Сейчас в Google Play более миллиона приложений, и чтобы привлечь внимание людей, нужно обязательно выделяться на общем фоне. Ещё пару лет назад пользователи Android были не слишком привередливы в том, что касается элементов интерфейса приложений, но сейчас они всё больше привыкают к прекрасному. Этот доклад — небольшой путеводитель в мир этому самого прекрасного. После него, я надеюсь, вы полюбите кастомные View не меньше чем я.

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ViewGroups
! FrameLayout
! LinearLayout
! RelativeLayout

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View positioning

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View positioning
! onMeasure
! onLayout

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onMeasure

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MeasureSpec
! Mode
– EXACTLY
– AT_MOST
– UNSPECIFIED
! Size

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MeasureSpec modes
! EXACTLY
– layout_width=“200dip”
– layout_height=“match_parent”
– layout_weight=“1”

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MeasureSpec modes
! AT_MOST
– layout_width=“wrap_content”

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MeasureSpec modes
! UNSPECIFIED
– ScrollView, ListView

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onMeasure

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onLayout
! getMeasuredWidth()
! getMeasuredHeight()
! сhild.layout(left, top, right, bottom);

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– How?

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– How?
– LayoutParams!

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attrs.xml

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main.xml

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LayoutParams
! ViewGroup.LayoutParams
! LinearLayout.LayoutParams
! RelativeLayout.LayoutParams
! …

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LayoutParams
! checkLayoutParams(ViewGroup.LayoutParams p)
! generateDefaultLayoutParams()
! generateLayoutParams(ViewGroup.LayoutParams p);
! generateLayoutParams(AttributeSet attrs)

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PavementLayout.LayoutParams

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onMeasure

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View interactions

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Yandex.Maps search card
Motion directions
! Up
! Left & right
! Down

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Yandex.Maps search card heirarchy
CardSlidingDrawer
ViewPager
Card

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Touch events
1. dispatchTouchEvent
2. onInterceptTouchEvent
3. children.dispatchTouchEvent
4. onTouchEvent

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Touch events sample #1
CardSlidingDrawer
TextView

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Touch events sample #1
1. dispatchTouchEventCardSlidingDrawer
TextView

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Touch events sample #1
1. dispatchTouchEvent
2. onInterceptTouchEvent
CardSlidingDrawer
TextView

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Touch events sample #1
1. dispatchTouchEvent
2. onInterceptTouchEvent
3. dispatchTouchEvent
CardSlidingDrawer
TextView

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Touch events sample #1
1. dispatchTouchEvent
2. onInterceptTouchEvent
3. dispatchTouchEvent
4. onTouchEvent
CardSlidingDrawer
TextView

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Touch events sample #1
1. dispatchTouchEvent
2. onInterceptTouchEvent
3. dispatchTouchEvent
4. onTouchEvent
CardSlidingDrawer
TextView

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Touch events sample #1
1. dispatchTouchEvent
2. onInterceptTouchEvent
3. dispatchTouchEvent
4. onTouchEvent
CardSlidingDrawer
TextView

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Touch events sample #2
1. dispatchTouchEventCardSlidingDrawer
Clickable TextView

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Touch events sample #2
1. dispatchTouchEvent
2. onInterceptTouchEvent
CardSlidingDrawer
Clickable TextView

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Touch events sample #2
1. dispatchTouchEvent
2. onInterceptTouchEvent
3. dispatchTouchEvent
CardSlidingDrawer
Clickable TextView

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Touch events sample #2
1. dispatchTouchEvent
2. onInterceptTouchEvent
3. dispatchTouchEvent
CardSlidingDrawer
Clickable TextView

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Touch events sample #2
1. dispatchTouchEvent
2. onInterceptTouchEvent
3. dispatchTouchEvent
CardSlidingDrawer
Clickable TextView

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Touch events sample #2
1. dispatchTouchEvent
2. onInterceptTouchEvent
3. dispatchTouchEvent
CardSlidingDrawer
Clickable TextView

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Touch events sample #2
1. dispatchTouchEvent
2. onInterceptTouchEvent
3. dispatchTouchEvent
CardSlidingDrawer
Clickable TextView

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Touch events sample #2
1. dispatchTouchEvent
2. onInterceptTouchEvent
3. dispatchTouchEvent
CardSlidingDrawer
Clickable TextView

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Touch events sample #2
1. dispatchTouchEvent
2. onInterceptTouchEvent
3. dispatchTouchEvent
4. onTouchEvent
CardSlidingDrawer
Clickable TextView

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Touch events sample #2
1. dispatchTouchEvent
2. onInterceptTouchEvent
3. dispatchTouchEvent
4. onTouchEvent
CardSlidingDrawer
Clickable TextView

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Touch events sample #2
1. dispatchTouchEvent
2. onInterceptTouchEvent
3. dispatchTouchEvent
4. onTouchEvent
CardSlidingDrawer
Clickable TextView

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TouchSlop
! deltaY = Math.abs( event.getY() – startY );
! ViewConfiguration.getScaledTouchSlop();
! view.scrollTo(x,y);

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VelocityTracker
! VelocityTracker.obtain();
! VelocityTracker.addMovement( event );
! VelocityTracker.computeCurrentVelocity(units);

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Scroller
! void fling(…);
! void View.computeScroll();
! boolean computeScrollOffset();
! int getCurrY();

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Scroller

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Wrap-up
! onMeasure & onLayout
! onIntercept & onTouchEvent
! GestureDetector & DragHelper

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Samples
https://github.com/ArikonUA/yac13

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Спасибо за внимание

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Поляков Алексей
Разработчик
alexpolyakov@yandex-team.ru
! @arikon