title: android: number picker can't scroll
body: <p>I want to implement a number picker:<br>
  My xml file:</p>
  
  <pre><code> &lt;NumberPicker
          android:id="@+id/np"
          android:layout_width="match_parent"
          android:layout_height="wrap_content"/&gt;
  </code></pre>
  
  <p>And in activity:</p>
  
  <pre><code>private NumberPicker mNumberpicker;
  private String[] nums;
  ...
  mNumberpicker = (NumberPicker) findViewById(R.id.np);
  nums = new String[21];
      for (int i = 0; i &lt; nums.length; i++) {
          nums[i] = Integer.toString(i * 5);
      }
  
      // Set the max and min values of the numberpicker, and give it the
      // array of numbers created above to be the displayed numbers
      mNumberpicker.setMaxValue(20);
      mNumberpicker.setMinValue(0);
      mNumberpicker.setWrapSelectorWheel(false);
      mNumberpicker.setDisplayedValues(nums);
  </code></pre>
  
  <p>But, the number picker have (+) button and (-) button. What I want is the number picker that cant scroll. Not the two button (+) and (-).<br>
  What's my wrong here?</p>