android DatePicker年月日重新排序，物理按键控制NumberPicker滚动

项目中需要用到时间设置，想到了系统自带的datepicker控件，因为项目没有触屏需要用物理按键控制datepicker的滚动，并且年月日的顺序需要重排，折腾了好一会功夫，做个记录。

1.datepicker初始化

 datePicker = findViewById(R.id.datepicker);
 datePicker.setCalendarViewShown(false); 
 timePicker = findViewById(R.id.timepicker);
 timePicker.setIs24HourView(true);
 
 xml文件中设置Theme
 android:theme="@android:style/Theme.Holo.Light.NoActionBar.Fullscreen"  // 不设置就是显示日历

效果图如下：

2.修改年月日的顺序

我们知道，系统中文时datePicker是年月日(yymmdd)的顺序，系统英文时是月日年(mmddyy)上图，所以源码中datePicker会根据语言不同来进行重排序。

• 源码路径：frameworks/base/core/java/android/widget/DatePicker.java

  int layoutResourceId = attributesArray.getResourceId(
                    R.styleable.DatePicker_legacyLayout, R.layout.date_picker_legacy);
  attributesArray.recycle();
  
  LayoutInflater inflater = (LayoutInflater) context
                    .getSystemService(Context.LAYOUT_INFLATER_SERVICE);  //  获取inflater，还没这样用过，以后可以试试
  inflater.inflate(layoutResourceId, mDelegator, true);
    // 省略部分代码
  mSpinners = (LinearLayout) mDelegator.findViewById(R.id.pickers);  

找到了datePicker的布局文件 R.layout.date_picker_legacy，看看xml文件

• 源码路径：frameworks/base/core/res/res/layout/date_picker_legacy.xml

<!-- Layout of date picker-->

<!-- Warning: everything within the "pickers" layout is removed and re-ordered
     depending on the date format selected by the user.
--> 
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent"
    android:layout_gravity="center_horizontal"
    android:orientation="horizontal"
    android:gravity="center">

    <LinearLayout android:id="@+id/pickers"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_weight="1"
        android:orientation="horizontal"
        android:gravity="center">

        <!-- Month -->
        <NumberPicker
            android:id="@+id/month"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_marginStart="1dip"
            android:layout_marginEnd="1dip"
            android:focusable="true"
            android:focusableInTouchMode="true"
            />

        <!-- Day -->
        <NumberPicker
            android:id="@+id/day"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_marginStart="1dip"
            android:layout_marginEnd="1dip"
            android:focusable="true"
            android:focusableInTouchMode="true"
            />

        <!-- Year -->
        <NumberPicker
            android:id="@+id/year"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_marginStart="1dip"
            android:layout_marginEnd="1dip"
            android:focusable="true"
            android:focusableInTouchMode="true"
            />

    </LinearLayout>

    <!-- calendar view -->
    <CalendarView
        android:id="@+id/calendar_view"
        android:layout_width="245dip"
        android:layout_height="280dip"
        android:layout_marginStart="44dip"
        android:layout_weight="1"
        android:focusable="true"
        android:focusableInTouchMode="true"
        android:visibility="gone"
        />

</LinearLayout>

可以看到datePicker就是横向排列的三个NumberPicker数字选择器外加一个隐藏的CalendarView，注释也说了会根据日期格式重新排序，现在去找找排序的方法。

• 源码路径：frameworks/base/core/java/android/widget/DatePicker.java

 /**
  * Reorders the spinners according to the date format that is
  * explicitly set by the user and if no such is set fall back
  * to the current locale's default format.
  */
  private void reorderSpinners() {
     mSpinners.removeAllViews();
     // We use numeric spinners for year and day, but textual months. Ask icu4c what
     // order the user's locale uses for that combination. http://b/7207103.
     String pattern = DateFormat.getBestDateTimePattern(Locale.getDefault(), "yyyyMMMdd");
     char[] order = ICU.getDateFormatOrder(pattern);
     final int spinnerCount = order.length;
     for (int i = 0; i < spinnerCount; i++) {
          switch (order[i]) {
            case 'd':
                 mSpinners.addView(mDaySpinner);
                 setImeOptions(mDaySpinner, spinnerCount, i);
                 break;
            case 'M':
                 mSpinners.addView(mMonthSpinner);
                 setImeOptions(mMonthSpinner, spinnerCount, i);
                 break;
            case 'y':
                 mSpinners.addView(mYearSpinner);
                 setImeOptions(mYearSpinner, spinnerCount, i);
                 break;
            default:
                 throw new IllegalArgumentException(Arrays.toString(order));
          }
     }
  }

可以看到，它的操作是先remove所有子view，然后根据排序再重新add。
现在我们来重新排序年月日

 datePicker = findViewById(R.id.datepicker);
 datePicker.setCalendarViewShown(false);
 timePicker = findViewById(R.id.timepicker);
 timePicker.setIs24HourView(true);

 // 可以在任何地方进行使用，但只能获取系统本身的资源。
 Resources resources = Resources.getSystem(); 
 // 获取布局LinearLayout 
 LinearLayout mSpinners = (LinearLayout) findViewById(resources.getIdentifier("pickers", "id", "android"));
 
 if(mSpinners != null){
 	 // 获取年月日numberpicker
 	yearPicker = (NumberPicker) datePicker.findViewById(resources.getIdentifier("year", "id", "android"));
 	monthPicker = (NumberPicker) datePicker.findViewById(resources.getIdentifier("month", "id", "android"));
 	dayPicker = (NumberPicker) datePicker.findViewById(resources.getIdentifier("day", "id", "android"));
 	
 	/*重新排列datepicker年月日的顺序*/
 	mSpinners.removeAllViews();
 	mSpinners.addView(yearPicker);
 	mSpinners.addView(monthPicker);
 	mSpinners.addView(dayPicker);
 	
	// 想要隐藏某个picker
	// dayPicker.setVisibility(View.GONE);
 }

使用getIdentifier()获取资源 链接地址
效果图如下：

3.使用物理按键控制numberpicker的滚动

NumberPicker可以滑动改变值，也可以上下点击改变数值，来看看numerpicker源码。

• 源码位置：frameworks/base/core/java/android/widget/NumberPicker.java

 /**
  * The resource id for the default layout.
  */
 private static final int DEFAULT_LAYOUT_RESOURCE_ID = R.layout.number_picker;

• 源码位置：frameworks/base/core/res/res/layout/number_picker.xml

<merge xmlns:android="http://schemas.android.com/apk/res/android">

    <ImageButton android:id="@+id/increment"
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:background="@android:drawable/numberpicker_up_btn"
        android:paddingTop="22dip"
        android:paddingBottom="22dip"
        android:contentDescription="@string/number_picker_increment_button" />

    <EditText
        android:id="@+id/numberpicker_input"
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:textAppearance="@style/TextAppearance.Large.Inverse.NumberPickerInputText"
        android:gravity="center"
        android:singleLine="true"
        android:background="@drawable/numberpicker_input" />

    <ImageButton android:id="@+id/decrement"
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:background="@android:drawable/numberpicker_down_btn"
        android:paddingTop="22dip"
        android:paddingBottom="22dip"
        android:contentDescription="@string/number_picker_decrement_button" />

</merge>

可以看到numberpicker是有上下各一个ImageButton 和中间的EditText组成，既然点击可以改变numberpicker的值，再来看看ImageButton的点击事件，还是在NumberPicker.java中。

//  ImageButton的点击事件
 OnClickListener onClickListener = new OnClickListener() {
         public void onClick(View v) {
            hideSoftInput();
            mInputText.clearFocus();
            if (v.getId() == R.id.increment) {
                changeValueByOne(true);
            } else {
                changeValueByOne(false);
            }
         }
 };
 
   // 省略部分代码
   
/**
 * Changes the current value by one which is increment or
 * decrement based on the passes argument.
 * decrement the current value.
 *
 * @param increment True to increment, false to decrement.
 */
 private void changeValueByOne(boolean increment) {
    if (mHasSelectorWheel) {
        mInputText.setVisibility(View.INVISIBLE);
        if (!moveToFinalScrollerPosition(mFlingScroller)) {
            moveToFinalScrollerPosition(mAdjustScroller);
        }
        mPreviousScrollerY = 0;
        if (increment) {
            mFlingScroller.startScroll(0, 0, 0, -mSelectorElementHeight, SNAP_SCROLL_DURATION);
        } else {
            mFlingScroller.startScroll(0, 0, 0, mSelectorElementHeight, SNAP_SCROLL_DURATION);
        }
        invalidate();
    } else {
        if (increment) {
            setValueInternal(mValue + 1, true);
        } else {
            setValueInternal(mValue - 1, true);
        }
    }
 }

点击就是调用changeValueByOne方法，滑动也是，有兴趣的可以自己研究源码。这个方法是private的，所以只能用反射了，看代码

/**
 * 控制numberpicker的滚动
 * @param inrecment
 */
 private void scrollPicker(boolean inrecment){
    int index = getSelectedImageIndex();
    NumberPicker picker = mPickerList.get(index);
    try {
        Class pickerClass = Class.forName(NumberPicker.class.getName());
        Method deMethod = pickerClass.getDeclaredMethod("changeValueByOne",boolean.class);
        deMethod.setAccessible(true);
        deMethod.invoke(picker,inrecment);
        Logger.d(deMethod);
    } catch (InvocationTargetException e) {
        e.printStackTrace();
    } catch (NoSuchMethodException e) {
        e.printStackTrace();
    } catch (IllegalAccessException e) {
        e.printStackTrace();
    } catch (ClassNotFoundException e) {
        e.printStackTrace();
    }
 }

完事。。。

附上一个在线阅读源码网站，各个版本都有 传送门