Android数据库SQLite的使用

//SQLiteOpenHelper类

package com.example.clover.sqliteactivity;

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

/**
* 作者：Jacky
* 邮箱：550997728@qq.com
*/
//DatabaseHelper作为一个访问SQLite的助手类，提供两个方面的功能，
//第一，getReadableDatabase(),getWritableDatabase()可以获得SQLiteDatabase对象，通过该对象可以对数据库进行操作
//第二，提供了onCreate()和onUpgrade()两个回调函数，允许我们在创建和升级数据库时，进行自己的操作
public class DatabaseHelper extends SQLiteOpenHelper{
private static final  int VERSION=1;
//在SQLiteOpenHelper的子类当中，必须有该构造函数
public DatabaseHelper(Context context,String name,SQLiteDatabase.CursorFactory factory,int version){
//必须通过super调用父类当中的构造函数
super(context,name,factory,version);
}
public DatabaseHelper(Context context,String name,int version){
this(context, name, null, version);
}
public DatabaseHelper(Context context,String name){
this(context, name, VERSION);
}
//该函数是在第一次创建数据库的时候执行,实际上是在第一次得到SQLiteDatabase对象的时候，才会调用这个方法
@Override
public void onCreate(SQLiteDatabase db) {
System.out.println("create a Database");
db.execSQL("create table user(id int,name varchar(20))");
}

@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
System.out.println("pdate a Database");
}

}

//SQLiteActivity类

package com.example.clover.sqliteactivity;

import android.content.ContentValues;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;
import android.os.Bundle;
import android.support.v7.app.ActionBarActivity;
import android.view.View;
import android.widget.Button;

public class SQLiteActivity extends ActionBarActivity  {
private Button createDatabase = null;
private Button updateDatabase = null;
private Button insert = null;
private Button update = null;
private Button query = null;

@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
createDatabase = (Button) findViewById(R.id.createDatabase);
updateDatabase = (Button) findViewById(R.id.updateDatabase);
insert = (Button) findViewById(R.id.insert);
update = (Button) findViewById(R.id.update);
query = (Button) findViewById(R.id.query);
createDatabase.setOnClickListener(new CreateDataListener());
updateDatabase.setOnClickListener(new UpdateDataListener());
insert.setOnClickListener(new InsertListener());
update.setOnClickListener(new UpdateListener());
query.setOnClickListener(new QueryListener());
}

private class CreateDataListener implements View.OnClickListener {
@Override
public void onClick(View v) {
//创建一个DatabaseHelper对象
DatabaseHelper dbHelper = new DatabaseHelper(SQLiteActivity.this,"test_mars_db");
//只有调用了DatabaseHelper对象的getReadableDatabase()方法，或者是getWritableDatabase()方法之后，才会创建，或打开一个数据库
SQLiteDatabase db = dbHelper.getReadableDatabase();
}
}

private class UpdateDataListener implements View.OnClickListener {
@Override
public void onClick(View v) {
DatabaseHelper dbHelper = new DatabaseHelper(SQLiteActivity.this,"test_mars_db",2);
SQLiteDatabase db = dbHelper.getReadableDatabase();
}
}

private class InsertListener implements View.OnClickListener {
@Override
public void onClick(View v) {
//生成ContentValues对象
ContentValues values = new ContentValues();
//想该对象当中插入键值对，其中键是列名，值是希望插入到这一列的值，值必须和数据库当中的数据类型一致
values.put("id", 1);
values.put("name","zhangsan");
DatabaseHelper dbHelper = new DatabaseHelper(SQLiteActivity.this,"test_mars_db",2);
SQLiteDatabase db = dbHelper.getWritableDatabase();
//调用insert方法，就可以将数据插入到数据库当中
db.insert("user", null, values);
d431
}
}
//更新操作就相当于执行SQL语句当中的update语句
//UPDATE table_name SET XXCOL=XXX WHERE XXCOL=XX...
private class UpdateListener implements View.OnClickListener {
@Override
public void onClick(View v) {
//得到一个可写的SQLiteDatabase对象
DatabaseHelper dbHelper = new DatabaseHelper(SQLiteActivity.this,"test_mars_db",2);
SQLiteDatabase db = dbHelper.getWritableDatabase();
ContentValues values = new ContentValues();
values.put("name", "zhangsanfeng");
//第一个参数是要更新的表名
//第二个参数是一个ContentValeus对象
//第三个参数是where子句
db.update("user", values, "id=?", new String[]{"1"});
}
}

private class QueryListener implements View.OnClickListener {
@Override
public void onClick(View v) {
//                              System.out.println("aaa------------------");
//                              Log.d("myDebug", "myFirstDebugMsg");

DatabaseHelper dbHelper = new DatabaseHelper(SQLiteActivity.this,"test_mars_db",2);
SQLiteDatabase db = dbHelper.getReadableDatabase();
Cursor cursor = db.query("user", new String[]{"id","name"}, "id=?", new String[]{"1"},null,null,null);
while(cursor.moveToNext()){
String name = cursor.getString(cursor.getColumnIndex("name"));
System.out.println("query--->" + name);
}
}
}
}

//布局文件main.xml

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
android:orientation="vertical"
android:paddingBottom="@dimen/activity_vertical_margin"
android:paddingLeft="@dimen/activity_horizontal_margin"
android:paddingRight="@dimen/activity_horizontal_margin"
android:paddingTop="@dimen/activity_vertical_margin"
tools:context=".SQLiteActivity">

<TextView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="@string/hello_world"/>
<Button
android:id="@+id/createDatabase"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:text="@string/createDatabase"/>
<Button
android:id="@+id/updateDatabase"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:text="@string/updateDatabase"/>
<Button
android:id="@+id/insert"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:text="@string/insert"/>
<Button
android:id="@+id/update"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:text="@string/update"/>
<Button
android:id="@+id/query"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:text="@string/query"/>
</LinearLayout>