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，