Sqlite DataBase ：數據庫存儲
應用場景：大量結構相似的數據，頻繁的增刪改查，需要用到數據庫
特性：輕量級 免費 多線程 跨平臺
SQL語句：
創建表：CREATE TABLE 表名 (_id INTEGER PRIMARY KEY AUTOINCREMENT,name VERCHAR(10),phone VERCHAR(10));
修改表：ALTER TABLE 表名 ADD 字段 屬性;
eg： ALTER TABLE student ADD COLUMN age INTEGER;
刪除表：DROP TABLE 表名;
(增)插入數據：INSERT INTO 表名 (字段名) VALUES (值);
eg: INSERT INTO student (name,phone) VALUES ("李娜","216516");
(刪)刪除數據：DELETE FROM 表名 WHERE 條件語句;
eg： DELETE FROM student WHERE name="李娜";
(改)修改數據：UPDATE 表名 SET 字段名=值 WHERE 條件語句;
eg： UPDATE student SET phone="110" WHERE name="李娜";
(查)查詢數據：SELECT * FROM 表名 //WHERE 條件語句 GROUP BY 分組語句 HAVING 分組條件 ORDER BY 排序; DESC 降序 ASC 升序
eg： SELECT * FORM student ;
代碼實例中：
注意：新建一個Class，給名字的時候，下面要繼承SqliteOpenHelper類，去掉main方法，重寫構造方法（初學時可以將構造方法中的String name 定死，這樣建立的數據庫名字就是固定的，Factory設爲null；）
例子：
新建的Class（MySqliteOpenHelper）中：
package com.example.lwk_0303_sqliteopenhelper;
import android.content.Context;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteDatabase.CursorFactory;
import android.database.sqlite.SQLiteOpenHelper;
public class MySqliteOpenHelper extends SQLiteOpenHelper {
public MySqliteOpenHelper(Context context,int version) {//本來有四個，String name代表數據庫名字，這裏給定值，後綴爲db！
super(context, "lwk.db", null, version); //光標設爲null
// TODO Auto-generated constructor stub//剩下的兩個參數是上下文和版本
}
@Override
public void onCreate(SQLiteDatabase db) {
//創建新表，用到數據庫語言
String sql="CREATE TABLE nvshen (id INTEGER PRIMARY KEY AUTOINCREMENT,name VERCHAR(10),age INTEGER,phone VERCHAR(10));";
db.execSQL(sql);
}
@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
// TODO Auto-generated method stub
}
}
上下文：
package com.example.lwk_0303_sqliteopenhelper;
import android.os.Bundle;
import android.app.Activity;
import android.view.Menu;
public class MainActivity extends Activity {
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
MySqliteOpenHelper mySqliteOpenHelper=new MySqliteOpenHelper(this, 1);//下次啓動時版本若是改變了，MySqliteOpenHelper會調用onUpgrade()方法！
mySqliteOpenHelper.getReadableDatabase();
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.main, menu);
return true;
}
}
增刪改查代碼示例：
package com.example.lwk_0303_sqliteopenhelper;
import java.util.ArrayList;
import android.os.Bundle;
import android.app.Activity;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;
import android.view.Menu;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.TextView;
public class MainActivity extends Activity implements OnClickListener{
private SQLiteDatabase mDb;
private TextView mTv_01;
ArrayList<Data> arrayList = new ArrayList<MainActivity.Data>();
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
findViewById(R.id.button1).setOnClickListener(this);//增
findViewById(R.id.button2).setOnClickListener(this);//刪
findViewById(R.id.button3).setOnClickListener(this);//改
findViewById(R.id.button4).setOnClickListener(this);//查
mTv_01 = (TextView) findViewById(R.id.textView1);
MySqliteOpenHelper mySqliteOpenHelper=new MySqliteOpenHelper(this, 1);
mDb = mySqliteOpenHelper.getReadableDatabase();
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.main, menu);
return true;
}
class Data{
String name;
int age;
String phone;
public Data(String name, int age, String phone) {
super();
this.name = name;
this.age = age;
this.phone = phone;
}
@Override
public String toString() {
return "Data [name=" + name + ", age=" + age + ", phone=" + phone
+ "]";
}
}
//爲使代碼可讀性更高，下面的方法可以另外封裝起來，筆者這裏未封裝！！
@Override
public void onClick(View v) {
switch (v.getId()) {
case R.id.button1:
String sql="insert into nvshen (name,age,phone) values ('麗麗',18,'45248')";
mDb.execSQL(sql);
break;
case R.id.button2:
String sql2="delete from nvshen where name='麗麗'";
mDb.execSQL(sql2);
break;
case R.id.button3:
String sql3="update nvshen set phone='120' where name='麗麗'";
mDb.execSQL(sql3);
break;
case R.id.button4:
arrayList.clear();
String sql4="select * from nvshen";
Cursor cursor = mDb.rawQuery(sql4, null);
//將光標移到第一個位置
boolean toFirst = cursor.moveToFirst();
while(toFirst){
String name=cursor.getString(cursor.getColumnIndex("name"));
int age = cursor.getInt(cursor.getColumnIndex("age"));
String phone = cursor.getString(cursor.getColumnIndex("phone"));
Data data=new Data(name, age, phone);
arrayList.add(data);
//把光標移到下一個位置
toFirst = cursor.moveToNext();
}
mTv_01.setText(arrayList.toString());
break;
default:
break;
}
}
}
ORM:關係對象映射（不需要SQL語句）：
package com.example.lwk_0303_sqliteopenhelper;
import java.util.ArrayList;
import android.os.Bundle;
import android.app.Activity;
import android.content.ContentValues;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;
import android.view.Menu;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.TextView;
public class MainActivity extends Activity implements OnClickListener{
private SQLiteDatabase mDb;
private TextView mTv_01;
ArrayList<Data> arrayList = new ArrayList<MainActivity.Data>();
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
findViewById(R.id.button1).setOnClickListener(this);//增
findViewById(R.id.button2).setOnClickListener(this);//刪
findViewById(R.id.button3).setOnClickListener(this);//改
findViewById(R.id.button4).setOnClickListener(this);//查
mTv_01 = (TextView) findViewById(R.id.textView1);
MySqliteOpenHelper mySqliteOpenHelper=new MySqliteOpenHelper(this, 1);
mDb = mySqliteOpenHelper.getReadableDatabase();
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.main, menu);
return true;
}
class Data{
String name;
int age;
String phone;
public Data(String name, int age, String phone) {
super();
this.name = name;
this.age = age;
this.phone = phone;
}
@Override
public String toString() {
return "Data [name=" + name + ", age=" + age + ", phone=" + phone
+ "]";
}
}
@Override
public void onClick(View v) {
switch (v.getId()) {
case R.id.button1:
add_data();
break;
case R.id.button2:
dele_data();
break;
case R.id.button3:
update_data();
break;
case R.id.button4:
find_data();
break;
default:
break;
}
}
private void find_data() {
arrayList.clear();
Cursor cursor = mDb.query("nvshen", new String[]{"name","age","phone"}, null, null, null, null, null);
//表名，需要被查找的列名，條件語句，佔位符參數，分組條件，佔位符，排序
boolean toFirst= cursor.moveToFirst();
while(toFirst){
String name = cursor.getString(cursor.getColumnIndex("name"));
String phone = cursor.getString(cursor.getColumnIndex("phone"));
int age = cursor.getInt(cursor.getColumnIndex("age"));
Data data=new Data(name, age, phone);
arrayList.add(data);
toFirst=cursor.moveToNext();
}
mTv_01.setText(arrayList.toString());
}
private void update_data() {
ContentValues values=new ContentValues();
values.put("age", 19);
mDb.update("nvshen", values, "name=?", new String[]{"娜娜"});
} //表名，修改的值（new出來），條件語句，條件語句的佔位符(條件語句的值)
private void dele_data() {
mDb.delete("nvshen", "name=?", new String[]{"娜娜"});
//表名，條件語句，條件語句的佔位符(條件語句的值)
}
private void add_data() {
ContentValues values=new ContentValues();
values.put("name", "娜娜");
values.put("age", 18);
values.put("phone", "5614665");
mDb.insert("nvshen", null, values);
} //表名，規避插入時語句的錯誤（沒有值的時候默認給的值），插入的值
}