android代码中的可扩展listview

Question

**我想在我的android代码片段中添加一个可扩展的列表视图，但我无法做到。我也在这个网站上看到了所有与这个主题相关的帖子，但我找不到一个好的答案。有人能帮忙吗？？**

HMCfragment.java
public class HMCfragment extends Fragment {
View rootView;
ExpandableListView lv;
 private String[] groups;
private String[][] children;
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
 groups = new String[] { "Test Header 1", "Test Header 2", "Test Header 3", "Test Header 4" };
 children = new String [][] {{"Debashish Dutta"},{"Deepok Baruah"},{"Rajan Kumar"},{"Aditya         Patel"},{"Piyush dwivedi"}};
rootView = inflater.inflate(R.layout.hmc_layout, container, false);  
return rootView;
}
@Override
public void onViewCreated(View view, Bundle savedInstanceState) {
super.onViewCreated(view, savedInstanceState);
lv = (ExpandableListView) view.findViewById(R.id.expandableListView1);
lv.setAdapter(new ExpandableListAdapter(groups, children));
lv.setGroupIndicator(null);
}
public class ExpandableListAdapter extends BaseExpandableListAdapter {
private final LayoutInflater inf;
private String[] groups;
private String[][] children;
public ExpandableListAdapter(String[] groups, String[][] children) {
    this.groups = groups;
    this.children = children;
    inf = LayoutInflater.from(getActivity());
}
@Override
public int getGroupCount() {
    return groups.length;
}
@Override
public int getChildrenCount(int groupPosition) {
    return children[groupPosition].length;
}
@Override
public Object getGroup(int groupPosition) {
    return groups[groupPosition];
}
@Override
public Object getChild(int groupPosition, int childPosition) {
    return children[groupPosition][childPosition];
}
@Override
public long getGroupId(int groupPosition) {
    return groupPosition;
}
@Override
public long getChildId(int groupPosition, int childPosition) {
    return childPosition;
}
@Override
public boolean hasStableIds() {
    return true;
}
@Override
public View getChildView(int groupPosition, final int childPosition, boolean isLastChild, View convertView, ViewGroup parent) {
     ViewHolder holder;
        if (convertView == null) {
            convertView = inf.inflate(R.layout.child_layout, parent, false);
            holder = new ViewHolder();
            holder.text = (TextView) convertView.findViewById(R.id.textView1);
            convertView.setTag(holder);
        } else {
            holder = (ViewHolder) convertView.getTag();
        }
        holder.text.setText(getChild(groupPosition, childPosition).toString());
        return convertView;
}
@Override
public View getGroupView(int groupPosition, boolean isExpanded, View convertView, ViewGroup parent) {
    ViewHolder holder;
    if (convertView == null) {
        convertView = inf.inflate(R.layout.parent_layout, parent, false);
        holder = new ViewHolder();
        holder.text = (TextView) convertView.findViewById(R.id.parent_txt);
        convertView.setTag(holder);
    } else {
        holder = (ViewHolder) convertView.getTag();
    }
    holder.text.setText(getGroup(groupPosition).toString());
    return convertView;
}
@Override
public boolean isChildSelectable(int groupPosition, int childPosition) {
    return true;
}
private class ViewHolder {
    TextView text;
}

}}

Answer 1

这是我创建的项目；

MyActivity.java

public class MyActivity extends Activity {
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_my);
        if (savedInstanceState == null) {
            getFragmentManager().beginTransaction()
                .add(R.id.container, new PlaceholderFragment())
                .commit();
        }
    }
    /**
     * A placeholder fragment containing a simple view.
     */
    public static class PlaceholderFragment extends Fragment {
        public PlaceholderFragment() {
        }
        View rootView;
        ExpandableListView lv;
        private String[] groups;
        private String[][] children;
        @Override
        public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
            groups = new String[]{"Test Header 1", "Test Header 2", "Test Header 3", "Test Header 4"};
            children = new String[][]{{"Debashish Dutta"}, {"Deepok Baruah"}, {"Rajan Kumar"}, {"Aditya         Patel"}, {"Piyush dwivedi"}};
            rootView = inflater.inflate(R.layout.fragment_my, container, false);
            return rootView;
        }
        @Override
        public void onViewCreated(View view, Bundle savedInstanceState) {
            super.onViewCreated(view, savedInstanceState);
            lv = (ExpandableListView) view.findViewById(R.id.exp);
            lv.setAdapter(new ExpandableListAdapter(groups, children));
            lv.setGroupIndicator(null);
        }
        public class ExpandableListAdapter extends BaseExpandableListAdapter {
            private final LayoutInflater inf;
            private String[] groups;
            private String[][] children;
            public ExpandableListAdapter(String[] groups, String[][] children) {
                this.groups = groups;
                this.children = children;
                inf = LayoutInflater.from(getActivity());
            }
            @Override
            public int getGroupCount() {
                return groups.length;
            }
            @Override
            public int getChildrenCount(int groupPosition) {
                return children[groupPosition].length;
            }
            @Override
            public Object getGroup(int groupPosition) {
                return groups[groupPosition];
            }
            @Override
            public Object getChild(int groupPosition, int childPosition) {
                return children[groupPosition][childPosition];
            }
            @Override
            public long getGroupId(int groupPosition) {
                return groupPosition;
            }
            @Override
            public long getChildId(int groupPosition, int childPosition) {
                return childPosition;
            }
            @Override
            public boolean hasStableIds() {
                return true;
            }
            @Override
            public View getChildView(int groupPosition, final int childPosition, boolean isLastChild, View convertView, ViewGroup parent) {
                ViewHolder holder;
                if (convertView == null) {
                    convertView = inf.inflate(R.layout.child_layout, parent, false);
                    holder = new ViewHolder();
                    holder.text = (TextView) convertView.findViewById(R.id.textView);
                    convertView.setTag(holder);
                } else {
                    holder = (ViewHolder) convertView.getTag();
                }
                holder.text.setText(getChild(groupPosition, childPosition).toString());
                return convertView;
            }
            @Override
            public View getGroupView(int groupPosition, boolean isExpanded, View convertView, ViewGroup parent) {
                ViewHolder holder;
                if (convertView == null) {
                    convertView = inf.inflate(R.layout.parent_layout, parent, false);
                    holder = new ViewHolder();
                    holder.text = (TextView) convertView.findViewById(R.id.textView);
                    convertView.setTag(holder);
                } else {
                    holder = (ViewHolder) convertView.getTag();
                }
                holder.text.setText(getGroup(groupPosition).toString());
                return convertView;
            }
            @Override
            public boolean isChildSelectable(int groupPosition, int childPosition) {
                return true;
            }
            private class ViewHolder {
                TextView text;
            }
        }
    }
}

fragment_my.xml

<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"
    android:paddingLeft="@dimen/activity_horizontal_margin"
    android:paddingRight="@dimen/activity_horizontal_margin"
    android:paddingTop="@dimen/activity_vertical_margin"
    android:paddingBottom="@dimen/activity_vertical_margin"
    tools:context=".MyActivity$PlaceholderFragment">
    <ExpandableListView
        android:id="@+id/exp"
        android:layout_width="match_parent"
        android:layout_height="match_parent"/>
</RelativeLayout>

child_layout.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:orientation="vertical" android:layout_width="match_parent"
    android:layout_height="match_parent">
    <TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="New Text"
        android:id="@+id/textView"
        android:layout_gravity="center_horizontal" />
</LinearLayout>

parent_layout.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:orientation="vertical" android:layout_width="match_parent"
    android:layout_height="match_parent">
    <TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="New Text"
        android:id="@+id/textView"
        android:layout_gravity="center_horizontal" />
</LinearLayout>