139_Transformer源码分析_对transformer官方源码解析

Transformer源码分析

刚刚用了官方提供的Transformer了

但是我们只会复制不行啊

我们要看看官方代码是怎么写的

来分析一下

 

代码分析

 

public class DepthPageTransformer implements ViewPager.PageTransformer {

    private static final float MIN_SCALE = 0.75f;

 

//这里来了一个常量,看MIN_SCALE这个名字应该是最小比例之类的东西

 

    public void transformPage(View view, float position) {

        int pageWidth = view.getWidth();

 

//获取宽度

 

        if (position < -1) { // [-Infinity,-1)

            // This page is way off-screen to the left.

            view.setAlpha(0);

 

//如果position小于-1,那么透明度为0

// This page is way off-screen to the left.

//这个页面从左边消失

 

        } else if (position <= 0) { // [-1,0]

            // Use the default slide transition when moving to the left page

            view.setAlpha(1);

            view.setTranslationX(0);

            view.setScaleX(1);

            view.setScaleY(1);

 

//如果position小于等于0,那么透明度为1,x平移为0,scaleX和scaleY为1

// Use the default slide transition when moving to the left page

//移向左边页面的时候使用默认平移

 

        } else if (position <= 1) { // (0,1]

            // Fade the page out.

            view.setAlpha(1 - position);

//隐藏page

 

            // Counteract the default slide transition

            view.setTranslationX(pageWidth * -position);

//抵消默认平移

 

            // Scale the page down (between MIN_SCALE and 1)

            float scaleFactor = MIN_SCALE

                    + (1 - MIN_SCALE) * (1 - Math.abs(position));

            view.setScaleX(scaleFactor);

            view.setScaleY(scaleFactor);

//页面向下变换

 

        } else { // (1,+Infinity]

            // This page is way off-screen to the right.

            view.setAlpha(0);

        }

//页面从右边消失

 

    }

}

 

 

总结

简而言之

就是滑动的时候,页面左右移动

加载的页面根据位置改变比例和透明度