我是eclipse和android编程的新手，我的数据库连接有问题。好吧，我找到了许多链接，我发布了我的2个课程。如果有人能找到错误。我拥有的数据库是用sqlite制作的，它有android_metadata和问题表。当我在模拟器中运行时，当我打开关于表单时，它会有一些消息“DrymVyzion的应用程序测验测试（进程dv.qtest.dvyzual）意外停止。请再试一次。” 在eclipse那是错误：
01-08 22:50:42.292: E/AndroidRuntime(1059): Uncaught handler: thread main exiting due to uncaught exception
01-08 22:50:42.312: E/AndroidRuntime(1059): java.lang.RuntimeException: Unable to start activity ComponentInfo{dv.qtest.dvyzual/dv.qtest.dvyzual.About}: android.database.sqlite.SQLiteException: no such table: questions: , while compiling: SELECT _id, question, qone, qtwo, qthree, qanswer FROM questions
01-08 22:50:42.312: E/AndroidRuntime(1059): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2401)
01-08 22:50:42.312: E/AndroidRuntime(1059): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2417)
01-08 22:50:42.312: E/AndroidRuntime(1059): at android.app.ActivityThread.access$2100(ActivityThread.java:116)
01-08 22:50:42.312: E/AndroidRuntime(1059): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1794)
01-08 22:50:42.312: E/AndroidRuntime(1059): at android.os.Handler.dispatchMessage(Handler.java:99)
01-08 22:50:42.312: E/AndroidRuntime(1059): at android.os.Looper.loop(Looper.java:123)
01-08 22:50:42.312: E/AndroidRuntime(1059): at android.app.ActivityThread.main(ActivityThread.java:4203)
01-08 22:50:42.312: E/AndroidRuntime(1059): at java.lang.reflect.Method.invokeNative(Native Method)
01-08 22:50:42.312: E/AndroidRuntime(1059): at java.lang.reflect.Method.invoke(Method.java:521)
01-08 22:50:42.312: E/AndroidRuntime(1059): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:791)
01-08 22:50:42.312: E/AndroidRuntime(1059): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:549)
01-08 22:50:42.312: E/AndroidRuntime(1059): at dalvik.system.NativeStart.main(Native Method)
01-08 22:50:42.312: E/AndroidRuntime(1059): Caused by: android.database.sqlite.SQLiteException: no such table: questions: , while compiling: SELECT _id, question, qone, qtwo, qthree, qanswer FROM questions
01-08 22:50:42.312: E/AndroidRuntime(1059): at android.database.sqlite.SQLiteProgram.native_compile(Native Method)
01-08 22:50:42.312: E/AndroidRuntime(1059): at android.database.sqlite.SQLiteProgram.compile(SQLiteProgram.java:110)
01-08 22:50:42.312: E/AndroidRuntime(1059): at android.database.sqlite.SQLiteProgram.<init>(SQLiteProgram.java:59)
01-08 22:50:42.312: E/AndroidRuntime(1059): at android.database.sqlite.SQLiteQuery.<init>(SQLiteQuery.java:49)
01-08 22:50:42.312: E/AndroidRuntime(1059): at android.database.sqlite.SQLiteDirectCursorDriver.query(SQLiteDirectCursorDriver.java:49)
01-08 22:50:42.312: E/AndroidRuntime(1059): at android.database.sqlite.SQLiteDatabase.rawQueryWithFactory(SQLiteDatabase.java:1118)
01-08 22:50:42.312: E/AndroidRuntime(1059): at android.database.sqlite.SQLiteDatabase.queryWithFactory(SQLiteDatabase.java:1006)
01-08 22:50:42.312: E/AndroidRuntime(1059): at android.database.sqlite.SQLiteDatabase.query(SQLiteDatabase.java:964)
01-08 22:50:42.312: E/AndroidRuntime(1059): at android.database.sqlite.SQLiteDatabase.query(SQLiteDatabase.java:1041)
01-08 22:50:42.312: E/AndroidRuntime(1059): at dv.qtest.dvyzual.About.getEvents(About.java:46)
01-08 22:50:42.312: E/AndroidRuntime(1059): at dv.qtest.dvyzual.About.onCreate(About.java:22)
01-08 22:50:42.312: E/AndroidRuntime(1059): at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1123)
01-08 22:50:42.312: E/AndroidRuntime(1059): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2364)
以下是我的两个课程：
quizData.java
package dv.qtest.dvyzual;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
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;
/** Helper to the database, manages versions and creation */
public class quizData extends SQLiteOpenHelper {
private static final String DB_PATH = "/data/data/dv.qtest.dvyzual/databases/";
private static final String DB_NAME = "q.db";
private static final int DATABASE_VERSION = 1;
private SQLiteDatabase myDataBase;
private final Context myContext;
// Table name
public static final String TABLE = "questions";
// Columns
public static final String qid = "_id";
public static final String question = "question";
public static final String qone = "qone";
public static final String qtwo = "qtwo";
public static final String qthree = "qthree";
public static final String qanswer = "qanswer";
public quizData(Context context) {
super(context, DB_NAME, null, DATABASE_VERSION);
this.myContext = context;
}
public void createDataBase() throws IOException{
boolean dbExist = checkDataBase();
if(dbExist){
}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 {
this.close(); // testing
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.
}
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);
// 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) {
}
}
About.java
package dv.qtest.dvyzual;
import java.io.IOException;
import android.app.Activity;
import android.database.Cursor;
import android.database.SQLException;
import android.database.sqlite.SQLiteDatabase;
import android.os.Bundle;
import android.widget.TextView;
public class About extends Activity {
/** Called when the activity is first created. */
private quizData eventsData = new quizData(About.this);
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.about);
Cursor cursor = getEvents();
showEvents(cursor);
try {
eventsData.createDataBase();
} catch (IOException ioe) {
throw new Error("Unable to create database");
}
try {
eventsData.openDataBase();
}catch(SQLException sqle){
throw sqle;
}
}
@Override
public void onDestroy() {
eventsData.close();
}
private Cursor getEvents() {
SQLiteDatabase db = eventsData.getReadableDatabase();
Cursor cursor = db.query("questions", new String[]{"_id","question","qone", "qtwo", "qthree", "qanswer"}, null, null, null, null, null);
startManagingCursor(cursor);
return cursor;
}
private void showEvents(Cursor cursor) {
StringBuilder ret = new StringBuilder("Saved Events:\n\n");
while (cursor.moveToNext()) {
long id = cursor.getLong(0);
String q = cursor.getString(1);
String q1 = cursor.getString(2);
ret.append(id + ": " + q + ": " + q1 + "\n");
}
TextView tv = new TextView(this);
tv.setText(ret);
setContentView(tv);
}
}
请帮助，如果有人能找到我做错了什么，我正在尝试那么多个小时！ 顺便说一下，它适用于数据库，而不是来自没有DB路径的文件。所以也许问题是我没有设置db helper correcty？有什么想法吗？
答案 0 :(得分：0)
在“关于”活动中，您在致电getEvents()之前呼叫eventsData.createDataBase()。这将尝试在数据库存在之前访问它。我想如果你颠倒onCreate中的通话顺序，它可能会起作用（除了其他问题）：
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.about);
try {
eventsData.createDataBase();
} catch (IOException ioe) {
throw new Error("Unable to create database");
}
try {
eventsData.openDataBase();
} catch(SQLException sqle){
throw sqle;
}
Cursor cursor = getEvents();
showEvents(cursor);
}