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ImageSwitcher 在 registerOnPageChangeCallback 中使用时未设置初始图像。但如果我把它包在里面Handler.postdelay()，它就可以工作了。

介绍片段.kg

class IntroFragment : BaseFragment() {

    override fun onCreateView(inflater: LayoutInflater, container: ViewGroup?, savedInstanceState: Bundle?): View {
        return inflater.inflate(R.layout.fragment_intro, container, false)
    }

    override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
        super.onViewCreated(view, savedInstanceState)

        val viewPagerAdapter = IntroViewPagerAdapter(childFragmentManager, lifecycle)

        viewPager2.adapter = viewPagerAdapter

        val images = arrayOf(R.drawable.ic_knowledge, R.drawable.ic_privacy)

        viewPager2.registerOnPageChangeCallback(object : ViewPager2.OnPageChangeCallback() {
            private var skipButtonVisible = true

            override fun onPageScrollStateChanged(state: Int) = Unit

            override fun onPageSelected(position: Int) {
                 imageSwitcher.setImageResource(images[position])
            }
        })

        imageSwitcher.setFactory { ImageView(activity?.applicationContext) }
        imageSwitcher.setImageResource(images[0])
 
    }
}

IntroViewPagerAdapter.kt

class IntroViewPagerAdapter(fragmentManager: FragmentManager, lifecycle: Lifecycle) : FragmentStateAdapter(fragmentManager, lifecycle) {
    private val fragments = listOf<Fragment>(
            SlideFragment.newInstance(titleText, R.string.Description1),
            SlideFragment.newInstance(titleText2, R.string.Description2),
    )

    override fun getItemCount(): Int = fragments.size

    override fun createFragment(position: Int): Fragment = fragments[position]
}

片段介绍.xml

<androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    android:id="@+id/introLayout"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:background="?android:windowBackground"
    android:clickable="true">

    <androidx.viewpager2.widget.ViewPager2
        android:id="@+id/viewPager2"
        android:layout_width="0dp"
        android:layout_height="0dp"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent"/>

    <ImageSwitcher
        android:id="@+id/imageSwitcher"
        android:layout_width="280dp"
        android:layout_height="280dp"
        android:inAnimation="@android:anim/fade_in"
        android:outAnimation="@android:anim/fade_out"
        android:transitionName="welcome_wallet_logo"
        app:layout_constraintBottom_toTopOf="@+id/verticalCenter"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent" />

</androidx.constraintlayout.widget.ConstraintLayout>
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1 回答 1

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除了设置工厂，我们还可以直接将视图添加到图像切换器。

   /**
     * Sets the factory used to create the two views between which the
     * ViewSwitcher will flip. Instead of using a factory, you can call
     * {@link #addView(android.view.View, int, android.view.ViewGroup.LayoutParams)}
     * twice.
     *
     * @param factory the view factory used to generate the switcher's content
     */
    public void setFactory(ViewFactory factory) {
        mFactory = factory;
        obtainView();
        obtainView();
    }

我们可以将视图添加到 imageSwitcher。确保我们只添加 2 次。一个 ViewSwitcher 只能有两个子视图。

imageSwitcher.addView(ImageView(activity?.applicationContext))
imageSwitcher.addView(ImageView(activity?.applicationContext))

我尝试手动添加视图并且它正在工作。无需环绕处理程序。

我还试图找出为什么当我们延迟包装在处理程序中时它工作的根本原因。

于 2021-02-12T10:06:57.293 回答