Android的 - 无法打开数据库 [英] Android - Could not open database
问题描述
我在资产
文件夹我的 db.sqlite
文件,当我试图打开我得到这个错误它:
android.database.sqlite.SQLiteCantOpenDatabaseException:未知
错误(code 14):无法打开数据库
块引用>我已经尝试了不同的路径和名称(带和不带扩展名),但我不能使它工作。
包com.example.APP.db;进口的java.io.File;
进口java.io.FileOutputStream中;
进口java.io.IOException异常;
进口的java.io.InputStream;
进口java.io.OutputStream中;进口android.content.Context;
进口android.database.SQLException;
进口android.database.sqlite.SQLiteDatabase;
进口android.database.sqlite.SQLiteException;
进口android.database.sqlite.SQLiteOpenHelper;
进口android.widget.Toast;公共类DataBaseHelper扩展SQLiteOpenHelper {//你的应用程序数据库的Android的默认系统路径。
私人静态字符串DB_PATH =/data/data/com.example.APP/databases/;
私人静态字符串DB_NAME =应用程序;
私人SQLiteDatabase MYDATABASE;
私人最终上下文myContext;/ **
*构造函数和不断传递的上下文中的一个参考,以
*访问应用程序的资产和资源。
*
* @参数方面
* /
公共DataBaseHelper(上下文的背景下){
超级(上下文,DB_NAME,空,1);
this.myContext =背景;
}/ **
*在系统上创建一个空数据库,然后用自己的重写它
*数据库。
* * /
公共无效的CreateDatabase()抛出IOException
布尔dbExist = checkDataBase(); 如果(dbExist){
//什么也不做 - 已存在于数据库
}其他{ //通过调用此方法与空的数据库将被创建成
//默认的系统路径
//你的应用程序,所以我们要能够覆盖
//数据库与我们的数据库。
this.getReadableDatabase();
尝试{
copyDataBase();
}赶上(IOException异常五){
抛出新的错误(错误复制数据库);
}
}
}/ **
*检查是否已存在于数据库,以避免重新复制每个文件
*一次打开应用程序。
*
*如果存在返回:真的,假的,如果它不
* /
私人布尔checkDataBase(){
布尔CHECKDB = FALSE;
尝试{
字符串mypath中= myContext.getFilesDir()getAbsolutePath()代替(文件,数据库)+文件分割符+ DB_NAME。;
文件DBFILE =新的文件(mypath中);
CHECKDB = dbfile.exists();
}
赶上(SQLiteException E){
的System.out.println(数据库不存在);
} 返回CHECKDB;
}/ **
*副本数据库从本地资产文件夹复制到刚创建
*在系统文件夹,空数据库从那里可以访问和
*处理。这是通过转流的字节流进行。
* * /
私人无效copyDataBase()抛出IOException //打开本地数据库的输入流
InputStream的myInput = myContext.getAssets()开(DB_NAME)。 //路径刚刚创建的空分贝
字符串outFileName = DB_PATH + DB_NAME; //打开空分贝的输出流
的OutputStream myOutput =新的FileOutputStream(outFileName); //传递从inputfile中字节到OUTPUTFILE
字节[]缓冲区=新的字节[1024];
INT长;
而((长度= myInput.read(缓冲液))大于0){
myOutput.write(缓冲液,0,长度);
} //关闭流
myOutput.flush();
myOutput.close();
myInput.close();
} 公共无效的openDatabase()抛出的SQLException { //打开数据库
字符串mypath中= DB_PATH + DB_NAME;
MYDATABASE = SQLiteDatabase.openDatabase(mypath中,空,SQLiteDatabase.OPEN_READONLY); }@覆盖
公共同步无效的close(){ 如果(MYDATABASE!= NULL)
myDataBase.close(); super.close();}@覆盖
公共无效的onCreate(SQLiteDatabase DB){}@覆盖
公共无效onUpgrade(SQLiteDatabase分贝,INT oldVersion,诠释静态网页){}
}我得到的错误,当我尝试在这里打开它:
包com.example.APP;进口android.app.Activity;
进口android.os.Bundle;
进口android.widget.TextView;
进口com.example.APP.db.DataBaseHelper;
公共类SpeakersListActivity延伸活动{公共无效的onCreate(捆绑savedInstanceState){
super.onCreate(savedInstanceState);
的setContentView(R.layout.mylayout); DataBaseHelper dbHelper =新DataBaseHelper(本);
dbHelper.openDataBase();
}
}
解决方案您需要检查数据库文件第一,你没有做这里的存在
DataBaseHelper dbHelper =新DataBaseHelper(本);
dbHelper.openDataBase();你只是做DataBaseHelper的对象,然后调用.openDataBase()
试试这个构造:
公共DataBaseHelper(上下文的背景下){
超级(上下文,DB_NAME,空,1);
this.myContext =背景;
尝试{
字符串mypath中= DB_PATH + DB_NAME; //还要检查你的扩展数据库文件
文件DBFILE =新的文件(mypath中);
如果(dbfile.exists());
Toast.makeText(背景下,数据库中不存在,Toast.LENGTH_LONG).show();
其他
Toast.makeText(背景下,不能找到数据库,Toast.LENGTH_LONG).show();
}
赶上(SQLiteException E){
的System.out.println(数据库不存在);
}}I have my
db.sqlite
file in theAsset
folder and I get this error when I try to open it:android.database.sqlite.SQLiteCantOpenDatabaseException: unknown error (code 14): Could not open database
I've tried different paths and names (with and without the extension) but I can't make it work.
package com.example.APP.db; import java.io.File; import java.io.FileOutputStream; import java.io.IOException; import java.io.InputStream; import java.io.OutputStream; import android.content.Context; import android.database.SQLException; import android.database.sqlite.SQLiteDatabase; import android.database.sqlite.SQLiteException; import android.database.sqlite.SQLiteOpenHelper; import android.widget.Toast; public class DataBaseHelper extends SQLiteOpenHelper { // The Android's default system path of your application database. private static String DB_PATH = "/data/data/com.example.APP/databases/"; private static String DB_NAME = "app"; 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(){ boolean checkdb = false; try{ String myPath = myContext.getFilesDir().getAbsolutePath().replace("files", "databases")+File.separator + DB_NAME; File dbfile = new File(myPath); checkdb = dbfile.exists(); } catch(SQLiteException e){ System.out.println("Database doesn't exist"); } return checkdb; } /** * 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); // 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) { } }
I get the error when I try to open it here:
package com.example.APP; import android.app.Activity; import android.os.Bundle; import android.widget.TextView; import com.example.APP.db.DataBaseHelper; public class SpeakersListActivity extends Activity { public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.mylayout); DataBaseHelper dbHelper = new DataBaseHelper(this); dbHelper.openDataBase(); } }
解决方案you need to check the existence of the database file first which you are not doing here
DataBaseHelper dbHelper = new DataBaseHelper(this); dbHelper.openDataBase();
you are simply making an object of DataBaseHelper and then calling .openDataBase()
try this constructor :
public DataBaseHelper(Context context) { super(context, DB_NAME, null, 1); this.myContext = context; try{ String myPath = DB_PATH + DB_NAME; // also check the extension of you db file File dbfile = new File(myPath); if( dbfile.exists()); Toast.makeText(context, "database exists", Toast.LENGTH_LONG).show(); else Toast.makeText(context, "cant find database", Toast.LENGTH_LONG).show(); } catch(SQLiteException e){ System.out.println("Database doesn't exist"); } }
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