Android Studio中的UCanAccess出现“给定文件不存在”错误

Question

我试图连接到Access数据库，但无论我尝试什么，我都会遇到同样的错误：

UCAExc ::: 0.0给定文件不存在：

我一直在使用UCanAccess和Android Studio v2.3。我尝试了YouTube，我到处搜索，但没有代码片段正在运行。

这是否与我使用的Windows 10有关，我必须将数据库放在一个特殊的文件夹中？

我在代码的末尾包含了错误日志

package com.example.david.dvd2;
// * Created by David on 2017-04-14.

import java.io.StringWriter;
import java.sql.*;
import java.util.Enumeration;
import android.util.Log;
import org.apache.commons.lang.exception.ExceptionUtils;

public class TestConnection {

public static void CreateDBConection() {
    Log.i("TESTConnection","Inside TestConnection [CreateDBConnection]");
    try {
        Statement st;
        ResultSet re;
/*
Layout of the Access Database, a simple database with DVD-Titles
tblDVD      Id, m,d,fldTitle, fldSweTitle, fldTime, fldComment, fktyp, 
            fkyear,
tblType     Id, fldType
tblYear     Id, fldYear
*/
        Class.forName("net.ucanaccess.jdbc.UcanaccessDriver");
        String dbFileName = "C:/db/dvd.mdb";
        String database = "jdbc:ucanaccess://" + dbFileName +  "";
        Connection cn = DriverManager.getConnection(database, "", "");
        st = cn.createStatement();
        re = st.executeQuery("SELECT Id, fldYear FROM tblYear WHERE Id=35");
        while (re.next()) {
            String idoo = re.getString("Id");
            String fldyearoo = re.getString("fldYear");
            Log.i("Result from SQL query", "A selected Year with ID=35: " + fldyearoo);
        }
    }
    catch(ClassNotFoundException | SQLException e)
    {
        Log.i("ERROR","Info:\n" + e.getMessage());
        String s = ExceptionUtils.getStackTrace(e);
        Log.i("ERROR","More detailed info\n" + s);
        e.printStackTrace(System.err);
    }
}

}

这是Err.log：

    04-21 16:19:04.466 1693-1693/com.example.david.dvd2 I/TESTConnection: Inside TestConnection [CreateDBConnection]
    04-21 16:19:04.554 1693-1700/com.example.david.dvd2 W/art: Suspending all threads took: 9.814ms
    04-21 16:19:04.648 1693-1709/com.example.david.dvd2 I/art: Background sticky concurrent mark sweep GC freed 8515(456KB) AllocSpace objects, 9(288KB) LOS objects, 16% free, 2MB/3MB, paused 6.486ms total 34.758ms
    04-21 16:19:04.680 1693-1709/com.example.david.dvd2 W/art: Suspending all threads took: 32.195ms
    04-21 16:19:04.785 1693-1709/com.example.david.dvd2 W/art: Suspending all threads took: 22.748ms
    04-21 16:19:04.897 1693-1693/com.example.david.dvd2 I/ERROR: Info:
    UCAExc:::0.0 given file does not exist: /C:/db/dvd.mdb
    04-21 16:19:04.933 1693-1693/com.example.david.dvd2 I/BERROR: More detailed info
    net.ucanaccess.jdbc.UcanaccessSQLException: UCAExc:::0.0 given file does not exist: /C:/db/dvd.mdb
    at net.ucanaccess.jdbc.UcanaccessDriver.connect(UcanaccessDriver.java:264)
    at java.sql.DriverManager.getConnection(DriverManager.java:179)
    at java.sql.DriverManager.getConnection(DriverManager.java:213)
    at com.example.david.dvd2.TestConnection.CreateDBConection(TestConnection.java:26)
    at com.example.david.dvd2.MainActivity.mastermind2(MainActivity.java:20)
    at com.example.david.dvd2.MainActivity.onCreate(MainActivity.java:12)
    at android.app.Activity.performCreate(Activity.java:5990)
    at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1106)
    at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2278)
    at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2387)
    at android.app.ActivityThread.access$800(ActivityThread.java:151)
    at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1303)
    at android.os.Handler.dispatchMessage(Handler.java:102)
    at android.os.Looper.loop(Looper.java:135)
    at android.app.ActivityThread.main(ActivityThread.java:5254)
    at java.lang.reflect.Method.invoke(Native Method)
    at java.lang.reflect.Method.invoke(Method.java:372)
    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:903)
    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:698)
    Caused by: java.io.FileNotFoundException: given file does not exist: /C:/db/dvd.mdb
    at com.healthmarketscience.jackcess.impl.DatabaseImpl.open(DatabaseImpl.java:372)
    at com.healthmarketscience.jackcess.DatabaseBuilder.open(DatabaseBuilder.java:252)
    at net.ucanaccess.jdbc.DefaultJackcessOpener.open(DefaultJackcessOpener.java:35)
    at net.ucanaccess.jdbc.DBReference.<init>(DBReference.java:161)
    at net.ucanaccess.jdbc.DBReferenceSingleton.loadReference(DBReferenceSingleton.java:51)
    at net.ucanaccess.jdbc.UcanaccessDriver.connect(UcanaccessDriver.java:99)
    at java.sql.DriverManager.getConnection(DriverManager.java:179) 
    at java.sql.DriverManager.getConnection(DriverManager.java:213) 
    at com.example.david.dvd2.TestConnection.CreateDBConection(TestConnection.java:26) 
    at com.example.david.dvd2.MainActivity.mastermind2(MainActivity.java:20) 
    at com.example.david.dvd2.MainActivity.onCreate(MainActivity.java:12) 
    at android.app.Activity.performCreate(Activity.java:5990) 
    at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1106) 
    at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2278) 
    at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2387) 
    at android.app.ActivityThread.access$800(ActivityThread.java:151) 
    at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1303) 
    at android.os.Handler.dispatchMessage(Handler.java:102) 
    at android.os.Looper.loop(Looper.java:135) 
    at android.app.ActivityThread.main(ActivityThread.java:5254) 
    at java.lang.reflect.Method.invoke(Native Method) 
    at java.lang.reflect.Method.invoke(Method.java:372) 
    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:903) 
    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:698) 
    04-21 16:19:04.933 1693-1693/com.example.david.dvd2 W/System.err: net.ucanaccess.jdbc.UcanaccessSQLException: UCAExc:::0.0 given file does not exist: /C:/db/dvd.mdb
    04-21 16:19:04.933 1693-1693/com.example.david.dvd2 W/System.err:     at net.ucanaccess.jdbc.UcanaccessDriver.connect(UcanaccessDriver.java:264)
    04-21 16:19:04.933 1693-1693/com.example.david.dvd2 W/System.err:     at java.sql.DriverManager.getConnection(DriverManager.java:179)
    04-21 16:19:04.933 1693-1693/com.example.david.dvd2 W/System.err:     at java.sql.DriverManager.getConnection(DriverManager.java:213)
    04-21 16:19:04.934 1693-1693/com.example.david.dvd2 W/System.err:     at com.example.david.dvd2.TestConnection.CreateDBConection(TestConnection.java:26)
    04-21 16:19:04.934 1693-1693/com.example.david.dvd2 W/System.err:     at com.example.david.dvd2.MainActivity.mastermind2(MainActivity.java:20)
    04-21 16:19:04.934 1693-1693/com.example.david.dvd2 W/System.err:     at com.example.david.dvd2.MainActivity.onCreate(MainActivity.java:12)
    04-21 16:19:04.934 1693-1693/com.example.david.dvd2 W/System.err:     at android.app.Activity.performCreate(Activity.java:5990)
    04-21 16:19:04.934 1693-1693/com.example.david.dvd2 W/System.err:     at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1106)
    04-21 16:19:04.934 1693-1693/com.example.david.dvd2 W/System.err:     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2278)
    04-21 16:19:04.934 1693-1693/com.example.david.dvd2 W/System.err:     at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2387)
    04-21 16:19:04.934 1693-1693/com.example.david.dvd2 W/System.err:     at android.app.ActivityThread.access$800(ActivityThread.java:151)
    04-21 16:19:04.934 1693-1693/com.example.david.dvd2 W/System.err:     at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1303)
    04-21 16:19:04.934 1693-1693/com.example.david.dvd2 W/System.err:     at android.os.Handler.dispatchMessage(Handler.java:102)
    04-21 16:19:04.934 1693-1693/com.example.david.dvd2 W/System.err:     at android.os.Looper.loop(Looper.java:135)
    04-21 16:19:04.934 1693-1693/com.example.david.dvd2 W/System.err:     at android.app.ActivityThread.main(ActivityThread.java:5254)
    04-21 16:19:04.934 1693-1693/com.example.david.dvd2 W/System.err:     at java.lang.reflect.Method.invoke(Native Method)
    04-21 16:19:04.934 1693-1693/com.example.david.dvd2 W/System.err:     at java.lang.reflect.Method.invoke(Method.java:372)
    04-21 16:19:04.934 1693-1693/com.example.david.dvd2 W/System.err:     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:903)
    04-21 16:19:04.934 1693-1693/com.example.david.dvd2 W/System.err:     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:698)
    04-21 16:19:04.934 1693-1693/com.example.david.dvd2 W/System.err: Caused by: java.io.FileNotFoundException: given file does not exist: /C:/db/dvd.mdb
    04-21 16:19:04.934 1693-1693/com.example.david.dvd2 W/System.err:     at com.healthmarketscience.jackcess.impl.DatabaseImpl.open(DatabaseImpl.java:372)
    04-21 16:19:04.934 1693-1693/com.example.david.dvd2 W/System.err:     at com.healthmarketscience.jackcess.DatabaseBuilder.open(DatabaseBuilder.java:252)
    04-21 16:19:04.934 1693-1693/com.example.david.dvd2 W/System.err:     at net.ucanaccess.jdbc.DefaultJackcessOpener.open(DefaultJackcessOpener.java:35)
    04-21 16:19:04.934 1693-1693/com.example.david.dvd2 W/System.err:     at net.ucanaccess.jdbc.DBReference.<init>(DBReference.java:161)
    04-21 16:19:04.934 1693-1693/com.example.david.dvd2 W/System.err:     at net.ucanaccess.jdbc.DBReferenceSingleton.loadReference(DBReferenceSingleton.java:51)
    04-21 16:19:04.934 1693-1693/com.example.david.dvd2 W/System.err:     at net.ucanaccess.jdbc.UcanaccessDriver.connect(UcanaccessDriver.java:99)

Answer 1

在Android Studio中的Android模拟器下运行的代码显然无法直接访问主机的文件系统。在这种情况下，Windows路径C:/db/dvd.mdb被解释为Android路径/C:/db/dvd.mdb

因此，我们需要将数据库文件导入Android“设备”上的文件系统，如this answer中所述。