無法在android studio中從sqlitedabse讀取數據

Question

我試圖在我的應用程序中使用現有的sqlite數據庫，並在android資產文件夾中放置我的數據庫文件（我通過db瀏覽器爲windows 7操作系統中的sqlite可移植軟件創建的）工作室，我寫了databaseOpenHelper類是這樣的：

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; 
} 

，我這樣修改主要活動的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); 

    } 
} 

但是當我運行這個程序，列表視圖不返回任何值我的數據庫和這條消息出現在logcat中：「打開trace fil的錯誤e：沒有這樣的文件或目錄（2）「和」E/SQLiteLog：（1）沒有這樣的表格：dataSheet「

看來，Android工作室無法找到或從我的數據庫文件中讀取信息，Any Ideas歡迎！

這裏是正在運行的應用程序後的logcat消息： http://textuploader.com/p9zt

Answer 1

首先，我們需要爲數據庫文件夾創建一個文件夾，然後複製 databaseFile然後它工作正常。

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()); 
    } 
} 

Answer 2

我有這有點兒遇到這樣。爲了解決這個問題，

• 檢查「數據庫」文件夾存在與否第一。如果不存在，請先創建「數據庫」文件夾。
• 如果「databases」文件夾存在，則調用「copyDataBase」函數。

有時候， 「數據庫」 文件夾中缺少早期Android版本。