TextView) rowView.findViewById(R.id.title);
            holder.names = (TextView) rowView.findViewById(R.id.names);
            holder.logo = (ImageView) rowView.findViewById(R.id.logo);
            rowView.setTag(holder);
        } 
        else 
        {
            holder = (ViewHolder) rowView.getTag();
        }

        holder.title.setText(posters[position].getTitle());
        holder.names.setText(posters[position].getNames());
        holder.logo.setImageResource(R.drawable.icon);

        return rowView;
    }
}   
}

这是我正在使用的 ListView 布局:

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:orientation="vertical"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent">
    <TextView android:id="@+id/textView1" 
        android:textAppearance="?android:attr/textAppearanceLarge" 
        android:layout_height="wrap_content" 
        android:layout_width="wrap_content" 
        android:text="@string/selectPoster" 
        android:layout_gravity="center_horizontal">
    </TextView>
    <ListView android:id="@android:id/list" 
        android:layout_height="wrap_content"  
        android:layout_width="match_parent">
    </ListView>
</LinearLayout>

这是我正在使用的列表元素布局:

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="wrap_content" android:layout_height="wrap_content">

    <LinearLayout android:id="@+id/linearLayout1"
        android:layout_height="match_parent" 
        android:layout_width="wrap_content" >

        <ImageView android:id="@+id/logo" 
            android:src="@drawable/icon" 
            android:layout_height="wrap_content"            
            android:layout_width="22px"
            android:layout_marginTop="4px" 
            android:layout_marginRight="4px"
            android:layout_marginLeft="4px">
        </ImageView>

        <LinearLayout android:id="@+id/linearLayout2" 
            android:layout_height="match_parent" 
            android:layout_width="fill_parent" 
            android:orientation="vertical">
            <TextView android:id="@+id/title"
                android:text="TextView" 
                android:layout_width="wrap_content"
                android:layout_height="wrap_content" 
                android:textSize="30px">
            </TextView>
            <TextView android:id="@+id/names"  
                android:text="TextView"             
                android:layout_width="wrap_content" 
                android:layout_height="wrap_content">
            </TextView>             
        </LinearLayout>

    </LinearLayout>
</LinearLayout>

Answer 1

确保 getCount() 已正确实现，因此:

     @Override
     public int getCount(){
           return posters!=null ? posters.length : 0;
     }

编辑:通过调用

   ArrayAdapter(Context context, int textViewResourceId)

构造函数您没有将对象数组传递给构造函数。

你应该调用

   ArrayAdapter(Context context, int textViewResourceId, T[] objects)

构造函数也将对象数组作为参数。