从数据库

Question

我是Android新手，我从列表视图中删除项目后刷新了我的列表视图。我已经尝试了所有的东西而且无法让它工作，所以我正在寻求帮助。我知道我必须在我的适配器上使用notifyDataSetChanged，但我不知道在哪里放它。先谢谢你们。 整个项目上传到zippyshare：http://www6.zippyshare.com/v/TZVGTFJp/file.html

public class MainActivity extends AppCompatActivity {


DBHandler handler;
Context context = this;
ListView listView;
ArrayAdapter arrayAdapter;


@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
    setSupportActionBar(toolbar);

    EditText etName = (EditText) findViewById(R.id.etNameID);
    EditText etPhone = (EditText) findViewById(R.id.etPhoneID);


    handler = new DBHandler(this);

    printDatabase();


    if (listView != null) {
        listView.setOnItemLongClickListener(new AdapterView.OnItemLongClickListener() {
            @Override
            public boolean onItemLongClick(AdapterView<?> parent, View view, final int position, final long id) {

                PopupMenu popup = new PopupMenu(context, view);
                popup.getMenuInflater().inflate(R.menu.menu_delete_popup, popup.getMenu());
                popup.show();

                popup.setOnMenuItemClickListener(new PopupMenu.OnMenuItemClickListener() {
                    @Override
                    public boolean onMenuItemClick(MenuItem item) {

                        switch (item.getItemId()) {

                            case R.id.deleteItemID:

                                handler.deleteContact(id);

                                printDatabase();


                                break;


                        }


                        return true;
                    }
                });


                return true;
            }
        });
    }


}

@Override
public boolean onCreateOptionsMenu(Menu menu) {
    // Inflate the menu; this adds items to the action bar if it is present.
    getMenuInflater().inflate(R.menu.menu_main, menu);
    return true;
}

@Override
public boolean onOptionsItemSelected(MenuItem item) {
    // Handle action bar item clicks here. The action bar will
    // automatically handle clicks on the Home/Up button, so long
    // as you specify a parent activity in AndroidManifest.xml.
    int id = item.getItemId();

    //noinspection SimplifiableIfStatement
    if (id == R.id.action_settings) {
        return true;
    }

    if (id == R.id.addContactID) {

        openAddDialog();


    }

    return super.onOptionsItemSelected(item);
}

public void printDatabase() {


    ArrayList array_list = handler.getAllCotacts();
    arrayAdapter = new ArrayAdapter(this, android.R.layout.simple_list_item_1, array_list);
    listView = (ListView) findViewById(R.id.listView);
    listView.setAdapter(arrayAdapter);


}

public void openAddDialog() {

    android.app.AlertDialog.Builder makeDialog = new android.app.AlertDialog.Builder(this);
    LayoutInflater li = getLayoutInflater();
    View v = li.inflate(R.layout.contacts_add_dialog, null);
    makeDialog.setView(v);

    //tu idu varijable

    final EditText etName = (EditText) v.findViewById(R.id.etNameID);
    final EditText etPhone = (EditText) v.findViewById(R.id.etPhoneID);

    makeDialog.setPositiveButton("Save", new DialogInterface.OnClickListener() {
        @Override
        public void onClick(DialogInterface dialog, int which) {

            String textFromEtName = etName.getText().toString();
            String textFromEtPhone = etPhone.getText().toString();

            handler.insertContact(textFromEtName, textFromEtPhone);

            printDatabase();


        }
    });

    makeDialog.setNegativeButton("Cancel", new DialogInterface.OnClickListener() {
        @Override
        public void onClick(DialogInterface dialog, int which) {
            dialog.cancel();
        }
    });

    android.app.AlertDialog ad = makeDialog.create();
    ad.show();


}

}

这是DBHandler代码：

public class DBHandler extends SQLiteOpenHelper {

public static final String DATABASE_NAME = "MyDBName.db";
public static final String CONTACTS_TABLE_NAME = "contacts";
public static final String CONTACTS_COLUMN_ID = "id";
public static final String CONTACTS_COLUMN_NAME = "name";
public static final String CONTACTS_COLUMN_PHONE = "phone";


public DBHandler(Context context)
{
    super(context, DATABASE_NAME , null, 1);
}

@Override
public void onCreate(SQLiteDatabase db) {
    // TODO Auto-generated method stub
    db.execSQL(
            "CREATE TABLE contacts " +
                    "(id INTEGER PRIMARY KEY, name TEXT,phone TEXT,email TEXT, street TEXT,place TEXT)"
    );
}

@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
    // TODO Auto-generated method stub
    db.execSQL("DROP TABLE IF EXISTS contacts");
    onCreate(db);
}

public boolean insertContact  (String name, String phone)
{
    SQLiteDatabase db = this.getWritableDatabase();
    ContentValues contentValues = new ContentValues();
    contentValues.put("name", name);
    contentValues.put("phone", phone);
    db.insert("contacts", null, contentValues);
    return true;
}

public Cursor getData(int id){
    SQLiteDatabase db = this.getReadableDatabase();
    Cursor res =  db.rawQuery( "select * from contacts where id="+id+"", null );
    return res;
}

public int numberOfRows(){
    SQLiteDatabase db = this.getReadableDatabase();
    int numRows = (int) DatabaseUtils.queryNumEntries(db, CONTACTS_TABLE_NAME);
    return numRows;
}

public boolean updateContact (Integer id, String name, String phone)
{
    SQLiteDatabase db = this.getWritableDatabase();
    ContentValues contentValues = new ContentValues();
    contentValues.put("name", name);
    contentValues.put("phone", phone);
    db.update("contacts", contentValues, "id = ? ", new String[] { Integer.toString(id) } );
    return true;
}


public void deleteContact(long id) {
    SQLiteDatabase db = this.getWritableDatabase();
    db.delete(CONTACTS_TABLE_NAME, CONTACTS_COLUMN_ID + " = ?",
            new String[] { String.valueOf(id) });
    db.close();
}
public ArrayList<String> getAllCotacts()
{
    ArrayList<String> array_list = new ArrayList<String>();

    //hp = new HashMap();
    SQLiteDatabase db = this.getReadableDatabase();
    Cursor res =  db.rawQuery( "select * from contacts", null );
    res.moveToFirst();

    while(res.isAfterLast() == false){
        array_list.add(res.getString(res.getColumnIndex(CONTACTS_COLUMN_NAME)));
        res.moveToNext();
    }
    return array_list;
}

}

Answer 1

更新您的 printDatabase 功能，如下所示：

BEGIN

Answer 2

删除一个元素后，从函数中调用另一个元素，从数据库中检索结果

Answer 3

您在此处使用索引编号行

添加项目

array_list.add（res.getString（res.getColumnIndex（CONTACTS_COLUMN_NAME）））;

在这里，您尝试使用列表视图

中视图对象的索引编号删除行

handler.deleteContact（ID）;

因此，您必须使用 CONTACTS_COLUMN_ID

而不是使用CONTACTS_COLUMN_NAME。

array_list.add（res.getString（res.getColumnIndex（CONTACTS_COLUMN_ID）））;

即使您这样做也可能无效，因为您无法保证Listview中的视图编号与表中的id匹配。 id号可能是99，视图号始终以0开头。

这是一个原始的解决方案 第1步

proc/self/maps

第2步 让它全球化

HashMap array_list

第3步

handler.deleteContact（array_list.get（ID）获得（＆＃34;指数＆＃34））;

最重要的是，这是一个原始的解决方案，我认为编写自己的适配器是最好的解决方案。