SQLite数据库增删改查
SQLite，是一款轻型的数据库，是遵守ACID的关系型数据库管理系统，它包含在一个相对小的C库中。它是D.RichardHipp建立的公有领域项目。它的设计目标是嵌入式的，而且目前已经在很多嵌入式产品中使用了它，它占用资源非常的低，在嵌入式设备中，可能只需要几百K的内存就够了。它能够支持Windows/Linux/Unix等等主流的操作系统，同时能够跟很多程序语言相结合，比如 Tcl、C#、PHP、Java等，还有ODBC接口，同样比起Mysql、PostgreSQL这两款开源的世界著名数据库管理系统来讲，它的处理速度比他们都快。SQLite第一个Alpha版本诞生于2000年5月。 至2018年已经有18个年头
布局文件activity_main.xml
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical"
tools:context="com.example.databaseoperate.MainActivity">
android:text="点击我将会为你创建数据库"
android:layout_width="wrap_content"
android:layout_height="wrap_content" />
android:text="点击我插入书籍"
android:layout_width="wrap_content"
android:layout_height="wrap_content" />
android:text="点击我删除数据"
android:layout_width="wrap_content"
android:layout_height="wrap_content" />
android:text="点击我更新数据"
android:layout_width="wrap_content"
android:layout_height="wrap_content" />
android:text="点击我查询数据"
android:layout_width="wrap_content"
android:layout_height="wrap_content" />
android:layout_width="match_parent"
android:layout_height="wrap_content" />
数据库文件MyDatabaseHelper.java
package com.example.databaseoperate;
import android.content.Context;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteOpenHelper;
import android.widget.Toast;
/**
* 创建数据库,必须继承SQLiteOpenHelper
*/
public class MyDatabaseHelper extends SQLiteOpenHelper {
//创建一本书的表
public static final String CREATE_BOOK = "create table Book(id integer primary key autoincrement," +
"name text,author text,price real,pages integer)";
//创建管理书籍的类别的表
public static final String CREATE_CATEGORY = "create table Category(id integer primary autocincrement,category_name text,category_code integer)";
private Context context;
/**
*
* //@param context上下文
* @param name 数据库的名称
* @param factory 返回的游标
* @param version 数据库的版本
*/
public MyDatabaseHelper(Context context, String name, SQLiteDatabase.CursorFactory factory, int version) {
super(context, name, factory, version);
this.context = context;
}
@Override
public void onCreate(SQLiteDatabase db) {//创建数据库的方法
db.execSQL(CREATE_BOOK);
db.execSQL(CREATE_CATEGORY);
Toast.makeText(context, "创建数据库成功!", Toast.LENGTH_LONG).show();
}
@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {//更新数据库
Toast.makeText(context, "更新了数据库", Toast.LENGTH_LONG).show();
db.execSQL("drop table if exists Book");
db.execSQL("drop table if exists Category");
}
}
布局代码MainActivity.java
package com.example.databaseoperate;
import android.content.ContentValues;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;
import android.os.Bundle;
import android.support.v7.app.AppCompatActivity;
import android.util.Log;
import android.view.View;
import android.widget.Button;
import android.widget.TextView;
public class MainActivity extends AppCompatActivity implements View.OnClickListener {
MyDatabaseHelper myDatabaseHelper;
private Button create_database;
private Button insertdata;
private Button deletedata;
private Button updatedata;
private Button query;
SQLiteDatabase writableDatabase;
private TextView showContent;
private String TAG = "MainActivity";
@Override
protected void onCreate(Bundle savedInstanceState) {
myDatabaseHelper = new MyDatabaseHelper(MainActivity.this, "BookStore.db", null, 3);
writableDatabase = myDatabaseHelper.getWritableDatabase();//获取数据库实例
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
initView();
}
private void initView() {
create_database = (Button) findViewById(R.id.create_database);
create_database.setOnClickListener(this);
insertdata = (Button) findViewById(R.id.insertdata);
insertdata.setOnClickListener(this);
deletedata = (Button) findViewById(R.id.deletedata);
deletedata.setOnClickListener(this);
updatedata = (Button) findViewById(R.id.updatedata);
updatedata.setOnClickListener(this);
query = (Button) findViewById(R.id.query);
query.setOnClickListener(this);
showContent = (TextView) findViewById(R.id.showContent);
showContent.setOnClickListener(this);
}
@Override
public void onClick(View v) {
switch (v.getId()) {
case R.id.create_database:
// MyDatabaseHelper(Context context, String name, SQLiteDatabase.CursorFactory factory, int version)
// SQLiteDatabase readableDatabase = myDatabaseHelper.getReadableDatabase();
break;
case R.id.insertdata://添加数据
//name text,author text,price real,pages integer
/* String insertSQL = "insert into Book(name,author,price,pages) values('Android第一行代码','郭霖',76.0,120)";
String insertSQL2 = "insert into Book(name,author,price,pages) values('Android第一行代码++','郭霖',76.0,120)";
writableDatabase.execSQL(insertSQL);
writableDatabase.execSQL(insertSQL2);*/
String[] bookNmae = new String[]{"三国演义","水浒传","西游记","红楼梦"};
String[] authors = new String[]{"罗贯中","施耐庵","吴承恩","曹雪芹"};
double[] prices = new double[]{21, 22, 23, 24};
int[] pages = new int[]{100, 120, 130, 140};
ContentValues insert = new ContentValues();
for(int i = 0;i
insert.put("name",bookNmae[i]);
insert.put("author", authors[i]);
insert.put("price", prices[i]);
insert.put("pages",pages[i]);
//insert(String table, String nullColumnHack, ContentValues values)
writableDatabase.insert("Book", null, insert);
insert.clear();
}
/* ContentValues insert = new ContentValues();
insert.put("name","西游记");
insert.put("author", "吴承恩");
insert.put("price", 99);
insert.put("pages",300);
//insert(String table, String nullColumnHack, ContentValues values)
writableDatabase.insert("Book", null, insert);*/
break;
case R.id.deletedata:
//delete(String table, String whereClause, String[] whereArgs)
writableDatabase.delete("Book","name = ?",new String[]{"Android第一行代码"});
break;
case R.id.updatedata:
ContentValues contentValues = new ContentValues();
contentValues.put("price", 99);
// update(String table, ContentValues values, String whereClause, String[] whereArgs)
writableDatabase.update("Book",contentValues,"name=?",new String[]{"三国演义"});
break;
case R.id.query:
/* String select = "select * from Book";
writableDatabase.execSQL(select);
writableDatabase.q*/
// Cursor query(String table, String[] columns, String selection,String[] selectionArgs, String groupBy, String having,String orderBy)
//name text,author text,price real,pages integer
//查询数据,Cursor表示的是查询的结果集
Cursor cursor = writableDatabase.query("Book", new String[]{"name", "price"}, null, null, null, null, null);
if (cursor.moveToFirst()) {
do {
String name = cursor.getString(cursor.getColumnIndex("name"));
double price = cursor.getDouble(cursor.getColumnIndex("price"));
Log.i(TAG, "name =" + name);
Log.i(TAG, "price =" + price);
} while (cursor.moveToNext());
}
break;
}
}
}