做完了主界面之后开始做添加和修改笔记功能，当用户点击主界面的添加之后跳转到另一个编辑界面，点击添加将数据保存到数据库。当用户选择某一条笔记然后点击修改之后跳转到另一个界面，把数据库里面的数据取出来放到对应的编辑框。

添加笔记功能的实现代码

package com.example.notebook;
import java.sql.Date;
import java.text.SimpleDateFormat;
import android.app.Activity;
import android.content.Intent;
import android.database.Cursor;
import android.os.Bundle;
import android.text.format.Time;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.EditText;
import android.widget.Toast;
/*----------------------------------添加功能------------------------------------*/
public class AddnoteActivity extends Activity {
        private EditText titleEditText,eventEditText;
        private Button addeventsButton;
        //添加功能代码
        protected void onCreate(Bundle savedInstanceState) {
                 super.onCreate(savedInstanceState);
                 setContentView(R.layout.activity_addnote);
                 //绑定组件
                 titleEditText=(EditText)findViewById(R.id.addnote_title);
                 eventEditText=(EditText)findViewById(R.id.addnote_edtnote);
                 addeventsButton=(Button)findViewById(R.id.addnote_btnadd);
                 //监听“添加”按钮事件
                 addeventsButton.setOnClickListener(new OnClickListener() {
                         public void onClick(View v) {
                                  // 调用数据库
                                  MydatabaseHelper mydatabaseHelper=new MydatabaseHelper(AddnoteActivity.this);
                                  //将编辑框里面的数据赋值
                                  String eventsString=eventEditText.getText().toString();
                                  String titleString=titleEditText.getText().toString();
                                  //获取时间
                                  Time t=new Time(); //或者Time t=new Time("GTM+8");
                                  t.setToNow(); // 取得系统时间。
                                  int year = t.year;
                                  int month = t.month+1;
                                  int day = t.monthDay;
                                  int hour = t.hour+8; //相差8小时+8
                                  int minute = t.minute;
                                  int second = t.second;
                                  String dateString=year+"年"+month+"月"+day+"日  "+hour+":"+minute+":"+second;
                                  //判断输入信息
                                  if (eventsString.equals("")) {
                                          //当输入框为空时
                                          Toast.makeText(AddnoteActivity.this, "请输入事件！", Toast.LENGTH_LONG).show();
                                  }
                                  else {
                                          //当输入框有内容时
                                          Toast.makeText(AddnoteActivity.this, "添加成功！", Toast.LENGTH_LONG).show();
                                          mydatabaseHelper.eventsinsert(titleString,eventsString, dateString);
                                          //添加成功后跳转到显示界面
                                          Intent intent = new Intent(AddnoteActivity.this, NoteActivity.class);
                                          startActivity(intent);
                                  }
                         }
                 });
        }
        }

修改笔记功能的实现代码

package com.example.notebook;
import android.content.Intent;
import android.os.Bundle;
import android.text.format.Time;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.EditText;
import android.widget.Toast;
/*----------------------------------修改功能------------------------------------*/
public class EditActivity extends MainActivity {
private EditText titleEditText,eventEditText;
private Button saveButton;
private String idString="";
        //修改功能主代码
        protected void onCreate(Bundle savedInstanceState) {
                 super.onCreate(savedInstanceState);
                 setContentView(R.layout.activity_edit);
                 //绑定组件
                 titleEditText=(EditText)findViewById(R.id.edit_title);
                 eventEditText=(EditText)findViewById(R.id.edit_change);
                 saveButton=(Button)findViewById(R.id.edit_save);
                 //获取从显示界面传过来的intent数据，调用getintent方法
                 Intent intent=getIntent();
                 //从intent对象取出数据
                 Bundle bundle=intent.getExtras();
                 Notelist notelist=(Notelist)bundle.getSerializable("note");
                 idString=String.valueOf(notelist.getId());
                 eventEditText.setText(notelist.getEventString());
                 titleEditText.setText(notelist.getTitleString());
                 //保存按钮点击事件
                saveButton.setOnClickListener(new OnClickListener() {
                         public void onClick(View v) {
                                  MydatabaseHelper mydatabaseHelper=new MydatabaseHelper(EditActivity.this);
                                  String titleString=titleEditText.getText().toString();
                                  String eventsString=eventEditText.getText().toString();
                                  //获取时间
                                  Time t=new Time(); //或者Time t=new Time("GTM+8");
                                  t.setToNow(); // 取得系统时间。
                                  int year = t.year;
                                  int month = t.month+1;
                                  int day = t.monthDay;
                                 int hour = t.hour+8; //相差8小时+8
                                  int minute = t.minute;
                                  int second = t.second;
                                  String dateString=year+"年"+month+"月"+day+"日  "+hour+":"+minute+":"+second;
                                  //判断修改内容
                                  if (eventEditText.getText().toString().equals("")) {
                                          //修改内容为空时
                                          Toast.makeText(EditActivity.this, "修改内容不能为空！", Toast.LENGTH_LONG).show();
                                  }
                                  else {
                                          //修改内容不为空时
                                          Toast.makeText(EditActivity.this, "添加成功", Toast.LENGTH_LONG).show();
                                          mydatabaseHelper.eventsupdate(idString,titleString,eventsString, dateString);
                                          //修改成功跳转到显示界面
                                          Intent intent=new Intent(EditActivity.this,NoteActivity.class);
                                          startActivity(intent);
                                  }
                         }
                 });
        }
}