java - The up and down sliding event in Fragment will be responded to the previous Fragment instead of the current one

Question

I am currently developing an Android app with only one activity. There is a ViewPager in the layout file, and its adapter is bound to three Fragments. The layout files of the first two Fragments are the outermost SwipeRefreshLayout for pull-down refresh, and then a ScrollView is nested. The third one is also accurate...

怪我咯 · Answer

Problem solved. .
There is a piece of information not described in the question. That is, in order to make the animation fade in and out instead of the default sliding when the ViewPager switches pages, I implemented an interface of the ViewPager class, ViewPager.PageTransformer. Then, I instantiate this class in Activity and execute mViewPager.setPageTransformer(true, pageTransformer); to set the switching animation to the animation I wrote myself. The problem lies in this animation. At the beginning, I implemented this interface like this:

import android.support.v4.view.ViewPager;
import android.view.View;

/*
*设置Fragment切换时的动画为淡入淡出
*/

public class NoSlidingPageTransformer implements ViewPager.PageTransformer {
    private static final float MIN_ALPHA = 0.0f;    //最小透明度

    public void transformPage(View view, float position) {
        int pageWidth = view.getWidth();    //得到view宽

        if (position < -1) { // [-Infinity,-1)
            // This page is way off-screen to the left. 出了左边屏幕
            view.setAlpha(0);

        } else if (position <= 1) { // [-1,1]
            view.setTranslationX(-pageWidth * position);  //阻止页面的滑动
            float alphaFactor = Math.max(MIN_ALPHA, 1 - Math.abs(position));
            //透明度改变
            view.setAlpha(alphaFactor);
            if (alphaFactor == 0)
                view.setVisibility(View.INVISIBLE);     //页面不在当前界面显示，则使其Invisible，这句是为了解决Fragment对上下滑动事件监听的错乱，暂不知原因
            else if (view.getVisibility() == View.INVISIBLE)
                view.setVisibility(View.VISIBLE);       //页面在当前界面显示，则使其Visible，这句是为了解决Fragment对上下滑动事件监听的错乱，暂不知原因
        } else { // (1,+Infinity]
            // This page is way off-screen to the right.    出了右边屏幕
            view.setAlpha(0);
        }
    }

}

This piece of code is what I temporarily used to solve the "supernatural" phenomenon described in the question:

if (alphaFactor == 0)
    view.setVisibility(View.INVISIBLE);     //页面不在当前界面显示，则使其Invisible，这句是为了解决Fragment对上下滑动事件监听的错乱，暂不知原因
    else if (view.getVisibility() == View.INVISIBLE)
        view.setVisibility(View.VISIBLE);       //页面在当前界面显示，则使其Visible，这句是为了解决Fragment对上下滑动事件监听的错乱，暂不知原因

What’s the problem? The problem lies in the view.setTranslationX() function. The position of the view set by this function is not only visual, but also the actual position. So look at the code I implemented. When the view leaves the current interface, When the value of position is [-Infinity,-1] and [1,+Infinity], I did not use setTranslationX() to set its position outside the current interface, but it was still at the same position as the newly appeared view. It's just that it's invisible because the transparency is set with setAlpha().
How did I discover this problem? Just comment out all the code that calls selAlpha() in this class, run it again, and finally find that when I switch Fragments, two Fragments will appear overlapping and displayed. Now I modify this class as follows and the problem is solved (the temporary code is commented out):

import android.support.v4.view.ViewPager;
import android.view.View;

/*
*设置Fragment切换时的动画为淡入淡出
*/

public class NoSlidingPageTransformer implements ViewPager.PageTransformer {

    public void transformPage(View view, float position) {
        int pageWidth = view.getWidth();    //得到view宽

        if (position <= -1) { // [-Infinity,-1]
            // This page is way off-screen to the left. 出了左边屏幕
            view.setTranslationX(0);

        } else if (position < 1) { // (-1,1)
            view.setTranslationX(-pageWidth * position);  //阻止页面的滑动,位置在左则设向右偏移位置，在右则设向左偏移位置
            float alphaFactor = 1 - Math.abs(position);
            //透明度改变
            view.setAlpha(alphaFactor);
            /*
            if (alphaFactor == 0)
                view.setVisibility(View.INVISIBLE);     //页面不在当前界面显示，则使其Invisible，这句是为了解决Fragment对上下滑动事件监听的错乱，暂不知原因
            else if (view.getVisibility() == View.INVISIBLE)
                view.setVisibility(View.VISIBLE);       //页面在当前界面显示，则使其Visible，这句是为了解决Fragment对上下滑动事件监听的错乱，暂不知原因
                */
        } else { // [1,+Infinity]
            // This page is way off-screen to the right.    出了右边屏幕
            view.setTranslationX(0);
        }
    }

}