content: /*
   * Copyright 2014 Toxic Bakery
   *
   * Licensed under the Apache License, Version 2.0 (the "License");
   * you may not use this file except in compliance with the License.
   * You may obtain a copy of the License at
   *
   *       http://www.apache.org/licenses/LICENSE-2.0
   *
   * Unless required by applicable law or agreed to in writing, software
   * distributed under the License is distributed on an "AS IS" BASIS,
   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   * See the License for the specific language governing permissions and
   * limitations under the License.
   */
  
  package com.msky.viewpageranimation.animationlibrary;
  
  import android.support.v4.view.ViewPager.PageTransformer;
  import android.view.View;
  
  public abstract class ABaseTransformer implements PageTransformer {
  
  	/**
  	 * Called each {@link #transformPage(View, float)}.
  	 * 
  	 * @param page
  	 *            Apply the transformation to this page
  	 * @param position
  	 *            Position of page relative to the current front-and-center position of the pager. 0 is front and
  	 *            center. 1 is one full page position to the right, and -1 is one page position to the left.
  	 */
  	protected abstract void onTransform(View page, float position);
  
  	/**
  	 * Apply a property transformation to the given page. For most use cases, this method should not be overridden.
  	 * Instead use {@link #transformPage(View, float)} to perform typical transformations.
  	 * 
  	 * @param page
  	 *            Apply the transformation to this page
  	 * @param position
  	 *            Position of page relative to the current front-and-center position of the pager. 0 is front and
  	 *            center. 1 is one full page position to the right, and -1 is one page position to the left.
  	 */
  	@Override
  	public void transformPage(View page, float position) {
  		onPreTransform(page, position);
  		onTransform(page, position);
  		onPostTransform(page, position);
  	}
  
  	/**
  	 * If the position offset of a fragment is less than negative one or greater than one, returning true will set the
  	 * fragment alpha to 0f. Otherwise fragment alpha is always defaulted to 1f.
  	 * 
  	 * @return
  	 */
  	protected boolean hideOffscreenPages() {
  		return true;
  	}
  
  	/**
  	 * Indicates if the default animations of the view pager should be used.
  	 * 
  	 * @return
  	 */
  	protected boolean isPagingEnabled() {
  		return false;
  	}
  
  	/**
  	 * Called each {@link #transformPage(View, float)} before {{@link #onTransform(View, float)}.
  	 * <p>
  	 * The default implementation attempts to reset all view properties. This is useful when toggling transforms that do
  	 * not modify the same page properties. For instance changing from a transformation that applies rotation to a
  	 * transformation that fades can inadvertently leave a fragment stuck with a rotation or with some degree of applied
  	 * alpha.
  	 * 
  	 * @param page
  	 *            Apply the transformation to this page
  	 * @param position
  	 *            Position of page relative to the current front-and-center position of the pager. 0 is front and
  	 *            center. 1 is one full page position to the right, and -1 is one page position to the left.
  	 */
  	protected void onPreTransform(View page, float position) {
  		final float width = page.getWidth();
  
  		page.setRotationX(0);
  		page.setRotationY(0);
  		page.setRotation(0);
  		page.setScaleX(1);
  		page.setScaleY(1);
  		page.setPivotX(0);
  		page.setPivotY(0);
  		page.setTranslationY(0);
  		page.setTranslationX(isPagingEnabled() ? 0f : -width * position);
  
  		if (hideOffscreenPages()) {
  			page.setAlpha(position <= -1f || position >= 1f ? 0f : 1f);
  			page.setEnabled(false);
  		} else {
  			page.setEnabled(true);
  			page.setAlpha(1f);
  		}
  	}
  
  	/**
  	 * Called each {@link #transformPage(View, float)} after {@link #onTransform(View, float)}.
  	 * 
  	 * @param page
  	 *            Apply the transformation to this page
  	 * @param position
  	 *            Position of page relative to the current front-and-center position of the pager. 0 is front and
  	 *            center. 1 is one full page position to the right, and -1 is one page position to the left.
  	 */
  	protected void onPostTransform(View page, float position) {
  	}
  
  	/**
  	 * Same as {@link Math#min(double, double)} without double casting, zero closest to infinity handling, or NaN support.
  	 * 
  	 * @param val
  	 * @param min
  	 * @return
  	 */
  	protected static final float min(float val, float min) {
  		return val < min ? min : val;
  	}
  
  }
  