Android 數據庫的創建、升級和數據的添加

一、數據庫的創建和數據的添加：

1.創建MyDatabaseHelper類繼承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;
    }

    //這個方法用來做數據庫的創建
    @Override
    public void onCreate(SQLiteDatabase sqLiteDatabase) {
        sqLiteDatabase.execSQL(CREATE_BOOK);
         Toast.makeText(mContext, "數據庫創建成功", Toast.LENGTH_SHORT).show();

    }
     //在這裏做數據庫的升級
    @Override
    public void onUpgrade(SQLiteDatabase sqLiteDatabase, int i, int i1) {
        sqLiteDatabase.execSQL("drop table if exists Book");
          onCreate(sqLiteDatabase);
    }
}

2、Activity的代碼：

public class MainActivity extends AppCompatActivity {

    private MyDatabaseHelper mHelper;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        //實例化MyDatabaseHelper的對象，傳入你要創建的數據庫的名稱以及版本號
        mHelper = new MyDatabaseHelper(this,"Book.db",null,1);

    }

    public void onClick(View view) {
        if (view != null) {
            switch (view.getId()){
                //點擊創建數據庫
               case  R.id.activity_main_crate:
                   mHelper.getWritableDatabase();
                break;
               //點擊添加數據
                case R.id.activity_main_add:
                    SQLiteDatabase database = mHelper.getReadableDatabase();
                    ContentValues values = new ContentValues();
                    //第一條數據
                    values.put("name","未知書名1");
                    values.put("author","未知1");
                    values.put("pages","245");
                    values.put("pice","30");
                    database.insert("Book",null,values);
                    values.clear();
                    //第二條數據
                    values.put("name","未知書名2");
                    values.put("author","未知2");
                    values.put("pages","123");
                    values.put("pice","22");
                    database.insert("Book",null,values);
                    break;
            }
        }
    }
}

3、XML文件的代碼：

<?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="創建數據庫" />
    <Button
        android:id="@+id/activity_main_add"
        android:onClick="onClick"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="添加數據" />
</RelativeLayout>

二、數據庫的更新與升級：

1、MyDatabaseHelper類的代碼

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;
    }

    //這個方法用來做數據庫的創建
    @Override
    public void onCreate(SQLiteDatabase sqLiteDatabase) {
        sqLiteDatabase.execSQL(CREATE_BOOK);
        sqLiteDatabase.execSQL(CREATE_CATEGORY);
        Toast.makeText(mContext, "數據庫創建成功", Toast.LENGTH_SHORT).show();

    }
     //在這裏做數據庫的升級
    @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的代碼(只是修改版本號，一定要大於原先的版本的號)：

public class MainActivity extends AppCompatActivity {

    private MyDatabaseHelper mHelper;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        //實例化MyDatabaseHelper的對象，傳入你要創建的數據庫的名稱以及版本號
        mHelper = new MyDatabaseHelper(this,"Book.db",null,2);

    }

    public void onClick(View view) {
        if (view != null) {
            switch (view.getId()){
                //點擊創建數據庫
               case  R.id.activity_main_crate:
                   mHelper.getWritableDatabase();
                break;
               //點擊添加數據
                case R.id.activity_main_add:
                    SQLiteDatabase database = mHelper.getReadableDatabase();
                    ContentValues values = new ContentValues();
                    //第一條數據
                    values.put("name","未知書名1");
                    values.put("author","未知1");
                    values.put("pages","245");
                    values.put("pice","30");
                    database.insert("Book",null,values);
                    values.clear();
                    //第二條數據
                    values.put("name","未知書名2");
                    values.put("author","未知2");
                    values.put("pages","123");
                    values.put("pice","22");
                    database.insert("Book",null,values);
                    break;
            }
        }
    }
}

3、XMl文件的中的代碼不變，也可以視情況修改。