Android:不确定为什么我的 ListView 变得困惑？

Question

我实现了一个可以正常工作的 ListView，直到我添加了超过 5 个项目和 2 个标题。我不完全确定为什么有些项目没有出现而其他项目多次出现。解决此问题的任何帮助将不胜感激。代码包含在下面。

工具箱.java

public class Toolbox extends Fragment {
    private ListView lstView;
    private View rootView;
    List<Tools> tools;

    public static Toolbox newInstance(Context context) {
        Toolbox fragment = new Toolbox();
        return fragment;
    }

    public Toolbox() {
        // Required empty public constructor
    }

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

    }

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
                             Bundle savedInstanceState) {
        // Inflate the layout for this fragment
        ((MainActivity) getActivity()).setActionBarTitle("Technical Toolbox");
        rootView = inflater.inflate(R.layout.fragment_toolbox, container, false);
        lstView =(ListView) rootView.findViewById(R.id.list);
        final FragmentActivity c = getActivity();
        //final RecyclerView recyclerView = (RecyclerView) recView.findViewById(R.id.reView);


        setToolBoxData();
        setToolBoxAdapter();
        return rootView;
    }

    private void setToolBoxAdapter() {
        ListArrayAdapter adapter = new ListArrayAdapter(getActivity(),tools);
        lstView.setAdapter(adapter);
    }

    private void setToolBoxData(){
        tools=new ArrayList<>();
        tools.add(new Header("Languages"));
        tools.add(new ListItem("Android",R.drawable.ic_android));
        tools.add(new ListItem("XML", R.drawable.ic_xml));
        tools.add(new ListItem("Java",R.drawable.ic_java));
        tools.add(new ListItem("JavaScript", R.drawable.ic_javascript));
        tools.add(new ListItem("C++", R.drawable.ic_cpp));
        tools.add(new ListItem("Visual Basic", R.drawable.ic_vb));
        tools.add(new ListItem("HTML", R.drawable.ic_html));
        tools.add(new ListItem("CSS", R.drawable.ic_css));
        tools.add(new Header("Source Control"));
        tools.add(new ListItem("Git", R.drawable.ic_git));
        tools.add(new ListItem("GitHub", R.drawable.ic_github_cat));
        tools.add(new ListItem("SourceTree", R.drawable.ic_sourcetree));
        tools.add(new ListItem("BitBucket", R.drawable.ic_bitbucket));
        tools.add(new Header("DataBase"));
        tools.add(new ListItem("Parse", R.drawable.ic_parse));
        tools.add(new ListItem("MS Access", R.drawable.ic_access));
        tools.add(new ListItem("SQL", R.drawable.ic_sql));
        tools.add(new Header("Design & IDE Tools"));
        tools.add(new ListItem("Android Studio", R.drawable.ic_androidstudio));
        tools.add(new ListItem("Visual Studio", R.drawable.ic_visual_studio));
        tools.add(new ListItem("Genymotion", R.drawable.ic_genymotion));
        tools.add(new ListItem("Ionic", R.drawable.ic_ionic));
        tools.add(new Header("Office Tools"));
        tools.add(new ListItem("MS Project", R.drawable.ic_project));
        tools.add(new ListItem("MS Visio", R.drawable.ic_visio));
        tools.add(new ListItem("MS Excel", R.drawable.ic_excel));
        tools.add(new ListItem("MS Word", R.drawable.ic_word));
    }
}

ListArrayAdapter.java

public class ListArrayAdapter extends ArrayAdapter<Tools> {
    private LayoutInflater mInflater;

    public enum RowType{ LIST_ITEM, HEADER_ITEM }

    public ListArrayAdapter(Context context, List<Tools> tools){
        super(context, 0, tools);
        mInflater = LayoutInflater.from(context);
    }

    @Override
    public int getViewTypeCount(){return RowType.values().length;}

    @Override
    public int getItemViewType(int pos){return getItem(pos).getViewType();}

    private static final int TYPE_ITEM = 0;
    private static final int TYPE_SEPARATOR = 1;

    public View getView(int position, View convertView, ViewGroup parent)  {
        ViewHolder holder = null;
        int rowType = getItemViewType(position);
        View View;
        if (convertView == null) {
            holder = new ViewHolder();
            switch (rowType) {
                case TYPE_ITEM:
                    convertView = mInflater.inflate(R.layout.listview_item, null);
                    holder.View=getItem(position).getView(mInflater, convertView);
                    break;
                case TYPE_SEPARATOR:
                    convertView = mInflater.inflate(R.layout.list_title, null);
                    holder.View=getItem(position).getView(mInflater, convertView);
                    break;
            }
            convertView.setTag(holder);
        }
        else
        {
            holder = (ViewHolder) convertView.getTag();
        }
        return convertView;
    }

    public static class ViewHolder {
        public  View View;
    }
}

工具.java

public interface Tools {
    public int getViewType();
    public View getView(LayoutInflater inflater, View convertView);
}

列表项.java

public class ListItem implements Tools {
    private final String str1;
    private final int pic1;

    public ListItem(String text1, int pic1) {
        this.str1 = text1;
        this.pic1 = pic1;
    }

    @Override
    public int getViewType() {
        return ListArrayAdapter.RowType.LIST_ITEM.ordinal();
    }

    @Override
    public View getView(LayoutInflater inflater, View convertView) {
        View view;
        if (convertView == null) {
            view = (View) inflater.inflate(R.layout.listview_item, null);
            // Do some initialization
        } else {
            view = convertView;
        }

        TextView text1 = (TextView) view.findViewById(R.id.listText);
        ImageView picture1 = (ImageView) view.findViewById(R.id.listIcon);
        text1.setText(str1);
        picture1.setImageResource(pic1);

        return view;
    }
}

头文件.java

public class Header implements Tools {
    private final String         name;

    public Header(String name) {
        this.name = name;
    }

    @Override
    public int getViewType() {
        return ListArrayAdapter.RowType.HEADER_ITEM.ordinal();
    }

    @Override
    public View getView(LayoutInflater inflater, View convertView) {
        View view;
        if (convertView == null) {
            view = (View) inflater.inflate(R.layout.header, null);
            // Do some initialization
        } else {
            view = convertView;
        }

        TextView text = (TextView) view.findViewById(R.id.separator);
        text.setText(name);

        return view;
    }
}

Answer 1

简要背景:

实际上，我今天遇到了同样的错误。正如所描述的那样，我也完成了 90-95% 的相同实现。但是我也看到了这个问答线程的公认答案。但我不能同意你的看法!因此，我搜索并搜索了为什么我的更简单的 ArrayAdapter 实现无法正常工作。在第一次它加载好的。但是在我滚动一次之后不久？所有类型的行都乱七八糟!

总结答案:
阅读 Android Developer Doc有关更多信息，您可能会直接找到线索。要为 ListView 的行实现多种类型的 Views，我们必须从根本上实现 getItemViewType() 和 getViewTypeCount()方法。并且 getItemViewType() 文档给了我们如下注释:

Note: Integers must be in the range 0 to getViewTypeCount() - 1. IGNORE_ITEM_VIEW_TYPE can also be returned.

因此，在您的 getItemViewType() 中，您应该返回 View 类型的值，从 0 开始，到最后一个类型为(类型数量 - 1)。例如，假设您只有两种类型的 View ？因此，根据 View 的数据对象，您只能在 getItemViewType() 方法中返回 0 或 1。

如果您没有得到线索或仍然无法解决并需要更多信息，请阅读下面的内容:

详细说明:

According to the Android Developer Documentation or the API Doc, it has mentioned that in order to implement multiple types of views within ListView adapter, we have to implement the following methods:

public int getItemViewType (int position)
public int getViewTypeCount ()

And out of the above two methods, getItemViewType is essential in our case (where we have multiple view types). That's true right? So what?

That's where me and @8BitYoda has gone wrong. The OP's wrong thing was he had defined an Enum where it doesn't give types as range of integers within the range of 0 to (getViewTypeCount() - 1).

我所做的是，我定义了如下类型:

private static final int TYPE_ITEM = 1;
private static final int TYPE_ITEM = 2;

而一开始我还没有实现，getViewTypeCount()，所以我实现如下:

public int getViewTypeCount() {
      return 2;
}

然后在我运行该应用程序并尝试使用 ListView 加载该 View 后不久，它崩溃了，并出现以下异常:

java.lang.ArrayIndexOutOfBoundsException: length=2; index=2 at android.widget.AbsListView$RecycleBin.addScrapView(AbsListView.java:6643) at android.widget.ListView.measureHeightOfChildren(ListView.java:1292) at android.widget.ListView.onMeasure(ListView.java:1188) :
:
:
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:616)

说什么？ :O

它间接表示它与我从方法 getViewTypeCount() 返回的整数相关，因为我返回 2。我返回 2 是因为我只有两种类型。所以我回到 Android 文档寻求最后的帮助。通过阅读与我实现的方法相关的文档，它确实帮助了我并解决了我的问题。

快速捕捉，看看下面的图片:

With a tiny little font, it has given a NOTE for us.

getItemViewType (int position) 方法的注释是什么意思？

Note: Integers must be in the range 0 to getViewTypeCount() - 1. IGNORE_ITEM_VIEW_TYPE can also be returned.

所以在看到这个之后我明白我需要重新分配我发送的 type integers 从 0 到我拥有的任何类型的数量，比如从零开始的数组索引。所以我重新纠正了这两行，之后它就像一个魅力!

private static final int TYPE_ITEM = 0;
private static final int TYPE_ITEM = 1;

抱歉，我知道我的回答比我预期的要长一些，几乎就像一个迷你教程。但对我来说没关系，我花了大约一个多小时来写这篇文章，因为我要花大约 5 个小时来弄清楚这个愚蠢的错误。谁认为类型应该从 0 开始分配，例如基于 0 的数组索引？

所以我希望我的回答可能对解决此错误的人有所帮助。

干杯!!!