numberpicker没有响应

Question

我对Android非常陌生我快速接受它但速度不够快。我的应用程序上有数字选择器小部件。窗口小部件加载在页面上但有两个问题。第一个是在小部件框内，没有显示预期为0的位置。第二个问题是，如果按下+或 - 按钮，应用程序崩溃。我的设备是Android 2.3.4（HTC Wildfire），我正在使用eclipse。

这是我的java文件

    public class NumberPickerActivity extends Activity {
    private Button upButton;
    private Button downButton;
    private EditText editText;
    private int uprange = 20;
    private int downrange = 0;
    private int values = 0;

    public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.main);

    upButton = (Button) findViewById(R.id.upButton);
    downButton = (Button) findViewById(R.id.downButton);
    editText = (EditText) findViewById(R.id.numberEditText);

    upButton.setOnClickListener(new View.OnClickListener() {

    public void onClick(View v) {
    downButton.setBackgroundResource(R.drawable.timepicker_down_normal);
    upButton.setBackgroundResource(R.drawable.timepicker_up_pressed);
    if (values >= downrange && values <= uprange)
    values++;
    if (values > uprange)
    values = downrange;
    editText.setText("" + values);

    }
    });

    downButton.setOnClickListener(new View.OnClickListener() {

    public void onClick(View v) {
    downButton .setBackgroundResource(R.drawable.timepicker_down_pressed);
    upButton.setBackgroundResource(R.drawable.timepicker_up_normal);
    if (values >= downrange && values <= uprange)
    values--;

    if (values < downrange)
    values = uprange;

    editText.setText(values + "");
    }
    });
    }
    }

这是我的xml

    <RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
  android:layout_width="fill_parent"
android:layout_height="fill_parent"
android:background="@drawable/background"
android:orientation="horizontal" >


    <Button
android:id="@+id/upButton"
android:layout_width="50sp"
android:layout_height="50sp"
android:layout_toLeftOf="@+id/numberEditText"
android:background="@drawable/timepicker_up_normal" 
android:onClick="onupButtonPress"/>



    <TextView
android:id="@+id/textView1"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_above="@+id/textView2"
android:layout_alignLeft="@+id/textView2"
android:layout_alignRight="@+id/textView2"
android:layout_marginRight="43dp"
android:text="Welcome whatever your name is"
android:textSize="24sp" />

    <Button
android:id="@+id/downButton"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignBottom="@+id/numberEditText"
android:layout_alignLeft="@+id/upButton"
android:layout_alignRight="@+id/upButton"
android:layout_below="@+id/upButton"
android:background="@drawable/timepicker_down_normal" 
android:onClick="ondownButtonPress"/>

    <EditText
android:id="@+id/numberEditText"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignBottom="@+id/scanButton"
android:layout_alignParentRight="true"
android:layout_alignParentTop="true"
android:background="@drawable/timepicker_input_selected"
android:ems="10"
android:gravity="center"
android:inputType="number" />

    </RelativeLayout>