小编Typ*_*man的帖子

当我在布局中创建 TextClock 小部件时，Android Studio 布局预览显示并没有显示更改。但在调试设计小部件工作完美。如果我评论它布局预览工作成功。另一台 PC Android Studio 工作成功并显示 TextClock。

错误布局预览

java.lang.NullPointerException
at android.content.ContentResolver.registerContentObserver(ContentResolver.java:2263)
at android.widget.TextClock.registerObserver(TextClock.java:626)
at android.widget.TextClock.onAttachedToWindow(TextClock.java:545)
at android.view.View.dispatchAttachedToWindow(View.java:19575)
at android.view.ViewGroup.dispatchAttachedToWindow(ViewGroup.java:3437)
at android.view.ViewGroup.dispatchAttachedToWindow(ViewGroup.java:3437)
at android.view.ViewGroup.dispatchAttachedToWindow(ViewGroup.java:3437)
at android.view.ViewGroup.dispatchAttachedToWindow(ViewGroup.java:3437)
at android.view.ViewGroup.dispatchAttachedToWindow(ViewGroup.java:3437)
at android.view.ViewGroup.dispatchAttachedToWindow(ViewGroup.java:3437)
at android.view.ViewGroup.dispatchAttachedToWindow(ViewGroup.java:3437)
at android.view.AttachInfo_Accessor.setAttachInfo(AttachInfo_Accessor.java:44)
at com.android.layoutlib.bridge.impl.RenderSessionImpl.inflate(RenderSessionImpl.java:355)
at com.android.layoutlib.bridge.Bridge.createSession(Bridge.java:404)
at com.android.tools.idea.layoutlib.LayoutLibrary.createSession(LayoutLibrary.java:141)
at com.android.tools.idea.rendering.RenderTask.createRenderSession(RenderTask.java:657)
at com.android.tools.idea.rendering.RenderTask.lambda$inflate$7(RenderTask.java:788)
at java.util.concurrent.CompletableFuture$AsyncSupply.run(CompletableFuture.java:1590)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
at java.lang.Thread.run(Thread.java:748)

文本时钟 XML 代码

<TextClock
            android:layout_width="120dp"
            android:layout_height="35dp"
            app:layout_constraintBottom_toBottomOf="parent"
            app:layout_constraintEnd_toEndOf="parent"
            app:layout_constraintTop_toTopOf="parent"
            android:layout_marginEnd="16dp"
            android:format24Hour="dd.MMMyyyy, HH:mm"
            android:format12Hour="dd.MMM.yyyy, hh:mm a"
            android:textColor="#d0ffffff"
            android:textSize="30sp" />

更改minSdkVersion为 17 并创建布局 v17 没有给出任何结果。在 Android …