如何给微调器的零位提示值? [英] How to give position zero of spinner a prompt value?

问题描述

然后数据库将数据传输到微调器，我想将位置0留空，这样我就可以向微调器添加一个没有任何值的项目，使其看起来像是提示.我整天都在努力.失败后失败

The database is then transferring the data to a spinner which I want to leave position 0 blank so I can add a item to the spinner with no value making it look like a prompt. I have been going at it all day. FAil after Fail

MainActivity

public class MainActivity extends Activity {

Button AddBtn;
EditText et;
EditText cal;
Spinner spn;
SQLController SQLcon;
ProgressDialog PD;

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

    AddBtn = (Button) findViewById(R.id.addbtn_id);
    et = (EditText) findViewById(R.id.et_id);
    cal = (EditText) findViewById(R.id.et_cal);
    spn = (Spinner) findViewById(R.id.spinner_id);

    spn.setOnItemSelectedListener(new OnItemSelectedListenerWrapper(
            new OnItemSelectedListener() {

                @Override
                public void onItemSelected(AdapterView<?> parent,
                        View view, int pos, long id) {

                    SQLcon.open();

                    Cursor c = SQLcon.readData();
                    if (c.moveToPosition(pos)) {

                        String name = c.getString(c
                                .getColumnIndex(DBhelper.MEMBER_NAME));
                        String calories = c.getString(c
                                .getColumnIndex(DBhelper.KEY_CALORIES));
                        et.setText(name);
                        cal.setText(calories);

                    }

                    SQLcon.close();
                    // closing database

                }

                @Override
                public void onNothingSelected(AdapterView<?> parent) {
                    // TODO Auto-generated method stub

                }

            }));
    SQLcon = new SQLController(this);
    // opening database

    SQLcon.open();

    loadtospinner();

    AddBtn.setOnClickListener(new OnClickListener() {

        @Override
        public void onClick(View v) {

            new MyAsync().execute();

        }
    });
}

public void loadtospinner() {

    ArrayList<String> al = new ArrayList<String>();

    Cursor c = SQLcon.readData();
    c.moveToFirst();
    while (!c.isAfterLast()) {

        String name = c.getString(c.getColumnIndex(DBhelper.MEMBER_NAME));
        String calories = c.getString(c
                .getColumnIndex(DBhelper.KEY_CALORIES));

        al.add(name + ", Calories: " + calories);

        c.moveToNext();
    }

    ArrayAdapter<String> aa1 = new ArrayAdapter<String>(
            getApplicationContext(), android.R.layout.simple_spinner_item,
            al);

    spn.setAdapter(aa1);

    // closing database
    SQLcon.close();

}

private class MyAsync extends AsyncTask<Void, Void, Void> {

    @Override
    protected void onPreExecute() {

        super.onPreExecute();
        PD = new ProgressDialog(MainActivity.this);
        PD.setTitle("Please Wait..");
        PD.setMessage("Loading...");
        PD.setCancelable(false);
        PD.show();

    }

    @Override
    protected Void doInBackground(Void... params) {
        String name = et.getText().toString();
        String calories = cal.getText().toString();
        // opening database
        SQLcon.open();
        // insert data into table

        SQLcon.insertData(name, calories);

        return null;
    }

    @Override
    protected void onPostExecute(Void result) {
        super.onPostExecute(result);
        loadtospinner();
        PD.dismiss();

    }
}
}

数据库

public class SQLController {
private DBhelper dbhelper;
private Context ourcontext;
private SQLiteDatabase database;

public SQLController(Context c) {
    ourcontext = c;
}

public SQLController open() throws SQLException {
    dbhelper = new DBhelper(ourcontext);
    database = dbhelper.getWritableDatabase();
    return this;

}

public void close() {
    dbhelper.close();
}

public void insertData(String name, String calories) {
    ContentValues cv = new ContentValues();
    cv.put(DBhelper.MEMBER_NAME, name);

    cv.put(DBhelper.KEY_CALORIES, calories);
    database.insert(DBhelper.TABLE_MEMBER, null, cv);
}

public Cursor readData() {
    String[] allColumns = new String[] { DBhelper.MEMBER_ID,
            DBhelper.MEMBER_NAME, DBhelper.KEY_CALORIES };
    Cursor c = database.query(DBhelper.TABLE_MEMBER, allColumns, null,
            null, null, null, null);
    if (c != null) {
        c.moveToFirst();
    }
    return c;
}
}

助手

public class DBhelper extends SQLiteOpenHelper {

// TABLE INFORMATTION
public static final String TABLE_MEMBER = "member";
public static final String MEMBER_ID = "_id";
public static final String MEMBER_NAME = "name";
public static final String KEY_CALORIES = "calories";

// DATABASE INFORMATION
static final String DB_NAME = "MEMBER.DB";
static final int DB_VERSION = 2;

// TABLE CREATION STATEMENT
private static final String CREATE_TABLE = "create table " + TABLE_MEMBER
        + "(" + MEMBER_ID + " INTEGER PRIMARY KEY AUTOINCREMENT, "
        + MEMBER_NAME + " TEXT NOT NULL," + KEY_CALORIES
        + " INT NOT NULL);";

public DBhelper(Context context) {
    super(context, DB_NAME, null, DB_VERSION);
}

@Override
public void onCreate(SQLiteDatabase db) {
    db.execSQL(CREATE_TABLE);
}

@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
    // TODO Auto-generated method stub

    db.execSQL("DROP TABLE IF EXISTS " + TABLE_MEMBER);
    onCreate(db);
}
}

推荐答案

使用以下内容:

Spinner spinner = (Spinner) findViewById(R.id.yourSpinner);
ArrayAdapter<String> spinnerArrayAdapter = new ArrayAdapter<String>(this, android.R.layout.simple_spinner_item, spinnerArray); 
spinnerArrayAdapter.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item);
spinner.setAdapter(spinnerArrayAdapter);

更新:

您的 spinnerArray 应该具有来自数据库的值，并以第一个值作为提示

Your spinnerArray should have values from database with first value as prompt

例如:

List<String> spinnerArray = new ArrayList<String>();
spinnerArray.add("YOU MESSAGE");

然后您可以使用 for循环将值添加到 spinnerArray ，如下所示:

And then you can use for loop to add values to spinnerArray as follow:

for(//loop until you need values to be added)

将值添加到spinnerArray中:

Add values to spinnerArray as:

spinnerArray.add(value1);
spinnerArray.add(value1);
spinnerArray.add(value1);
//so on.

最后将其作为最后一个参数传递，同时如上所述创建 spinnerArrayAdapter .这应该可以解决您的问题.

and finally pass it as last argument while creating spinnerArrayAdapter as above. And this should solve your problem.

更新1:

如果您不想在第0位获得商品，可以执行以下操作:

If you don't want to get item at position 0 you can do the following:

if(spinner.getSelectedItem().equals("YOUR MESSAGE"){//may be you want to ignorecase using equalsIgnoreCase() method
//display message that you haven't selected anything
}else{
//do anything you want
}

填充伪数据:

将DBhelper类中的 onCreate()更改为:

Change your onCreate() in DBhelper class to:

@Override
public void onCreate(SQLiteDatabase db) {
    db.execSQL(CREATE_TABLE);

    ContentValues cv = new ContentValues();
        cv.put(DBhelper.MEMBER_NAME, "DUMMY NAME");

        cv.put(DBhelper.KEY_CALORIES, "DUMMY CALORIES");
        database.insert(DBhelper.TABLE_MEMBER, null, cv);
}

这篇关于如何给微调器的零位提示值?的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！