Question

我使用“DB Browser for SQLite”创建了我的文件。请检查我的数据库文件是否正常： https://www.file-upload.net/download-12324299/neueAB.db.html

我使用此文档https://blog.reigndesign.com/blog/using-your-own-sqlite-database-in-android-applications/将外部数据库加载到我的Android应用程序中。但经过5个小时的工作，我终于放弃了自己找到问题的方法。这是DataBaseHelper类：

package com.example.avraham.databases;

import android.content.Context;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteOpenHelper;
import android.widget.Toast;

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

public class DataBaseHelper extends SQLiteOpenHelper {
    //Attributes#######
    public final static String DATABASE_NAME = "neueAB.db";
    public String DB_PATH;
    private Context cont;
    SQLiteDatabase db;

    //Constructor#######
    public DataBaseHelper(Context context) {
        super(context, DATABASE_NAME, null , 1);
        cont = context;
    }

    //Methods#######
    public void createDatabase() throws IOException{
        DB_PATH = "/data/data/" + "com.example.avraham.databases" + "/databases/";
        boolean dbExist = checkDataBase();
        if(dbExist != true){
            try{
                getReadableDatabase(); //create database whis is empty. There we will copy the entries of the assets database.
                copyDataBase();
                Toast.makeText(cont, "Copied succ!", Toast.LENGTH_SHORT).show();
            }
            catch (Exception e){
                Toast.makeText(cont, "Error:" + e.getMessage(), Toast.LENGTH_SHORT).show();
            }
        }else{
            Toast.makeText(cont, "Database already exists", Toast.LENGTH_SHORT).show();
        }
    }

    public boolean checkDataBase() {
        File dbFile = new File(DB_PATH + DATABASE_NAME);
        return dbFile.exists();
    }

    public void copyDataBase() {
        try {
            //Open your local db as the input stream
            InputStream myInput = cont.getAssets().open(DATABASE_NAME);
            // Path to the just created empty db
            String outFileName = DB_PATH + DATABASE_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();
            Toast.makeText(cont, "Copy erfolgreich!", Toast.LENGTH_SHORT).show();
        } catch (IOException e) {
            MainActivity.showMessage("Error copyDataBase()", e.getMessage(),cont);
        }
    }

    public Cursor getAllData(){
        try {
            //db = this.getWritableDatabase(); //Create Database
            String myPath = DB_PATH+DATABASE_NAME;
            db = SQLiteDatabase.openDatabase(myPath, null, SQLiteDatabase.OPEN_READONLY);
            Cursor res = db.rawQuery("SELECT * FROM student_table", null);
            return res;
        }
        catch (Exception e){
            MainActivity.showMessage("Error getAllData()", e.getMessage(),cont);
            return null;
        }
    }

    @Override
    public synchronized void close() {

        if(db != null)
            db.close();

        super.close();
    }

    public boolean openDataBase(){
        try{
            String myPath = DB_PATH+DATABASE_NAME;
            db = SQLiteDatabase.openDatabase(myPath, null, SQLiteDatabase.OPEN_READONLY);
            return db != null;
        }
        catch(Exception e){
            MainActivity.showMessage("Error openDataBase()", e.getMessage(),cont);
            return false;
        }
    }

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

}

这是活动文件：

package com.example.avraham.databases;

import android.content.Context;
import android.content.DialogInterface;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteException;
import android.support.v7.app.AlertDialog;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.Toast;

import java.io.IOException;

public class MainActivity extends AppCompatActivity {
    DataBaseHelper myHelper;
    EditText txtName, txtSurname, txtAge, txtId;
    Button btnShow, btnAdd, btnUpdate, btnDelete;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        initializeVariables();;
        myHelper = new DataBaseHelper(this);



    /* ######################################################*/
        btnAdd.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {

            }
        });

        btnShow.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                try {
                    myHelper.createDatabase();
                } catch (IOException e) {
                    showMessage("Error", e.getMessage(),MainActivity.this);
                }
                myHelper.openDataBase();
                showAll();
            }
        });

        btnUpdate.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {

            }
        });

        btnDelete.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {

            }
        });

    }

    public void showAll(){
        try{
        Cursor res = myHelper.getAllData();
        if(res.getColumnCount() == 0){
            showMessage("Info", "No Data available",MainActivity.this);
        }
        else{
                StringBuffer buffer = new StringBuffer();
                while(res.moveToNext()){
                    buffer.append("id: " + res.getString(0) + "\n");
                    buffer.append("Name: " + res.getString(1) + "\n");
                    buffer.append("Surname: " + res.getString(2) + "\n");
                    buffer.append("Age: " + res.getString(3) + "\n\n");
                }
                showMessage("Data:", buffer.toString(),MainActivity.this);
            }
        }
        catch (Exception e){
            showMessage("Error showAll():",e.getMessage(),MainActivity.this);
        }
    }
    /*############################################################################################*/
    /*############################################################################################*/
    /*############################################################################################*/

    public static void showMessage(String Title, String Message, Context c){
        AlertDialog.Builder dlg = new AlertDialog.Builder(c);
        dlg.setTitle(Title);
        dlg.setMessage(Message);
        dlg.setCancelable(true);
        dlg.setPositiveButton("OK", new DialogInterface.OnClickListener(){
            public void onClick(DialogInterface dialog, int which) {

            }
        });
        dlg.create().show();
    }

    public void initializeVariables(){
        txtName = (EditText) findViewById(R.id.editTxt_name);
        txtSurname = (EditText) findViewById(R.id.editTxt_surname);
        txtAge = (EditText) findViewById(R.id.editTxt_age);
        btnAdd = (Button) findViewById(R.id.btn_add);
        btnShow = (Button) findViewById(R.id.btn_show);
        btnUpdate = (Button) findViewById(R.id.btn_update);
        txtId = (EditText) findViewById(R.id.txt_id);
        btnDelete = (Button) findViewById(R.id.btn_delete);
    }
}

我在getAllData（）函数中遇到错误：

“文件已加密或不是数据库（Sqlite代码26）:,同时编译：SELECT * FROM student_table，（操作系统错误 - 2：没有此类文件或目录））”

请帮帮我。

Answer 1

尝试替换此

public final static String DATABASE_NAME = "neueAB.db";

与

public final static String DATABASE_NAME = "neueAB";

Answer 2

答案在这里： buffer.append（＆＃34; id：＆＃34; + res.getString（0）+＆＃34; \ n＆＃34;）;

它应该是： buffer.append（＆＃34; _id：＆＃34; + res.getString（0）+＆＃34; \ n＆＃34;）;

Android：SQLITE数据库文件已加密或不是数据库

2 个答案: