android - 如何在 BaseAdapter.getView 中为创建的 View 保持稳定的位置？

Question

在 BaseAdapter.getView() 中为已创建的 View 保留位置似乎是个问题。

在我的例子中，我创建了一个数据对象(-array)来保存 ListView 的所有数据。列表项分为三种类型:分隔符、带复选框的项目和带有可点击图像以打开对话框的项目。该数据将由定制的阵列适配器执行，始终具有单独的布局。为此，我使用了不同的取景器。创建不是问题，但如果回收商开始工作，所有索引/位置都会更改。但是我的数据基于那个指示。

我知道回收器是如何工作的，但程序员应该如何(在 hell )保持与其自己数据的关系？

在 stackoverflow.com 上，有些人问了同样的问题，答案是“覆盖 getItemViewType-Methode”。没问题，但如果位置总是变化，那也没什么用，对吧？

有人有解决方案吗？

问候皮埃尔

这是我的概念验证代码:

// *** Activity: onCreate()

...
ArrayList<DataObj> data = getData();

    final ListView list = (ListView)findViewById( R.id.listView1 );
    list.setAdapter( new PackedListAdapter( this, data ) );
...

// *** Activity: getData()

private ArrayList<DataObj> getData() {
ArrayList<DataObj> dataArr = new ArrayList<DataObj>();
DataObj dataset;
int i;

dataset = new DataObj();
dataset.setType( DataObj.TYPE_CATEGORY );
dataset.setItemText( "Category CheckItems" );
dataArr.add( dataset );

for ( i = 0; i < 5; i++ ) {
            dataset = new DataObj();
    dataset.setType( DataObj.TYPE_ITEM_CHECK );
    dataset.setItemText( "ItemCheck #" + i );
    dataArr.add( dataset );
}

dataset = new DataObj();
dataset.setType( DataObj.TYPE_CATEGORY );
dataset.setItemText( "Category DialogItems" );
dataArr.add( dataset );

for ( i = 0; i < 5; i++ ) {
     dataset = new DataObj();
    dataset.setType( DataObj.TYPE_ITEM_DLG );
    dataset.setItemText( "ItemDlg #" + i );
    dataArr.add( dataset );
}

return dataArr;
}

// *** Data-Object:

public class DataObj {
private int type = 1;
// further variables here (e.g. String text1 ) ...

public final static int TYPE_CATEGORY = 1;
public final static int TYPE_ITEM_CHECK = 2;
public final static int TYPE_ITEM_DLG = 3;

public void setType( int type ) { this.type = type; }
public int getType() { return type; }

// further setter/getter-methodes for variables here ...
}

// *** BaseAdapter:

public class PackedListAdapter extends BaseAdapter {

private static ArrayList<DataObj> mData;
private LayoutInflater mInflater;

PackedListAdapter( Context context, ArrayList<DataObj> data ) {
    mData = data;
    mInflater = LayoutInflater.from( context );
}

public int getCount() {
    return mData.size();
}

public Object getItem( int position ) {
    return mData.get( position );
}

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

public int getItemViewType( int position ) { 
    return mData.get( position ).getType();
}

public boolean hasStableIds() { return false; }

public int getViewTypeCount() { return 3; }

public View getView( int position, View convertView, ViewGroup parent ) {
    int type = this.getItemViewType( position );

    if ( convertView == null ) {
        switch ( type ) {
            case DataObj.TYPE_CATEGORY:
            {
                convertView = mInflater.inflate( R.layout.listcat, null );
                ViewHolderCat holder = new ViewHolderCat();
                // setting up data from mData(position) here
                convertView.setTag( holder );
                break;
            }
            case DataObj.TYPE_ITEM_CHECK:
            {
                convertView = mInflater.inflate( R.layout.listrow, null );
                ViewHolderItem holder = new ViewHolderItem();
                // setting up data from mData(position) here
                convertView.setTag( holder );
                break;
            }
            case DataObj.TYPE_ITEM_DLG:
            {
                convertView = mInflater.inflate( R.layout.listdlg, null );
                ViewHolderDlg holder = new ViewHolderDlg();
                // setting up data from mData(position) here
                convertView.setTag( holder );
                break;
            }
        }
    } else {
        switch ( type ) {
            case DataObj.TYPE_CATEGORY:
            {
                ViewHolderCat holder = (ViewHolderCat)convertView.getTag();
                // setting up data from mData(position) here
                break;
            }
            case DataObj.TYPE_ITEM_CHECK:
            {
                ViewHolderItem holder = (ViewHolderItem)convertView.getTag();
                // setting up data from mData(position) here
                break;
            }
            case DataObj.TYPE_ITEM_DLG:
            {
                ViewHolderDlg holder = (ViewHolderDlg)convertView.getTag();
                // setting up data from mData(position) here
                break;
            }
        }
    }

    return convertView;
}

public static class ViewHolderCat {
    public TextView txtCat;
}

public static class ViewHolderItem {
    public TextView txtItem;
    public TextView txtDescr;
    public ImageView imgCheckButton;
}

public static class ViewHolderDlg {
    public TextView txtItem;
    public TextView txtDescr;
    public ImageView imgDlgButton;
}

}

Answer 1

你应该覆盖 hasStableIds除了getItemViewType和 getViewTypeCount .这看起来像:

@Override
public boolean hasStableIds() {
    /* the view types for rows will change over time */
    return false;
}

@Override
public int getViewTypeCount() {
    return 3;
}

@Override
public int getItemViewType(int position) {
    /* calculate the view type for this row */
    return ... ;
}

我相信这会让框架知道它不应该根据项目 ID 进行缓存。