Question

我正在使用ViewPager2，并且有一个按钮可以将其当前页面更改为第二页面，如下所示：

button_next.setOnClickListener {
            setup_view_pager.currentItem = 1
}

它有效，直到用手滑动页面，然后抛出此错误：

E/AndroidRuntime: FATAL EXCEPTION: main
    Process: rs.ac.bg.matf.risk.matfasistent, PID: 32028
    java.lang.IllegalStateException: Expected position values between -1 and 1.
        at androidx.core.util.Preconditions.checkState(Preconditions.java:96)
        at androidx.viewpager2.widget.MarginPageTransformer.transformPage(MarginPageTransformer.java:56)
        at androidx.viewpager2.widget.PageTransformerAdapter.onPageScrolled(PageTransformerAdapter.java:72)
        at androidx.viewpager2.widget.CompositeOnPageChangeCallback.onPageScrolled(CompositeOnPageChangeCallback.java:59)
        at androidx.viewpager2.widget.ScrollEventAdapter.dispatchScrolled(ScrollEventAdapter.java:407)
        at androidx.viewpager2.widget.ScrollEventAdapter.onScrolled(ScrollEventAdapter.java:188)
        at androidx.recyclerview.widget.RecyclerView.dispatchOnScrolled(RecyclerView.java:5100)
        at androidx.recyclerview.widget.RecyclerView$ViewFlinger.run(RecyclerView.java:5265)
        at android.view.Choreographer$CallbackRecord.run(Choreographer.java:1012)
        at android.view.Choreographer.doCallbacks(Choreographer.java:824)
        at android.view.Choreographer.doFrame(Choreographer.java:756)
        at android.view.Choreographer$FrameDisplayEventReceiver.run(Choreographer.java:998)
        at android.os.Handler.handleCallback(Handler.java:873)
        at android.os.Handler.dispatchMessage(Handler.java:99)
        at android.os.Looper.loop(Looper.java:193)
        at android.app.ActivityThread.main(ActivityThread.java:6745)
        at java.lang.reflect.Method.invoke(Native Method)
        at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:495)
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:858)

这仅发生在这些单击上，当用手轻拂片段时，一切正常。错误跟踪的位置都没有指向我的代码：（

这是我的ViewPager适配器：

class SetupAdapter(fragmentManager: FragmentManager, lifecycle: Lifecycle)
    : FragmentStateAdapter(fragmentManager, lifecycle) {

    override fun getItemCount() = 3

    override fun createFragment(position: Int): Fragment {
        return when (position) {
            0, 1, 2 -> StudentSelectionFragment()
            else -> throw IllegalStateException()
        }
    }
}

这是Activity的全部相关代码：

override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)

        val adapter = SetupAdapter(supportFragmentManager, lifecycle)

        setup_view_pager.orientation = ViewPager2.ORIENTATION_HORIZONTAL
        setup_view_pager.adapter = adapter
        setup_view_pager.setPageTransformer(MarginPageTransformer(1500))

        button_next.setOnClickListener {
            setup_view_pager.setCurrentItem(1, true)
        }
    }

Answer 1

问题出在这一行：

setup_view_pager.setPageTransformer(MarginPageTransformer(1500))

我不确定它能做什么，但我仍然不确定，但是我从一个示例实现中复制了代码。删除它可以解决问题。

ViewPager2 setCurrentItem方法抛出错误

1 个答案: