Question

我尝试在我的应用程序中使用现有的sqlite数据库并将我的数据库文件（我在Windows 7 OS中为db浏览器创建sqlite可移植软件）放在android studio的assets文件夹中，我写了一个像这样的databaseOpenHelper类：

package com.example.javad.dbproject;
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;
import android.util.Log;

import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.util.ArrayList;
import java.util.List;
public class myDatabaseHelper extends SQLiteOpenHelper {
private static String DB_PATH = "/data/data/com.example.javad.dbproject/databases/";
private static String DB_NAME = "database1.sqlite";
public static final String TB_USER = "dataSheet";

private SQLiteDatabase myDB;
private final Context context;

//constructor
public myDatabaseHelper(Context context) {
    super(context, DB_NAME, null, 1);
    this.context = context;
}

@Override
public void onCreate(SQLiteDatabase db) {
    //Handle creation tasks, etc.
}
@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
    //Handle upgrade tasks, etc.
}
    @Override
public synchronized void close() {
    if(myDB != null)
        myDB.close();
    super.close();
}
//Check if our database already exists
private boolean checkDataBase() {
    SQLiteDatabase tempDB = null;
    try {
        String myPath = DB_PATH + DB_NAME;
        tempDB = SQLiteDatabase.openDatabase(myPath, null, SQLiteDatabase.OPEN_READWRITE);
    } catch (SQLiteException e) {
        Log.e("tle99 - check", e.getMessage());
    }
    if (tempDB != null)
        tempDB.close();
    return tempDB != null ? true : false;
}
/***
 * Copy database from source code assets to device
 * @throws IOException
 */
public void copyDataBase() throws IOException{
    try {
        InputStream myInput = context.getAssets().open(DB_NAME);
        String outputFileName = DB_PATH + DB_NAME;
        OutputStream myOutput = new FileOutputStream(outputFileName);

        byte[] buffer = new byte[1024];
        int length;

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

        myOutput.flush();
        myOutput.close();
        myInput.close();
    } catch (Exception e) {
        Log.e("tle99 - copyDatabase", e.getMessage());
    }

}
/***
 * Open database
 * @throws SQLException
 */
public void openDataBase() throws SQLException{
    String myPath = DB_PATH + DB_NAME;
    myDB = SQLiteDatabase.openDatabase(myPath, null, SQLiteDatabase.OPEN_READWRITE);
}
/***
 * Check if the database doesn't exist on device, create new one
 * @throws IOException
 */
public void createDataBase() throws IOException {
    boolean dbExist = checkDataBase();

    if (dbExist) {

    } else {
        this.getReadableDatabase();
        try {
            copyDataBase();
        } catch (IOException e) {
            Log.e("tle99 - create", e.getMessage());
        }
    }
}

public List<String> getAllUsers(){
    List<String> listUsers = new ArrayList<String>();
    SQLiteDatabase db = this.getWritableDatabase();
    Cursor c;

    try {
        c = db.rawQuery("SELECT * FROM " + TB_USER , null);
        if(c == null) return null;

        String name;
        c.moveToFirst();
        do {
            name = c.getString(1);
            listUsers.add(name);
        } while (c.moveToNext());
        c.close();
    } catch (Exception e) {
        Log.e("tle99", e.getMessage());
    }

    db.close();

    return listUsers;
}

我以这种方式修改了主要活动java文件：

public class MainActivity extends ActionBarActivity {
myDatabaseHelper dbHeplper;
ListView lvUsers;
ListAdapter adapter;


@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);

    dbHeplper = new myDatabaseHelper(getApplicationContext());
    try {
        dbHeplper.createDataBase();
    } catch (IOException e) {
        e.printStackTrace();
    }

    lvUsers = (ListView) findViewById(R.id.lvUsers);
    List<String> listUsers = dbHeplper.getAllUsers();

    if (listUsers != null) {
        adapter = new ArrayAdapter<String>(getApplicationContext(),
                android.R.layout.simple_list_item_1, android.R.id.text1,
                listUsers);
        lvUsers.setAdapter(adapter);

    }
}

但是当我运行这个应用程序时，列表视图不会从我的数据库返回任何值，并且此消息出现在logcat中：“错误打开跟踪文件：没有这样的文件或目录（2）”和“E / SQLiteLog：（1 ）没有这样的表：dataSheet“

有人认为Android工作室无法找到或读取我的数据库文件中的信息，欢迎Any Ideas！

这是运行app后的logcat消息： http://textuploader.com/p9zt

Answer 1

我有那样的经历。要解决这个问题，

检查＆＃34;数据库＆＃34;文件夹是否存在或不存在。如果不存在，请创建＆＃34;数据库＆＃34;文件夹优先。

如果＆＃34;数据库＆＃34;文件夹已存在，然后调用＆＃34; copyDataBase＆＃34;功能

有时，＆＃34;数据库＆＃34;早期Android版本中缺少文件夹。

Answer 2

首先，我们需要为数据库文件夹创建一个文件夹然后复制 databaseFile然后它工作正常。

public void copyDataBase() throws IOException{
    try {
        InputStream myInput = context.getAssets().open(DB_NAME);

        File dbFile=new dbFile(DB_PATH);
        dbFile.mkdirs();

        String outputFileName = DB_PATH + DB_NAME;
        OutputStream myOutput = new FileOutputStream(outputFileName);

        byte[] buffer = new byte[1024];
        int length;

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

        myOutput.flush();
        myOutput.close();
        myInput.close();
    } catch (Exception e) {
        Log.e("tle99 - copyDatabase", e.getMessage());
    }
}

无法从android studio中的sqlitedabse读取数据

2 个答案: