GreenDao 数据库：使用Raw文件夹下的数据库文件以及数据库升级
一、使用Raw文件夹下的数据库文件
在使用GreenDao框架时，数据库和数据表都是根据生成的框架代码来自动创建的，从生成的DaoMaster中的OpenHelper类可以看出：
public static abstract class OpenHelper extends SQLiteOpenHelper {
public OpenHelper(Context context, String name, CursorFactory factory) {
super(context, name, factory, SCHEMA_VERSION);
}
@Override
public void onCreate(SQLiteDatabase db) {
Log.i("greenDAO", "Creating tables for schema version " + SCHEMA_VERSION); //修改第二个参数为true
createAllTables(db, false);
}
} 对应的createAllTables函数代码：
/** Creates underlying database table using DAOs. */
public static void createAllTables(SQLiteDatabase db, boolean ifNotExists) {
xxxxxDao.createTable(db, ifNotExists);
} 再接着往下看：
/** Creates the underlying database table. */
public static void createTable(SQLiteDatabase db, boolean ifNotExists) {
String constraint = ifNotExists? "IF NOT EXISTS ": "";
db.execSQL("CREATE TABLE " + constraint + "'DOCTOR' (" + //
"'_id' INTEGER PRIMARY KEY AUTOINCREMENT ," + // 0: id
"'NAME' TEXT," + // 1: name
} 从以上的代码可以看出GreenDao在第一次使用的时候会强制创建数据表，如果这样的话很可能就会导致程序崩溃。
public static abstract class OpenHelper extends SQLiteOpenHelper {
public OpenHelper(Context context, String name, CursorFactory factory) {
super(context, name, factory, SCHEMA_VERSION);
}
@Override
public void onCreate(SQLiteDatabase db) {
Log.i("greenDAO", "Creating tables for schema version " + SCHEMA_VERSION);
//修改第二个参数为true
createAllTables(db, true);
}
} 所以要使用Raw文件中的数据库文件需要以下几步：
1）修改参数：
public static abstract class OpenHelper extends SQLiteOpenHelper {
public OpenHelper(Context context, String name, CursorFactory factory) {
super(context, name, factory, SCHEMA_VERSION);
}
@Override
public void onCreate(SQLiteDatabase db) {
Log.i("greenDAO", "Creating tables for schema version " + SCHEMA_VERSION);
//修改第二个参数为true
createAllTables(db, true);
}
} 2）添加GreenDaoContextWrapper.java文件到项目中
public class GreenDaoContextWrapper extends ContextWrapper { private Context mContext; public GreenDaoContextWrapper(Context base) { super(base); this.mContext= base; } @Override public File getDatabasePath(String name) { Log.d("GreenDao","getDatabasePath"); Log.d("GreenDao",mContext.getDatabasePath(name).getAbsolutePath()); String filePath=mContext.getDatabasePath(name).getAbsolutePath(); File file=new File(filePath); if (!file.exists()){ buildDatabase(filePath); } return file; } /** * 创建数据库文件，其实就是将raw文件夹下的数据库文件复制到应用的database文件夹下： * /data/data/com.xxxx/databases/ * @param filePath */ private void buildDatabase(String filePath){Log.d("GreenDao","buildDatabase"); InputStream inputStream=mContext.getResources().openRawResource(R.raw.accurmedicine); FileOutputStream fos= null; try { fos = new FileOutputStream(filePath); byte[] buffer=new byte[1024]; int length; while ((length=inputStream.read(buffer))>0){ fos.write(buffer,0,length); } fos.close(); inputStream.close(); } catch (Exception e) { e.printStackTrace(); } } @Override public SQLiteDatabase openOrCreateDatabase(String name, int mode, SQLiteDatabase.CursorFactory factory) { Log.d("GreenDao","openOrCreateDatabase"); SQLiteDatabase result= SQLiteDatabase.openOrCreateDatabase(getDatabasePath(name),factory); return result; } @Override public SQLiteDatabase openOrCreateDatabase(String name, int mode, SQLiteDatabase.CursorFactory factory, DatabaseErrorHandler errorHandler) { Log.d("GreenDao","openOrCreateDatabase"); SQLiteDatabase result= SQLiteDatabase.openOrCreateDatabase(getDatabasePath(name),factory); return result; }} 这里提一下：ContextWrapper是一个Context包装类，需要包含一个真正的Context，详细介绍看：
http://www.jianshu.com/p/94e0f9ab3f1d
3）在创建DevOpenHelper的时候使用GreenDaoContextWrapper
String DBName="xxx"; DaoMaster.DevOpenHelper helper=new DaoMaster.DevOpenHelper(new GreenDaoContextWrapper(context),DBName,null);
这样就大功告成了！
二、数据库版本升级
这个办法是从网上看到的，还不错，就搬过来了。
public class MigrationHelper {
private static MigrationHelper instance;
public static MigrationHelper getInstance() {
if (instance==null){
instance=new MigrationHelper();
}
return instance;
}
/**
* 创建临时表->删除旧表->创建新表->导入数据
* @param database
* @param daoClasses
*/
public void migrate(SQLiteDatabase database, Class<? extends AbstractDao<?,?>>...daoClasses){
generateTempTables(database,daoClasses);
DaoMaster.dropAllTables(database,true);
DaoMaster.createAllTables(database,false);
restoreData(database,daoClasses);
}
/**
* 临时表生产
* @param database
* @param daoClasses
*/
private void generateTempTables(SQLiteDatabase database,Class<? extends AbstractDao<?,?>>...daoClasses){
for (int i=0;i<daoClasses.length;i++){
DaoConfig config=new DaoConfig(database,daoClasses[i]);
String divider="";
String tableName=config.tablename;
String tmpTableName=config.tablename.concat("_TEMP");
ArrayList<String > properties=new ArrayList<>();
StringBuilder createTableStringBuilder=new StringBuilder();
createTableStringBuilder.append("CREATE TABLE ").append(tmpTableName).append(" (");
List<String> columns = getColumns(database, tableName);
for (int j=0;j<config.properties.length;j++){
String columnName=config.properties[j].columnName;
if (columns.contains(columnName)){
properties.add(columnName);
String type=null;
try {
type=getTypeByClass(config.properties[j].type);
} catch (Exception e) {
e.printStackTrace();
}
createTableStringBuilder.append(divider).append(columnName).append(" ").append(type);
if (config.properties[j].primaryKey){
createTableStringBuilder.append(" PRIMARY KEY");
}
divider=",";
}
}
createTableStringBuilder.append(");");
Log.d("xxxxx","sql="+createTableStringBuilder.toString());
database.execSQL(createTableStringBuilder.toString());
StringBuilder insertTableString=new StringBuilder();
insertTableString.append("insert into ").append(tmpTableName).append(" (");
insertTableString.append(TextUtils.join(",",properties));
insertTableString.append(") select ");
insertTableString.append(TextUtils.join(",",properties));
insertTableString.append(" from ").append(tableName).append(";");
Log.d("xxxxx","sql="+insertTableString.toString());
database.execSQL(insertTableString.toString());
}
}
/**
* 数据字段与Java数据类型匹配
* @param type
* @return
* @throws Exception
*/
private String getTypeByClass(Class<?> type) throws Exception {
if (type.equals(String.class)){
return "TEXT";
}
if (type.equals(Long.class)||type.equals(Integer.class)){
return "INTEGER";
}
if (type.equals(Boolean.class)){
return "BOOLEAN";
}
String strException="数据表数据类型匹配错误";
Exception exception=new Exception(strException.concat("- Class").concat(type.toString()));
throw exception;
}
/**
* 获取当前数据表字段列表
* @param database
* @param tableName
* @return
*/
private static List<String > getColumns(SQLiteDatabase database,String tableName){
List<String > columns=new ArrayList<>();
Cursor cursor=null;
/**
* 通过查询数据表
*/
cursor=database.rawQuery("select * from "+tableName+" limit 1",null);
try {
if (cursor!=null){
String[] columnNames = cursor.getColumnNames();
for (String name:columnNames){
columns.add(name.toUpperCase());
}
// columns=new ArrayList<>(Arrays.asList(cursor.getColumnNames()));
}
}catch (Exception e){
e.printStackTrace();
}finally {
if (cursor!=null){
cursor.close();
}
}
return columns;
}
/**
* 数据恢复->删除临时表
* @param database
* @param daoClasses
*/
private void restoreData(SQLiteDatabase database,Class<? extends AbstractDao<?,?>>...daoClasses){
for (int i=0;i<daoClasses.length;i++){
DaoConfig config=new DaoConfig(database,daoClasses[i]);
String tableName=config.tablename;
String tmpTableName=config.tablename.concat("_TEMP");
ArrayList<String > properties=new ArrayList<>();
for (int j=0;j<config.properties.length;j++){
String columnName = config.properties[j].columnName;
if(getColumns(database, tmpTableName).contains(columnName)) {
properties.add(columnName);
}
}
StringBuilder insertTableStringBuilder = new StringBuilder();
insertTableStringBuilder.append("INSERT INTO ").append(tableName).append(" (");
insertTableStringBuilder.append(TextUtils.join(",", properties));
insertTableStringBuilder.append(") SELECT ");
insertTableStringBuilder.append(TextUtils.join(",", properties));
insertTableStringBuilder.append(" FROM ").append(tmpTableName).append(";");
StringBuilder dropTableStringBuilder = new StringBuilder();
dropTableStringBuilder.append("DROP TABLE ").append(tmpTableName);
database.execSQL(insertTableStringBuilder.toString());
database.execSQL(dropTableStringBuilder.toString());
}
}
} 然后在需要数据库版本设计的时候修改DaoMaster中的SCHEMA_VERSION
public static final int SCHEMA_VERSION = 1;
这个变量就是用于在创建OpenHelper时指定数据库版本号。
紧接着修改DevOpenHelper的onUpgrade代码：
@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
Log.i("greenDAO", "Upgrading schema from version " + oldVersion + " to " + newVersion + " by dropping all tables");
// dropAllTables(db, true);
// onCreate(db);
MigrationHelper.getInstance()
.migrate(db,
paramsDao.class,
);
} 最后大功告成！
顺带需要补充一下，查看SQLite数据库版本可以执行以下这句语句：
PRAGMA user_version
设置SQLite数据库版本的语句：
PRAGMA user_version =<你的版本号>
以上的这两句话其实可以在SQLiteDatabase以及SQLiteOpenHelper的源码中看到：
在android-24的SQLiteOpenHelper源码中可以看到：
/**
* Gets the database version.
*
* @return the database version
*/
public int getVersion() {
return ((Long) DatabaseUtils.longForQuery(this, "PRAGMA user_version;", null)).intValue();
}
/**
* Sets the database version.
*
* @param version the new database version
*/
public void setVersion(int version) {
execSQL("PRAGMA user_version = " + version);
} 而SQLiteOpenHelper设置和获取数据库版本就是通过调用这两句话来实现的，具体源码可以查看SQLiteOpenHelper的getDatabaseLocked函数，这里不再赘述。