我有个问题。我有 2 个安卓项目。一是“主要”项目。另一个是一个项目，我尝试根据互联网上的教程实现一个基本的测验应用程序。
测验应用程序工作正常，所以我想在“主要”项目中实现它。（在“主”项目中，我有 2 个包，一个用于测验的类）我创建了类、布局，将数据库复制到 assets 文件夹。一切都与第二个项目相同。但它不能复制数据库。我有找不到表的错误。
它使数据库，我用 ddms 检查它（拉数据库），但不能复制表。“主项目”中的代码与第二个项目相同（！）。（在第二个项目中一切都很好）
这是代码片段：
package com.thesis.Quiz;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.util.ArrayList;
import java.util.List;
import com.thesis.eliminations.R;
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;
public class DBHelperForQuiz extends SQLiteOpenHelper{
//The Androids default system path of your application database.
private static String DB_PATH = "/data/data/com.thesis.eliminations/databases/";
private static String DB_NAME = "QuizDB";
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 DBHelperForQuiz(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();
//SQLiteDatabase db_Read = null;
//SQLiteDatabase db = null;
if(dbExist){
//do nothing - database already exist
//db = super.getReadableDatabase();
}else{
this.getReadableDatabase();
//db_Read = this.getReadableDatabase();
//db_Read.close();
try {
copyDataBase();
// db = super.getReadableDatabase();
} catch (IOException e) {
//throw new Error("Error copying database");
e.printStackTrace();
}
}
}
/**
* 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.
}
if(checkDB != null){
checkDB.close();
}
return checkDB != null ? true : false;
}
/**
* 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);
InputStream myInput = myContext.getResources().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();
}
public List<Question> getQuestionsList(int difficulty, int numberOfQuestions) {
Log.d("NOQ",Integer.toString(numberOfQuestions));
List<Question> questionsList = new ArrayList<Question>();
Cursor c = myDataBase
.rawQuery("SELECT * FROM QUESTIONS WHERE DIFFICULTY="
+ difficulty + " ORDER BY RANDOM() LIMIT "
+ numberOfQuestions, null);
while (c.moveToNext()) {
Question q = new Question();
q.setQuestionText(c.getString(1));
q.setRightAnswer(c.getString(2));
q.setAnswerOption1(c.getString(3));
q.setAnswerOption2(c.getString(4));
q.setAnswerOption3(c.getString(5));
q.setQuestionDiffLevel(difficulty);
questionsList.add(q);
}
return questionsList;
}
@Override
public void onCreate(SQLiteDatabase db) {
// TODO Auto-generated method stub
}
@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
// TODO Auto-generated method stub
}
}
和：
public class QuizActivityMain extends Activity implements OnClickListener {
Button bStart, bQuit, bSetDiff;
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.quizmenu);
initialize();
}
private void initialize() {
bStart = (Button) findViewById(R.id.bStartQuiz);
bQuit = (Button) findViewById(R.id.bExitQuiz);
bSetDiff = (Button) findViewById(R.id.bSetDiff);
bSetDiff.setOnClickListener(this);
bQuit.setOnClickListener(this);
bStart.setOnClickListener(this);
Log.d("init", "initialize..");
}
@Override
public void onClick(View v) {
Intent i;
switch (v.getId()) {
case R.id.bStartQuiz:
List<Question> questionsList = getQuestionsFromDB();
QuizGame currentQuizGame = new QuizGame();
currentQuizGame.setNumberOfRounds(this.getNumOfQuestions());
currentQuizGame.setQuestions(questionsList);
Log.d("ql set", "ql set");
/* ((QuizApplication) getApplication())
.setCurrentQuizGame(currentQuizGame);*/
((QuizApplication)getApplication()).setCurrentQuizGame(currentQuizGame);
Log.d("cqg set", "cqg set");
i = new Intent(this, AskedQuestion.class);
Log.d("i started", "intent");
startActivity(i);
Log.d("i started", "intent started");
break;
case R.id.bExitQuiz:
finish();
break;
case R.id.bSetDiff:
i = new Intent(this, QuizSettings.class);
startActivity(i);
break;
}
}
private List<Question> getQuestionsFromDB() throws Error{
int tmpDifficulty = getDifficulty();
int tmpNumberOfQuestions = getNumOfQuestions();
DBHelperForQuiz myDbHelper = new DBHelperForQuiz(this.getApplicationContext());
myDbHelper = new DBHelperForQuiz(this);
try {
myDbHelper.createDataBase();
} catch (IOException e) {
throw new Error("Unable to create database");
}
try {
myDbHelper.openDataBase();
Log.d("openeddb", "open db success");
} catch (SQLException sqle) {
throw sqle;
}
Log.d("ql try", "ql making");
List<Question> qL = myDbHelper.getQuestionsList(tmpDifficulty, tmpNumberOfQuestions);
Log.d("TMPNOQ",Integer.toString(tmpNumberOfQuestions));
Log.d("ql rdy", "ql done");
myDbHelper.close();
Log.d("db cls", "closed");
return qL;
}
private int getNumOfQuestions() {
return 5;
}
private int getDifficulty() {
return 2;
}
}