指定数据库存储路径

SQLite创建的数据库默认的存放路径：阅读SQLiteOpenHelper的源码可以发现，创建数据库文件的路径是使用传入的contex的getDatabasePath获取的，这个

是不允许修改的。也就是说SQLiteOpenHelper源码中的存储路径是由方法getDatabasePath（）获得的。接下来就好办了，我们虽然不能够改变这个路径，但是我们可

以覆盖这个方法。

所以如果要创建指定路径的数据库，我们只需要新建一个类MySQLiteOpenHelper，将SQLiteOpenHelper得源码拷贝下来，然后在其中添加我们覆盖的方法

getDatabasePath（）。getDatabasePath（）的覆盖可以是实例化的覆盖（即在MySQLiteOpenHelper中直接创建方法getDatabasePath（））

也可以使抽象的覆盖（只在MySQLiteOpenHelper中声明getDatabasePath（）的接口，然后具体的路径就由使用者去确定了））。

最后，当我们我们编写操作数据库的代码时，helper类直接继承我们自定的抽象类MySQLiteOpenHelper就可以了。我的MySQLiteOpenHelper源码如下：

import java.io.File;
import android.content.Context;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteException;
import android.database.sqlite.SQLiteDatabase.CursorFactory;
import android.util.Log;

public abstract class MyDatabaseHelper {
private static final String TAG = MyDatabaseHelper.class.getSimpleName();
private final Context mContext;
private final String mName;
private final CursorFactory mFactory;
private final int mNewVersion;
private SQLiteDatabase mDatabase = null;
private boolean mIsInitializing = false;

public MyDatabaseHelper(Context context, String name, CursorFactory factory, int version) {
if (version < 1) throw new IllegalArgumentException("Version must be >= 1, was " + version);
mContext = context;
mName = name;
mFactory = factory;
mNewVersion = version;
}

public synchronized SQLiteDatabase getWritableDatabase() {
if (mDatabase != null && mDatabase.isOpen() && !mDatabase.isReadOnly()) {
return mDatabase; // The database is already open for business
}
if (mIsInitializing) {
throw new IllegalStateException("getWritableDatabase called recursively");
}

boolean success = false;
SQLiteDatabase db = null;
try {
mIsInitializing = true;
if (mName == null) {
db = SQLiteDatabase.create(null);
} else {
String path = getDatabasePath(mName).getPath();
db = SQLiteDatabase.openOrCreateDatabase(path, mFactory);
}
int version = db.getVersion();
if (version != mNewVersion) {
db.beginTransaction();
try {
if (version == 0) {
onCreate(db);
} else {
onUpgrade(db, version, mNewVersion);
}
db.setVersion(mNewVersion);
db.setTransactionSuccessful();
} finally {
db.endTransaction();
}
}
onOpen(db);
success = true;
return db;
} finally {
mIsInitializing = false;
if (success) {
if (mDatabase != null) {
try { mDatabase.close(); } catch (Exception e) { }
}
mDatabase = db;
} else {
if (db != null) db.close();
}
}
}

public synchronized SQLiteDatabase getReadableDatabase() {
if (mDatabase != null && mDatabase.isOpen()) {
return mDatabase; // The database is already open for business
}
if (mIsInitializing) {
throw new IllegalStateException("getReadableDatabase called recursively");
}
try {
return getWritableDatabase();
} catch (SQLiteException e) {
if (mName == null) throw e; // Can't open a temp database read-only!
Log.e(TAG, "Couldn't open " + mName + " for writing (will try read-only):", e);
}
SQLiteDatabase db = null;
try {
mIsInitializing = true;
String path = getDatabasePath(mName).getPath();
db = SQLiteDatabase.openDatabase(path, mFactory, SQLiteDatabase.OPEN_READWRITE);
if (db.getVersion() != mNewVersion) {
throw new SQLiteException("Can't upgrade read-only database from version " +
db.getVersion() + " to " + mNewVersion + ": " + path);
}
onOpen(db);
Log.w(TAG, "Opened " + mName + " in read-only mode");
mDatabase = db;
return mDatabase;
} finally {
mIsInitializing = false;
if (db != null && db != mDatabase) db.close();
}
}

public synchronized void close() {
if (mIsInitializing) throw new IllegalStateException("Closed during initialization");
if (mDatabase != null && mDatabase.isOpen()) {
mDatabase.close();
mDatabase = null;
}
}

/*public File getDatabasePath(String name)
*{
* return new File("/sdcard/Project/" + name);
*}
*/
public abstract File getDatabasePath(String name);//我们需要添加的只是这一句

public abstract void onCreate(SQLiteDatabase db);

public abstract void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion);

public void onOpen(SQLiteDatabase db) {}
}

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