这是 Bug 了吗？

https://zippy.gfycat.com/GratefulKeyChamois.webm

情况如上， PagerTabStrip 的 title 刚打开程序不显示，必须要拉动到下一个界面才会出现。

在网上找了个遍，都没发现原因，代码也是最基本的初始化，没做任何自定义，感觉要么是 Bug 、要么是手机问题。

这是代码：

MainActivity.java

package com.example.system.myapplication;

import android.app.Activity;
import android.os.Bundle;
import android.support.annotation.Nullable;
import android.support.v4.view.ViewPager;
import android.view.View;

import java.util.ArrayList;
import java.util.List;

public class MainActivity extends Activity {

    @Override
    protected void onCreate(@Nullable Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main_activity);

        List<View> viewList = new ArrayList<>();
        View view1 = View.inflate(this, R.layout.view1, null);
        View view2 = View.inflate(this, R.layout.view2, null);
        View view3 = View.inflate(this, R.layout.view3, null);
        View view4 = View.inflate(this, R.layout.view4, null);
        viewList.add(view1);
        viewList.add(view2);
        viewList.add(view3);
        viewList.add(view4);

        List<String> titleList = new ArrayList<>();
        titleList.add("第一个页面");
        titleList.add("第二个页面");
        titleList.add("第三个页面");
        titleList.add("第四个页面");

        MyPagerAdapter myPagerAdapter = new MyPagerAdapter(viewList, titleList);

        ViewPager viewPager = (ViewPager) findViewById(R.id.viewPager);
        viewPager.setAdapter(myPagerAdapter);
    }
}

PagerAdapter 适配器

package com.example.system.myapplication;

import android.support.v4.view.PagerAdapter;
import android.view.View;
import android.view.ViewGroup;

import java.util.List;

public class MyPagerAdapter extends PagerAdapter {
    private List<View> viewList;
    private List<String> titleList;

    public MyPagerAdapter(List<View> viewList, List<String> titleList) {
        this.viewList = viewList;
        this.titleList = titleList;
    }

    @Override
    public int getCount() {
        return viewList.size();
    }

    @Override
    public boolean isViewFromObject(View view, Object object) {
        return view == object;
    }

    @Override
    public Object instantiateItem(ViewGroup container, int position) {
        View view = viewList.get(position);
        container.addView(view);
        return view;
    }

    @Override
    public void destroyItem(ViewGroup container, int position, Object object) {
        View view = viewList.get(position);
        container.removeView(view);
    }

    @Override
    public CharSequence getPageTitle(int position) {
        return titleList.get(position);
    }
}

main_activity.xml

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
              android:orientation="vertical"
              android:layout_width="match_parent"
              android:layout_height="match_parent">

    <android.support.v4.view.ViewPager
            android:id="@+id/viewPager"
            android:layout_gravity="center"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content">

        <android.support.v4.view.PagerTabStrip
                android:id="@+id/tab"
                android:layout_gravity="top"
                android:layout_width="wrap_content"
                android:layout_height="wrap_content">
        </android.support.v4.view.PagerTabStrip>
    </android.support.v4.view.ViewPager>

</LinearLayout>