編輯：關於android開發
public class MyDatabaseHelper extends SQLiteOpenHelper {
private static final String db_name = "SQLite_db.db";//數據文件的名字
private static int NUMBER = 1;//當前數據庫版本，用於升級
private static final String table_name = "students";//表名
private static String sql = null;//sql語句
public MyDatabaseHelper(Context context) {
super(context, db_name, null, NUMBER);//數據庫文件保存在當前應用所在包名:<包>/database/
}
@Override
public void onCreate(SQLiteDatabase db) {
sql = "CREATE TABLE " + table_name + " (" +
"id INTEGER PRIMARY KEY ," +
"name VARCHAR(50) NOT NULL)";//創建數據庫的SQL語句
db.execSQL(sql);//執行SQL語句
}
/**
* 當數據庫進行升級是調用，這裡通過NUMBER值來進行判斷，數據庫是否升級
*/
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
//第一種寫法
sql = "ALTER TABLE " + table_name + " ADD sex VARCHAR(2) NULL";
Log.i("sql", sql);
db.execSQL(sql);
//第二種寫法
//db.execSQL("ALTER TABLE students ADD sex VARCHAR(10) NULL");
}
}
下面我們在主Activity中創建這個類，然後進行數據的生成：
public class Activityone extends Activity {
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_one);
//創建SqlLite數據庫
SQLiteOpenHelper helper = new MyDatabaseHelper(this);
helper.getWritableDatabase();
}
}
到這裡我們關於SQLite的創建就為大家分享完畢，需要提示的就是onUpgrade()方法，這個方法一般不執行，當我們的數據庫版本發生變化時，才會被執行。
下面我們來一起學習一下如何在Android中來使用SQLite數據庫，來完成對數據的增、刪、改、查、統計。
我們通過創建一個管理學生信息的數據庫來完成對SQLite功能的介紹展示，首先為了方便對學生類進行管理，我們先創建一個學生類:
public class tab_students {
public Integer id;//學生Id
public String name;//學生姓名
public String password;//學生密碼
public String school;//學生學校
public tab_students(){
}
public tab_students(int _id,String _name,String _password){
id=_id;
name=_name;
password=_password;
}
public Integer getId() {
return id;
}
public void setId(int id) {
this.id = id;
}
public String getName() {
return name;
}
public void setName(String _name) {
name = _name;
}
public String getPassword() {
return password;
}
public void setPassword(String _password) {
password = _password;
}
public String getSchool() {
return school;
}
public void setSchool(String _school) {
school = _school;
}
@Override
public String toString() {
return "id:"+this.getId()+" name:"+this.getName()+" password:"+this.getPassword();
}
}
有了學生類，下面我們創建數據庫配置文件：
public class MyTabOpen extends SQLiteOpenHelper{
private static final String db_sql = "SQLiter.db";
private static int NUMBER = 1;
private static final String tab_name = "students";
private static String sql = null;
public MyTabOpen(Context context) {
super(context, db_sql, null, NUMBER);
}
@Override
public void onCreate(SQLiteDatabase db) {
sql = "CREATE TABLE " + tab_name + " (" +
"id INTEGER PRIMARY KEY ," +
"name VARCHAR(20) NOT NULL ," +
"password VARCHAR(20) NOT NULL)";
db.execSQL(sql);
}
@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
//在更新數據庫時，因原先數據庫表中已有數據，所以新增加的列屬性只能設置為“可以為空”
db.execSQL("ALTER TABLE students ADD school VARCHAR(10) NULL");
}
}
對於這個文件，大家有什麼疑問請看上面的SQLite數據庫創建講解。
這裡我們的主Activity的代碼如下，對於主Activity的布局文件，就不在粘代碼了，布局文件全是Button按鈕:
public class Activityone extends Activity {
private static tab_students stu = null;
private static tab_service ser = null;
private static int conn = 1;
private TextView mytext = null;
private Button mybutton1 = null;//添加數據
private Button mybutton2 = null;//刪除數據
private Button mybutton3 = null;//修改數據
private Button mybutton4 = null;//查詢數據
private Button mybutton5 = null;//分頁獲取數據
private Button mybutton6 = null;//獲取數據總數
private Button mybutton7 = null;//普通頁面跳轉
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_one);
mytext = (TextView)findViewById(R.id.textview);
mytext.setText("增刪改查序"+"("+"sql語句"+")");
mybutton1 = (Button)findViewById(R.id.button1);
mybutton2 = (Button)findViewById(R.id.button2);
mybutton3 = (Button)findViewById(R.id.button3);
mybutton4 = (Button)findViewById(R.id.button4);
mybutton5 = (Button)findViewById(R.id.button5);
mybutton6 = (Button)findViewById(R.id.button6);
mybutton7 = (Button)findViewById(R.id.button7);
mybutton1.setOnClickListener(new mybuttonlistener());
mybutton2.setOnClickListener(new mybuttonlistener());
mybutton3.setOnClickListener(new mybuttonlistener());
mybutton4.setOnClickListener(new mybuttonlistener());
mybutton5.setOnClickListener(new mybuttonlistener());
mybutton6.setOnClickListener(new mybuttonlistener());
mybutton7.setOnClickListener(new mybuttonlistener());
}
class mybuttonlistener implements OnClickListener{
@Override
public void onClick(View v) {
switch (v.getId()) {
case R.id.button1://添加數據
ser =new tab_service(getApplicationContext());
stu = new tab_students(conn++,"小米","abc123");
ser.save(stu);
break;
case R.id.button2://刪除數據
ser =new tab_service(getApplicationContext());
ser.del(1);
break;
case R.id.button3://修改數據
ser =new tab_service(getApplicationContext());
stu = new tab_students(1,"HTC","acm123");
ser.update(stu);
break;
case R.id.button4://查詢數據
ser =new tab_service(getApplicationContext());
stu=ser.find(1);
System.out.println(stu.toString());
break;
case R.id.button5://分頁獲取數據
ser =new tab_service(getApplicationContext());
List<tab_students> list = ser.getScrollDate(0,5);
for(tab_students stu : list){
System.out.println(stu.toString());
}
break;
case R.id.button6://獲取數據總數
long number = 0;
ser =new tab_service(getApplicationContext());
number=ser.gettab();
System.out.println("數據庫中共有："+number+"條記錄.");
break;
default:
Activityone.this.startActivity(new Intent(Activityone.this,Activitytwo.class));//普通跳轉
break;
}
}
}
}
大家可能已經看到了，這裡我們對SQLite的操作，都是通過tab_service.java類完成了，下面就為大家揭曉如何對SQLite進行操作：
public class tab_service {
private MyTabOpen mytabopen = null;
private static SQLiteDatabase db = null;
private static String sql = null;
private static final String tab_name = "students";
public tab_service(Context context) {
this.mytabopen = new MyTabOpen(context);//獲得數據庫操作實例
}
//添加數據
public void save(tab_students students){
db = mytabopen.getWritableDatabase();
sql = "insert into "+tab_name+"(id,name,password) values(?,?,?)";
db.execSQL(sql, new Object[]{students.getId(),students.getName(),students.getPassword()});
db.close(); //為了提高性能sqliter數據庫可以不關閉
}
//刪除數據
public void del(Integer id){
db = mytabopen.getWritableDatabase();
sql = "delete from "+tab_name+" where id = ?";
db.execSQL(sql, new Object[]{id});
db.close();
}
//更新數據
public void update(tab_students students){
db = mytabopen.getWritableDatabase();
sql = "update "+tab_name+" set name=?,password=? where id=?";
db.execSQL(sql, new Object[]{students.getName(), students.getPassword(), students.getId()});
db.close();
}
//查詢數據
public tab_students find(Integer id){
//getReadableDatabase()與getWritableDatabase()通過查看源代碼知道，getReadableDatabase()方法在磁盤空間滿的時候，仍能返回數據庫操作實例，不過此時的實例只能用於讀不能寫
db = mytabopen.getReadableDatabase();
sql = "select * from "+tab_name+ " where id=?";
Cursor cur = db.rawQuery(sql, new String[]{id.toString()});
if(cur.moveToFirst()){
String name = cur.getString(cur.getColumnIndex("name"));
String password = cur.getString(cur.getColumnIndex("password"));
return new tab_students(id,name,password);
}
cur.close();
db.close();
return null;
}
//分頁獲取數據
public List<tab_students> getScrollDate(int again,int last){
List<tab_students> list = new ArrayList<tab_students>();
db = mytabopen.getReadableDatabase();
sql = "select * from "+tab_name+ "limit ?,? order by id asc";//根據查詢結果的id對數據進行升序排列
//sql = "select * from " +tab_name+ " limit ?,?";
Cursor cur = db.rawQuery(sql, new String[]{String.valueOf(again), String.valueOf(last)});
while (cur.moveToNext()) {
int id = cur.getInt(cur.getColumnIndex("id"));
String name = cur.getString(cur.getColumnIndex("name"));
String password = cur.getString(cur.getColumnIndex("password"));
tab_students stu = new tab_students(id, name, password);
list.add(stu);
}
cur.close();
db.close();
return list;
}
//獲取數據總數目
public long gettab(){
db = mytabopen.getReadableDatabase();
sql = "select count(*) from "+tab_name;
Cursor cur = db.rawQuery(sql, null);
cur.moveToFirst();
long result = cur.getLong(0);
return result;
}
}
是不是感覺和我們的SQL數據庫操作一樣，sql語句沒有什麼區別，是的，他們完全一致。沒學過數據庫的小朋友是不是已經抓狂啦，不要擔心，Android工程師想到了你們，Android為我們封裝好了一套對SQLite數據庫進行操作的規范，下面我們就一起來學習一下，如何通過Android提供的規范晚場上面的操作。
這裡我們只需要修改一下，我們上面對數據庫操作的類：
public class tab_service_two {
private MyTabOpen mytabopen = null;
private static SQLiteDatabase db = null;
private static final String tab_name = "students";
public tab_service_two(Context context) {
this.mytabopen = new MyTabOpen(context);//獲得數據庫操作實例
}
//添加數據
public void save(tab_students students){
db = mytabopen.getWritableDatabase();
ContentValues values = new ContentValues();
values.put("id", students.getId());
values.put("name", students.getName());
values.put("password", students.getPassword());
db.insert(tab_name, null, values);
db.close();
}
//刪除數據
public void del(Integer id){
db = mytabopen.getWritableDatabase();
db.delete(tab_name, "id=?", new String[]{id.toString()});
db.close();
}
//修改數據
public void update(tab_students students){
db = mytabopen.getWritableDatabase();
ContentValues values = new ContentValues();
values.put("name", students.getName());
values.put("password", students.getPassword());
db.update(tab_name, values, "id=?", new String[]{students.getId().toString()});
db.close();
}
//查詢數據
public tab_students find(Integer id){
//getReadableDatabase()與getWritableDatabase()通過查看源代碼知道，getReadableDatabase()方法在磁盤空間滿的時候，仍能返回數據庫操作實例，不過此時的實例只能用於讀不能寫
db = mytabopen.getReadableDatabase();
//當要查詢數據庫表中的所以信息時，第二個參數可以使用設置為空來代替數組
Cursor cur = db.query(tab_name, new String[]{"name","password"}, "id=?", new String[]{id.toString()}, null, null, null);
if(cur.moveToFirst()){
String name = cur.getString(cur.getColumnIndex("name"));
String password = cur.getString(cur.getColumnIndex("password"));
return new tab_students(id,name,password);
}
cur.close();
db.close();
return null;
}
//分頁獲取數據
public List<tab_students> getScrollDate(int again,int last){
List<tab_students> list = new ArrayList<tab_students>();
db = mytabopen.getReadableDatabase();
Cursor cur = db.query(tab_name, null, null, null, null, null, "id asc", again+","+last);
while (cur.moveToNext()) {
int id = cur.getInt(cur.getColumnIndex("id"));
String name = cur.getString(cur.getColumnIndex("name"));
String password = cur.getString(cur.getColumnIndex("password"));
tab_students stu = new tab_students(id, name, password);
list.add(stu);
}
cur.close();
db.close();
return list;
}
//獲取數據總數
public long gettab(){
db = mytabopen.getReadableDatabase();
Cursor cur = db.query(tab_name, new String[]{"count(*)"}, null, null, null, null, null);
cur.moveToFirst();
long result = cur.getLong(0);
return result;
}
}
好了關於SQLite在Android平台的使用，就為大家介紹完畢，內容很簡單，沒有太大的難度，相信小伙伴一定能理解。新手學習，高手交流。
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