似乎创建了数据库，但是当我尝试访问创建的数据库时出现错误。每当调用doQuery()时，应用程序都会崩溃。你能帮我弄清楚我做错了什么吗？
private class LoadCursorTask extends AsyncTask<Void, Void, Void>
{
Cursor constantCursor=null;
@Override
protected Void doInBackground(Void... params)
{
// TODO Auto-generated method stub
Log.d("Action1","in doInBacground()");
constantCursor=doQuery();
Log.d("Action1","after doQuery ");
constantCursor.getCount();
return null;
}
}
private Cursor doQuery()
{
Log.d("Action1","in doQuery()");
Cursor localCursor= db.getReadableDatabase().rawQuery("SELECT _id, title, value"+" FROM constants ORDER BY title; ", null);
Log.d("Action1","before returning from doQuery()");
return localCursor;
}
stacktrack上的错误报告显示如下：
08-02 11:23:31.012: E/SQLiteLog(1829): (1) no such table: constants
08-02 11:23:31.040: W/dalvikvm(1829): threadid=11: thread exiting with uncaught exception (group=0x40a71930)
08-02 11:23:31.173: E/AndroidRuntime(1829): FATAL EXCEPTION: AsyncTask #1
08-02 11:23:31.173: E/AndroidRuntime(1829): java.lang.RuntimeException: An error occured while executing doInBackground()
08-02 11:23:31.173: E/AndroidRuntime(1829): at android.os.AsyncTask$3.done(AsyncTask.java:299)
08-02 11:23:31.173: E/AndroidRuntime(1829): at java.util.concurrent.FutureTask.finishCompletion(FutureTask.java:352)
08-02 11:23:31.173: E/AndroidRuntime(1829): at java.util.concurrent.FutureTask.setException(FutureTask.java:219)
08-02 11:23:31.173: E/AndroidRuntime(1829): at java.util.concurrent.FutureTask.run(FutureTask.java:239)
08-02 11:23:31.173: E/AndroidRuntime(1829): at android.os.AsyncTask$SerialExecutor$1.run(AsyncTask.java:230)
08-02 11:23:31.173: E/AndroidRuntime(1829): at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1080)
08-02 11:23:31.173: E/AndroidRuntime(1829): at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:573)
08-02 11:23:31.173: E/AndroidRuntime(1829): at java.lang.Thread.run(Thread.java:856)
08-02 11:23:31.173: E/AndroidRuntime(1829): Caused by: android.database.sqlite.SQLiteException: no such table: constants (code 1): , while compiling: SELECT _id, title, value FROM constants ORDER BY title;
08-02 11:23:31.173: E/AndroidRuntime(1829): at android.database.sqlite.SQLiteConnection.nativePrepareStatement(Native Method)
08-02 11:23:31.173: E/AndroidRuntime(1829): at android.database.sqlite.SQLiteConnection.acquirePreparedStatement(SQLiteConnection.java:882)
08-02 11:23:31.173: E/AndroidRuntime(1829): at android.database.sqlite.SQLiteConnection.prepare(SQLiteConnection.java:493)
08-02 11:23:31.173: E/AndroidRuntime(1829): at android.database.sqlite.SQLiteSession.prepare(SQLiteSession.java:588)
08-02 11:23:31.173: E/AndroidRuntime(1829): at android.database.sqlite.SQLiteProgram.<init>(SQLiteProgram.java:58)
08-02 11:23:31.173: E/AndroidRuntime(1829): at android.database.sqlite.SQLiteQuery.<init>(SQLiteQuery.java:37)
08-02 11:23:31.173: E/AndroidRuntime(1829): at android.database.sqlite.SQLiteDirectCursorDriver.query(SQLiteDirectCursorDriver.java:44)
08-02 11:23:31.173: E/AndroidRuntime(1829): at android.database.sqlite.SQLiteDatabase.rawQueryWithFactory(SQLiteDatabase.java:1314)
08-02 11:23:31.173: E/AndroidRuntime(1829): at android.database.sqlite.SQLiteDatabase.rawQuery(SQLiteDatabase.java:1253)
08-02 11:23:31.173: E/AndroidRuntime(1829): at com.example.database_constants.ConstantsFragment.doQuery(ConstantsFragment.java:28)
08-02 11:23:31.173: E/AndroidRuntime(1829): at com.example.database_constants.ConstantsFragment.access$0(ConstantsFragment.java:25)
08-02 11:23:31.173: E/AndroidRuntime(1829): at com.example.database_constants.ConstantsFragment$LoadCursorTask.doInBackground(ConstantsFragment.java:47)
08-02 11:23:31.173: E/AndroidRuntime(1829): at com.example.database_constants.ConstantsFragment$LoadCursorTask.doInBackground(ConstantsFragment.java:1)
08-02 11:23:31.173: E/AndroidRuntime(1829): at android.os.AsyncTask$2.call(AsyncTask.java:287)
08-02 11:23:31.173: E/AndroidRuntime(1829): at java.util.concurrent.FutureTask.run(FutureTask.java:234)
08-02 11:23:31.173: E/AndroidRuntime(1829): ... 4 more
以下是我创建数据库的方法：
db.execSQL("CREATE TABLE constants (_id INTEGER PRIMARY KEY AUTOINCREMENT, title TEXT, value REAL);");
[更新1]
这是DatabaseHelper.class
public class DatabaseHelper extends SQLiteOpenHelper
{
private static final String DATABASE_NAME="constants.db";
private static final int SCHEMA=1;
static final String TITLE="title";
static final String VALUE="value";
static final String TABLE="constants";
public DatabaseHelper(Context context) {
super(context, DATABASE_NAME, null, SCHEMA);
// TODO Auto-generated constructor stub
Log.d("Action1","in DatabaseHelper constructor");
}
@Override
public void onCreate(SQLiteDatabase db)
{
Log.d("Action1","in onCreate");
try
{
db.beginTransaction();
db.execSQL("CREATE TABLE constants (_id INTEGER PRIMARY KEY AUTOINCREMENT, title TEXT, value REAL)");
ContentValues cv=new ContentValues();
cv.put(TITLE, "Gravity, Death Star I");
cv.put(VALUE, SensorManager.GRAVITY_DEATH_STAR_I);
db.insert("constants", TITLE, cv);
cv.put(TITLE, "Gravity, Earth");
cv.put(VALUE, SensorManager.GRAVITY_EARTH);
db.insert("constants", TITLE, cv);
cv.put(TITLE, "Gravity, Jupiter");
cv.put(VALUE, SensorManager.GRAVITY_JUPITER);
db.insert("constants", TITLE, cv);
}
finally
{
db.endTransaction();
}
}
}
答案 0 :(得分：0)
可能找不到您的数据库文件，并在您尝试打开它时创建一个新的空文件。检查数据库的名称和位置。如果您是在代码中创建它，请确保在尝试访问它之前创建表。
编辑：
找到您的问题，您需要在endTransaction之前将事务标记为成功，否则它将被回滚。
@Override
public void onCreate(SQLiteDatabase db)
{
Log.d("Action1","in onCreate");
try
{
db.beginTransaction();
db.execSQL("CREATE TABLE constants (_id INTEGER PRIMARY KEY AUTOINCREMENT, title TEXT, value REAL)");
ContentValues cv=new ContentValues();
cv.put(TITLE, "Gravity, Death Star I");
cv.put(VALUE, SensorManager.GRAVITY_DEATH_STAR_I);
db.insert("constants", TITLE, cv);
cv.put(TITLE, "Gravity, Earth");
cv.put(VALUE, SensorManager.GRAVITY_EARTH);
db.insert("constants", TITLE, cv);
cv.put(TITLE, "Gravity, Jupiter");
cv.put(VALUE, SensorManager.GRAVITY_JUPITER);
db.insert("constants", TITLE, cv);
db.setTransactionSuccessful();
}
finally
{
db.endTransaction();
}
}