Question

在我的Android应用中，我正在尝试构建我的第一个自定义listadapter。我现在设法让它显示一个项目，但遗憾的是只有列表中有8个项目的一个项目。我的适配器看起来像这样：

public class PossibilitiesAdapter extends BaseAdapter {
    private AdapterCallbacks callbacks;
    private List<String> possibilitiesList = new ArrayList<String>();
    private LayoutInflater inflater;

    public PossibilitiesAdapter(Context context) {
        inflater = (LayoutInflater) context.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
    }

    public void setPossibilitiesList(List<String> possibilitiesList) {
        for (String possibility : possibilitiesList) {
            addItem(possibility);
        }
    }

    public void addItem (final String item) {
        possibilitiesList.add(item);
        notifyDataSetChanged();
    }

    private class ViewHolder {
        TextView possibilityTitle;
    }

    @Override
    public View getView(final int position, View convertView, ViewGroup viewGroup) {
        ViewHolder holder = new ViewHolder();
        convertView = inflater.inflate(R.layout.list_item_posibility, viewGroup, false);
        holder.possibilityTitle = (TextView) convertView.findViewById(R.id.text_possibility);
        holder.possibilityTitle.setText(possibilitiesList.get(position));

        return convertView;
    }

    @Override
    public int getCount() {
        return possibilitiesList.size();
    }
    // And here are some more things like getItemId() and getItem()
}

我从我的片段中设置了possibilitiesList，如下所示：

List<String> list = Arrays.asList(getResources().getStringArray(R.array.the_possibilities));
Log.e(this, new Integer(list.size()).toString()); // Outputs 8, so there are enough in the array.
adapter.setPossibilitiesList(list);

我的fragment_possibilities.xml如下所示：

<ListView
    android:id="@+id/list_possibilities"
    android:layout_width="match_parent"
    android:layout_height="match_parent"/>

和我的list_item_possibility.xml：

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

    <TextView
        android:id="@+id/text_possibility"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content" />

</LinearLayout>

所以问题是它只显示第一个项目，仅此而已。有谁知道问题是什么以及如何解决它？

Answer 1

您是否将列表嵌套在ScrollView中？它通常表现为只显示一个项目。尽量避免使用以下方法。

/**
 * read all adapter views and calculate total length
 *
 * @param listView
 */
public static void setListViewHeightBasedOnChildren(ListView listView) {
    ListAdapter listAdapter = listView.getAdapter();
    if (listAdapter == null) {
        return;
    }

    int totalHeight = 0;
    int desiredWidth = MeasureSpec.makeMeasureSpec(listView.getWidth(), MeasureSpec.AT_MOST);
    for (int i = 0; i < listAdapter.getCount(); i++) {
        View listItem = listAdapter.getView(i, null, listView);
        listItem.measure(desiredWidth, MeasureSpec.UNSPECIFIED);
        totalHeight += listItem.getMeasuredHeight();
    }

    setListViewHeight(listView, totalHeight);
}

/**
 * set listview height
 *
 * @param listView
 * @param height
 */
public static void setListViewHeight(ListView listView, int height) {
    ViewGroup.LayoutParams params = listView.getLayoutParams();
    params.height = height + (listView.getDividerHeight() * (listView.getAdapter().getCount() - 1));
    listView.setLayoutParams(params);
    listView.requestLayout();
}

不，这不会起作用，正如我所说，你不能把一个ListView放在ScrollView里面。

试试这个：

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical">
<ListView
    android:id="@+id/list_possibilities"
    android:layout_width="match_parent"
    android:layout_height="match_parent" />
</LinearLayout>

Answer 2

你的getView方法实现错误，更确切地说是视图持有者模式。我猜你看到了相同数量的条目，但都有相同的内容

试试这个：

@Override
public View getView(final int position, View convertView, ViewGroup viewGroup) {
    ViewHolder holder = null;
    if (convertView == null) {
        convertView = inflater.inflate(R.layout.list_item_posibility, viewGroup, false);
        holder = new Holder();
        holder.possibilityTitle = (TextView) convertView.findViewById(R.id.text_possibility);
            convertView.setTag(holder);
    } else {
        holder = (ViewHolder)convertView.getTag();
    }

    holder.possibilityTitle.setText(possibilitiesList.get(position));

    return convertView;
}

并且我认为你的setPossibilitesMethod看起来很奇怪。 id可能使用类似这样的东西

public void setPossibilitiesList(List<String> possibilitiesList) {
    this.possibilitiesList = possibilitiesList;
    notifyDataSetChanged();
}

public void addItem (final String item) {
    possibilitiesList.add(item);
    notifyDataSetChanged();
}

public void addItems (List<String> possibilitiesList) {
    this.possibilitiesList.addAll(possibilitiesList);
    notifyDataSetChanged();
}

您可以缩短检索inflaterService的代码，如下所示：

public PossibilitiesAdapter(Context context) {
    inflater = LayoutInflater.fromContext(context);
}

此外你没有必要施展它

<强>更新

@Override
public int getCount(){
    for (String possibility : this.possibilities){
        System.out.println(possibility);
    }
    int size = this.possibilities();
    System.out.println("getCount: " + size);
    return size;
}

Answer 3

更改方法addItem并从那里删除notify，在metghod setList中为for后添加notify

Answer 4

最可能的情况是，当您执行possibilitiesList.size()方法时，您将getCount()作为 1 。打印日志以检查值。

为什么我的Android ListAdapter只显示一个项目？

4 个答案: