android – 如何将Viewholder与ExpandableListView一起使用？
作者：互联网
我正在尝试在我的应用程序中创建一个ExpandableListView.它有两组：第一组是颜色,第二组是符号.点击的第一组工作正常.但是,第二组显示第一组中的行(如果第二组中有更多项,那么’额外’将是正确的).
例如,我们说’颜色’是白色,黑色,红色和蓝色,符号是’/’和’.’.
如果我启动活动并单击颜色,则它们会正确显示.如果我然后点击“符号”,我会看到白色和黑色.
如果我先点击’符号’,然后我会看到’/’和’.’,但是当我点击颜色时,我会看到’/’,’.’,红色,蓝色.
我在网上搜索并确定我需要使用ViewHolders以避免在我更改组时重复使用相同的视图.我虽然无法实现它.起初它没有任何区别,当我点击第二组时,当前版本崩溃了.我认为问题的一部分是我为每个组设置了不同的子布局(即符号的显示方式与颜色不同).
目前这就是我所拥有的(我已经展示了我认为的相关内容;如果我遗漏了任何重要内容,我可以添加它)：
public class ColourSymbolKeyAdapter extends BaseExpandableListAdapter {
private Context context;
private HashMap<String, List<KeyItem>> childDataSource;
private List<String> parentDataSource;
public ColourSymbolKeyAdapter(Context context,
List<String> childParent,
HashMap<String, List<KeyItem>> child) {
this.context = context;
this.parentDataSource = childParent;
this.childDataSource = child;
}
... Left out various override functions ...
@Override
public View getGroupView(int groupPosition, boolean isExpanded, View convertView, ViewGroup parent) {
View v = convertView;
GroupViewHolder holder;
if(v == null) {
LayoutInflater inflater =
(LayoutInflater) context.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
v = inflater.inflate(R.layout.expandablelist_parent, parent, false);
holder = new GroupViewHolder();
holder.mGroupName = (TextView) v.findViewById(R.id.textViewParent);
v.setTag(holder);
}else {
holder = (GroupViewHolder) v.getTag();
}
String parentHeader = (String) getGroup(groupPosition);
holder.mGroupName.setText(parentHeader);
return v;
}
@Override
public View getChildView(int groupPosition, int childPosition, boolean isLastChild, View convertView, ViewGroup parent) {
View row = convertView;
KeyItem childItem = (KeyItem) getChild(groupPosition, childPosition);
ColourViewHolder colourviewholder;
SymbolViewHolder symbolviewholder;
LayoutInflater inflater =
(LayoutInflater) context.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
if(childItem.getPatternColour() == null) { // This is a symbol row
if(row == null) {
symbolviewholder = new SymbolViewHolder();
row = inflater.inflate(R.layout.expandablelist_child_symbol, parent, false);
symbolviewholder.mChildName = (TextView) row.findViewById(R.id.symbol_desc);
symbolviewholder.mSymbolCell = (SymbolCell) row.findViewById(R.id.symbol_cell);
row.setTag(symbolviewholder);
}else {
symbolviewholder = (SymbolViewHolder) row.getTag();
}
String drawableName = childItem.getPatternSymbol().getDrawable();
final int resourceId = context.getResources().getIdentifier(drawableName, "drawable", context.getPackageName());
Drawable drawable;
if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.LOLLIPOP) {
drawable = context.getResources().getDrawable(resourceId, context.getTheme());
} else {
drawable = context.getResources().getDrawable(resourceId);
}
symbolviewholder.mSymbolCell.setDrawable(drawable);
symbolviewholder.mChildName.setText(childItem.getPatternSymbol().getSymbolDescription());
}else { // This is a colour row
if(row == null) {
colourviewholder = new ColourViewHolder();
row = inflater.inflate(R.layout.expandablelist_child_colour, parent, false);
colourviewholder.mChildName = (TextView) row.findViewById(R.id.colour_name);
colourviewholder.mChildDesc = (TextView) row.findViewById(R.id.colour_desc);
colourviewholder.mColourCell = (ColourCell) row.findViewById(R.id.colour_cell);
row.setTag(colourviewholder);
}else {
colourviewholder = (ColourViewHolder) row.getTag();
}
colourviewholder.mColourCell.setColour(childItem.getPatternColour());
colourviewholder.mChildName.setText(childItem.getPatternColour().getName());
colourviewholder.mChildDesc.setText(childItem.getPatternColour().getDescription());
}
return row;
}
public final class GroupViewHolder {
TextView mGroupName;
}
public final class ColourViewHolder {
ColourCell mColourCell;
TextView mChildName, mChildDesc;
}
public final class SymbolViewHolder {
SymbolCell mSymbolCell;
TextView mChildName;
}
}
父级布局(expandablelist_parent.xml)：
<?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:id="@+id/parentView">
<TextView xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:id="@+id/textViewParent"
android:textColor="#000000"
android:textAppearance="@style/ParagraphBold">
</TextView>
</LinearLayout>
颜色行的布局(expandablelist_child_colour.xml)：
<?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:padding="@dimen/small_padding"
android:id="@+id/childViewColour"
android:orientation="horizontal">
<com.myname.appname.ColourCell xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="@dimen/grid_cell_column_width"
android:layout_height="@dimen/grid_cell_column_width"
android:id="@+id/colour_cell"
android:layout_marginRight="@dimen/small_padding" />
<LinearLayout
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:orientation="vertical">
<TextView xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:textAppearance="@style/ParagraphBold"
android:textColor="@color/colorPrimaryDark"
android:id="@+id/colour_name">
</TextView>
<TextView xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:textAppearance="@style/Paragraph"
android:textColor="@color/colorPrimaryDark"
android:id="@+id/colour_desc">
</TextView>
</LinearLayout>
</LinearLayout>
对于符号行(expandablelist_child_symbol.xml)：
<?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:id="@+id/childViewSymbol"
android:padding="@dimen/small_padding">
<com.myname.appname.SymbolCell xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="@dimen/grid_cell_column_width"
android:layout_height="@dimen/grid_cell_column_width"
android:textAppearance="@style/Paragraph"
android:id="@+id/symbol_cell"
android:layout_marginRight="@dimen/small_padding" />
<TextView xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:textColor="@color/colorPrimaryDark"
android:id="@+id/symbol_desc">
</TextView>
</LinearLayout>
如果我先单击“颜色”组,然后单击“符号”组,它会在行上崩溃：symbolviewholder =(SymbolViewHolder)row.getTag().
解决方法:
由于您有2个不同的子布局,因此需要覆盖getChildTypeCount()和getChildType(),以便适配器将接收要重用的正确视图类型.否则,在某些情况下,在尝试检索ViewHolder时会出现ClassCastException.
@Override
public int getChildTypeCount() {
return 2;
}
@Override
public int getChildType(int groupPosition, int childPosition) {
KeyItem childItem = (KeyItem) getChild(groupPosition, childPosition);
return (childItem.getPatternColour() == null) ? 0 : 1;
}
有关详细信息,请参阅HeterogeneousExpandableList文档.
标签：android-viewholder,android,android-studio,expandablelistview 来源： https://codeday.me/bug/20190828/1756783.html