ListView 与 ArrayAdapter 和 ViewHolder 将图标添加到错误的项目

Question

我有一个动态的ListView，它使用ArrayAdapter。当从微调器中选择一个名字时，该名字连同一个显示他们是男性还是女性的图标被添加到ListView。

大多数情况下一切都很好（名称被正确添加到列表中，并带有一个图标）。但是显示性别的图标被添加到ListView 中的错误项目中。该名称被添加到列表的底部，但图标被放置在列表顶部的名称处。我不知道这是否是我使用ViewHolder 的方式，但Android website 中的文档为零。

// Listview inflater
inflater = (LayoutInflater) (this).getSystemService(LAYOUT_INFLATER_SERVICE);

// List Array.
mAdapter = new ArrayAdapter<String>(this, R.layout.player_simple_list, 
                                                 R.id.label, mStrings) {

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

        Log.i("ANDY","View getView Called");
        // A ViewHolder keeps references to children views to 
        // avoid unneccessary calls to findViewById() on each row.
        ViewHolder holder;

        if (null == convertView) {
            Log.i("ANDY","Position not previously used, so inflating");
            convertView = inflater.inflate(R.layout.player_simple_list, null);
            // Creates a ViewHolder and store references to the
            // two children views we want to bind data to.
            holder = new ViewHolder();
            holder.text = (TextView) convertView.findViewById(R.id.label);
            holder.icon = (ImageView) convertView.findViewById(R.id.icon);
            if (sexmale == true) {
                holder.icon.setImageBitmap(maleicon);
            }
            else {
                holder.icon.setImageBitmap(femaleicon);
            }
            convertView.setTag(holder);
        } else {
            // Get the ViewHolder back to get fast access to the TextView
            // and the ImageView.
            holder = (ViewHolder) convertView.getTag();

        }
        // Bind the data efficiently with the holder.
        holder.text.setText(getItem(position));
        // Change icon depending is the sexmale variable is true or false.
        Log.i("ANDY","getCount = "+mAdapter.getCount());
        return convertView;
    }
};
setListAdapter(mAdapter);

Answer 1

您必须在if-else-if 之后设置图标才能创建或绑定holder。否则，图标只会正确显示在列表的前几个项目中，即直到 ListView 未被填充。

public View getView(int position, View convertView, ViewGroup parent) {

    Log.i("ANDY","View getView Called");
    // A ViewHolder keeps references to children views
    // to avoid unneccessary calls to findViewById() on each row.
    ViewHolder holder;

        if (null == convertView) {
            Log.i("ANDY","Position not previously used, so inflating");
            convertView = inflater.inflate(R.layout.player_simple_list, null);

            // Creates a ViewHolder and store references to
            // the two children views we want to bind data to.
            holder = new ViewHolder();
            holder.text = (TextView) convertView.findViewById(R.id.label);
            holder.icon = (ImageView) convertView.findViewById(R.id.icon);
            convertView.setTag(holder);
        } else {
            // Get the ViewHolder back to get fast access to the TextView
            // and the ImageView.
            holder = (ViewHolder) convertView.getTag();

        }
        // Bind the data efficiently with the holder.
        holder.text.setText(getItem(position));

        // Change icon depending is the sexmale variable is true or false.
        if (sexmale == true) {
            holder.icon.setImageBitmap(maleicon);
        }
        else {
            holder.icon.setImageBitmap(femaleicon);
        }
        Log.i("ANDY","getCount = "+mAdapter.getCount());
        return convertView;
}

Answer 2

你必须在注释后从 if 中移出几行数据，如question is explained

// Bind the data efficiently with the holder.

所以它看起来像这样

if (null == convertView) {
    Log.i("ANDY","Position not previously used, so inflating");
    convertView = inflater.inflate(R.layout.player_simple_list, null);
    // Creates a ViewHolder and store references to the two children views
    // we want to bind data to.
    holder = new ViewHolder();
    convertView.setTag(holder);
} else {
    // Get the ViewHolder back to get fast access to the TextView
    // and the ImageView.
    holder = (ViewHolder) convertView.getTag();
}

// Bind the data efficiently with the holder.
holder.text = (TextView) convertView.findViewById(R.id.label);
holder.icon = (ImageView) convertView.findViewById(R.id.icon);
if (sexmale == true) {
    holder.icon.setImageBitmap(maleicon);
}
else {
    holder.icon.setImageBitmap(femaleicon);
}
holder.text.setText(getItem(position));

Answer 3

更新： ViewHolder 仅用于保存对项目布局内的组件视图的引用。这有助于避免调用 findViewById 以在具有多个组件的复杂项目布局中渲染每个组件的开销（如本例中的 TextView 和 ImageView）。

我通过使用例程（称为getSex）来检索性数据并设置所有视图数据（包括if-else 块之外的图标）来修复它。

现在的工作代码如下所示：

if (null == convertView) {
    Log.i("ANDY","Position not previously used, so inflating");
    convertView = inflater.inflate(R.layout.player_simple_list, null);

    // Creates a ViewHolder and store references to the two children views
    // we want to bind data to.
    holder = new ViewHolder();
    holder.text = (TextView) convertView.findViewById(R.id.label);
    holder.icon = (ImageView) convertView.findViewById(R.id.icon);
    convertView.setTag(holder);
} else {
    // Get the ViewHolder back to get fast access to the TextView
    // and the ImageView.
    holder = (ViewHolder) convertView.getTag();
}

// Bind the data efficiently with the holder.
holder.text.setText(getItem(position));
// Change icon depending is the sexmale variable is true or false.
if (getSex (getItem(position)) == true)  {
    holder.icon.setImageBitmap(maleicon);
}
else {
    holder.icon.setImageBitmap(femaleicon);
}
return convertView;