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StriBog
Asked:2020-05-26 15:56:30 +0000 UTC2020-05-26 15:56:30 +0000 UTC

android 上的 libgdx sqlite，.db 不可移植到 android

  • 772

机器人工作室。在 PC 上，从数据库读取成功，在 Android 上数据库为空。我将数据库本身存储在 assets 目录中，与所有图片所在的位置相同。所有在android中没有问题的图片都是用的

dbHandler = DatabaseHandlerFactory.getNewDatabaseHandler(DATABASE_NAME, DATABASE_VERSION, DATABASE_CREATE, null);
dbHandler.setupDatabase();
dbHandler.openOrCreateDatabase();

dbHandler 在手机中找不到 .db 文件并创建新的空数据库，我如何将数据库传输到 android 以便我可以读取它？

AndroidLauncher 代码基于 Chaynik 的回答（有效）

import android.content.Context;
import android.os.Bundle;

import com.badlogic.gdx.backends.android.AndroidApplication;
import com.badlogic.gdx.backends.android.AndroidApplicationConfiguration;

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

public class AndroidLauncher extends AndroidApplication {
    Context mycontext;
    private static String DB_NAME = "database.db";
    private String DB_PATH;
    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(mycontext.getDatabasePath(DB_NAME));

        // transfer byte to inputfile to 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();
    }
    @Override
    protected void onCreate (Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        AndroidApplicationConfiguration config = new AndroidApplicationConfiguration();
        mycontext = getContext();
        DB_PATH = getApplicationContext().getPackageName()+"/databases/";
        try {
            copydatabase();
        } catch(IOException e) {};
        initialize(new ReactionTeacher(1), config);
    }
}
android

1 个回答

  1. Best Answer

    您将无法使用应用程序资源目录中的数据库 - 您首先需要将其复制到存储卡上的应用程序目录中。算法很简单。

    • 您检查应用程序目录中是否存在基本文件
    • 如果找不到该文件，请从资产中复制。

    这是从enSO上的类似问题中获取的代码

    public class DataBaseHelper extends SQLiteOpenHelper {
    private Context mycontext;

    //private String DB_PATH = mycontext.getApplicationContext().getPackageName()+"/databases/";
    private static String DB_NAME = "(datbasename).sqlite";//the extension may be .sqlite or .db
    public SQLiteDatabase myDataBase;
    /*private String DB_PATH = "/data/data/"
                        + mycontext.getApplicationContext().getPackageName()
                        + "/databases/";*/

    public DataBaseHelper(Context context) throws IOException {
        super(context,DB_NAME,null,1);
        this.mycontext=context;
        boolean dbexist = checkdatabase();
        if (dbexist) {
            //System.out.println("Database exists");
            opendatabase(); 
        } else {
            System.out.println("Database doesn't exist");
            createdatabase();
        }
    }

    public void createdatabase() throws IOException {
        boolean dbexist = checkdatabase();
        if(dbexist) {
            //System.out.println(" Database exists.");
        } else {
            this.getReadableDatabase();
            try {
                copydatabase();
            } catch(IOException e) {
                throw new Error("Error copying database");
            }
        }
    }   

    private boolean checkdatabase() {
        //SQLiteDatabase checkdb = null;
        boolean checkdb = false;
        try {
            String myPath = DB_PATH + DB_NAME;
            File dbfile = new File(myPath);
            //checkdb = SQLiteDatabase.openDatabase(myPath,null,SQLiteDatabase.OPEN_READWRITE);
            checkdb = dbfile.exists();
        } catch(SQLiteException e) {
            System.out.println("Database doesn't exist");
        }
        return checkdb;
    }

    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("/data/data/(packagename)/databases   /(datbasename).sqlite");

        // transfer byte to inputfile to 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_READWRITE);
    }

    public synchronized void close() {
        if(myDataBase != null) {
            myDataBase.close();
        }
        super.close();
    }

}
    • 2

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