package cn.flightfeather.thirdapp.view;
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import android.support.v4.view.ViewPager;
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import android.view.View;
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/**
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* Created by Nate on 2016/7/22.
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*/
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public abstract class VerticalBaseTransformer implements ViewPager.PageTransformer {
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/**
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* Called each {@link #transformPage(View, float)}.
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*
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* @param page Apply the transformation to this page
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* @param position Position of page relative to the current front-and-center position of the pager. 0 is front and
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* center. 1 is one full page position to the right, and -1 is one page position to the left.
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*/
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protected abstract void onTransform(View page, float position);
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/**
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* Apply a property transformation to the given page. For most use cases, this method should not be overridden.
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* Instead use {@link #transformPage(View, float)} to perform typical transformations.
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*
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* @param page Apply the transformation to this page
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* @param position Position of page relative to the current front-and-center position of the pager. 0 is front and
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* center. 1 is one full page position to the right, and -1 is one page position to the left.
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*/
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@Override
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public void transformPage(View page, float position) {
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onPreTransform(page, position);
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onTransform(page, position);
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onPostTransform(page, position);
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}
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/**
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* If the position offset of a fragment is less than negative one or greater than one, returning true will set the
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* fragment alpha to 0f. Otherwise fragment alpha is always defaulted to 1f.
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*
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* @return
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*/
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protected boolean hideOffscreenPages() {
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return true;
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}
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/**
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* Indicates if the default animations of the view pager should be used.
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*
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* @return
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*/
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protected boolean isPagingEnabled() {
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return false;
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}
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/**
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* Called each {@link #transformPage(View, float)} before {{@link #onTransform(View, float)}.
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* <p/>
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* The default implementation attempts to reset all view properties. This is useful when toggling transforms that do
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* not modify the same page properties. For instance changing from a transformation that applies rotation to a
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* transformation that fades can inadvertently leave a fragment stuck with a rotation or with some degree of applied
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* alpha.
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*
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* @param page Apply the transformation to this page
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* @param position Position of page relative to the current front-and-center position of the pager. 0 is front and
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* center. 1 is one full page position to the right, and -1 is one page position to the left.
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*/
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protected void onPreTransform(View page, float position) {
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final float width = page.getWidth();
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final float height = page.getHeight();
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page.setRotationX(0);
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page.setRotationY(0);
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page.setRotation(0);
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page.setScaleX(1);
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page.setScaleY(1);
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page.setPivotX(0);
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page.setPivotY(0);
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page.setTranslationX(0);
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page.setTranslationY(isPagingEnabled() ? 0f : -height * position);
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if (hideOffscreenPages()) {
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page.setAlpha(position <= -1f || position >= 1f ? 0f : 1f);
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} else {
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page.setAlpha(1f);
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}
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/*final float normalizedposition = Math.abs(Math.abs(position) - 1);
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page.setAlpha(normalizedposition);*/
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}
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/**
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* Called each {@link #transformPage(View, float)} after {@link #onTransform(View, float)}.
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*
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* @param page Apply the transformation to this page
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* @param position Position of page relative to the current front-and-center position of the pager. 0 is front and
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* center. 1 is one full page position to the right, and -1 is one page position to the left.
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*/
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protected void onPostTransform(View page, float position) {
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}
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/**
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* Same as {@link Math#min(double, double)} without double casting, zero closest to infinity handling, or NaN support.
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*
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* @param val
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* @param min
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* @return
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*/
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protected static final float min(float val, float min) {
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return val < min ? min : val;
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}
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}
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