《Android进阶》Sqlite的使用

之前认为Sqlite只能一次性创建多个表,其实不是

关键是对Sqlite的操作需要一些技巧:

package com.example.mydemo;

import android.content.Context;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteDatabase.CursorFactory;
import android.database.sqlite.SQLiteOpenHelper;
import android.widget.Toast;

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,
            CursorFactory factory, int version) {
        super(context, name, factory, version);
        mContext = context;
    }

    @Override
    public void onCreate(SQLiteDatabase db) {
        db.execSQL(CREATE_BOOK);
//        db.execSQL(CREATE_CATEGORY);
    /*    db.execSQL("insert into Book (name, author, pages, price) values(?, ?, ?, ?)",
                new String[] { "The Da Vinci Code", "Dan Brown", "454", "16.96" });*/
        Toast.makeText(mContext, "Create succeeded", Toast.LENGTH_SHORT).show();
        
    }

    @Override
    public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
        // TODO Auto-generated method stub
         switch(oldVersion){
           case 3:
               db.execSQL(CREATE_CATEGORY);
           case 4:
           case 5:
           case 6:
               db.execSQL("alter table Book add column category_idd integer");
           default:
               
         }
    }

}

目前很好奇,怎么得到数据库的版本(当然db.getVersion())肯定可以

但如果仅仅是一个.db文件,没发现哪个可视化工具可以直接查看

package com.example.mydemo;

import android.app.Activity;
import android.app.Fragment;
import android.content.ContentValues;
import android.database.sqlite.SQLiteDatabase;
import android.os.Bundle;
import android.view.LayoutInflater;
import android.view.View;
import android.view.View.OnClickListener;
import android.view.ViewGroup;
import android.widget.Button;
import android.widget.TextView;

/**
 * A placeholder fragment containing a simple view.
 */
public class PlaceholderFragment extends Fragment {

    OnDtaReceivedListener mCallback;
    private MyDatabaseHelper dbHelper;

    // Container Activity must implement this interface
    public interface OnDtaReceivedListener {
        public void onTextSelected(View view);
    }

    public PlaceholderFragment() {
    }

    @Override
    public void onAttach(Activity activity) {
        // TODO Auto-generated method stub
        super.onAttach(activity);
        try {
            mCallback = (OnDtaReceivedListener) activity;
        } catch (ClassCastException e) {
            throw new ClassCastException(activity.toString()
                    + " must implement OnDtaReceivedListener");
        }
    }

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
            Bundle savedInstanceState) {

        View rootView = inflater.inflate(R.layout.fragment_main, container,
                false);
        dbHelper = new MyDatabaseHelper(getActivity(), "BookStore.db", null, 7);
        Button createDatabase = (Button) rootView
                .findViewById(R.id.create_database);
        createDatabase.setOnClickListener(new OnClickListener() {
            @Override
            public void onClick(View v) {
                dbHelper.getWritableDatabase();
            }
        });
        Button addData = (Button) rootView.findViewById(R.id.add_data);
        addData.setOnClickListener(new OnClickListener() {
            @Override
            public void onClick(View v) {
                SQLiteDatabase db = dbHelper.getWritableDatabase();
                ContentValues values = new ContentValues();
                // 开始组装第一条数据
                values.put("name", "The DaVinci Code");
                values.put("author", "Dan Brown");
                values.put("pages", 454);
                values.put("price", 16.96);
                db.insert("Book", null, values); // 插入第一条数据
                values.clear();
                // 开始组装第二条数据
                values.put("name", "The Lost Symbol");
                values.put("author", "Dan Brown");
                values.put("pages", 510);
                values.put("price", 19.95);
                db.insert("Book", null, values); // 插入第二条数据
                values.clear();
                // 开始组装第三条数据  可以允许某条数据为空
                values.put("name", "The Lost1");
                values.put("pages", 510);
                values.put("price", 19.95);
                db.insert("Book", null, values); // 插入第二条数据
            }
        });

        Button updateData = (Button) rootView.findViewById(R.id.update_data);
        updateData.setOnClickListener(new OnClickListener() {
            @Override
            public void onClick(View v) {
                SQLiteDatabase db = dbHelper.getWritableDatabase();
                ContentValues values = new ContentValues();
                values.put("price", 10.99);
                db.update("Book", values, "name = ?",
                        new String[] { "The DaVinci Code" });
                
                //上述代码想表达的意图就是，将名字是 The Da Vinci Code的这本书的价格改成 10.99
            }
        });
        
        Button deleteButton = (Button) rootView.findViewById(R.id.delete_data);
        deleteButton.setOnClickListener(new OnClickListener() {

            @Override
            public void onClick(View v) {
                SQLiteDatabase db = dbHelper.getWritableDatabase();
                db.beginTransaction(); // 开启事务
                db.delete("book", "name = ?", new String[] { "The Da Vinci Code" });
                db.delete("book", "id = ?", new String[] { "4" });
            }
            
        });
        return rootView;

    }

}

布局文件:

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical" >

    <Button
        android:id="@+id/create_database"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="Create database" />

    <Button
        android:id="@+id/add_data"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="Add data" />

    <Button
        android:id="@+id/update_data"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="Update data" />

    <Button
        android:id="@+id/delete_data"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="Delete data" />

</LinearLayout>