Android 无法在向上滑动面板的第二个子项中添加按钮

我的布局中有一个滑动面板。 在第一个子级中有一个按钮可以正常工作，但当我在第二个子级中添加一个按钮时，会抛出一个NullPointerException。 如果我移除按钮，布局就可以了。 我无法理解我做错了什么

布局如下所示：

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

    <com.sothree.slidinguppanel.SlidingUpPanelLayout 
        xmlns:sothree="http://schemas.android.com/apk/res-auto"
        android:id="@+id/sliding_layout"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:gravity="bottom"
        sothree:umanoPanelHeight="68dp"
        sothree:umanoShadowHeight="4dp">

        <LinearLayout
            android:layout_width="match_parent"
            android:layout_height="match_parent"
            android:orientation="vertical">

            <TextView
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                android:gravity="center|top"
                android:text="The Awesome Sliding Up Panel"
                android:textSize="16sp" />

            <Button
                android:id="@+id/toggle_upper"
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                android:text="Upper" />
        </LinearLayout>

        <LinearLayout
            android:layout_width="match_parent"
            android:layout_height="match_parent"
            android:orientation="vertical">

            <EditText
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                android:hint="Edit this" />

            <Button
                android:id="@+id/toggle_upper2"
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                android:text="Upper" />

        </LinearLayout>
    </com.sothree.slidinguppanel.SlidingUpPanelLayout>
</LinearLayout>

---

我运行的是旧版本的Android Studio。 Android Studio 1.0不支持此布局的预览

我更新了Android Studio，现在可以看到布局了

java.lang.NullPointerException
    at android.view.ViewGroup_Delegate.drawShadow(ViewGroup_Delegate.java:74)
    at android.view.ViewGroup_Delegate.drawChild(ViewGroup_Delegate.java:61)
    at android.view.ViewGroup.drawChild(ViewGroup.java:3404)
    at android.view.ViewGroup.dispatchDraw(ViewGroup.java:3198)
    at android.view.View.draw(View.java:15017)
    at android.view.ViewGroup.drawChild_Original(ViewGroup.java:3404)
    at android.view.ViewGroup_Delegate.drawChild(ViewGroup_Delegate.java:53)
    at android.view.ViewGroup.drawChild(ViewGroup.java:3404)
    at com.sothree.slidinguppanel.SlidingUpPanelLayout.drawChild(SlidingUpPanelLayout.java:1024)
    at android.view.ViewGroup.dispatchDraw(ViewGroup.java:3198)
    at android.view.View.draw(View.java:15017)
    at android.view.ViewGroup.drawChild_Original(ViewGroup.java:3404)
    at android.view.ViewGroup_Delegate.drawChild(ViewGroup_Delegate.java:53)
    at android.view.ViewGroup.drawChild(ViewGroup.java:3404)
    at android.view.ViewGroup.dispatchDraw(ViewGroup.java:3198)
    at android.view.View.draw(View.java:15017)
    at android.view.ViewGroup.drawChild_Original(ViewGroup.java:3404)
    at android.view.ViewGroup_Delegate.drawChild(ViewGroup_Delegate.java:53)
    at android.view.ViewGroup.drawChild(ViewGroup.java:3404)
    at android.view.ViewGroup.dispatchDraw(ViewGroup.java:3198)
    at android.view.View.draw(View.java:15017)
    at android.view.ViewGroup.drawChild_Original(ViewGroup.java:3404)
    at android.view.ViewGroup_Delegate.drawChild(ViewGroup_Delegate.java:53)
    at android.view.ViewGroup.drawChild(ViewGroup.java:3404)
    at android.view.ViewGroup.dispatchDraw(ViewGroup.java:3198)
    at android.view.View.draw(View.java:15117)
    at android.view.View.draw(View.java:15022)
    at android.view.ViewGroup.drawChild_Original(ViewGroup.java:3404)
    at android.view.ViewGroup_Delegate.drawChild(ViewGroup_Delegate.java:53)
    at android.view.ViewGroup.drawChild(ViewGroup.java:3404)
    at android.view.ViewGroup.dispatchDraw(ViewGroup.java:3198)
    at android.view.View.draw(View.java:15117)
    at com.android.layoutlib.bridge.impl.RenderSessionImpl.render(RenderSessionImpl.java:587)
    at com.android.layoutlib.bridge.Bridge.createSession(Bridge.java:334)
    at com.android.ide.common.rendering.LayoutLibrary.createSession(LayoutLibrary.java:350)
    at com.android.tools.idea.rendering.RenderService$5.compute(RenderService.java:688)
    at com.android.tools.idea.rendering.RenderService$5.compute(RenderService.java:677)
    at com.intellij.openapi.application.impl.ApplicationImpl.runReadAction(ApplicationImpl.java:932)
    at com.android.tools.idea.rendering.RenderService.createRenderSession(RenderService.java:677)
    at com.android.tools.idea.rendering.RenderService.render(RenderService.java:815)
    at org.jetbrains.android.uipreview.AndroidLayoutPreviewToolWindowManager.doRender(AndroidLayoutPreviewToolWindowManager.java:646)
    at org.jetbrains.android.uipreview.AndroidLayoutPreviewToolWindowManager.access$1700(AndroidLayoutPreviewToolWindowManager.java:82)
    at org.jetbrains.android.uipreview.AndroidLayoutPreviewToolWindowManager$7$1.run(AndroidLayoutPreviewToolWindowManager.java:589)
    at com.intellij.openapi.progress.impl.ProgressManagerImpl$2.run(ProgressManagerImpl.java:178)
    at com.intellij.openapi.progress.ProgressManager.executeProcessUnderProgress(ProgressManager.java:209)
    at com.intellij.openapi.progress.impl.ProgressManagerImpl.executeProcessUnderProgress(ProgressManagerImpl.java:212)
    at com.intellij.openapi.progress.impl.ProgressManagerImpl.runProcess(ProgressManagerImpl.java:171)
    at org.jetbrains.android.uipreview.AndroidLayoutPreviewToolWindowManager$7.run(AndroidLayoutPreviewToolWindowManager.java:584)
    at com.intellij.util.ui.update.MergingUpdateQueue.execute(MergingUpdateQueue.java:320)
    at com.intellij.util.ui.update.MergingUpdateQueue.execute(MergingUpdateQueue.java:310)
    at com.intellij.util.ui.update.MergingUpdateQueue$2.run(MergingUpdateQueue.java:254)
    at com.intellij.util.ui.update.MergingUpdateQueue.flush(MergingUpdateQueue.java:269)
    at com.intellij.util.ui.update.MergingUpdateQueue.flush(MergingUpdateQueue.java:227)
    at com.intellij.util.ui.update.MergingUpdateQueue.run(MergingUpdateQueue.java:217)
    at com.intellij.util.concurrency.QueueProcessor.runSafely(QueueProcessor.java:238)
    at com.intellij.util.Alarm$Request$1.run(Alarm.java:327)
    at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:471)
    at java.util.concurrent.FutureTask.run(FutureTask.java:262)
    at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1145)
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:615)
    at java.lang.Thread.run(Thread.java:745)