我想在 MySQL 中使用我的外部数据库。我有一个归档数据库databse.db.zip，并将其复制到我的Android Java项目的assets文件夹中。最后，我创建了一个用于打开数据库的类：
import android.content.Context;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteQueryBuilder;
import com.readystatesoftware.sqliteasset.SQLiteAssetHelper;
public class databaseOpen extends SQLiteAssetHelper {
private static final String DATABASE_NAME = "parole.db";
private static final int DATABASE_VERSION = 1;
public databaseOpen(Context context) {
super(context, DATABASE_NAME, null, DATABASE_VERSION);
}
public String risposta(String parolain ){
SQLiteDatabase db = getReadableDatabase();
SQLiteQueryBuilder qb = new SQLiteQueryBuilder();
String[] selectionArgs = {"ciao"};
Cursor c =db.query("prima", null, null,selectionArgs, null, null, null);
c.moveToFirst();
return c.getString(0);
}
}
我已经在main：
private databaseOpen db;
@Override
protected void onCreate(Bundle savedInstanceState) {
db = new databaseOpen(this);
Toast toast=Toast.makeText(this, db.risposta("ciao"), Toast.LENGTH_LONG);
}
但它不起作用。这是我得到的输出：
09-26 15:20:23.761 1099-1099/? I/SQLiteAssetHelper successfully opened database parole.db
09-26 15:20:23.764 1099-1099/? E/SQLiteLog (1) no such table: prima
09-26 15:20:23.783 1099-1099/? D/AndroidRuntime Shutting down VM
09-26 15:20:23.801 1099-1099/? E/AndroidRuntime FATAL EXCEPTION: main
Process: com.example.roby.jarvis, PID: 1099
java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.roby.jarvis/com.example.roby.jarvis.Home}: android.database.sqlite.SQLiteException: no such table: prima (code 1): , while compiling: SELECT * FROM prima
答案 0 :(得分：0)
我想在mysql中使用我的外部数据库，我已经压缩了这个（databse.db.zip）并将其复制到我的java项目的assents文件夹中
为了记录， 要么你使用错误的术语，要么混淆。 Android和您帖子中的代码适用于SQLite。 它无法与MySQL一起使用。
当某些事情不起作用时， 阅读错误信息， 这通常解释了问题，例如：
09-26 15：20：23.764 1099-1099 /？ E / SQLiteLog：（1）没有这样的表：prima
名为＆＃34; prima＆＃34;文件中不存在。
调试的下一步是检查PC上文件的内容，
使用s命令行工具或类似工具，
并查看它有哪些表（sqlite3命令）。
答案 1 :(得分：0)
首先：您没有将资产文件中的Database文件复制到您的设备，这显然会导致no such table found。
试试这段代码，它适合我。 （我也评论了不同的部分供您理解）
import android.content.ContentValues;
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.os.Build;
import android.util.Log;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
/**
* Created by HP-HP on 23-07-2015.
*/
public class DataBaseHelper extends SQLiteOpenHelper {
//The Android's default system path of your application database.
private static String DB_PATH ;
private static String DB_NAME = "profanityv2";
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);
if(android.os.Build.VERSION.SDK_INT >= 4.2){
DB_PATH = context.getApplicationInfo().dataDir + "/databases/";
} else {
DB_PATH = "/data/data/" + context.getPackageName() + "/databases/";
}
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(){
SQLiteDatabase checkDB = null;
try{
String myPath = DB_PATH + DB_NAME;
checkDB = SQLiteDatabase.openDatabase(myPath, null, SQLiteDatabase.OPEN_READONLY);
}catch(SQLiteException e){
//database does't exist yet.
try {
myContext.deleteDatabase("profanity");
} catch (Exception e1) {
e1.printStackTrace();
}
}
if(checkDB != null){
checkDB.close();
}
return checkDB != null;
}
/**
* 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.NO_LOCALIZED_COLLATORS|SQLiteDatabase.CREATE_IF_NECESSARY );
}
@Override
public synchronized void close() {
if(myDataBase != null)
myDataBase.close();
super.close();
}
public Cursor getData() {
Cursor c = null;
try {
c = myDataBase.rawQuery("SELECT * FROM profanity_table", null);
} catch (Exception e) {
e.printStackTrace();
}
// Note: Master is the one table in External db. Here we trying to access the records of table from external db.
return c;
}
@Override
public void onCreate(SQLiteDatabase db) {
}
@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
}
// Add your public helper methods to access and get content from the database.
// You could return cursors by doing "return myDataBase.query(....)" so it'd be easy
// to you to create adapters for your views.
}
用法：
DataBaseHelper dataBaseHelper = new DataBaseHelper(this);
try {
dataBaseHelper.createDataBase();
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
try {
dataBaseHelper.openDataBase();
}catch(SQLException sqle){
throw sqle;
}
Cursor c = dataBaseHelper.getData();
if(c!=null) {
/* your cursor code */
c.close();
}
dataBaseHelper.close();
*注意：某些设备可能无法将数据库复制到设备。（已知设备：OnePlus）
不要忘记添加此权限
<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />
。
编辑1： OnePlus能够将数据库复制到/data/data/<package-name>/databases/<filename>.db，但它不允许访问该数据，我对此没有任何线索。