java - Sqlite 不会保存添加的数据

Question

我正在制作一个应用程序，它需要一个 sqlite 数据库。我可以添加数据并查看它，但在每次重新启动应用程序时，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 Activity ，在启动时添加 1 条记录只是为了在那里有一些东西。我的 Activity/fragment :

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被保存？我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!

Answer 1

这是因为您要从每个 openAndQueryDatabase() 中的表中删除所有记录

finally {
        if (newDB != null) 
            newDB.execSQL("DELETE FROM " + tableName);
            newDB.close();
    }