我希望在我的应用程序中使用AsyncTask复制数据库。该应用程序有4个片段，任何片段显示数据库中的一个表（数据库有4个表）。但是当我运行应用程序时，请告诉我错误：
注意：我是业余爱好者。请指导我而不是给我负面的一点！
03-07 12:49:18.775 11190-11190/com.tellfa.dastanak E/AndroidRuntime: FATAL EXCEPTION: main
Process: com.tellfa.dastanak, PID: 11190
android.database.sqlite.SQLiteException: no such table: tbl_Book (code 1): , while compiling: SELECT * FROM tbl_Book WHERE Cat_ID = ?
at android.database.sqlite.SQLiteConnection.nativePrepareStatement(Native Method)
at android.database.sqlite.SQLiteConnection.acquirePreparedStatement(SQLiteConnection.java:897)
at android.database.sqlite.SQLiteConnection.prepare(SQLiteConnection.java:508)
at android.database.sqlite.SQLiteSession.prepare(SQLiteSession.java:726)
at android.database.sqlite.SQLiteProgram.<init>(SQLiteProgram.java:58)
at android.database.sqlite.SQLiteQuery.<init>(SQLiteQuery.java:37)
at android.database.sqlite.SQLiteDirectCursorDriver.query(SQLiteDirectCursorDriver.java:44)
at android.database.sqlite.SQLiteDatabase.rawQueryWithFactory(SQLiteDatabase.java:1426)
at android.database.sqlite.SQLiteDatabase.rawQuery(SQLiteDatabase.java:1365)
at com.tellfa.dastanak.Database.DataBase.getCat1_Datas(DataBase.java:157)
at com.tellfa.dastanak.Fragments.Home_Frag.onCreateView(Home_Frag.java:49)
at android.support.v4.app.Fragment.performCreateView(Fragment.java:1962)
at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:1067)
at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:1248)
at android.support.v4.app.BackStackRecord.run(BackStackRecord.java:738)
at android.support.v4.app.FragmentManagerImpl.execPendingActions(FragmentManager.java:1613)
at android.support.v4.app.FragmentManagerImpl.executePendingTransactions(FragmentManager.java:570)
at android.support.v4.app.FragmentPagerAdapter.finishUpdate(FragmentPagerAdapter.java:141)
at android.support.v4.view.ViewPager.populate(ViewPager.java:1106)
at android.support.v4.view.ViewPager.populate(ViewPager.java:952)
at android.support.v4.view.ViewPager.onMeasure(ViewPager.java:1474)
at android.view.View.measure(View.java:17496)
at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5466)
at android.support.design.widget.CoordinatorLayout.onMeasureChild(CoordinatorLayout.java:610)
at android.support.design.widget.CoordinatorLayout.onMeasure(CoordinatorLayout.java:677)
at android.view.View.measure(View.java:17496)
at android.support.v4.widget.DrawerLayout.onMeasure(DrawerLayout.java:940)
at android.view.View.measure(View.java:17496)
at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5466)
at android.widget.FrameLayout.onMeasure(FrameLayout.java:430)
at android.support.v7.widget.ContentFrameLayout.onMeasure(ContentFrameLayout.java:135)
at android.view.View.measure(View.java:17496)
at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5466)
at android.widget.LinearLayout.measureChildBeforeLayout(LinearLayout.java:1438)
at android.widget.LinearLayout.measureVertical(LinearLayout.java:724)
at android.widget.LinearLayout.onMeasure(LinearLayout.java:615)
at android.view.View.measure(View.java:17496)
at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5466)
at android.widget.FrameLayout.onMeasure(FrameLayout.java:430)
at android.view.View.measure(View.java:17496)
at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5466)
at android.widget.LinearLayout.measureChildBeforeLayout(LinearLayout.java:1438)
at android.widget.LinearLayout.measureVertical(LinearLayout.java:724)
at android.widget.LinearLayout.onMeasure(LinearLayout.java:615)
at android.view.View.measure(View.java:17496)
at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5466)
at android.widget.FrameLayout.onMeasure(FrameLayout.java:430)
at com.android.internal.policy.impl.PhoneWindow$DecorView.onMeasure(PhoneWindow.java:2636)
at android.view.View.measure(View.java:17496)
at android.view.ViewRootImpl.performMeasure(ViewRootImpl.java:2031)
at android.view.ViewRootImpl.measureHierarchy(ViewRootImpl.java:1193)
at android.view.ViewRootImpl.performTraversals(ViewRootImpl.java:1400)
at android.view.ViewRootImpl.doTraversal(ViewRootImpl.java:1078)
at android.view.Vi
AsyncTask代码：
public class LoadDB_AsyncTask extends AsyncTask<Void, Void, Boolean> {
Context mContext;
boolean loadedDB = false;
private DataBase dataBase;
private ProgressDialog progressDialog;
private static final String LOG_TAG = "log : ";
public LoadDB_AsyncTask(Context context) {
this.mContext = context;
}
@Override
protected void onPreExecute() {
super.onPreExecute();
Log.i(LOG_TAG, "onPreExecute in loadDB");
progressDialog = new ProgressDialog(mContext);
progressDialog.setMessage("Data loading ...");
progressDialog.setCancelable(false);
progressDialog.setProgressStyle(ProgressDialog.STYLE_SPINNER);
}
@Override
protected void onProgressUpdate(Void... values) {
super.onProgressUpdate(values);
Log.i(LOG_TAG, "onProgressUpdate in loadDB");
progressDialog.show();
}
@Override
protected Boolean doInBackground(Void... params) {
Log.i(LOG_TAG, "doInBackground in loadDB");
dataBase = new DataBase(mContext);
boolean dbExist = dataBase.checkDataBase();
if (dbExist) {
loadedDB = true;
} else {
publishProgress(null);
}
try {
dataBase.createDataBase();
} catch (IOException e) {
throw new Error("Error on create DataBase");
}
dataBase.close();
return null;
}
@Override
protected void onPostExecute(Boolean result) {
super.onPostExecute(result);
Log.i(LOG_TAG, "onPostExecute in loadDB");
if (!loadedDB) {
progressDialog.dismiss();
Log.i(LOG_TAG, "Loaded DataBase");
Toast.makeText(mContext, "Data Loaded", Toast.LENGTH_SHORT).show();
} else {
Log.i(LOG_TAG, "The database was already loaded");
}
try {
finalize();
} catch (Throwable throwable) {
throwable.printStackTrace();
}
}
}
数据库代码：
public class DataBase extends SQLiteOpenHelper {
private static String DB_PATH = "";
private static String DB_NAME = "Dastansara";
private static int DB_VERSION = 1;
private SQLiteDatabase sqLiteDatabase;
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 DataBase(Context context) {
super(context, DB_NAME, null, DB_VERSION);
if (android.os.Build.VERSION.SDK_INT >= 17) {
DB_PATH = context.getApplicationInfo().dataDir + "/databases/";
} else {
DB_PATH = "/data/data/" + context.getPackageName() + "/databases/";
}
this.myContext = context;
}
@Override
public void onCreate(SQLiteDatabase db) {
}
@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
}
/**
* 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 alerdy exist
} else {
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
*/
public 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;
}
/**
* Open DataBase
*
* @throws SQLException
*/
public void openDataBase() throws SQLException {
String myPATH = DB_PATH + DB_NAME;
sqLiteDatabase = SQLiteDatabase.openDatabase(myPATH, null, SQLiteDatabase.OPEN_READONLY);
}
/**
* Close DataBase
*/
public void closeDataBase() {
sqLiteDatabase.close();
}
/**
* 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.
*/
public 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 myPath = DB_PATH + DB_NAME;
//Open the empty db as the output stream
OutputStream myOutput = new FileOutputStream(myPath);
byte[] buffer = new byte[1024];
int length;
//transfer bytes from the inputfile to the outputfile
while ((length = myInput.read(buffer)) > 0) {
myOutput.write(buffer, 0, length);
}
//Close the streams
myOutput.flush();
myOutput.close();
myInput.close();
}
@Override
public synchronized void close() {
if (sqLiteDatabase != null) {
sqLiteDatabase.close();
}
super.close();
}
public Cursor getCat1_Datas(SQLiteDatabase sqLiteDatabase) {
try {
String query = "SELECT * FROM tbl_Book WHERE Cat_ID = ?";
Cursor cursor = sqLiteDatabase.rawQuery(query, new String[] {"1"});
if (cursor != null) {
cursor.moveToNext();
}
return cursor;
} catch (SQLException e) {
Log.e("Data Adapter", "getTestData >>" + e.toString());
throw e;
}
}
}
片段代码：
public class Home_Frag extends Fragment {
DataProvider dataProvider;
DataBase dataBase;
SQLiteDatabase sqLiteDatabase;
Cursor cursor;
ListView listView;
Cat1_frag_adapter cat1FragAdapter;
private LoadDB_AsyncTask task;
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View rootView = inflater.inflate(R.layout.frag_home,
container, false);
task = new LoadDB_AsyncTask(getContext());
task.execute();
dataBase = new DataBase(getActivity());
sqLiteDatabase = dataBase.getReadableDatabase();
cursor = dataBase.getCat1_Datas(sqLiteDatabase);
listView = (ListView) rootView.findViewById(R.id.list);
cat1FragAdapter = new Cat1_frag_adapter(getActivity(), R.layout.list_card_layout);
listView.setAdapter(cat1FragAdapter);
if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.LOLLIPOP) {
listView.setNestedScrollingEnabled(true);
}
if (cursor.moveToFirst()) {
do {
String id;
String title;
//id = cursor.getString(0);
title = cursor.getString(2);
dataProvider = new DataProvider(title);
cat1FragAdapter.add(dataProvider);
} while (cursor.moveToNext());
}
return rootView;
}
如何修复此错误并在我的应用程序中使用Asynctask？ tnx＆lt; 3
答案 0 :(得分：0)
task = new LoadDB_AsyncTask(getContext());
task.execute();
您将首先执行上述任务，完成上述任务后，您将执行以下任务。
@Override
protected void onPostExecute(Boolean result) {
super.onPostExecute(result);
Log.i(LOG_TAG, "onPostExecute in loadDB");
if (!loadedDB) {
progressDialog.dismiss();
Log.i(LOG_TAG, "Loaded DataBase");
Toast.makeText(mContext, "Data Loaded", Toast.LENGTH_SHORT).show();
} else {
Log.i(LOG_TAG, "The database was already loaded");
}
try {
finalize();
} catch (Throwable throwable) {
throwable.printStackTrace();
}
dataBase = new DataBase(getActivity());
sqLiteDatabase = dataBase.getReadableDatabase();
cursor = dataBase.getCat1_Datas(sqLiteDatabase);
listView = (ListView) rootView.findViewById(R.id.list);
cat1FragAdapter = new Cat1_frag_adapter(getActivity(), R.layout.list_card_layout);
listView.setAdapter(cat1FragAdapter);
if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.LOLLIPOP) {
listView.setNestedScrollingEnabled(true);
}
if (cursor.moveToFirst()) {
do {
String id;
String title;
//id = cursor.getString(0);
title = cursor.getString(2);
dataProvider = new DataProvider(title);
cat1FragAdapter.add(dataProvider);
} while (cursor.moveToNext());
}
}
希望这会对你有所帮助。