《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>