SQLite的簡介
SQLite，是一款輕型的資料庫，是遵守ACID的關系型資料庫管理系統，它包含在一個相對小的C庫中。它是D.RichardHipp建立的公有領域項目。它的設計目标是嵌入式的，而且已經在很多嵌入式産品中使用了它，它占用資源非常的低，在嵌入式裝置中，可能隻需要幾百K的記憶體就夠了。它能夠支援Windows/Linux/Unix等等主流的作業系統，同時能夠跟很多程式語言相結合，比如 Tcl、C#、PHP、Java等，還有ODBC接口，同樣比起Mysql、PostgreSQL這兩款開源的世界著名資料庫管理系統來講，它的處理速度比他們都快。SQLite第一個Alpha版本誕生于2000年5月。 至2021年已經接近有21個年頭，SQLite也迎來了一個版本 SQLite 3已經釋出。
至于它的原理有很多大佬對他的詳細介紹，我就不在這裡累述了。
這篇文章主要是想記錄一下sqlite的詳細使用，我主要是通過一個執行個體了解sqlite 的增删改查。
實驗效果：
工程結構：
源代碼：
DBAdapter.java
import android.annotation.SuppressLint;
import android.content.ContentValues;
import android.content.Context;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteException;
import android.database.sqlite.SQLiteOpenHelper;
import android.database.sqlite.SQLiteDatabase.CursorFactory;
public class DBAdapter {
private static final String DB_NAME = "student.db";
private static final String DB_TABLE = "peopleinfo";
private static final int DB_VERSION = 1;
public static final String KEY_ID = "_id";
public static final String KEY_NAME = "name";
public static final String KEY_BANJI = "banji";
public static final String KEY_XUEHAO = "xuehao";
private SQLiteDatabase db;
private final Context context;
private DBOpenHelper dbOpenHelper;
public DBAdapter(Context _context) {
context = _context;
}
public void close() {
if(db !=null)
{
db.close();
db=null;
}
}
public void open() throws SQLiteException {
dbOpenHelper = new DBOpenHelper(context, DB_NAME, null, DB_VERSION);
try {
db = dbOpenHelper.getWritableDatabase();
}
catch (SQLiteException ex) {
db = dbOpenHelper.getReadableDatabase();
}
}
public long insert(People people) {
ContentValues newValues = new ContentValues();
newValues.put(KEY_NAME, people.Name);
newValues.put(KEY_BANJI, people.Banji);
newValues.put(KEY_XUEHAO, people.Xuehao);
return db.insert(DB_TABLE, null, newValues);
}
public People[] queryAllData() {
Cursor results = db.query(DB_TABLE, new String[] { KEY_ID, KEY_NAME, KEY_BANJI, KEY_XUEHAO},
null, null, null, null, null);
return ConvertToPeople(results);
}
public People[] queryOneData(long id) {
Cursor results = db.query(DB_TABLE, new String[] { KEY_ID, KEY_NAME, KEY_BANJI, KEY_XUEHAO},
KEY_ID + "=" + id, null, null, null, null);
return ConvertToPeople(results);
}
@SuppressLint("Range")
private People[] ConvertToPeople(Cursor cursor){
int resultCounts = cursor.getCount();
if (resultCounts == 0 || !cursor.moveToFirst()){
return null;
}
People[] peoples = new People[resultCounts];
for (int i = 0 ; i<resultCounts; i++){
peoples[i] = new People();
peoples[i].ID = cursor.getInt(0);
peoples[i].Name = cursor.getString(cursor.getColumnIndex(KEY_NAME));
peoples[i].Banji = cursor.getString(cursor.getColumnIndex(KEY_BANJI));
peoples[i].Xuehao = cursor.getString(cursor.getColumnIndex(KEY_XUEHAO));
cursor.moveToNext();
}
return peoples;
}
public long deleteAllData() {
return db.delete(DB_TABLE, null, null);
}
public long deleteOneData(long id) {
return db.delete(DB_TABLE, KEY_ID + "=" + id, null);
}
public long updateOneData(long id , People people){
ContentValues updateValues = new ContentValues();
updateValues.put(KEY_NAME, people.Name);
updateValues.put(KEY_BANJI, people.Banji);
updateValues.put(KEY_XUEHAO, people.Xuehao);
return db.update(DB_TABLE, updateValues, KEY_ID + "=" + id, null);
}
private static class DBOpenHelper extends SQLiteOpenHelper {
public DBOpenHelper(Context context, String name, CursorFactory factory, int version) {
super(context, name, factory, version);
}
private static final String DB_CREATE = "create table " +
DB_TABLE + " (" + KEY_ID + " integer primary key autoincrement, " +
KEY_NAME+ " text not null, " + KEY_BANJI+ " text not null," + KEY_XUEHAO + " text not null);";
@Override
public void onCreate(SQLiteDatabase _db) {
_db.execSQL(DB_CREATE);
}
@Override
public void onUpgrade(SQLiteDatabase _db, int _oldVersion, int _newVersion) {
_db.execSQL("DROP TABLE IF EXISTS " + DB_TABLE);
onCreate(_db);
}
}
}
People.java
public class People {
public int ID = -1;
public String Name;
public String Banji;
public String Xuehao;
@Override
public String toString(){
String result = "";
result += "ID：" + this.ID + "，";
result += "姓名：" + this.Name + "，";
result += "班級：" + this.Banji + "， ";
result += "學号：" + this.Xuehao;
return result;
}
}
MainActivity.java
package com.example.shiyan6_sqlite;
import androidx.appcompat.app.AppCompatActivity;
import android.database.sqlite.SQLiteDatabase;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.TextView;
public class MainActivity extends AppCompatActivity {
EditText e_xm,e_nl,e_sg,e_id;
TextView t_1;
Button b_add,b_allsee,b_clearsee,b_alldel,b_delid,b_seeid,b_updid;
DBAdapter dbAdapter;
SQLiteDatabase db;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
e_xm=findViewById(R.id.e_xm);
e_nl=findViewById(R.id.e_nl);
e_sg=findViewById(R.id.e_sg);
b_add=findViewById(R.id.b_add);
b_allsee=findViewById(R.id.b_allsee);
b_clearsee=findViewById(R.id.b_clearall);
b_alldel=findViewById(R.id.b_delall);
b_delid=findViewById(R.id.b_delid);
b_seeid=findViewById(R.id.b_seeid);
b_updid=findViewById(R.id.b_updid);
e_id=findViewById(R.id.e_id);
t_1=findViewById(R.id.t_1);
dbAdapter=new DBAdapter(this);
dbAdapter.open();
b_add.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
People t=new People();
t.Name=e_xm.getText().toString();
t.Banji=e_nl.getText().toString();
t.Xuehao=e_sg.getText().toString();
long colunm=dbAdapter.insert(t);
if (colunm == -1 ){
t_1.setText("添加過程錯誤！");
} else {
t_1.setText("成功添加資料，ID："+String.valueOf(colunm));
}
}
});
b_allsee.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
People [] peoples =dbAdapter.queryAllData();
if (peoples == null){
t_1.setText("資料庫中沒有資料");
return;
}
String t="資料庫:\n";
for(int i=0;i<peoples.length;++i){
t+=peoples[i].toString()+"\n";
}
t_1.setText(t);
}
});
b_clearsee.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
t_1.setText("");
}
});
b_alldel.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
dbAdapter.deleteAllData();
t_1.setText("已删除所有資料！");
}
});
b_delid.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
int id=Integer.parseInt(e_id.getText().toString());
long result=dbAdapter.deleteOneData(id);
String msg = "删除ID為"+e_id.getText().toString()+"的資料" + (result>0?"成功":"失敗");
t_1.setText(msg);
}
});
b_seeid.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
int id=Integer.parseInt(e_id.getText().toString());
People people[]=dbAdapter.queryOneData(id);
if(people==null){
t_1.setText("Id為"+id+"的記錄不存在！");
}
else{
t_1.setText("查詢成功：\n"+people[0].toString());
}
}
});
b_updid.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
int id=Integer.parseInt(e_id.getText().toString());
People t=new People();
t.Name=e_xm.getText().toString();
t.Banji=e_nl.getText().toString();
t.Xuehao=e_sg.getText().toString();
long n=dbAdapter.updateOneData(id,t);
if (n<0){
t_1.setText("更新過程錯誤！");
} else {
t_1.setText("成功更新資料，"+String.valueOf(n)+"條");
}
}
});
}
@Override
protected void onStop() {
super.onStop();
dbAdapter.close();
}
}