Android笔记之数据库操作

1、创建数据库

你只要继承 SQLiteOpenHelper 类，就可以轻松的创建数据库。SQLiteOpenHelper 类根据开发应用程序的需要，封装了创建和更新数据库使用的逻辑。SQLiteOpenHelper 的子类，至少需要实现三个方法：

• 构造函数，调用父类 SQLiteOpenHelper 的构造函数。这个方法需要四个参数：上下文环境（例如，一个 Activity），数据库名字，一个可选的游标工厂（通常是 Null），一个代表你正在使用的数据库模型版本的整数。
• onCreate（）方法，它需要一个 SQLiteDatabase 对象作为参数，根据需要对这个对象填充表和初始化数据。
• onUpgrage() 方法，它需要三个参数，一个 SQLiteDatabase 对象，一个旧的版本号和一个新的版本号，这样你就可以清楚如何把一个数据库从旧的模型转变到新的模型。

 

下面示例代码展示了如何继承 SQLiteOpenHelper 创建数据库：

public class CourseOpenHelper extends SQLiteOpenHelper {

    private static String name="MyCourse.db";// 数据库名称
    private static int version=2;// 数据库版本号

    public CourseOpenHelper(Context context) {
        // name 若为空，则创建在内存中
        super(context, name, null, version);
        // TODO Auto-generated constructor stub
    }
    /*
     * The database is not actually created or opened until one of
     * getWritableDatabase() or getReadableDatabase() is called.
     */

    @Override
    public void onCreate(SQLiteDatabase db) {
        // TODO 创建数据库后，对数据库的操作
        //在数据库中创建表Course
        String sql = "create table Course(_id integer primary key autoincrement,coursename text,room text)";
        db.execSQL(sql);
    }

     //更改数据库版本的操作
    @Override
    public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
        // TODO 更改数据库版本的操作
    }

}

 2 数据库操作

package dao;

import java.sql.Timestamp;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;

import service.StudentInfoService;
import android.content.Context;
import android.database.Cursor;
import android.database.sqlite.SQLiteConstraintException;
import android.database.sqlite.SQLiteDatabase;
import android.util.Log;

import com.utils.CommonUrl;
import com.utils.DbOpenHelper;
import com.utils.GsonUlits;
import com.utils.HttpClientUtils;

public class StudentInfoDao implements StudentInfoService {

    private DbOpenHelper helper = null;

    public StudentInfoDao(Context context) {
        super();
        helper = new DbOpenHelper(context);
    }

    @Override
    public boolean fillStudentInfo(Object[] infolist) {
        // TODO Auto-generated method stub
        boolean flag = false;
        // 实现对数据库的添加，删除和修改功能
        SQLiteDatabase database = null;
        try {
            String sql = "insert into StuInfo(stuid ,name ,sex ,birthday ,xueyuan ,zhuanye, banhao,tel ,qq) values (?,?,?,?,?,?,?,?,?)";
            database = helper.getWritableDatabase();
            database.execSQL(sql, infolist);
            flag = true;
        } catch (SQLiteConstraintException e) {
            // column stuid is not unique (code 19)
            e.printStackTrace();
        }
        if (!flag) {
            String sql = "update StuInfo set name=? ,sex=? ,birthday=? ,xueyuan=? ,zhuanye=?, banhao=? ,tel=?,qq=? where stuid=?";
            database = helper.getWritableDatabase();
            String stuid = (String) infolist[0];
            for (int i = 0; i < 8; i++) {
                infolist[i] = infolist[i + 1];
            }
            infolist[8] = stuid;
            database.execSQL(sql, infolist);
            flag = true;
        }
        return flag;
    }

    @Override
    public Map<String, String> getSimpleInfo(String selection,
            String[] selectionArgs) {
        // TODO Auto-generated method stub

        Map<String, String> map = new HashMap<String, String>();
        SQLiteDatabase database = null;
        Cursor cursor = null;// query返回的对象是Cursor
        try {
            database = helper.getWritableDatabase();
            // String[] co = { "coursename", "room", "teacher", "week" };
            // 在2.X版本下query方法汇出错误：
            // java.lang.NoSuchMethodError:
            // android.database.sqlite.SQLiteDatabase.query
            cursor = database.query(true, "StuInfo", null, selection,
                    selectionArgs, null, null, null, null, null);
            int cols_num = cursor.getColumnCount();
            while (cursor.moveToNext()) {
                for (int i = 0; i < cols_num; i++) {
                    String cols_name = cursor.getColumnName(i);
                    String cols_value = cursor.getString(cursor
                            .getColumnIndex(cols_name));
                    if (cols_value == null) {
                        cols_value = "";
                    }
                    Log.i(i + "", "cols_name=" + cols_name + ",cols_value="
                            + cols_value);
                    map.put(cols_name, cols_value);
                }
            }

        } catch (Exception e) {
            // TODO: handle exception
            e.printStackTrace();
        } finally {
            if (database != null) {
                database.close();
            }
        }
        return map;
    }

    @Override
    public boolean poststudent(Map<String, String> map) {
        // TODO Auto-generated method stub
        Map<String, String> info = new HashMap<String, String>();
        info.put("student.stuid", map.get("stuid"));
        info.put("student.name", map.get("name"));
        info.put("student.sex", map.get("sex"));
        info.put("student.xueyuan", map.get("xueyuan"));
        info.put("student.zhuanye", map.get("zhuanye"));
        info.put("student.banhao", map.get("banhao"));
        info.put("student.birthday", map.get("birthday"));
        String result = HttpClientUtils.sendHttpclientPost(
                CommonUrl.Add_Student, info, "utf8");
        if (result.contains("成功"))
            return true;
        return false;
    }

    @Override
    public List<Map<String, Object>> getstudentlist(String banhao) {
        Map<String, String> map = new HashMap<String, String>();
        map.put("tmp", "");
        // TODO Auto-generated method stub
        String jsonString = HttpClientUtils.sendHttpclientPost(
                CommonUrl.Student_List, map, CommonUrl.encode);
        if (jsonString.equals(""))
            return null;
        List<Map<String, Object>> list = GsonUlits
                .getListKeyapFromGson(jsonString);
        return list;
    }

    @Override
    public List<Map<String, String>> getMoreInfo(String selection,
            String[] selectionArgs) {
        // TODO Auto-generated method stub
        List<Map<String, String>> list = new ArrayList<Map<String, String>>();
        SQLiteDatabase database = null;
        Cursor cursor = null;// query返回的对象是Cursor
        try {
            database = helper.getWritableDatabase();

            cursor = database.query(true, "StuInfo", null, selection,
                    selectionArgs, null, null, null, null, null);
            int cols_num = cursor.getColumnCount();
            while (cursor.moveToNext()) {
                Map<String, String> map = new HashMap<String, String>();
                for (int i = 0; i < cols_num; i++) {
                    String cols_name = cursor.getColumnName(i);
                    String cols_value = cursor.getString(cursor
                            .getColumnIndex(cols_name));
                    if (cols_value == null) {
                        cols_value = "";
                    }
                    Log.i(i + "", "cols_name=" + cols_name + ",cols_value="
                            + cols_value);

                    map.put(cols_name, cols_value);
                }
                list.add(map);
            }

        } catch (Exception e) {
            // TODO: handle exception
            e.printStackTrace();
        } finally {
            if (database != null) {
                database.close();
            }
        }
        return list;
    }

    @Override
    public boolean addMessage(String body, String stuid, String type) {
        // TODO Auto-generated method stub

        boolean flag = false;
        // 实现对数据库的添加，删除和修改功能
        SQLiteDatabase database = null;
        Timestamp ts = new Timestamp(System.currentTimeMillis());
        Object[] infolist = { stuid, body, ts, type };
        try {
            String sql = "insert into Message(stuid ,body ,timestamp,type) values (?,?,?,?)";
            database = helper.getWritableDatabase();

            database.execSQL(sql, infolist);
            flag = true;
        } catch (SQLiteConstraintException e) {
            // column stuid is not unique (code 19)
            e.printStackTrace();
        }
        return flag;
    }

    @Override
    public List<Map<String, String>> getMessageList(String stuid) {
        // TODO Auto-generated method stub
        List<Map<String, String>> list = new ArrayList<Map<String, String>>();
        SQLiteDatabase database = null;
        Cursor cursor = null;// query返回的对象是Cursor
        try {
            database = helper.getWritableDatabase();

            String selection = "stuid=?";
            String[] selectionArgs = { stuid };
            cursor = database.query(true, "Message", null, selection,
                    selectionArgs, null, null, "timestamp", null, null);
            int cols_num = cursor.getColumnCount();
            while (cursor.moveToNext()) {
                Map<String, String> map = new HashMap<String, String>();
                for (int i = 0; i < cols_num; i++) {
                    String cols_name = cursor.getColumnName(i);
                    String cols_value = cursor.getString(cursor
                            .getColumnIndex(cols_name));
                    if (cols_value == null) {
                        cols_value = "";
                    }

                    map.put(cols_name, cols_value);
                }
                list.add(map);
            }

        } catch (Exception e) {
            // TODO: handle exception
            e.printStackTrace();
        } finally {
            if (database != null) {
                database.close();
            }
        }
        return list;
    }
}

 

Done!