我有一个 android 报价应用程序，其中我使用 SQLite 数据库来存储报价。我已经使用这个 DatabaseHelper 启动了该应用程序的第一个版本。
public class DataBaseHandler extends SQLiteOpenHelper {
private static String DB_PATH;
private static String DB_NAME = "SuccessQuotes";
private SQLiteDatabase myDataBase;
private static int DATABASE_VERSION = 1;
private final Context myContext;
public DataBaseHandler(Context context) {
super(context, DB_NAME, null, 1);
this.myContext = context;
DB_PATH = context.getDatabasePath(DB_NAME).toString();
Log.e("path", DB_PATH);
}
// ==============================================================================
public void createDataBase() throws IOException {
boolean dbExist = checkDataBase();
if (dbExist) {
// do nothing - database already exist
} else {
this.getReadableDatabase();
try {
copyDataBase();
} catch (IOException e) {
throw new Error("Error copying database");
}
}
}
// ==============================================================================
private boolean checkDataBase() {
SQLiteDatabase checkDB = null;
try {
String myPath = DB_PATH;
checkDB = SQLiteDatabase.openDatabase(myPath, null, SQLiteDatabase.OPEN_READONLY);
} catch (SQLiteException e) {
// database does't exist yet.
}
if (checkDB != null) {
checkDB.close();
}
return checkDB != null ? true : false;
}
// ==============================================================================
private void copyDataBase() throws IOException {
// Open your local db as the input stream
InputStream myInput = myContext.getAssets().open(DB_NAME);
// Path to the just created empty db
String outFileName = DB_PATH;
// Open the empty db as the output stream
OutputStream myOutput = new FileOutputStream(outFileName);
// transfer bytes from the inputfile to the outputfile
byte[] buffer = new byte[1024];
int length;
while ((length = myInput.read(buffer)) > 0) {
myOutput.write(buffer, 0, length);
}
// Close the streams
myOutput.flush();
myOutput.close();
myInput.close();
}
// ==============================================================================
public void openDataBase() throws SQLException {
// Open the database
String myPath = DB_PATH;
myDataBase = SQLiteDatabase.openDatabase(myPath, null, SQLiteDatabase.OPEN_READONLY);
}
// ==============================================================================
@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) {
}
}
我的数据库 Activity 是:
public class DAO {
// All Static variables
private SQLiteDatabase database;
private DataBaseHandler dbHandler;
private static final String TABLE_QUOTES = "quotes";
private static final String TABLE_AUTHORS = "authors";
private static final String TABLE_SETTINGS = "settings";
// Pages Table Columns names
private static final String QU_ID = "_quid";
private static final String QU_TEXT = "qu_text";
private static final String QU_AUTHOR = "qu_author";
private static final String QU_FAVORITE = "qu_favorite";
private static final String QU_WEB_ID = "qu_web_id";
private static final String AU_ID = "_auid";
private static final String AU_NAME = "au_name";
private static final String AU_PICTURE = "au_picture";
private static final String AU_PICTURE_SDCARD = "au_picture_sdcard";
private static final String AU_WEB_ID = "au_web_id";
// ==============================================================================
public DAO(Context context) {
dbHandler = new DataBaseHandler(context);
try {
dbHandler.createDataBase();
} catch (IOException ioe) {
throw new Error("Unable to create database");
}
try {
dbHandler.openDataBase();
} catch (SQLException sqle) {
throw sqle;
}
// Log.e("path2", context.getDatabasePath("SuccessQuotes").toString());
// open();
}
// ==============================================================================
// Getting All Quotes
public Cursor getQuotes(String start) {
// Select All Query
String limit = "15";
if (start.equals("5000")) {
String query_count = "SELECT COUNT(" + QU_ID + ") AS count FROM "
+ TABLE_QUOTES;
Cursor c_count = database.rawQuery(query_count, null);
c_count.moveToFirst();
Integer count = c_count.getInt(c_count.getColumnIndex("count"));
limit = String.valueOf(count);
}
String query = "SELECT * FROM " + TABLE_QUOTES + " JOIN "
+ TABLE_AUTHORS + " ON " + QU_AUTHOR + " = " + AU_WEB_ID
+ " ORDER BY " + QU_WEB_ID + " DESC "+ " LIMIT " + start + ", " + limit;
//Log.i("query",query);
Cursor cursor = database.rawQuery(query, null);
cursor.moveToFirst();
return cursor;
}
// ==============================================================================
// Getting All Quotes
public Cursor getFavoriteQuotes(String start) {
// Select All Query
String limit = "15";
String query = "SELECT * FROM " + TABLE_QUOTES + " JOIN "
+ TABLE_AUTHORS + " ON " + QU_AUTHOR + " = " + AU_WEB_ID
+ " WHERE " + QU_FAVORITE + " = " + "1"+" ORDER BY " + QU_WEB_ID + " DESC "+ " LIMIT " + start + ", " + limit;
Cursor cursor = database.rawQuery(query, null);
cursor.moveToFirst();
return cursor;
}
//======================================================================
// Getting Fav Quote from ID
public String getFavQuotes(String strkey_id) {
// Select All Query
String fav = "";
String query = "SELECT * FROM " + TABLE_QUOTES + " JOIN "
+ TABLE_AUTHORS + " ON " + QU_AUTHOR + " = " + AU_WEB_ID
+ " WHERE " + QU_FAVORITE + " = " + "1 AND " + QU_ID + " = " +strkey_id;
Cursor cursor = database.rawQuery(query, null);
if(cursor.getCount() != 0)
{
cursor.moveToFirst();
fav = cursor.getString(cursor.getColumnIndex(QU_FAVORITE));
}
return fav;
}
// ==============================================================================
// Getting All Author Quotes
public Cursor getAuthorQuotes(String authorID,String start) {
// Select All Query
String limit="15";
String query = "SELECT * FROM " + TABLE_QUOTES + " JOIN "
+ TABLE_AUTHORS + " ON " + QU_AUTHOR + " = " + AU_WEB_ID
+ " WHERE " + QU_AUTHOR + " = " + authorID + " ORDER BY "+ QU_WEB_ID +" DESC "+ " LIMIT " + start + ", " + limit;
Cursor cursor = database.rawQuery(query, null);
cursor.moveToFirst();
return cursor;
}
// ==============================================================================
// Getting Selected Quote
public Cursor getOneQuote(String quoteID) {
// Select All Query
String query = "SELECT * FROM " + TABLE_QUOTES + " JOIN "
+ TABLE_AUTHORS + " ON " + QU_AUTHOR + " = " + AU_WEB_ID
+ " WHERE " + QU_ID + " = '" + quoteID + "'";
Cursor cursor = database.rawQuery(query, null);
cursor.moveToFirst();
return cursor;
}
// ==============================================================================
public void addOrRemoveFavorites(String id, String value) {
ContentValues values = new ContentValues();
values.put(QU_FAVORITE, value);
// Update Row
// database.update(TABLE_QUOTES, values, QU_ID + "=?", new String[] { id });
database.update(TABLE_QUOTES, values, QU_ID + "=?", new String[] { id });
}
// ==============================================================================
// Getting All Authors
public Cursor getAllAuthors() {
// Select All Query
String query = "SELECT *, COUNT(" + QU_AUTHOR + ") AS count FROM "
+ TABLE_AUTHORS + " LEFT JOIN " + TABLE_QUOTES + " ON " + AU_WEB_ID
+ " = " + QU_AUTHOR + " GROUP BY " + AU_NAME ;
Cursor cursor = database.rawQuery(query, null);
cursor.moveToFirst();
return cursor;
}
// ==============================================================================
// Getting Quotes Count
public Integer getQuotesCount() {
String query = "SELECT COUNT(" + QU_TEXT + ") AS count FROM "
+ TABLE_QUOTES;
Cursor cursor = database.rawQuery(query, null);
cursor.moveToFirst();
Integer count = cursor.getInt(cursor.getColumnIndex("count"));
return count;
}
// ==============================================================================
// Getting Quote ID
public Integer getQotdId() {
String query = "SELECT " + QU_ID + " FROM " + TABLE_QUOTES
+ " ORDER BY RANDOM() LIMIT 1";
Cursor cursor = database.rawQuery(query, null);
cursor.moveToFirst();
Integer id = cursor.getInt(cursor.getColumnIndex(QU_ID));
return id;
}
// ==============================================================================
public void updateSetting(String field, String value) {
open();
ContentValues values = new ContentValues();
values.put(field, value);
// Update Row
database.update(TABLE_SETTINGS, values, null, null);
}
// ==============================================================================
public Cursor getSettings() {
open();
String query = "SELECT * FROM " + TABLE_SETTINGS;
Cursor cursor = database.rawQuery(query, null);
cursor.moveToFirst();
return cursor;
}
// ==============================================================================
public int getLastAuthor() {
String query = "SELECT " + AU_WEB_ID + " FROM " + TABLE_AUTHORS
+ " ORDER BY " + AU_WEB_ID + " DESC LIMIT 1";
Cursor cursor = database.rawQuery(query, null);
cursor.moveToFirst();
return cursor.getInt(cursor.getColumnIndex(AU_WEB_ID));
}
// ==============================================================================
public int getLastQuote() {
String query = "SELECT " + QU_WEB_ID + " FROM " + TABLE_QUOTES
+ " ORDER BY " + QU_WEB_ID + " DESC LIMIT 1";
Cursor cursor = database.rawQuery(query, null);
cursor.moveToFirst();
return cursor.getInt(cursor.getColumnIndex(QU_WEB_ID));
}
// ==============================================================================
public void addAuthor(String au_name, String au_picture, int au_web_id) {
open();
ContentValues v = new ContentValues();
v.put(AU_NAME, au_name);
v.put(AU_PICTURE, au_picture);
v.put(AU_PICTURE_SDCARD, 1);
v.put(AU_WEB_ID, au_web_id);
database.insert(TABLE_AUTHORS, null, v);
}
// ==============================================================================
public void addQuote(String qu_text, int qu_author, int qu_web_id) {
open();
ContentValues v = new ContentValues();
v.put(QU_TEXT, qu_text);
v.put(QU_AUTHOR, qu_author);
v.put(QU_FAVORITE, "0");
v.put(QU_WEB_ID, qu_web_id);
database.insert(TABLE_QUOTES, null, v);
}
// ==============================================================================
public void open() throws SQLException {
// database = dbHandler.getReadableDatabase();
database = dbHandler.getWritableDatabase();
}
// ==============================================================================
public void closeDatabase() {
dbHandler.close();
}
现在，如果我想用更多报价更新应用程序，我应该进行哪些更改，以便新老用户不会遇到任何问题？
我知道数据库版本应该增加，我会的，但是我应该在 onUpgrade 方法中放入什么？
我不是 Android 开发专家，所以如果可能的话请多解释一下，我将非常感谢。 谢谢
谢谢
最佳答案
Java 文档几乎解释了需要做什么。
来自 Java 文档
当数据库需要升级时调用。实现情况 应该使用此方法删除表、添加表或执行其他任何操作 需要升级到新的架构版本。
我们所做的是，只要我们更改了表架构，就更改表。 此外，如果需要，您还可以执行一些数据迁移。基本上它是您获得的一个钩子(Hook)，您可以执行任何类型的兼容性逻辑。
干杯，
索拉夫
关于java - SQLite数据库升级条件，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/35617047/