package com.github.paolorotolo.appintro;
import android.annotation.SuppressLint;
import android.support.v4.view.ViewPager;
import android.view.View;
class ViewPageTransformer implements ViewPager.PageTransformer {
private static final float MIN_SCALE_DEPTH = 0.75f;
private static final float MIN_SCALE_ZOOM = 0.85f;
private static final float MIN_ALPHA_ZOOM = 0.5f;
private static final float SCALE_FACTOR_SLIDE = 0.85f;
private static final float MIN_ALPHA_SLIDE = 0.35f;
private final TransformType mTransformType;
ViewPageTransformer(TransformType transformType) {
mTransformType = transformType;
}
@SuppressLint("NewApi")
public void transformPage(View page, float position) {
final float alpha;
final float scale;
final float translationX;
switch (mTransformType) {
case FLOW:
page.setRotationY(position * -30f);
return;
case SLIDE_OVER:
if (position < 0 && position > -1) {
// this is the page to the left
scale = Math.abs(Math.abs(position) - 1) * (1.0f - SCALE_FACTOR_SLIDE) +
SCALE_FACTOR_SLIDE;
alpha = Math.max(MIN_ALPHA_SLIDE, 1 - Math.abs(position));
int pageWidth = page.getWidth();
float translateValue = position * -pageWidth;
if (translateValue > -pageWidth) {
translationX = translateValue;
} else {
translationX = 0;
}
} else {
alpha = 1;
scale = 1;
translationX = 0;
}
break;
case DEPTH:
if (position > 0 && position < 1) {
// moving to the right
alpha = (1 - position);
scale = MIN_SCALE_DEPTH + (1 - MIN_SCALE_DEPTH) * (1 - Math.abs(position));
translationX = (page.getWidth() * -position);
} else {
// use default for all other cases
alpha = 1;
scale = 1;
translationX = 0;
}
break;
case ZOOM:
if (position >= -1 && position <= 1) {
scale = Math.max(MIN_SCALE_ZOOM, 1 - Math.abs(position));
alpha = MIN_ALPHA_ZOOM +
(scale - MIN_SCALE_ZOOM) / (1 - MIN_SCALE_ZOOM) * (1 - MIN_ALPHA_ZOOM);
float vMargin = page.getHeight() * (1 - scale) / 2;
float hMargin = page.getWidth() * (1 - scale) / 2;
if (position < 0) {
translationX = (hMargin - vMargin / 2);
} else {
translationX = (-hMargin + vMargin / 2);
}
} else {
alpha = 1;
scale = 1;
translationX = 0;
}
break;
case FADE:
if (position <= -1.0F || position >= 1.0F) {
page.setAlpha(0.0F);
page.setClickable(false);
} else if (position == 0.0F) {
page.setAlpha(1.0F);
page.setClickable(true);
} else {
// position is between -1.0F & 0.0F OR 0.0F & 1.0F
page.setAlpha(1.0F - Math.abs(position));
}
default:
return;
}
page.setAlpha(alpha);
page.setTranslationX(translationX);
page.setScaleX(scale);
page.setScaleY(scale);
}
enum TransformType {
FLOW,
DEPTH,
ZOOM,
SLIDE_OVER,
FADE
}
}