Android 更改数字选择器样式

我想更改数字选择器的样式。 这是我的号码选择器

我想从上面和下面的数字选择器中删除+和-符号。可能吗？我该怎么做

这是我使用的代码：

public class MainActivity extends Activity implements OnClickListener {

EditText etSearch;
int mStackLevel = 1;
Button btn, btnSearch, btnCancel;
Dialog dialog;
NumberPicker np;
final String[] values_data = {"Belgium", "France", "United Kingdom"};

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    FrameLayout f = (FrameLayout)findViewById(R.id.simple_fragment);

    btn = (Button) findViewById(R.id.btn);
    btn.setOnClickListener((OnClickListener) this);
}

protected void showCustomDialog() {
    btn.setEnabled(false);

    dialog = new Dialog(MainActivity.this,
            android.R.style.Theme_Translucent);
    dialog.requestWindowFeature(Window.FEATURE_NO_TITLE);

    dialog.setCancelable(true);
    dialog.setContentView(R.layout.dialog);

    np = (NumberPicker) dialog.findViewById(R.id.numberPicker1);

    np.setMaxValue(2);
    np.setMinValue(0);
    Log.i(null, "State three");
    np.setDisplayedValues(values_data);
    Log.i(null, "State four");
    np.setWrapSelectorWheel(false);


    btnSearch = (Button) dialog.findViewById(R.id.btnsearch);
    btnCancel = (Button) dialog.findViewById(R.id.btncancel);

    btnSearch.setOnClickListener(this);
    btnCancel.setOnClickListener(this);

    dialog.show();
}

@Override
public void onClick(View v) {
    switch (v.getId()) {
    case R.id.btn:
        btn.setEnabled(true);
        showCustomDialog();
        break;
    case R.id.btnsearch:
        //btn.setVisibility(View.VISIBLE);
        Log.i(String.valueOf(np.getValue()), "HHHHHHH");
        int value = (np.getValue());
          Log.i(String.valueOf(value), "MSGGGGGGGGGG");

          btn.setText(String.valueOf(values_data[value]));

          dialog.dismiss();
          break;
    case R.id.btncancel:
        dialog.dismiss();
        break;
    default:
        break;
    }
}

public static class CountingFragment extends Fragment {
    int mNum;

    static CountingFragment newInstance(int num) {
        CountingFragment f = new CountingFragment();

        // Supply num input as an argument.
        Bundle args = new Bundle();
        args.putInt("num", num);
        f.setArguments(args);

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

---

}

有两种类型的数字选择器小部件可用，具体取决于应用程序主题。

---

要获得不带+和-按钮的数字选择器，请使用从theme_Holo或theme_Holo_Light派生的主题。

我应该在哪里更改主题？？