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这是我的主要课程

public class HomeScreenActivity extends Activity {

    private Button contactButton;
    private Button groupContactButton;
    private Button historyButton;
    private Button optionsButton;
    private ListView contactsView;

    public static int selectedContactIndex = -1;

    DatabaseHandler db;
    List<Contact> contactList;
    ArrayAdapter<Contact> adapter;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_home_screen);

        contactButton = (Button) findViewById(R.id.contactButton);
        contactButton.setSelected(true);
        groupContactButton = (Button) findViewById(R.id.groupContactButton);
        historyButton = (Button) findViewById(R.id.historyButton);
        optionsButton = (Button) findViewById(R.id.optionsButton);
        contactsView = (ListView) findViewById(R.id.contactsView);

        // Set up contact adaptor so the contact list can be viewed in the
        // homescreen   
        db = new DatabaseHandler(this);
        contactList = db.getAllContacts();
        adapter = new ArrayAdapter<Contact>(this,
                R.layout.home_screen_contacts_view, contactList);
        contactsView.setAdapter(adapter);
        adapter.setNotifyOnChange(true);

        // Set Listeners
        contactButton.setOnClickListener(new OnClickListener() {

            public void onClick(View v) {
                v.setSelected(true);
                groupContactButton.setSelected(false);
                historyButton.setSelected(false);
            }
        });

        groupContactButton.setOnClickListener(new OnClickListener() {

            public void onClick(View v) {
                v.setSelected(true);
                historyButton.setSelected(false);
                contactButton.setSelected(false);
            }
        });

        historyButton.setOnClickListener(new OnClickListener() {

            public void onClick(View v) {
                v.setSelected(true);
                groupContactButton.setSelected(false);
                contactButton.setSelected(false);
            }
        });

        optionsButton.setOnClickListener(new OnClickListener() {

            public void onClick(View v) {
                openOptionsMenu();
            }
        });

        contactsView.setOnItemClickListener(new OnItemClickListener() {

            @Override
            public void onItemClick(AdapterView<?> arg0, View arg1, int arg2,
                    long arg3) {
                selectedContactIndex = (int) arg3;
            }
        });

    }

    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        getMenuInflater().inflate(R.menu.options_menu, menu);
        return true;
    }

    public boolean onOptionsItemSelected(MenuItem item) {
        switch (item.getItemId()) {
        case R.id.viewContactDetails:
            return true;

        case R.id.editContactDetails:
            if (selectedContactIndex == -1) {// When no contact is selected,
                                                // inform user.
                makeAToast("Please select a contact to edit!");
                return true;
            }
            startActivity(new Intent(this, EditContactActivity.class));
            return true;

        case R.id.newContact:
            startActivity(new Intent(this, NewContactActivity.class));
            return true;

        case R.id.deleteContact:
            if (selectedContactIndex == -1) {// When no contact is selected,
                                                // inform user.
                makeAToast("Please select a contact to delete!");
                return true;
            }
            // Create an alert asking for contact deletion confirmation.
            AlertDialog.Builder myAlertDialog = new AlertDialog.Builder(this,
                    AlertDialog.THEME_DEVICE_DEFAULT_DARK);
            myAlertDialog.setTitle("Confirm Contact Deletion");
            myAlertDialog.setMessage("Are you sure you want to delete "
                    + db.getContact(selectedContactIndex).getFullName() +"?"); //ADD THE CONTACT NAME

            // Set listener for when they press yes, delete contact and inform
            // user.
            myAlertDialog.setPositiveButton("Yes",
                    new DialogInterface.OnClickListener() {
                        public void onClick(DialogInterface arg0, int arg1) {
                            db.deleteContact(db.getContact(selectedContactIndex + 1));
                            makeAToast("Contact successfully deleted.");
                            Log.d("Reading: ", "Reading all contacts.."); 
                            List<Contact> contacts = db.getAllContacts(); 
                            for (Contact cn : contacts) {
                                String log = "Id: "+cn.getID()+" ,First Name: " + cn.getFirstName()
                                        +" ,Last Name: " + cn.getLastName()
                                        +" ,Mobile Number: " + cn.getMobileNumber()
                                        +" ,Home Number: " + cn.getHomeNumber()
                                        +" ,Work Number: " + cn.getWorkNumber()
                                        +" ,Home Address: " + cn.getHomeAddress()
                                        +" ,Email Address: " + cn.getEmailAddress()
                                        +" ,Work Address: " + cn.getWorkAddress()
                                        +" ,Contact Notes: " + cn.getContactNotes();
                                    // Writing Contacts to log
                                Log.d("Name: ", log);
                            }
                        }
                    });

这是我的数据库处理程序类:

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
    private static final String TABLE_CONTACTS = "contacts";

    // Contacts Table Columns names
    private static final String KEY_ID = "id";
    private static final String KEY_FIRST_NAME = "first_name";
    private static final String KEY_LAST_NAME = "last_name";
    private static final String KEY_MOB_NO = "mobile_number";
    private static final String KEY_HOME_NO = "home_number";
    private static final String KEY_WORK_NO = "work_number";
    private static final String KEY_HOME_ADDR = "home_address";
    private static final String KEY_EMAIL_ADDR = "email_address";
    private static final String KEY_WORK_ADDR = "work_address";
    private static final String KEY_NOTES = "notes";

    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 AUTOINCREMENT,"
                + KEY_FIRST_NAME + " TEXT," + KEY_LAST_NAME + " TEXT,"
                + KEY_MOB_NO + " TEXT," + KEY_HOME_NO + " TEXT," + KEY_WORK_NO
                + " TEXT," + KEY_HOME_ADDR + " TEXT," + KEY_EMAIL_ADDR
                + " TEXT," + KEY_WORK_ADDR + " TEXT," + KEY_NOTES + " 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
     */

    // Adding new contact
    void addContact(Contact contact) {
        SQLiteDatabase db = this.getWritableDatabase();

        ContentValues values = new ContentValues();
        values.put(KEY_ID, Contact.totalContacts);
        values.put(KEY_FIRST_NAME, contact.getFirstName());
        values.put(KEY_LAST_NAME, contact.getLastName());
        values.put(KEY_MOB_NO, contact.getMobileNumber());
        values.put(KEY_HOME_NO, contact.getHomeNumber());
        values.put(KEY_WORK_NO, contact.getWorkNumber());
        values.put(KEY_HOME_ADDR, contact.getHomeAddress());
        values.put(KEY_EMAIL_ADDR, contact.getEmailAddress());
        values.put(KEY_WORK_ADDR, contact.getWorkAddress());
        values.put(KEY_NOTES, contact.getContactNotes());

        // Inserting Row
        db.insert(TABLE_CONTACTS, null, values);
        db.close(); // Closing database connection
    }

    // Getting single contact
    Contact getContact(int id) {
        SQLiteDatabase db = this.getReadableDatabase();

        Cursor cursor = db.query(TABLE_CONTACTS, new String[] { KEY_ID,
                KEY_FIRST_NAME, KEY_LAST_NAME, KEY_MOB_NO, KEY_HOME_NO,
                KEY_WORK_NO, KEY_HOME_ADDR, KEY_EMAIL_ADDR, KEY_WORK_ADDR,
                KEY_NOTES }, KEY_ID + "=?",
                new String[] { String.valueOf(id) }, null, null, null, null);
        if (cursor != null)
            cursor.moveToFirst();

        Contact contact = new Contact(Integer.parseInt(cursor.getString(0)),
                cursor.getString(1), cursor.getString(2), cursor.getString(3),
                cursor.getString(4), cursor.getString(5), cursor.getString(6),
                cursor.getString(7), cursor.getString(8), cursor.getString(9));
        return contact;
    }

    // Getting All Contacts
    public List<Contact> getAllContacts() {
        List<Contact> contactList = new ArrayList<Contact>();
        // 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 {
                Contact contact = new Contact();
                contact.setID(Integer.parseInt(cursor.getString(0)));
                contact.setFirstName(cursor.getString(1));
                contact.setLastName(cursor.getString(2));
                contact.setMobileNumber(cursor.getString(3));
                contact.setHomeNumber(cursor.getString(4));
                contact.setWorkNumber(cursor.getString(5));
                contact.setHomeAddress(cursor.getString(6));
                contact.setEmailAddress(cursor.getString(7));
                contact.setWorkAddress(cursor.getString(8));
                contact.setContactNotes(cursor.getString(9));
                // Adding contact to list
                contactList.add(contact);
            } while (cursor.moveToNext());
        }

        // return contact list
        return contactList;
    }

    // Updating single contact
    public int updateContact(Contact contact) {
        SQLiteDatabase db = this.getWritableDatabase();

        ContentValues values = new ContentValues();
        values.put(KEY_FIRST_NAME, contact.getFirstName());
        values.put(KEY_LAST_NAME, contact.getLastName());
        values.put(KEY_MOB_NO, contact.getMobileNumber());
        values.put(KEY_HOME_NO, contact.getHomeNumber());
        values.put(KEY_WORK_NO, contact.getWorkNumber());
        values.put(KEY_HOME_ADDR, contact.getHomeAddress());
        values.put(KEY_EMAIL_ADDR, contact.getEmailAddress());
        values.put(KEY_WORK_ADDR, contact.getWorkAddress());
        values.put(KEY_NOTES, contact.getContactNotes());

        // updating row
        return db.update(TABLE_CONTACTS, values, KEY_ID + " = ?",
                new String[] { String.valueOf(contact.getID()) });
    }

    // Deleting single contact
    public void deleteContact(Contact 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();
    }
}

现在,当我删除一个联系人时,它不仅不会更新我的主联系人屏幕中的列表视图,而且当我将所有联系人写入日志 cat 时,该联系人甚至从未从数据库中删除。关于为什么会这样的任何想法?

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