Android学习笔记_57_ExpandableListView控件应用

1、布局文件：

<?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" >



    <ExpandableListView

        android:id="@+id/elv"

        android:layout_width="match_parent"

        android:layout_height="match_parent" >

    </ExpandableListView>

</LinearLayout>

2、填充数据：与listview使用比较像

package cn.itcast.mobilesafe.ui;



import java.io.File;

import java.io.FileOutputStream;

import java.io.IOException;

import java.io.InputStream;



import cn.itcast.mobilesafe.R;

import android.annotation.SuppressLint;

import android.app.Activity;

import android.content.res.AssetManager;

import android.database.Cursor;

import android.database.sqlite.SQLiteDatabase;

import android.os.Bundle;

import android.os.Environment;

import android.view.View;

import android.view.ViewGroup;

import android.widget.BaseExpandableListAdapter;

import android.widget.ExpandableListView;

import android.widget.TextView;



public class CommonNumActivity extends Activity {

    private ExpandableListView elv;

    private BaseExpandableListAdapter adapter;



    @Override

    protected void onCreate(Bundle savedInstanceState) {

        // TODO Auto-generated method stub

        super.onCreate(savedInstanceState);

        setContentView(R.layout.common_num_query);

        elv = (ExpandableListView) this.findViewById(R.id.elv);



        // 判断这个commonnum.db的数据库是否被放置到了sd卡上

        // 如果不在sd卡上 要把db从asset目录拷贝到数据库

        File file = new File("/sdcard/commonnum.db");

        if (!file.exists()) {

            copyfile();

        }



        // listview 是怎么设置数据的?

        // lv.setAdapter(); ->BaseAdapter

        // elv.setAdapter ExpendAdapter ->BaseExpendAdapter



        elv.setAdapter(new MyAdapter());

    }



    

    private class MyAdapter extends BaseExpandableListAdapter {



        // 返回有多少个分组

        public int getGroupCount() {

            int count=0;

            SQLiteDatabase db = SQLiteDatabase.openDatabase("/sdcard/commonnum.db", null, SQLiteDatabase.OPEN_READONLY);

            if(db.isOpen()){

                Cursor cursor = db.rawQuery("select count(*) from classlist", null);

                if(cursor.moveToFirst()){

                    count = cursor.getInt(0);

                }

                cursor.close();

                db.close();

            }

            return count;

        }



        // 返回某个分组对应的子孩子的条目个数



        public int getChildrenCount(int groupPosition) {

    

            int count=0;

            int tableindex = groupPosition+1;

            String sql = "select count(*) from table"+tableindex;

            

            SQLiteDatabase db = SQLiteDatabase.openDatabase("/sdcard/commonnum.db", null, SQLiteDatabase.OPEN_READONLY);

            if(db.isOpen()){

                Cursor cursor = db.rawQuery(sql, null);

                if(cursor.moveToFirst()){

                    count = cursor.getInt(0);

                }

                cursor.close();

                db.close();

            }

            return count;



        }



        // 返回当前groupPosition 对应位置的对象

        public Object getGroup(int groupPosition) {

            return null;

        }



        // 返回groupPosition第childPosition个子孩子对应的条目

        public Object getChild(int groupPosition, int childPosition) {

            return null;

        }



        // 获取分组的id

        public long getGroupId(int groupPosition) {

            return groupPosition;

        }



        // 获取分组中子孩子id

        public long getChildId(int groupPosition, int childPosition) {

            return 0;

        }

        // 是否允许子孩子有点击事件，默认子孩子没有点击事件

        public boolean hasStableIds() {

            return false;

        }



        //获取组视图

        @SuppressLint("SdCardPath")

        public View getGroupView(int groupPosition, boolean isExpanded,

                View convertView, ViewGroup parent) {

            TextView tv = new TextView(CommonNumActivity.this);

            String text ="";

            int currentpos = groupPosition+1;

            if (Environment.getExternalStorageState().equals(

                    Environment.MEDIA_MOUNTED)){

                SQLiteDatabase db = SQLiteDatabase.openDatabase("/sdcard/commonnum.db", null, SQLiteDatabase.OPEN_READONLY);

                if(db.isOpen()){

                    Cursor cursor = db.rawQuery("select name from classlist where idx=?", new String[]{currentpos+""});

                    if(cursor.moveToFirst()){

                        text = cursor.getString(0);

                    }

                    cursor.close();

                    db.close();

                }

                tv.setText("             "+text);

            }

            return tv;

        }



        //获取孩子视图

        public View getChildView(int groupPosition, int childPosition,

                boolean isLastChild, View convertView, ViewGroup parent) {

            TextView tv = new TextView(CommonNumActivity.this);

            StringBuilder sb = new StringBuilder();

            int tableindex = groupPosition+1;

            int childindex = childPosition+1;

            String sql = "select number,name from table"+tableindex;

            

            SQLiteDatabase db = SQLiteDatabase.openDatabase("/sdcard/commonnum.db", null, SQLiteDatabase.OPEN_READONLY);

            if(db.isOpen()){

                Cursor cursor = db.rawQuery(sql+ " where _id=?", new String[]{childindex+""});

                if(cursor.moveToFirst()){

                   sb.append(    cursor.getString(0)); //number

                   sb.append(":");

                   sb.append(    cursor.getString(1)); //name

                    

                }

                cursor.close();

                db.close();

            }

            String text = sb.toString();

            tv.setText(text);

            return tv;

        }



        public boolean isChildSelectable(int groupPosition, int childPosition) {

            return true;

        }



    }

    private void copyfile() {

        AssetManager manager = getAssets();

        try {

            InputStream is = manager.open("commonnum.db");

            File file = new File("/sdcard/commonnum.db");

            FileOutputStream fos = new FileOutputStream(file);

            byte[] buffer = new byte[1024];

            int len = 0;

            while ((len = is.read(buffer)) != -1) {

                fos.write(buffer, 0, len);

            }

            fos.flush();

            fos.close();



        } catch (IOException e) {

            e.printStackTrace();

        }

    }



}

3、如何优化：

　　A:考虑重用convertView 

　　B：不用关闭数据库，