Android：了解可扩展列表

Question

我是Android的新手。我想了解使用自定义适配器的Expandable ListView实现。有人请向我解释这个代码，以便我能够操纵它。我有一些问题，比如为什么变量'groupStatus'被视为数组变量，我们只是将textview放在可扩展列表的子节点中等等。提前感谢。

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

  

Android中的ExpandableListView

     

此Android可展开列表视图需要三个布局文件;一个   显示包含ExpandableListView的主布局，一个用于   子项目布局和其他子项目布局。

     

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

     

根据您的要求，您需要在子视图中使用按钮和textview

<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>

  

每个子项包含一个TextView以显示文本和一个按钮   删除项目。

     

现在让我们创建一个ExpandableListAdapter.java类

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;
    }

}