标签：android style blog color io os ar java sp
经过一天的学习，终于对数据库的操作有了一定成度的了解，但是期间出现了几次bug,真心体会到bug销魂，让人醉生梦死啊，不多说了上代码
涉及的主要内容
1 创建 数据库的帮助类sqliteophelper，并重写其构造方法
package com.djf.salary.db; import android.content.Context; import android.database.sqlite.SQLiteDatabase; import android.database.sqlite.SQLiteDatabase.CursorFactory; import android.database.sqlite.SQLiteOpenHelper; /** * 创建一个数据库打开的帮助类，实现默认的构造方法，名称 游标工厂 数据库的版本 在oncreate方法中执行sql语句，创建一张表格 * * */ public class SalaryInfoDBOpenHelper extends SQLiteOpenHelper { public SalaryInfoDBOpenHelper(Context context, String name, CursorFactory factory, int version) { super(context, name, factory, version); // TODO Auto-generated constructor stub } // 实现一些默认的构造方法 // 数据库被创建的的时候开始调用，用于数据表结构的初始化 @Override public void onCreate(SQLiteDatabase db) { // TODO Auto-generated method stub db.execSQL("create table salaryinfo(_id integer primary key autoincrement,name varchar(10),company varchar(20),salary integer)"); } @Override public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) { // TODO Auto-generated method stub } }
2 创建数据库
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
helper = new SalaryInfoDBOpenHelper(MainActivity.this, "student.db",
null, 1);
dao = new StudentInfoDao(this);
tv = (TextView) findViewById(R.id.tv);
}
3 创建学生信息对象，并写出get set 方法
package com.djf.salary.domain;
public class StudentInfo {
private int id;
private String name;
private String company;
private int salary;
public int getId() {
return id;
}
public void setId(int id) {
this.id = id;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public String getCompany() {
return company;
}
public void setCompany(String company) {
this.company = company;
}
public int getSalary() {
return salary;
}
public void setSalary(int salary) {
this.salary = salary;
}
@Override
public String toString() {
return "StudentInfo [id=" + id + ", name=" + name + ", company="
+ company + ", salary=" + salary + "]";
}
}
4 创建数据库增删改查的方法
package com.djf.salary.db.dao;
import android.content.Context;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;
import com.djf.salary.db.SalaryInfoDBOpenHelper;
import com.djf.salary.domain.StudentInfo;
public class StudentInfoDao {
private Context context;
private SalaryInfoDBOpenHelper helper;
public StudentInfoDao(Context context) {
this.context = context;
helper = new SalaryInfoDBOpenHelper(context, "student.db", null, 1);
// TODO Auto-generated constructor stub
}
public void insert(String name, String company, int salary) {
SQLiteDatabase db = helper.getWritableDatabase();
db.execSQL(
"insert into salaryinfo (name,company,salary) values (? ,? ,?)",
new Object[] { name, company, salary });
db.close();
}
public void delete(int id) {
SQLiteDatabase db = helper.getWritableDatabase();
db.execSQL("delete from salaryinfo where _id=?", new Object[] { id });
db.close();
}
public void upgreadsalary(int salary, int id) {
SQLiteDatabase db = helper.getWritableDatabase();
db.execSQL("update salaryinfo set salary=? where _id=?", new Object[] {
salary, id });
db.close();
}
public StudentInfo find(int id) {
SQLiteDatabase db = helper.getReadableDatabase();
// 得到结果的游标集
Cursor cursor = db.rawQuery("select * from salaryinfo where _id= ? ",
new String[] { String.valueOf(id) });
boolean result = cursor.moveToNext();
StudentInfo studentInfo = null;
if (result) {
String name = cursor.getString(cursor.getColumnIndex("name"));
String company = cursor.getString(cursor.getColumnIndex("company"));
int salary = cursor.getInt(cursor.getColumnIndex("salary"));
studentInfo = new StudentInfo();
studentInfo.setCompany(company);
studentInfo.setName(name);
studentInfo.setSalary(salary);
studentInfo.setId(id);
}
cursor.close();
db.close();
return studentInfo;
}
}
5 对数据库进行操作
public void add(View view) {
dao.insert("张三", "小米科技", 10000);
}
public void delete(View view) {
dao.delete(32);
}
public void update(View view) {
dao.upgreadsalary(9999, 2);
}
public void query(View view) {
StudentInfo info = dao.find(3);
int id =info.getId();
String name = info.getName();
String company = info.getCompany();
int salary = info.getSalary();
tv.setText("id=" + id + "\n" + "name=" + name + "\n" + "company="
+ company + "\n" + "salary=" + salary);
System.out.println("学生信息："+info.toString()
);
// if (info==null) {
// tv.setText("duanjiefei");
// }
// else{
// tv.setText("liudandan");
// }
// db = helper.getReadableDatabase();
// Cursor cursor = db.query("salaryinfo", new String[] { "_id", "name",
// "company" }, null, null, null, null, null);
// while (cursor.moveToNext()) {
// int id = cursor.getInt(cursor.getColumnIndex("_id"));
// String name = cursor.getString(cursor.getColumnIndex("name"));
// String company = cursor.getString(cursor.getColumnIndex("company"));
// String result = id+" "+name+" "+company+" \n";
// tv.setText(result);
// }
// if (info == null) {
// tv.setText("duanjiefi");
// } else {
// // tv.setText("liudandan");
// String name = info.getName();
// String company =info.getCompany();
// int id = info.getId();
// int salary = info.getSalary();
// tv.setText("姓名："+name+"\n"+"公司："+company+"\n"+"薪水："+salary);
// }
// String name = info.getName();
// String company =info.getCompany();
// int id = info.getId();
// int salary = info.getSalary();
// tv.setText("姓名："+name+"\n"+"公司："+company+"\n"+"薪水："+salary);
}
期间出现了空指针异常，改了一下午，迷迷糊糊的bug竟然消失了，一直感觉没有操作新的东西，希望在后续的学习中的能够解决类似的问题~~~~~~~
标签：android style blog color io os ar java sp
原文地址：http://www.cnblogs.com/jiefeiduan/p/4033636.html
