android - 微调器提示不显示

Question

我想使用像“选择城市”这样的微调提示。我确实在布局 android:prompt="@string/select_city" 的字符串布局中为 select_city 设置了一个值，但它没有用。还尝试使用 sp_city.setPrompt("Select City"); 也没有用。

我的问题是什么？如何修复它并设置提示？

布局:

<Spinner
    android:id="@+id/spinner_poi_city"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:background="@android:drawable/btn_dropdown"
    android:spinnerMode="dropdown"/>

类:

public class FirstPOIPreference extends DialogPreference {

    private Spinner sp_city;
    private ArrayAdapter<String> adapter;
    private POI poiDialog = new POI();

    public FirstPOIPreference(Context context, AttributeSet attrs) {
        super(context, attrs);
        init();
    }

    private void init() {
        setPersistent(false);
        setDialogLayoutResource(R.layout.pref_poi_dialog);
        setPositiveButtonText(android.R.string.ok);
        setNegativeButtonText(android.R.string.cancel);
    }

    @Override
    protected void onBindDialogView(View view) {
        super.onBindDialogView(view);
        initViews(view);
    }

    private void initViews(View view) {
        sp_city = (Spinner) view.findViewById(R.id.spinner_poi_city);
        sp_city.setPrompt("City");
        String[] arrayCity = new String[]{"Erie", "Pittsburgh", "Cleveland", "Buffalo", "Niagara Falls", "Jamestown"};
        adapter = new ArrayAdapter <> (this.getContext(), android.R.layout.simple_spinner_dropdown_item, arrayCity);
        sp_city.setAdapter(adapter);

        sp_city.setOnItemSelectedListener(new AdapterView.OnItemSelectedListener() {
            @Override
            public void onItemSelected(AdapterView <?> parentView, View selectedItemView, int position, long id) {
                poiDialog.setCity(sp_city.getSelectedItem().toString());
            }

            @Override
            public void onNothingSelected(AdapterView <?> parentView) {
            }
        });
    }

}

Answer 1

你可以这样做，我已经做到了一些棘手的方式。它可以帮助你

private void initViews(View view) {

sp_city = (Spinner) view.findViewById(R.id.spinner_poi_city);

ArrayAdapter<String> adapter = new ArrayAdapter<String>(this, android.R.layout.simple_spinner_dropdown_item) {

                @Override
                public View getView(int position, View convertView, ViewGroup parent) {

                    View v = super.getView(position, convertView, parent);
                    if (position == getCount()) {
                        ((TextView) v.findViewById(android.R.id.text1)).setText("");
                        ((TextView) v.findViewById(android.R.id.text1)).setHint(getItem(getCount())); //"Hint to be displayed"
                    }
                    return v;
                }

                @Override
                public int getCount() {
                    return super.getCount() - 1; // you dont display last item. It is used as hint.
                }
            };
            adapter.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item);
            adapter.add("Erie");
            adapter.add("Pittsburgh");
            adapter.add("Cleveland");
            adapter.add("Buffalo");
            adapter.add("Niagara Falls");
            adapter.add("Jamestown");
            adapter.add("Select City"); //This is the text that will be displayed as hint.

            sp_city.setOnItemSelectedListener(new AdapterView.OnItemSelectedListener() {
                @Override
                public void onItemSelected(AdapterView<?> parentView, View selectedItemView, int position, long id) {
                    String spinnerValue = String.valueOf(sp_city.getSelectedItem().toString());
                    if (!spinnerValue.equalsIgnoreCase("Select City")) {
                        //do your code
                        Toast.makeText(this, sp_city.getSelectedItem().toString(), Toast.LENGTH_LONG).show();
                    }
                }
                @Override
                public void onNothingSelected(AdapterView<?> parentView) {
                }
            });

            sp_city.setAdapter(adapter);
            sp_city.setSelection(adapter.getCount()); //set the hint the default selection so it appears on launch.
        }