java - sqlite无法打开数据库

Question

我在使用 sqlite 时遇到了一个奇怪的错误，尽管我当前正在使用 DataBaseHelper，但我过去曾经使用过它。发生此错误的任何原因，

DataBaseHelper类:

package com.itspirits.animalsforkids;

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

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


public class DataBaseHelper extends SQLiteOpenHelper{
    //The Android's default system path of your application database.
    private static String DB_PATH = "/data/data/com.itspirits.animalsforkids/databases/";
    private static String DB_NAME = "life.sqlite";
    private SQLiteDatabase myDataBase;
    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 DataBaseHelper(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.
            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_READWRITE );

        }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);
        System.out.println(myInput);
        // 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 void openDataBase() throws SQLException{

        //Open the database
        String myPath = DB_PATH + DB_NAME;
        myDataBase = 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) {

    }

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

    }

    // Add your public helper methods to access and get content from the database.
    // You could return cursors by doing "return myDataBase.query(....)" so it'd be easy
    // to you to create adapters for your views.

}

我只是想创建 DataBaseHelper 类的实例:

DataBaseHelper myDbHelper = new DataBaseHelper(this);

堆栈跟踪:

05-10 08:18:18.661  26478-26478/com.itspirits.animalsforkids E/SQLiteLog﹕ (14) cannot open file at line 30191 of [00bb9c9ce4]
05-10 08:18:18.661  26478-26478/com.itspirits.animalsforkids E/SQLiteLog﹕ (14) os_unix.c:30191: (2) open(/data/data/com.itspirits.animalsforkids/databases/life.sqlite) -
05-10 08:18:18.661  26478-26478/com.itspirits.animalsforkids E/SQLiteDatabase﹕ Failed to open database '/data/data/com.itspirits.animalsforkids/databases/life.sqlite'.
    android.database.sqlite.SQLiteCantOpenDatabaseException: unknown error (code 14): Could not open database
            at android.database.sqlite.SQLiteConnection.nativeOpen(Native Method)
            at android.database.sqlite.SQLiteConnection.open(SQLiteConnection.java:209)
            at android.database.sqlite.SQLiteConnection.open(SQLiteConnection.java:193)
            at android.database.sqlite.SQLiteConnectionPool.openConnectionLocked(SQLiteConnectionPool.java:463)
            at android.database.sqlite.SQLiteConnectionPool.open(SQLiteConnectionPool.java:185)
            at android.database.sqlite.SQLiteConnectionPool.open(SQLiteConnectionPool.java:177)
            at android.database.sqlite.SQLiteDatabase.openInner(SQLiteDatabase.java:804)
            at android.database.sqlite.SQLiteDatabase.open(SQLiteDatabase.java:789)
            at android.database.sqlite.SQLiteDatabase.openDatabase(SQLiteDatabase.java:694)
            at android.database.sqlite.SQLiteDatabase.openDatabase(SQLiteDatabase.java:669)
            at com.itspirits.animalsforkids.DataBaseHelper.checkDataBase(DataBaseHelper.java:70)
            at com.itspirits.animalsforkids.DataBaseHelper.createDataBase(DataBaseHelper.java:37)
            at com.itspirits.animalsforkids.MainActivity.onCreate(MainActivity.java:21)
            at android.app.Activity.performCreate(Activity.java:5231)
            at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1087)
            at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2159)
            at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2245)
            at android.app.ActivityThread.access$800(ActivityThread.java:135)
            at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1196)
            at android.os.Handler.dispatchMessage(Handler.java:102)
            at android.os.Looper.loop(Looper.java:136)
            at android.app.ActivityThread.main(ActivityThread.java:5017)
            at java.lang.reflect.Method.invokeNative(Native Method)
            at java.lang.reflect.Method.invoke(Method.java:515)
            at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:779)
            at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:595)
            at dalvik.system.NativeStart.main(Native Method)

Answer 1

private boolean tableExists() {
    Boolean exists = false;
    String query = "SELECT * FROM " + TABLE_NOTES;

    SQLiteDatabase db = this.getWritableDatabase();
    try{
        Cursor cursor = db.rawQuery(query, null);
        if(cursor.moveToFirst()){
            exists = true;
        }else{
            exists = true;
        }
    }catch (Exception e){

    }
    return exists;

}

这是我用来检查我的一个应用程序中数据库内的表的方法。如果您知道您正在查找的表名称是什么，这可能会起作用。