为什么打开数据库时无法打开文件异常?

时间:2012-10-12 06:15:56

标签: android

package com.example.expdb;

import java.io.FileOutputStream;
import java.io.IOException;
import java.io.OutputStream;

import android.content.Context;
import android.database.Cursor;
import android.database.SQLException;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteException;
import android.database.sqlite.SQLiteOpenHelper;



public class RestauDBHelper extends SQLiteOpenHelper {

    // The Android's default system path of your application database.
    private static String DB_PATH = "/data/data/com.example.expdb/databases/";
    private static String DB_NAME = "restauDB";
    private SQLiteDatabase restauBase;
    private final Context myContext;

    /**
     * Constructor Takes and keeps a reference of the passed context in order to
     * access to the application assets and resources.
     * 
     * @param context
     */
    public RestauDBHelper(Context context) {
        super(context, DB_NAME, null, 1);
        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 and empty database will be created into
            // the default system path
            // of your application so we are gonna be able to overwrite that
            // database with our database.
            restauBase = this.getWritableDatabase();
            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 {
        String text;
        // InputStream is = this.getResources().openRawResource (R.raw.sql);
        try {
            InputStream myInput = myContext.getResources().openRawResource(
                R.raw.restau_db);

            // We guarantee that the available method returns the total
            // size of the asset... of course, this does mean that a single
            // asset can't be more than 2 gigs.
            int size = myInput.available();

    String outFileName = DB_PATH + DB_NAME;

//gettting failed to open file exception here , i can see DB file iscreated         //through file explorer .Its present. 
    OutputStream myOutput = new FileOutputStream(outFileName);

            // Read the entire asset into a local byte buffer.
            byte[] buffer = new byte[size];

             while ((length = myInput.read(buffer))>0){
myOutput.write(buffer, 0, length);
}

//Close the streams
myOutput.flush();
myOutput.close();
myInput.close();




        } catch (IOException e) {
            // Should never happen!
            throw new RuntimeException(e);
        } 

    }

    public void openDataBase() throws SQLException {

        // Open the database
        String myPath = DB_PATH + DB_NAME;
        restauBase = SQLiteDatabase.openDatabase(myPath, null,
                SQLiteDatabase.OPEN_READONLY);

    }

    @Override
    public synchronized void close() {

        if (restauBase != null)
            restauBase.close();
        super.close();

    }

    @Override
    public void onCreate(SQLiteDatabase db) {

    }

    @Override
    public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {

    }



}

这是日志消息:

10-12 11:31:07.793: E/SQLiteLog(8679): (14) cannot open file at line 30174 of [00bb9c9ce4]
10-12 11:31:07.803: E/SQLiteLog(8679): (14) os_unix.c:30174: (2) open(/data/data/com.example.expdb/databases/restauDB) - 
10-12 11:31:08.053: E/SQLiteDatabase(8679): Failed to open database '/data/data/com.example.expdb/databases/restauDB'.
10-12 11:31:08.053: E/SQLiteDatabase(8679): android.database.sqlite.SQLiteCantOpenDatabaseException: unknown error (code 14): Could not open database
10-12 11:31:08.053: E/SQLiteDatabase(8679):     at android.database.sqlite.SQLiteConnection.nativeOpen(Native Method)
10-12 11:31:08.053: E/SQLiteDatabase(8679):     at android.database.sqlite.SQLiteConnection.open(SQLiteConnection.java:209)
10-12 11:31:08.053: E/SQLiteDatabase(8679):     at android.database.sqlite.SQLiteConnection.open(SQLiteConnection.java:193)
10-12 11:31:08.053: E/SQLiteDatabase(8679):     at android.database.sqlite.SQLiteConnectionPool.openConnectionLocked(SQLiteConnectionPool.java:463)
10-12 11:31:08.053: E/SQLiteDatabase(8679):     at android.database.sqlite.SQLiteConnectionPool.open(SQLiteConnectionPool.java:185)
10-12 11:31:08.053: E/SQLiteDatabase(8679):     at android.database.sqlite.SQLiteConnectionPool.open(SQLiteConnectionPool.java:177)
10-12 11:31:08.053: E/SQLiteDatabase(8679):     at android.database.sqlite.SQLiteDatabase.openInner(SQLiteDatabase.java:804)
10-12 11:31:08.053: E/SQLiteDatabase(8679):     at android.database.sqlite.SQLiteDatabase.open(SQLiteDatabase.java:789)
10-12 11:31:08.053: E/SQLiteDatabase(8679):     at android.database.sqlite.SQLiteDatabase.openDatabase(SQLiteDatabase.java:694)
10-12 11:31:08.053: E/SQLiteDatabase(8679):     at android.database.sqlite.SQLiteDatabase.openDatabase(SQLiteDatabase.java:669)
10-12 11:31:08.053: E/SQLiteDatabase(8679):     at com.example.expdb.RestauDBHelper.checkDataBase(RestauDBHelper.java:71)
10-12 11:31:08.053: E/SQLiteDatabase(8679):     at com.example.expdb.RestauDBHelper.createDataBase(RestauDBHelper.java:41)
10-12 11:31:08.053: E/SQLiteDatabase(8679):     at com.example.expdb.MainActivity.onCreate(MainActivity.java:22)
10-12 11:31:08.053: E/SQLiteDatabase(8679):     at android.app.Activity.performCreate(Activity.java:5008)
10-12 11:31:08.053: E/SQLiteDatabase(8679):     at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1079)
10-12 11:31:08.053: E/SQLiteDatabase(8679):     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2023)
10-12 11:31:08.053: E/SQLiteDatabase(8679):     at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2084)
10-12 11:31:08.053: E/SQLiteDatabase(8679):     at android.app.ActivityThread.access$600(ActivityThread.java:130)
10-12 11:31:08.053: E/SQLiteDatabase(8679):     at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1195)
10-12 11:31:08.053: E/SQLiteDatabase(8679):     at android.os.Handler.dispatchMessage(Handler.java:99)
10-12 11:31:08.053: E/SQLiteDatabase(8679):     at android.os.Looper.loop(Looper.java:137)
10-12 11:31:08.053: E/SQLiteDatabase(8679):     at android.app.ActivityThread.main(ActivityThread.java:4745)
10-12 11:31:08.053: E/SQLiteDatabase(8679):     at java.lang.reflect.Method.invokeNative(Native Method)
10-12 11:31:08.053: E/SQLiteDatabase(8679):     at java.lang.reflect.Method.invoke(Method.java:511)
10-12 11:31:08.053: E/SQLiteDatabase(8679):     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:786)
10-12 11:31:08.053: E/SQLiteDatabase(8679):     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:553)
10-12 11:31:08.053: E/SQLiteDatabase(8679):     at dalvik.system.NativeStart.main(Native Method)

1 个答案:

答案 0 :(得分:0)

为什么你需要为数据库提供路径,它会自动从数据/数据中的应用程序包中获取数据库的实例。

您可以使用以下代码段打开并获取数据库实例: -

如果您在扩展SQLiteOpenHelper的类中,则使用

SQLiteDatabase db = this.getWritableDatabase();

如果您在其他地方,您可以实例化SQLiteOpenHelper,如下所示: -

RestauDBHelper dbHelper = new RestauDBHelper();
 SQLiteDatabase db = dbHelper .getWritableDatabase();

通过这种方式,你可以打开你的数据库,如果你想以READ_ONLY模式打开,那么而不是

getWritableDatabase() make use of getReadableDatabase()

希望这会帮助你。祝你好运