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，

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