我的应用程序允许我打开/复制存储在assets文件夹中的数据库。我正在使用DatabaseHelper类以及以下构造函数和方法。
public DatabaseHelper(Context context) {
super(context, DB_NAME, null, DATABASE_VERSION);
this.myContext = context;
}
/**
* Creates a empty database on the system and rewrites it with your own database.
* */
public void createDataBase() throws IOException{
boolean dbExist = checkDataBase();
if(dbExist){
//do nothing - database already exist
}else{
//By calling this method an empty database will be created into the default system path
//of your application so we are going be able to overwrite that database with our database.
this.getReadableDatabase();
try {
copyDataBase();
} catch (IOException e) {
throw new Error("Error copying database");
}
}
}
/**
* Check if the database already exist to avoid re-copying the file each time you open the application.
* @return true if it exists, false if it doesn't
*/
private boolean checkDataBase(){
SQLiteDatabase checkDB = null;
try{
String myPath = DB_PATH + DB_NAME;
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;
}
/**
* Copies your database from your local assets-folder to the just created empty database in the
* system folder, from where it can be accessed and handled.
* This is done by transfering bytestream.
* */
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 + DB_NAME;
//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 SQLiteDatabase openDataBase() throws SQLException{
//Open the database
String myPath = DB_PATH + DB_NAME;
return 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) {
// TODO Auto-generated method stub
}
@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
// TODO Auto-generated method stub
}
}
我在我的应用程序类的onCreate方法中打开帮助器：
mDBHelper = new DatabaseHelper(getApplicationContext());
然后，我使用以下代码在我的片段中执行查询，以从应用程序类中检索数据库。
readingDb = cpcApplication.prepareDatabase();
Cursor cursor = readingDb.rawQuery("select Z_PK, ZNAME, ZMAP_PIN_ICON from ZFILTER", null);
这是我的Logcat日志：
08-25 14:35:39.896: E/SQLiteLog(11090): (14) cannot open file at line 30174 of [00bb9c9ce4]
08-25 14:35:39.896: E/SQLiteLog(11090): (14) os_unix.c:30174: (2) open(/data/data/com.mcgarrybowen.CPC/databases/cpcmodel.sqlite) -
08-25 14:35:39.920: E/SQLiteDatabase(11090): Failed to open database '/data/data/com.mcgarrybowen.CPC/databases/cpcmodel.sqlite'.
08-25 14:35:39.920: E/SQLiteDatabase(11090): android.database.sqlite.SQLiteCantOpenDatabaseException: unknown error (code 14): Could not open database
08-25 14:35:39.920: E/SQLiteDatabase(11090): at android.database.sqlite.SQLiteConnection.nativeOpen(Native Method)
08-25 14:35:39.920: E/SQLiteDatabase(11090): at android.database.sqlite.SQLiteConnection.open(SQLiteConnection.java:209)
08-25 14:35:39.920: E/SQLiteDatabase(11090): at android.database.sqlite.SQLiteConnection.open(SQLiteConnection.java:193)
08-25 14:35:39.920: E/SQLiteDatabase(11090): at android.database.sqlite.SQLiteConnectionPool.openConnectionLocked(SQLiteConnectionPool.java:463)
08-25 14:35:39.920: E/SQLiteDatabase(11090): at android.database.sqlite.SQLiteConnectionPool.open(SQLiteConnectionPool.java:185)
08-25 14:35:39.920: E/SQLiteDatabase(11090): at android.database.sqlite.SQLiteConnectionPool.open(SQLiteConnectionPool.java:177)
08-25 14:35:39.920: E/SQLiteDatabase(11090): at android.database.sqlite.SQLiteDatabase.openInner(SQLiteDatabase.java:804)
08-25 14:35:39.920: E/SQLiteDatabase(11090): at android.database.sqlite.SQLiteDatabase.open(SQLiteDatabase.java:789)
08-25 14:35:39.920: E/SQLiteDatabase(11090): at android.database.sqlite.SQLiteDatabase.openDatabase(SQLiteDatabase.java:694)
08-25 14:35:39.920: E/SQLiteDatabase(11090): at android.database.sqlite.SQLiteDatabase.openDatabase(SQLiteDatabase.java:669)
08-25 14:35:39.920: E/SQLiteDatabase(11090): at com.mcgarrybowen.CPC.Data.DatabaseHelper.checkDataBase(DatabaseHelper.java:69)
08-25 14:35:39.920: E/SQLiteDatabase(11090): at com.mcgarrybowen.CPC.Data.DatabaseHelper.createDataBase(DatabaseHelper.java:37)
08-25 14:35:39.920: E/SQLiteDatabase(11090): at com.mcgarrybowen.CPC.CPCApplication.prepareDatabase(CPCApplication.java:148)
08-25 14:35:39.920: E/SQLiteDatabase(11090): at com.mcgarrybowen.CPC.SiteCategoryFragment.setUpTypes(SiteCategoryFragment.java:160)
08-25 14:35:39.920: E/SQLiteDatabase(11090): at com.mcgarrybowen.CPC.SiteCategoryFragment.onCreate(SiteCategoryFragment.java:55)
08-25 14:35:39.920: E/SQLiteDatabase(11090): at android.support.v4.app.Fragment.performCreate(Fragment.java:1455)
08-25 14:35:39.920: E/SQLiteDatabase(11090): at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:893)
08-25 14:35:39.920: E/SQLiteDatabase(11090): at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:1104)
08-25 14:35:39.920: E/SQLiteDatabase(11090): at android.support.v4.app.BackStackRecord.run(BackStackRecord.java:682)
08-25 14:35:39.920: E/SQLiteDatabase(11090): at android.support.v4.app.FragmentManagerImpl.execPendingActions(FragmentManager.java:1460)
08-25 14:35:39.920: E/SQLiteDatabase(11090): at android.support.v4.app.FragmentManagerImpl$1.run(FragmentManager.java:440)
08-25 14:35:39.920: E/SQLiteDatabase(11090): at android.os.Handler.handleCallback(Handler.java:615)
08-25 14:35:39.920: E/SQLiteDatabase(11090): at android.os.Handler.dispatchMessage(Handler.java:92)
08-25 14:35:39.920: E/SQLiteDatabase(11090): at android.os.Looper.loop(Looper.java:137)
08-25 14:35:39.920: E/SQLiteDatabase(11090): at android.app.ActivityThread.main(ActivityThread.java:5059)
08-25 14:35:39.920: E/SQLiteDatabase(11090): at java.lang.reflect.Method.invokeNative(Native Method)
08-25 14:35:39.920: E/SQLiteDatabase(11090): at java.lang.reflect.Method.invoke(Method.java:511)
08-25 14:35:39.920: E/SQLiteDatabase(11090): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:792)
08-25 14:35:39.920: E/SQLiteDatabase(11090): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:555)
08-25 14:35:39.920: E/SQLiteDatabase(11090): at dalvik.system.NativeStart.main(Native Method)
我没有将我的数据库ID字段更改为_id，因为我继承了使用非整数且具有其他名称的主字段的数据库。
提前感谢您的帮助。