我正在制作一个需要 sqlite 数据库的应用程序。我可以添加数据并查看它，但每次重新启动应用程序、关闭、重新打开数据都会被删除。这是为什么？
数据库处理程序：
package com.spxc.wakeuptext.sql;
import java.util.ArrayList;
import java.util.List;
import android.content.ContentValues;
import android.content.Context;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteOpenHelper;
public class DatabaseHandler extends SQLiteOpenHelper {
// All Static variables
// Database Version
private static final int DATABASE_VERSION = 1;
// Database Name
private static final String DATABASE_NAME = "contactsManager";
// Contacts table name
public static final String TABLE_CONTACTS = "contacts";
// Contacts Table Columns names
private static final String KEY_ID = "id";
private static final String KEY_NAME = "name";
private static final String KEY_PH_NO = "phone_number";
public DatabaseHandler(Context context) {
super(context, DATABASE_NAME, null, DATABASE_VERSION);
}
// Creating Tables
@Override
public void onCreate(SQLiteDatabase db) {
String CREATE_CONTACTS_TABLE = "CREATE TABLE " + TABLE_CONTACTS + "("
+ KEY_ID + " INTEGER PRIMARY KEY," + KEY_NAME + " TEXT,"
+ KEY_PH_NO + " TEXT" + ")";
db.execSQL(CREATE_CONTACTS_TABLE);
}
// Upgrading database
@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
// Drop older table if existed
db.execSQL("DROP TABLE IF EXISTS " + TABLE_CONTACTS);
// Create tables again
onCreate(db);
}
/**
* All CRUD(Create, Read, Update, Delete) Operations
*/
public // Adding new contact
void addContact(WhiteList contact) {
SQLiteDatabase db = this.getWritableDatabase();
ContentValues values = new ContentValues();
values.put(KEY_NAME, contact.getName()); // Contact Name
values.put(KEY_PH_NO, contact.getPhoneNumber()); // Contact Phone
// Inserting Row
db.insert(TABLE_CONTACTS, null, values);
db.close(); // Closing database connection
}
// Getting single contact
WhiteList getContact(int id) {
SQLiteDatabase db = this.getReadableDatabase();
Cursor cursor = db.query(TABLE_CONTACTS, new String[] { KEY_ID,
KEY_NAME, KEY_PH_NO }, KEY_ID + "=?",
new String[] { String.valueOf(id) }, null, null, null, null);
if (cursor != null)
cursor.moveToFirst();
WhiteList contact = new WhiteList(Integer.parseInt(cursor.getString(0)),
cursor.getString(1), cursor.getString(2));
// return contact
return contact;
}
// Getting All Contacts
public List<WhiteList> getAllContacts() {
List<WhiteList> contactList = new ArrayList<WhiteList>();
// Select All Query
String selectQuery = "SELECT * FROM " + TABLE_CONTACTS;
SQLiteDatabase db = this.getWritableDatabase();
Cursor cursor = db.rawQuery(selectQuery, null);
// looping through all rows and adding to list
if (cursor.moveToFirst()) {
do {
WhiteList contact = new WhiteList();
contact.setID(Integer.parseInt(cursor.getString(0)));
contact.setName(cursor.getString(1));
contact.setPhoneNumber(cursor.getString(2));
// Adding contact to list
contactList.add(contact);
} while (cursor.moveToNext());
}
// return contact list
return contactList;
}
// Updating single contact
public int updateContact(WhiteList contact) {
SQLiteDatabase db = this.getWritableDatabase();
ContentValues values = new ContentValues();
values.put(KEY_NAME, contact.getName());
values.put(KEY_PH_NO, contact.getPhoneNumber());
// updating row
return db.update(TABLE_CONTACTS, values, KEY_ID + " = ?",
new String[] { String.valueOf(contact.getID()) });
}
// Deleting single contact
public void deleteContact(WhiteList contact) {
SQLiteDatabase db = this.getWritableDatabase();
db.delete(TABLE_CONTACTS, KEY_ID + " = ?",
new String[] { String.valueOf(contact.getID()) });
db.close();
}
// Getting contacts Count
public int getContactsCount() {
String countQuery = "SELECT * FROM " + TABLE_CONTACTS;
SQLiteDatabase db = this.getReadableDatabase();
Cursor cursor = db.rawQuery(countQuery, null);
cursor.close();
// return count
return cursor.getCount();
}
}
我有我的活动，即在启动时添加 1 条记录只是为了在那里有一些东西。我的活动/片段：
package com.spxc.wakeuptext.frag;
import java.util.ArrayList;
import java.util.List;
import android.app.AlertDialog;
import android.app.Dialog;
import android.app.AlertDialog.Builder;
import android.content.Context;
import android.content.DialogInterface;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteException;
import android.os.Bundle;
import android.util.Log;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.view.inputmethod.InputMethodManager;
import android.widget.ArrayAdapter;
import android.widget.EditText;
import android.widget.LinearLayout;
import android.widget.TextView;
import android.widget.Toast;
import com.actionbarsherlock.app.SherlockListFragment;
import com.actionbarsherlock.view.Menu;
import com.actionbarsherlock.view.MenuInflater;
import com.actionbarsherlock.view.MenuItem;
import com.spxc.wakeuptext.R;
import com.spxc.wakeuptext.sql.DatabaseHandler;
import com.spxc.wakeuptext.sql.WhiteList;
public class Fragment_2 extends SherlockListFragment{
private ArrayList<String> results = new ArrayList<String>();
private String tableName = DatabaseHandler.TABLE_CONTACTS;
private SQLiteDatabase newDB;
private static final int ADD = 1;
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
setHasOptionsMenu(true);
View v = inflater.inflate(R.layout.fragment_2, null);
return v;
}
public void onActivityCreated(Bundle savedInstanceState) {
super.onActivityCreated(savedInstanceState);
DatabaseHandler db = new DatabaseHandler(getActivity());
db.addContact(new WhiteList("Ravi", "9100000000"));
openAndQueryDatabase();
displayResultList();
}
private void openAndQueryDatabase() {
try {
DatabaseHandler dbHelper = new DatabaseHandler(getActivity().getApplicationContext());
newDB = dbHelper.getWritableDatabase();
Cursor c = newDB.rawQuery("SELECT name, phone_number FROM " +
tableName, null);
if (c != null ) {
if (c.moveToFirst()) {
do {
String firstName = c.getString(c.getColumnIndex("name"));
int age = c.getInt(c.getColumnIndex("phone_number"));
results.add("Name: " + firstName + ",Pne: " + age);
}while (c.moveToNext());
}
}
} catch (SQLiteException se ) {
Log.e(getClass().getSimpleName(), "Could not create or Open the database");
} finally {
if (newDB != null)
newDB.execSQL("DELETE FROM " + tableName);
newDB.close();
}
}
private void displayResultList() {
TextView tView = new TextView(getActivity());
tView.setText("This data is retrieved from the database and only 4 " +
"of the results are displayed");
getListView().addHeaderView(tView);
setListAdapter(new ArrayAdapter<String>(getActivity(),
android.R.layout.simple_list_item_1, results));
getListView().setTextFilterEnabled(true);
}
@Override
public void onCreateOptionsMenu(Menu menu, MenuInflater inflater) {
super.onCreateOptionsMenu(menu, inflater);
MenuItem search = menu.add(0, ADD, 0, "Refresh");
search.setIcon(android.R.drawable.ic_menu_add);
search.setShowAsAction(MenuItem.SHOW_AS_ACTION_IF_ROOM);
}
@Override
public boolean onOptionsItemSelected(MenuItem item) {
switch (item.getItemId()) {
case ADD:
addNumber();
return true;
default:
return super.onOptionsItemSelected(item);
}
}
public void addNumber(){
LayoutInflater factory = LayoutInflater.from(getActivity());
final View textEntryView = factory.inflate(R.layout.text_entry, null);
final EditText name = (EditText) textEntryView.findViewById(R.id.editText1);
final EditText phone = (EditText) textEntryView.findViewById(R.id.editText2);
name.setHint("Name");
phone.setHint("Phone Number");
final AlertDialog.Builder alert = new AlertDialog.Builder(getActivity());
alert.setTitle(
"Contact information").setView(
textEntryView).setPositiveButton("Save",
new DialogInterface.OnClickListener() {
public void onClick(DialogInterface dialog,
int whichButton) {
DatabaseHandler db = new DatabaseHandler(getActivity());
db.addContact(new WhiteList(name.getText().toString(), phone.getText().toString()));
openAndQueryDatabase();
displayResultList();
}
}).setNegativeButton("Cancel",
new DialogInterface.OnClickListener() {
public void onClick(DialogInterface dialog,
int whichButton) {
/*
* User clicked cancel so do some stuff
*/
}
});
alert.show();
}
}
为什么我的数据库数据没有保存？我正在真实设备上运行该应用程序。重新打开应用程序时，所有数据都会被删除。任何帮助深表感谢！