填充SQLite数据库 [英] Populating SQLite Database
问题描述
我不是很熟悉Android的SQLite数据库。我只有填充SQLite数据库的大概的了解。我按照一些教程，但他们告诉不同的东西。 我有一个Android项目和它的packeges之一是名为.db 该套件包括5个不同的类别。它们是：
I am not very much familiar with android sqlite database. I only have rough idea of populating sqlite database. I have followed some tutorials but they tells different things. I have an android project and one of its' packeges is a .db This package consists of 5 different classes. They are:
- DataAdapter.java
- DataBaseHelper.java
- DBAdapter.java
- LoadDBActivity.java
- SelectDBAdapter.java
我知道SelectDBAdapter类是用来选择数据库中的数据。我的数据库是这是.JPEG format.I可以从sqliteBrowser打开资源文件夹。 其实，我想知道的是为什么要使用这些不同的类？什么是每个类的目的是什么？
I know SelectDBAdapter class is used to select data from the database. My database is in asset folder which is in .jpeg format.I can open it from sqliteBrowser. Actually, what I want to know is why should we use these different classes ? and what's the purpose of each and every class ?
我真的很抱歉，我不能发表codeS，因为这个项目是属于另外一个人（我的朋友）。 我将非常感谢，如果有人可以这么好心足以说明使用这些不同类别的含义，我们为什么要使用这样的塞纳里奥？
I am really sorry, I cannot post codes since this projects belongs to another person (my friend). I would be much obliged if anyone could be so kind enough to explain the meaning of using these different classes and why should we use such a senario ?
推荐答案
从我的开发经验，我总是preFER在/ RES加prepared SQLite数据库文件/原folder.You创建/管理使用Firefox的SQLite的经理插件SQLite数据库，这是一个伟大的工具。这种方法实在是太棒了，因为
From my development experience , I always prefer to add a prepared sqlite database file in the /res/raw folder.You create/manage sqlite database using Sqlite Manager addon of Firefox , it's a great tool. This method is really great because
- 首先，我并不需要写C $ CS一堆$创建/管理数据库。
- 最重要的是，一些应用程序需要从pre-填充数据库中读取。我并不需要关心什么应用程序需要和数据库是否为空或者已经填满。它为所有的目的。我只需要编写的软件运行所需要的sql语句简单一些的方法。
下面是我自己的定制DatabaseHelper类。要使用这个类，你需要遵循一些指示。
Here is my own customised DatabaseHelper class. To use this class you'll need to follow some instructions.
- 如果SQLite数据库大小为1MB以上，然后将文件分割成块，我preFER 512KB块，并把它们放入/ RES / raw目录。
-
编辑包名，并在下面的类你的数据库文件名。
- If sqlite database size is more than 1MB then split the file into chunks , I prefer 512KB chunks and place them into /res/raw directory.
Edit the package name and your db file names in the following class.
package your.packagee.name;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import android.content.Context;
import android.content.res.Resources;
import android.database.Cursor;
import android.database.SQLException;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteException;
import android.database.sqlite.SQLiteOpenHelper;
import android.util.Log;
import android.widget.Toast;
public class DataBaseHelper extends SQLiteOpenHelper {
private static final String pkg = "your package name";
private static String DB_PATH = "/data/data/" + pkg + "/databases/";
private static String DB_NAME = "yourDBFile.sqlite";
int[] dbfiles = { R.raw.chunk1 , R.raw.chunk2 ..... };
private SQLiteDatabase myDataBase;
private final Context myContext;
public DataBaseHelper(Context context) {
super(context, DB_NAME, null, 1);
this.myContext = context;
}
public void createDataBase() {
boolean dbExist = checkDataBase();
if (dbExist) {
// do nothing - database already exist
} else {
this.getReadableDatabase();
try {
CopyDataBase();
} catch (IOException e) {
Toast.makeText(myContext, e.getMessage(), Toast.LENGTH_SHORT)
.show();
Log.d("Create DB", e.getMessage());
}
}
}
private boolean checkDataBase() {
SQLiteDatabase checkDB = null;
try {
String myPath = DB_PATH + DB_NAME;
checkDB = SQLiteDatabase.openDatabase(myPath, null,
SQLiteDatabase.NO_LOCALIZED_COLLATORS);
} catch (SQLiteException e) {
Toast.makeText(myContext, e.getMessage(), Toast.LENGTH_SHORT)
.show();
Log.d("Check DB", e.getMessage());
}
if (checkDB != null) {
checkDB.close();
}
return checkDB != null ? true : false;
}
private void CopyDataBase() throws IOException {
InputStream databaseInput = null;
Resources resources = myContext.getResources();
String outFileName = DB_PATH + DB_NAME;
OutputStream databaseOutput = new FileOutputStream(outFileName);
byte[] buffer = new byte[512];
int length;
for (int i = 0; i < dbfiles.length; i++) {
databaseInput = resources.openRawResource(dbfiles[i]);
while ((length = databaseInput.read(buffer)) > 0) {
databaseOutput.write(buffer, 0, length);
databaseOutput.flush();
}
databaseInput.close();
}
databaseOutput.flush();
databaseOutput.close();
}
public void openDataBase() throws SQLException {
String myPath = DB_PATH + DB_NAME;
myDataBase = SQLiteDatabase.openDatabase(myPath, null,
SQLiteDatabase.NO_LOCALIZED_COLLATORS);
}
@Override
public synchronized void close() {
if (myDataBase != null)
myDataBase.close();
super.close();
}
@Override
public void onCreate(SQLiteDatabase db) {
}
@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
}
public boolean deleteItem (String ID){
String query = "delete from item where id='" + ID + "'" ;
Log.d("Query : ", query);
try{
myDataBase.execSQL(query);
return true ;
} catch (Exception e){
Log.d("Exception", e.toString());
return false ;
}
}
public Cursor getSearchFromID(String id) {
return myDataBase.rawQuery("select * from item where id = \"" + id + "\"", null);
}
public boolean addSave(String type, String data , String time) {
String query = "insert into item (type, data , timestamp) values ('" + type
+ "', '" + data + "', '" + time + "')";
try {
myDataBase.execSQL(query);
return true ;
} catch (Exception e) {
return false ;
}
}
}
下面是写为样本，如何使用它的一些方法。
Here's some methods written as a sample , how to use it.
用法很简单。当你的应用程序启动，这意味着在你的启动活动中使用这种code初始化数据库
Usage is simple. When your application starts , that means in your Launcher activity use this code to initialize your database
DataBaseHelper helper = new DataBaseHelper(this);
helper.createDataBase();
helper.openDataBase();
helper.close();
就用写在DatabaseHelper类中的方法。样本会是这样
Then just use the methods written in DatabaseHelper class. A sample will be like this
String id = "1";
DataBaseHelper helper = new DataBaseHelper(this);
helper.openDataBase();
Cursor c = helper.getSearchFromID(id);
if(c.getCount() > 0){
c.moveToFirst();
while(!c.isAfterLast()){
// extract your data from cursor
c.MoveToNext();
}
}
希望这本书能解决你的所有关于Android的SQLite数据库的问题。至少它解决了我。谢谢你。
Hope it will solve your all problems about sqlite database in Android. At least it solved for me. Thank you.
这篇关于填充SQLite数据库的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！
