LayoutTransition

LayoutTransition是用于ViewGroup的过渡动画，其本质也是同于PropertyAnimator形成的动画

• 1.一个LayoutTransition对象中包含四个Animator对象：

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    int LayoutTransitionType=LayoutTransition.APPEARING//ViewGroup中子View显示(View.VISIBLE出来时，显示的子view调用的动画

    int LayoutTransitionType=LayoutTransition.DisAPPEARING//ViewGroup中子View隐藏（View.INVISIBLE）出来，被隐藏的子View调用的动画

    int LayoutTransitionType=LayoutTransition.CHANGE_APPEARING//ViewGroup中子View显示出来，其他布局发生变化的子view调用的动画

    int LayoutTransitionType=LayoutTransition.CHANGE_DISAPPEARING//ViewGroup中子View隐藏（如View.GONE）或移除时，其他布局发生变动的子View调用的动画

• 2.为ViewGroup设置LayoutTransition

LayoutTransition layoutTransition = new LayoutTransition();//创建一个LayoutTransition对象，里面包含了默认的四种类型的AnimatorviewGroup.setLayoutTransition(layoutTransition);//将layoutTransition对象设置给viewGroup

• 3.设置自定义的LayoutTransition

        //设置窗体的左右上下距离父容器的像素距离为从0到1 的动画        PropertyValuesHolder pvh_left = PropertyValuesHolder.ofInt("left", 0, 1);        PropertyValuesHolder pvh_top = PropertyValuesHolder.ofInt("top", 0, 1);        PropertyValuesHolder pvh_right = PropertyValuesHolder.ofInt("right", 0, 1);        PropertyValuesHolder pvh_bottom = PropertyValuesHolder.ofInt("bottom", 0, 1);        PropertyValuesHolder pvh_scaleX = PropertyValuesHolder.ofInt("scaleX", 1, 0, 1);        PropertyValuesHolder pvh_scaleY = PropertyValuesHolder.ofInt("scaleY", 1, 0, 1);        //通过ObjectAnimator的ofPropertyValuesHolder来生成动画；        ObjectAnimator customChangingAppearAnim = ObjectAnimator.ofPropertyValuesHolder(this, pvh_left, pvh_top, pvh_right, pvh_bottom, pvh_scaleX, pvh_scaleY).setDuration(transition.getDuration(LayoutTransition.CHANGE_APPEARING));        //设置动画的监听时间，动画结束时，将窗体的属性设置为需要的值        customChangingAppearAnim.addListener(new AnimatorListenerAdapter() {            @Override            public void onAnimationEnd(Animator animation) {                View view = (View) ((ObjectAnimator) animation).getTarget();                view.setScaleY(1f);                view.setScaleX(1f);            }        });        //将这个自定义的动画设置为layoutTransition的一个内含的Animator         layoutTransition.setAnimator(LayoutTransition.APPEARING, customAppearAnim);//用该动画替换掉了默认的Appearing动画，当viewgroup的子view显示且viewGroup布局不变时，会自动调用该动画

• 4.在xml中为viewGroup设置默认的layoutTransition

<LinearLayout    android:orientation="vertical"    android:layout_width="wrap_content"    android:layout_height="match_parent"    android:id="@+id/verticalContainer"    android:animateLayoutChanges="true" />//animateLayoutChanges设置为true既为它添加了系统默认的布局动画