SQLiteOpenHelper学习笔记

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:paddingBottom="@dimen/activity_vertical_margin"
android:paddingLeft="@dimen/activity_horizontal_margin"
android:paddingRight="@dimen/activity_horizontal_margin"
android:paddingTop="@dimen/activity_vertical_margin"
android:orientation="vertical"
tools:context="com.user.android2_lesson5_sqlitedatabasehelper.MainActivity">
<Button
android:id="@+id/create"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:text="创建表"/>
<Button
android:id="@+id/insert"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:text="添加数据"/>
<Button
android:id="@+id/delete"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:text="删除数据"/>
<Button
android:id="@+id/updata"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:text="修改数据"/>
<Button
android:id="@+id/select"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:text="查询数据"/>

</LinearLayout>

创建一个datahelper继承SQLiteOpenHelper
package com.user.android2_lesson5_sqlitedatabasehelper;

import android.content.Context;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteOpenHelper;
import android.util.Log;

/**
* Created by user on 2016/7/8.
*/
public class MyDataHelper extends SQLiteOpenHelper {
//    构造方法 这个方法必须要有
//
public MyDataHelper(Context context,String name ,SQLiteDatabase.CursorFactory factory,int version){
super(context,name,factory,version);
}
//    当第一次创建数据库的时候会调用该方法
@Override
public void onCreate(SQLiteDatabase sqLiteDatabase) {
Log.i("DataHelper","创建数据库，初始化数据库");
//        因为是第一次数据库创建的时候调用的，所以这里通常进行的是数据库表的创建
String sql = "CREATE TABLE IF NOT EXISTS student(sid int,name text,sex text,age int)";
//        执行表创建语句
sqLiteDatabase.execSQL(sql);
}
//    当更新数据库（数据库版本更新）的时候调用该方法
@Override
public void onUpgrade(SQLiteDatabase sqLiteDatabase, int i, int i1) {
Log.i("DataHelper","更新数据库");
}
}

package com.user.android2_lesson5_sqlitedatabasehelper;

import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.util.Log;
import android.view.View;
import android.widget.Button;

public class MainActivity extends AppCompatActivity {
private Button create;
private Button insert;
private Button delete;
private Button updata;
private Button select;
private SQLiteDatabase db;

@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
create = (Button) findViewById(R.id.create);
insert = (Button) findViewById(R.id.insert);
delete = (Button) findViewById(R.id.delete);
updata  = (Button) findViewById(R.id.updata);
select = (Button) findViewById(R.id.select);

create.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
//                创建Helper对象
MyDataHelper helper = new MyDataHelper(MainActivity.this,"student_data2",null,1);
//                获取一个可读的数据库对象
db = helper.getReadableDatabase();

}
});
//        插入数据
insert.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
//                这里注意处理好版本号
MyDataHelper helper = new MyDataHelper(MainActivity.this,"student_data2",null,2);
//                得到一个可写入的数据库
db = helper.getWritableDatabase();
//
//                ContentValues con = new ContentValues();
//                con.put("sid",1);
//                con.put("name","张三");
//                con.put("sex","男");
//                con.put("age",18);
//                db.insert("student",null,con);

//                或者这样写
String sql  = "INSERT INTO student(sid,name,sex,age) VALUES(2,'李三炮','人妖',99); ";
db.execSQL(sql);
//                关闭数据库
Log.i("123","321");
db.close();
}
});
delete.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
String sql = "DELETE FROM student where sid = 1;";
db.execSQL(sql);
Log.i("1","删除成功");
}
});

updata.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
MyDataHelper helper = new MyDataHelper(MainActivity.this,"student_data2",null,2);
db = helper.getReadableDatabase();

}
});
select.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
Cursor cursor = db.query("student",null,null,null,null,null,null);
Log.i("2","ssss");
if (cursor.moveToFirst()){
do {
int sid = cursor.getInt(0);
String name = cursor.getString(1);
String sex = cursor.getString(2);
int age = cursor.getInt(3);
}while(cursor.moveToNext());
}

}
});
}
}