Android：理解Expandable List里面出来

Question

我是Android的新手。我想了解使用自定义适配器的Expandable ListView实现。有人请向我解释这段代码，以便我能够操纵它。我有一些问题想起，为什么变量'groupStatus'被视为一个数组变量，不能我们把textview放在可扩展列表的子节点等。在此先感谢。

public class ExpandableListAdapter extends BaseExpandableListAdapter { 

private Context mContext; 
private ExpandableListView mExpandableListView; 
private List<GroupEntity> mGroupCollection; 
private int[] groupStatus; 

public ExpandableListAdapter(Context pContext, ExpandableListView pExpandableListView, List<GroupEntity> pGroupCollection) { 
mContext = pContext; 
mGroupCollection = pGroupCollection; 
mExpandableListView = pExpandableListView; 
groupStatus = new int[mGroupCollection.size()]; 

setListEvent(); 
} 

private void setListEvent() { 

mExpandableListView.setOnGroupExpandListener(new OnGroupExpandListener() { 

@Override 
public void onGroupExpand(int arg0) { 
// TODO Auto-generated method stub 
groupStatus[arg0] = 1; 
} 
}); 

mExpandableListView.setOnGroupCollapseListener(new OnGroupCollapseListener() { 

@Override 
public void onGroupCollapse(int arg0) { 
// TODO Auto-generated method stub 
groupStatus[arg0] = 0; 
} 
}); 
} 

@Override 
public String getChild(int arg0, int arg1) { 
// TODO Auto-generated method stub 
return mGroupCollection.get(arg0).GroupItemCollection.get(arg1).Name; 
} 

@Override 
public long getChildId(int arg0, int arg1) { 
// TODO Auto-generated method stub 
return 0; 
} 

@Override 
public View getChildView(int arg0, int arg1, boolean arg2, View arg3, 
ViewGroup arg4) { 
// TODO Auto-generated method stub 

ChildHolder childHolder; 
if (arg3 == null) { 
arg3 = LayoutInflater.from(mContext).inflate(
R.layout.list_group_item, null); 

childHolder = new ChildHolder(); 

childHolder.title = (TextView) arg3.findViewById(R.id.item_title); 
arg3.setTag(childHolder); 
}else { 
childHolder = (ChildHolder) arg3.getTag(); 
} 

    childHolder.title.setText(mGroupCollection.get(arg0).GroupItemCollection.get(arg1).Name); 

return arg3; 
} 

@Override 
public int getChildrenCount(int arg0) { 
// TODO Auto-generated method stub 
return mGroupCollection.get(arg0).GroupItemCollection.size(); 
} 

@Override 
public Object getGroup(int arg0) { 
// TODO Auto-generated method stub 
return mGroupCollection.get(arg0); 
} 

@Override 
public int getGroupCount() { 
    // TODO Auto-generated method stub 
return mGroupCollection.size(); 
} 

@Override 
public long getGroupId(int arg0) { 
// TODO Auto-generated method stub 
return arg0; 
} 

@Override 
public View getGroupView(int arg0, boolean arg1, View arg2, ViewGroup arg3) { 
// TODO Auto-generated method stub 
GroupHolder groupHolder; 
if (arg2 == null) { 
arg2 = LayoutInflater.from(mContext).inflate(R.layout.list_group, 
null); 
groupHolder = new GroupHolder(); 
groupHolder.img = (ImageView) arg2.findViewById(R.id.tag_img); 
groupHolder.title = (TextView) arg2.findViewById(R.id.group_title); 
arg2.setTag(groupHolder); 
} else { 
groupHolder = (GroupHolder) arg2.getTag(); 
} 
if (groupStatus[arg0] == 0) { 
groupHolder.img.setImageResource(R.drawable.group_down); 
} else { 
groupHolder.img.setImageResource(R.drawable.group_up); 
} 
groupHolder.title.setText(mGroupCollection.get(arg0).Name); 

return arg2; 
} 

class GroupHolder { 
ImageView img; 
TextView title; 
} 

class ChildHolder { 
TextView title; 
} 

@Override 
public boolean hasStableIds() { 
// TODO Auto-generated method stub 
return true; 
} 

@Override 
public boolean isChildSelectable(int arg0, int arg1) { 
// TODO Auto-generated method stub 
return true; 
} 

} 

Answer 1

ExpandableListView Android中

这个Android的可扩展列表视图需要三个布局文件;一个用于 显示包含ExpandableListView的主布局，一个用于 组项目布局以及其他子项目布局。

activity_main.xml中

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android" 
    xmlns:tools="http://schemas.android.com/tools" 
    android:layout_width="match_parent" 
    android:layout_height="match_parent" 
    tools:context=".MainActivity" > 

    <ExpandableListView 
     android:id="@+id/my_list" 
     android:layout_width="match_parent" 
     android:layout_height="fill_parent" > 
    </ExpandableListView> 

</RelativeLayout> 

group_item.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:orientation="vertical" 
    android:padding="10dp" > 

    <TextView 
     android:id="@+id/group" 
     android:layout_width="wrap_content" 
     android:layout_height="wrap_content" 
     android:paddingLeft="25dp"/> 
</LinearLayout> 

child_item.xml

根据乌拉圭回合的要求ü需要一个按钮， TextView的儿童视图

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android" 
    android:layout_width="fill_parent" 
    android:layout_height="wrap_content" 
    android:padding="10dp" > 

    <TextView 
     android:id="@+id/child_text" 
     android:layout_width="wrap_content" 
     android:layout_height="wrap_content" 
     android:layout_alignParentLeft="true" 
     android:layout_centerVertical="true" 
     android:paddingLeft="25dp" 
     android:text="child_item" /> 

    <Button 
     android:id="@+id/button1" 
     style="?android:attr/buttonStyleSmall" 
     android:layout_width="wrap_content" 
     android:layout_height="wrap_content" 
     android:layout_alignParentTop="true" 
     android:layout_marginLeft="51dp" 
     android:layout_toRightOf="@+id/laptop" 
     android:text="Button" /> 

</RelativeLayout> 

每个子项都包含一个TextView的显示文字和一个按钮 删除项目。

现在，让我们做一个类ExpandableListAdapter.java

public class ExpandableListAdapter extends BaseExpandableListAdapter { 

    // Variable Declartion 
    private Activity context; 

    // 1st parameter is the name of Item 
    // 2nd parameter is the child's of that of particular Item 
    private Map<String, List<String>> itemCollections; 

    // here parameter is the name of Item 
    private List<String> item; 

    // here is the constructor 
    // here we just inilize the class variable with the variable you passed to 
    // this adapter 
    public ExpandableListAdapter(Activity context, List<String> item_names, 
      Map<String, List<String>> Collections) { 
     this.context = context; 
     this.itemCollections = Collections; 
     this.item = item_names; 
    } 

    // if we want to get any child Object from its position this method will 
    // provide the same . for example if i click 1st item in group1 and 1st item 
    // in its childlist then in this case method will be like getChild(1, 1); 
    @Override 
    public Object getChild(int groupPosition, int childPosition) { 
     // 1. we get the Actuall group clicked -> item.get(groupPosition) 
     // 2. we get the child of its -> 
     // item.get(groupPosition).get(childPosition) 
     // 3. we return it as object from its collection -> 
     // itemCollections.get(item.get(groupPosition)).get(childPosition); 
     return itemCollections.get(item.get(groupPosition)).get(childPosition); 
    } 

    // when the child item is clicked this method will be called and it's will 
    // return its id 
    @Override 
    public long getChildId(int groupPosition, int childPosition) { 
     return childPosition; 
    } 

    // here is where we put all data u passed to adapter to its view 
    @Override 
    public View getChildView(final int groupPosition, final int childPosition, 
      boolean isLastChild, View convertView, ViewGroup parent) { 

     LayoutInflater inflater = context.getLayoutInflater(); 

     // get the layout of child and convertView will hold its instance 
     if (convertView == null) { 
      convertView = inflater.inflate(R.layout.child_item, null); 
     } 

     // referance of textview in child layout 
     TextView item1 = (TextView) convertView.findViewById(R.id.child_text); 
     // referance of button in child layout 
     Button delete = (Button) convertView.findViewById(R.id.button1); 
     // on click of the button do whatever u want 
     delete.setOnClickListener(new View.OnClickListener() { 

      @Override 
      public void onClick(View v) { 

       // do whatever u want 
      } 
     }); 

     return convertView; 
    } 

    // here its provide the total child to be placed into particular group 
    @Override 
    public int getChildrenCount(int groupPosition) { 
     return itemCollections.get(item.get(groupPosition)).size(); 
    } 

    // here we provide the group object itself from its position 
    @Override 
    public Object getGroup(int groupPosition) { 
     return item.get(groupPosition); 
    } 

    // the size of group items 
    @Override 
    public int getGroupCount() { 
     return item.size(); 
    } 

    // provide id of group on which it is clicked 
    @Override 
    public long getGroupId(int groupPosition) { 
     return groupPosition; 
    } 

    @Override 
    public View getGroupView(int groupPosition, boolean isExpanded, 
      View convertView, ViewGroup parent) { 
     String itemName = (String) getGroup(groupPosition); 
     if (convertView == null) { 
      LayoutInflater infalInflater = (LayoutInflater) context 
        .getSystemService(Context.LAYOUT_INFLATER_SERVICE); 
      convertView = infalInflater.inflate(R.layout.group_item, null); 
     } 
     TextView item = (TextView) convertView.findViewById(R.id.group); 
     // here u can set data to item variable that is text view of group 
     // layout 
     return convertView; 
    } 

    @Override 
    public boolean hasStableIds() { 
     // TODO Auto-generated method stub 
     return false; 
    } 

    @Override 
    public boolean isChildSelectable(int groupPosition, int childPosition) { 
     // TODO Auto-generated method stub 
     return false; 
    } 

}