Android实现简易记事本

本文实例为大家分享了android实现简易记事本的具体代码，供大家参考，具体内容如下

下面实现了一个简易的记事本，效果如下：

主要使用数据库存储数据。

完整代码链接：android实现简易记事本

下面是部分代码：

mainactivity:

public class mainactivity extends appcompatactivity implements view.onclicklistener {

 private edittext subject;
 private edittext body;
 private edittext date;
 private button choosedate;
 private button add;
 private button query;
 private listview result;
 private linearlayout title;
 private mydatabasehelper mmydatabasehelper;
 @override
 protected void oncreate(bundle savedinstancestate) {
 super.oncreate(savedinstancestate);
 setcontentview(r.layout.activity_main);
 initview();
 }

 private void initview() {
 //控件初始化
 subject=(edittext)findviewbyid(r.id.subject);
 body=(edittext)findviewbyid(r.id.body);
 date=(edittext)findviewbyid(r.id.date);
 choosedate=(button)findviewbyid(r.id.choosedate);
 add=(button)findviewbyid(r.id.add);
 query=(button)findviewbyid(r.id.query);
 result=(listview)findviewbyid(r.id.result);
 title=(linearlayout)findviewbyid(r.id.title);

 //选择日期，添加，查询的监听事件
 choosedate.setonclicklistener(this);
 add.setonclicklistener(this);
 query.setonclicklistener(this);
 //查询情况默认隐藏，只有点击查询时才有效果
 title.setvisibility(view.invisible);
 }

 @override
 public void onclick(view v) {
 //创建数据库
 mmydatabasehelper=new mydatabasehelper(mainactivity.this,"memento.db",null,1);
 sqlitedatabase sqlitedatabase=mmydatabasehelper.getreadabledatabase();
 //获取输入框的内容
 string strsubject=subject.gettext().tostring().trim();
 string strbody=body.gettext().tostring().trim();
 string strdate=date.gettext().tostring().trim();

 switch (v.getid()){
 case r.id.choosedate:
 calendar calendar=calendar.getinstance();
 //选择时间，并将时间设置在date中
 new datepickerdialog(mainactivity.this, new datepickerdialog.ondatesetlistener() {
  @override
  public void ondateset(datepicker view, int year, int month, int dayofmonth) {
  date.settext(year+"-"+month+"-"+dayofmonth);
  }
 },calendar.get(calendar.year),calendar.get(calendar.month),calendar.get(calendar.day_of_month)).show();
 break;
 case r.id.add:
 //添加内容到数据库中，添加方法是add
 title.setvisibility(view.invisible);
 add(sqlitedatabase,strsubject,strbody,strdate);
 toast.maketext(this, "success!", toast.length_short).show();
 result.setadapter(null);
 break;
 case r.id.query:
 //查询时显示结果设置为visible
 title.setvisibility(view.visible);
 //查询的结果保存在cursor中
 cursor cursor=query(sqlitedatabase,strsubject,strbody,strdate);
 simplecursoradapter simplecursoradapter=new simplecursoradapter(mainactivity.this,r.layout.result,cursor,new string[]{"_id", "subject", "body", "date"},
  new int[]{r.id.memento_num, r.id.memento_subject, r.id.memento_body, r.id.memento_date});
 //为listview添加适配器
 result.setadapter(simplecursoradapter);
 break;
 }
 }

 //添加数据到数据库中的方法
 public void add(sqlitedatabase sqlitedatabase,string subject,string body,string date){
 sqlitedatabase.execsql("insert into memento_tb values(null,?,?,?)",new string[]{subject,body,date});
 //初始设置为空
 this.subject.settext("");
 this.body.settext("");
 this.date.settext("");
 }

 //查询的方法，返回值为cursor
 public cursor query(sqlitedatabase sqlitedatabase, string subject, string body, string date){
 cursor cursor = sqlitedatabase.rawquery(
 "select * from memento_tb where subject like ? and body like ? and date like ? ",
 new string[]{"%" + subject + "%", "%" + body + "%",
  "%" + date + "%"});//对表的查询（insert的操作）
 return cursor;
 }

 protected void ondestroy() {
 super.ondestroy();
 if (mmydatabasehelper != null) {
 mmydatabasehelper.close();
 }
 }
}

mydatabasehelper：

public class mydatabasehelper extends sqliteopenhelper {
 //创建数据库的语句
 final string create_table_sql =
 "create table memento_tb(_id integer primary " +
  "key autoincrement,subject,body,date)"; //建表


 public mydatabasehelper(context context, string name, sqlitedatabase.cursorfactory factory, int version) {
 super(context, name, factory, version);
 }

 //执行建表的操作
 @override
 public void oncreate(sqlitedatabase db) {
 db.execsql(create_table_sql);
 }

 @override
 public void onupgrade(sqlitedatabase db, int oldversion, int newversion) {
 system.out.println("---------" + oldversion + "------->" + newversion);
 }
}

以上就是本文的全部内容，希望对大家的学习有所帮助，也希望大家多多支持。