android数据存储之SQLite（个人日记本）
如何利用SQLite来开发数据库应用，在Android系统，为我们提供了一个名为SQLiteOpenHelper的抽象类，必须继承它才能使用。
SQLiteOpenHelper类提供了两个重要的方法，分别是onCreate(SQLiteDatabase db)和onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion)，前者用于初次使用软件时生成数据库表，后者用于升级软件时更新数据库表结构。当调用SQLiteOpenHelper的getWritableDatabase()或者getReadableDatabase()方法获取用于操作数据库的SQLiteDatabase实例的时候，如果数据库不存在，Android系统会自动生成一个数据库，接着调用onCreate()方法，onCreate()方法在初次生成数据库时才会被调用，在onCreate()方法里可以生成数据库表结构及添加一些应用使用到的初始化数据。
一：新建Android项目，命名为MyDiary .然后使用SQLiteOpenHelper(抽象类)来完成数据库的创建.新建DBHelper类，让它继承SQLiteOpenHelper类
import android.content.Context;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteDatabase.CursorFactory;
import android.database.sqlite.SQLiteOpenHelper;
public class DBHelper extends SQLiteOpenHelper {
private static final String DATABASE_NAME = "diary.db";
private static final int DATABASE_VERSION = 1;
public DBHelper(Context context) {
super(context, DATABASE_NAME, null, DATABASE_VERSION);
}
@Override
public void onCreate(SQLiteDatabase db) {
db.execSQL("create table diary(_id integer primary key autoincrement,title varchar(20),content varchar(1000),pubdate)");
}
@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
}
}
二：配置好单元测试的环境：
然后进行单元测试：看数据库究竟有没有被创建出来，进入DDMS观察存放位置：data/data/应用的包名/databases/diary.db
import java.text.SimpleDateFormat;
import java.util.Date;
import com.lks.mydiary.entity.Diary;
import com.lks.mydiary.service.DBHelper;
import com.lks.mydiary.service.DiaryService;
import android.test.AndroidTestCase;
public class DiaryServiceTest extends AndroidTestCase {
public void testOncreate() {
DBHelper dbHelper = new DBHelper(getContext());
dbHelper.getWritableDatabase();
}
}
如何观察数据库中建立的表呢？
打开数据库：借助于第三方工具SQLiteDeveloper（注册数据库）
导出数据库后，借助于第三方工具注册数据库
三：定义实体类Diary类.
public class Diary {
private Integer id;
private String title;
private String content;
private String pubdate;
public Diary(String title, String content, String pubdate) {
super();
this.title = title;
this.content = content;
this.pubdate = pubdate;
}
public Integer getId() {
return id;
}
public void setId(Integer id) {
this.id = id;
}
public String getTitle() {
return title;
}
public void setTitle(String title) {
this.title = title;
}
public String getContent() {
return content;
}
public void setContent(String content) {
this.content = content;
}
public String getPubdate() {
return pubdate;
}
public void setPubdate(String pubdate) {
this.pubdate = pubdate;
}
}
四：定义数据库访问类DiaryService类，搭建框架.
import java.util.ArrayList;
import java.util.List;
import android.content.Context;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;
import com.lks.mydiary.entity.Diary;
public class DiaryService {
private SQLiteDatabase sqLiteDatabase;
private DBHelper dbHelper;
public DiaryService(Context context) {
dbHelper = new DBHelper(context);
}
/*
* 保存日记
*/
public void save(Diary diary) {
sqLiteDatabase = dbHelper.getWritableDatabase();
String sql = "insert into diary(title,content,pubdate) values(?,?,?)";
sqLiteDatabase.execSQL(
sql,
new String[] { diary.getTitle(), diary.getContent(),
diary.getPubdate() });
}
/*
* 更新日记
*/
public void update(Diary diary){
sqLiteDatabase = dbHelper.getWritableDatabase();
String sql = "update diary set title=?,content=?,pubdate=? where _id=?";
sqLiteDatabase.execSQL(
sql,
new Object[] { diary.getTitle(), diary.getContent(),
diary.getPubdate(), diary.getId()});
}
/*
* 根据id删除日记
*/
public void delete(Integer id) {
sqLiteDatabase = dbHelper.getWritableDatabase();// 得到的是同一个数据库实例
sqLiteDatabase.execSQL("delete from diary where _id=?",new Object[]{id});
}
/*
* 根据id查询日记
*/
public Diary find(Integer id) {
Diary diary = null;
sqLiteDatabase = dbHelper.getReadableDatabase();
// 得到游标，最多只有一条数据
Cursor cursor = sqLiteDatabase.rawQuery(
"select * from diary where _id=?",
new String[] { id.toString() });
// 如果移动成功就代表存在
if (cursor.moveToFirst()) {
// 只能根据列的索引来获得相应的字段值
String title = cursor.getString(cursor.getColumnIndex("title"));
String content = cursor.getString(cursor.getColumnIndex("content"));
String pubdate = cursor.getString(cursor.getColumnIndex("pubdate"));
diary = new Diary(title, content, pubdate);
}
return diary;
}
/*
* 分页查询
*/
public List getDiariesByPage(Integer offset, Integer maxResult) {
Diary diary = null;
List diaryList = new ArrayList();
sqLiteDatabase = dbHelper.getReadableDatabase();
// 得到游标，最多只有一条数据
Cursor cursor = sqLiteDatabase.rawQuery(
"select * from diary limit ?,?",
new String[] { offset.toString(), maxResult.toString() });
while (cursor.moveToNext()) {
String title = cursor.getString(cursor.getColumnIndex("title"));
String content = cursor.getString(cursor.getColumnIndex("content"));
String pubdate = cursor.getString(cursor.getColumnIndex("pubdate"));
diary = new Diary(title, content, pubdate);
diaryList.add(diary);
}
cursor.close();
return diaryList;
}
/*
* 获取所有日记
*/
public Cursor getAllDiaries(){
sqLiteDatabase=dbHelper.getReadableDatabase();
Cursor cursor=sqLiteDatabase.rawQuery("select * from diary", null);
return cursor;
}
/*
* 获取记录总数
*/
public long count() {
long count=0;
sqLiteDatabase=dbHelper.getReadableDatabase();
Cursor cursor=sqLiteDatabase.rawQuery("select count(*) from diary ",null);
cursor.moveToFirst();
count=cursor.getLong(0);
return count;
}
}
五：界面和功能设计。当运行程序，主界面显示日志列表。当没有日记时显示“你好懒，还没开始写日记呢”
activity_diary.xml:
item_diary.xml:
当点击菜单键时，会弹出菜单：添加一篇日记 ，删除一篇日记
当点击“添加一篇日记”，跳转至另一页面SaveActivity.
具体代码如下：
activity_save.xml:
填写好标题和内容，保存之后页面自动跳转到显示日志列表的主界面。可以点击某一篇日记进行查看，同时进行编辑修改。
当选中某篇日记，点击菜单中的删除日记按钮可以删除当前选中的日记。
六：编辑Activity,进行对个人日记本增删改查的功能实现。具体代码如下：
阶段六：编辑Activity,进行对个人日记本增删改查的功能实现。具体代码如下：
DiaryActivity.java:
import bzu.sys.mydiary.entity.Diary;
import bzu.sys.mydiary.service.DiaryService;
import android.os.Bundle;
import android.app.AlertDialog;
import android.app.ListActivity;
import android.content.DialogInterface;
import android.content.DialogInterface.OnClickListener;
import android.content.Intent;
import android.database.Cursor;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.widget.AdapterView;
import android.widget.AdapterView.OnItemClickListener;
import android.widget.AdapterView.OnItemSelectedListener;
import android.support.v4.widget.SimpleCursorAdapter;
public class DiaryActivity extends ListActivity {
private DiaryService diaryService;
private int idSelect;
public static final int MENU_INSERT = 0;// 关于菜单
public static final int MENU_DELETE = 1;// 退出菜单
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_diary);
refreshList();
//点击事件，当点击某篇日记时..
getListView().setOnItemClickListener(new OnItemClickListener() {
public void onItemClick(AdapterView adapter, View view,
int position, long id) {
Intent intent = new Intent();
intent.putExtra("button", "find");
intent.setClass(DiaryActivity.this, SaveActivity.class);
Bundle bundle = new Bundle();
Diary diary = diaryService.find((int) id);
bundle.putString("title", diary.getTitle());
bundle.putString("content", diary.getContent());
bundle.putInt("id", (int)id);
intent.putExtras(bundle);
startActivity(intent);
}
});
getListView().setOnItemSelectedListener(new OnItemSelectedListener() {
public void onItemSelected(AdapterView adapterView, View view,
int position, long id) {
idSelect = (int) id;
}
public void onNothingSelected(AdapterView arg0) {
}
});
}
private void refreshList() {
diaryService = new DiaryService(this);
Cursor cursor = diaryService.getAllDiaries();
startManagingCursor(cursor);
SimpleCursorAdapter simpleCursorAdapter = new SimpleCursorAdapter(this,
R.layout.item_diary, cursor, new String[] { "title", "pubdate" },
new int[] { R.id.title, R.id.pubdate });
setListAdapter(simpleCursorAdapter);
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
menu.add(0, MENU_INSERT, 0, R.string.insert);// 第一个参数为组号，便于对整个组进行操作；第二个参数为菜单的ID，为了标识菜单项；第三个参数为显示顺序
menu.add(0, MENU_DELETE, 1, R.string.delete);
return true;
}
/**
* 当点击菜单项时调用此方法
*/
@Override
public boolean onOptionsItemSelected(MenuItem item) {
int itemId = item.getItemId();// 获取菜单项的唯一编号
switch (itemId) {
//添加日记
case MENU_INSERT:
Intent intent = new Intent();
intent.putExtra("button", "insert");
intent.setClass(DiaryActivity.this, SaveActivity.class);
startActivity(intent);
break;
//删除日记
case MENU_DELETE:
AlertDialog.Builder builder = new AlertDialog.Builder(this);
builder.setIcon(android.R.drawable.ic_menu_delete)
.setTitle(R.string.delete)
.setMessage(R.string.info)
.setPositiveButton(R.string.ok, new OnClickListener() {
public void onClick(DialogInterface dialog, int which) {
diaryService = new DiaryService(DiaryActivity.this);
diaryService.delete(idSelect);
refreshList();
}
})
.setNegativeButton(R.string.cancel, new OnClickListener() {
public void onClick(DialogInterface dialog, int which) {
}
}).create().show();
break;
default:
break;
}
return true;
}
}
SaveActivity.java:
import java.text.SimpleDateFormat;
import java.util.Date;
import bzu.sys.mydiary.entity.Diary;
import bzu.sys.mydiary.service.DiaryService;
import android.os.Bundle;
import android.app.Activity;
import android.content.Intent;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.EditText;
import android.widget.Toast;
public class SaveActivity extends Activity {
private EditText titleText;
private EditText contentText;
private Button save;
private DiaryService diaryService;
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_save);
titleText = (EditText) this.findViewById(R.id.title);
contentText = (EditText) this.findViewById(R.id.content);
save = (Button) this.findViewById(R.id.save);
Intent intent = this.getIntent();
String msg = intent.getStringExtra("button");
//实现添加日记
if (msg.equals("insert")) {
save.setOnClickListener(new OnClickListener() {
public void onClick(View v) {
Diary diary = new Diary(titleText.getText().toString(),
contentText.getText().toString(),
getCurrentTime(new Date()));
diaryService = new DiaryService(SaveActivity.this);
diaryService.save(diary);
Intent intent=new Intent();
intent.setClass(SaveActivity.this, DiaryActivity.class);
startActivity(intent);
Toast.makeText(SaveActivity.this, R.string.save_success,
Toast.LENGTH_LONG).show();
}
});
//实现修改日记
} else if (msg.equals("find")) {
final Bundle bundle = this.getIntent().getExtras();
if (bundle != null) {
String title = bundle.getString("title");
String content = bundle.getString("content");
if (titleText != null) {
titleText.setText(title);
}
if (contentText != null) {
contentText.setText(content);
}
}
save.setOnClickListener(new OnClickListener() {
public void onClick(View v) {
Diary diary = new Diary(titleText.getText().toString(),
contentText.getText().toString(),
getCurrentTime(new Date()));
diary.setId(bundle.getInt("id"));
diaryService = new DiaryService(SaveActivity.this);
diaryService.update(diary);
Intent intent = new Intent(SaveActivity.this,DiaryActivity.class);
startActivity(intent);
Toast.makeText(SaveActivity.this, R.string.update_success,
Toast.LENGTH_LONG).show();
}
});
}
}
public String getCurrentTime(Date date) {
SimpleDateFormat simpleDateFormat = new SimpleDateFormat(
"yyyy年MM月dd日hh时mm分ss秒");
return simpleDateFormat.format(date);
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
getMenuInflater().inflate(R.menu.activity_save, menu);
return true;
}
}