Android 数据库的创建、升级和数据的添加

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一、数据库的创建和数据的添加：

1.创建MyDatabaseHelper类继承SQLiteOpenHelper：

public class MyDatabaseHelper extends SQLiteOpenHelper {    public static final String CREATE_BOOK ="create table Book("            + "id integer primary key autoincrement,"            +"author text,"+"price real,"+"pages integer,"+"name text)";    private Context mContext;    public MyDatabaseHelper(Context context, String name, SQLiteDatabase.CursorFactory factory, int version) {        super(context, name, factory, version);        mContext = context;    }    //这个方法用来做数据库的创建    @Override    public void onCreate(SQLiteDatabase sqLiteDatabase) {        sqLiteDatabase.execSQL(CREATE_BOOK);         Toast.makeText(mContext, "数据库创建成功", Toast.LENGTH_SHORT).show();    }     //在这里做数据库的升级    @Override    public void onUpgrade(SQLiteDatabase sqLiteDatabase, int i, int i1) {        sqLiteDatabase.execSQL("drop table if exists Book");          onCreate(sqLiteDatabase);    }}

2、Activity的代码：

public class MainActivity extends AppCompatActivity {    private MyDatabaseHelper mHelper;    @Override    protected void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        setContentView(R.layout.activity_main);        //实例化MyDatabaseHelper的对象，传入你要创建的数据库的名称以及版本号        mHelper = new MyDatabaseHelper(this,"Book.db",null,1);    }    public void onClick(View view) {        if (view != null) {            switch (view.getId()){                //点击创建数据库               case  R.id.activity_main_crate:                   mHelper.getWritableDatabase();                break;               //点击添加数据                case R.id.activity_main_add:                    SQLiteDatabase database = mHelper.getReadableDatabase();                    ContentValues values = new ContentValues();                    //第一条数据                    values.put("name","未知书名1");                    values.put("author","未知1");                    values.put("pages","245");                    values.put("pice","30");                    database.insert("Book",null,values);                    values.clear();                    //第二条数据                    values.put("name","未知书名2");                    values.put("author","未知2");                    values.put("pages","123");                    values.put("pice","22");                    database.insert("Book",null,values);                    break;            }        }    }}

3、XML文件的代码：

<?xml version="1.0" encoding="utf-8"?><RelativeLayout    xmlns:android="http://schemas.android.com/apk/res/android"    xmlns:tools="http://schemas.android.com/tools"    android:id="@+id/activity_main"    android:layout_width="match_parent"    android:layout_height="match_parent"    android:paddingLeft="@dimen/activity_horizontal_margin"    android:paddingRight="@dimen/activity_horizontal_margin"    android:paddingTop="@dimen/activity_vertical_margin"    android:paddingBottom="@dimen/activity_vertical_margin"    tools:context="com.example.zhangguangyi.sqldemo.MainActivity">    <Button        android:id="@+id/activity_main_crate"        android:onClick="onClick"        android:layout_width="match_parent"        android:layout_height="wrap_content"        android:text="创建数据库" />    <Button        android:id="@+id/activity_main_add"        android:onClick="onClick"        android:layout_width="match_parent"        android:layout_height="wrap_content"        android:text="添加数据" /></RelativeLayout>

二、数据库的更新与升级：

1、MyDatabaseHelper类的代码

public class MyDatabaseHelper extends SQLiteOpenHelper {    public static final String CREATE_BOOK ="create table Book("            + "id integer primary key autoincrement,"            +"author text,"+"price real,"+"pages integer,"+"name text)";    public static final String CREATE_CATEGORY ="create table Category("            + "id integer primary key autoincrement,"    +"category_name text,"+"category_code integer)";    private Context mContext;    public MyDatabaseHelper(Context context, String name, SQLiteDatabase.CursorFactory factory, int version) {        super(context, name, factory, version);        mContext = context;    }    //这个方法用来做数据库的创建    @Override    public void onCreate(SQLiteDatabase sqLiteDatabase) {        sqLiteDatabase.execSQL(CREATE_BOOK);        sqLiteDatabase.execSQL(CREATE_CATEGORY);        Toast.makeText(mContext, "数据库创建成功", Toast.LENGTH_SHORT).show();    }     //在这里做数据库的升级    @Override    public void onUpgrade(SQLiteDatabase sqLiteDatabase, int i, int i1) {        sqLiteDatabase.execSQL("drop table if exists Book");        sqLiteDatabase.execSQL("drop table if exists category");        onCreate(sqLiteDatabase);    }}

2、Activity的代码(只是修改版本号，一定要大于原先的版本的号)：

public class MainActivity extends AppCompatActivity {    private MyDatabaseHelper mHelper;    @Override    protected void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        setContentView(R.layout.activity_main);        //实例化MyDatabaseHelper的对象，传入你要创建的数据库的名称以及版本号        mHelper = new MyDatabaseHelper(this,"Book.db",null,2);    }    public void onClick(View view) {        if (view != null) {            switch (view.getId()){                //点击创建数据库               case  R.id.activity_main_crate:                   mHelper.getWritableDatabase();                break;               //点击添加数据                case R.id.activity_main_add:                    SQLiteDatabase database = mHelper.getReadableDatabase();                    ContentValues values = new ContentValues();                    //第一条数据                    values.put("name","未知书名1");                    values.put("author","未知1");                    values.put("pages","245");                    values.put("pice","30");                    database.insert("Book",null,values);                    values.clear();                    //第二条数据                    values.put("name","未知书名2");                    values.put("author","未知2");                    values.put("pages","123");                    values.put("pice","22");                    database.insert("Book",null,values);                    break;            }        }    }}

3、XMl文件的中的代码不变，也可以视情况修改。

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