在 Android 中以编程方式创建微调器

Question

I want to create a spinner without using XML. I am new in android and my knowledge is limited. By now I have this code (see above) and I want my spinner in one of the tabs of my TabActivity . There is no obvious error but when I open my activity the tab is empty. I would appreciate some help.

public void onCreate(Bundle savedInstanceState) {

    super.onCreate(savedInstanceState);

    ArrayList<String> spinnerArray = new ArrayList<String>();
    spinnerArray.add("one");
    spinnerArray.add("two");
    spinnerArray.add("three");
    spinnerArray.add("four");
    spinnerArray.add("five");

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

}

Answer 1

You need to add the Spinner to a layout.

First create a container for the Spinner and then create the Spinner and add it to your container . Next set content of you Activity to your container .

This could be done like this, in your onCreate method:

@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_my);

    LinearLayout layout = new LinearLayout(this);

    ArrayList<String> spinnerArray = new ArrayList<String>();
    spinnerArray.add("one");
    spinnerArray.add("two");
    spinnerArray.add("three");
    spinnerArray.add("four");
    spinnerArray.add("five");

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

    layout.addView(spinner);

    setContentView(layout);
}

EDIT:

Just to clarify: if the Spinner isn't added to the content of the Activity inside a layout, it isn't visible, so that's why you don't get any errors or anything, because there isn't any errors in your code, per se ;-)

Answer 2

public class MainActivity extends AppCompatActivity {

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

        // The following can also be done using a loop
        ArrayList<String> spinnerArray = new ArrayList<String>();
        spinnerArray.add("one");
        spinnerArray.add("two");
        spinnerArray.add("three");
        spinnerArray.add("four");
        spinnerArray.add("five");


        Spinner spinner = new Spinner(MainActivity.this);
        ArrayAdapter<String> spinnerArrayAdapter = new ArrayAdapter<String>(MainActivity.this, android.R.layout.simple_spinner_dropdown_item, spinnerArray);
        spinner.setAdapter(spinnerArrayAdapter);
        layout.addView(spinner);
        setContentView(layout);
    }
    }