在styles.xml中向按钮添加自定义样式会产生错误

Question

根据这个this教程，每当我尝试复制styles.xml文件中的代码时，只要<style name = " ">属性从AppTheme更改为button_text，它就会给我一个渲染错误 - java。空指针异常。我正在使用Android Studio。

styles.xml：

    <?xml version="1.0" encoding="utf-8" ?>
   <resources>
  <style name="button_text" >
  <item name="android:layout_width" >fill_parent</item>
  <item name="android:layout_height" >wrap_content</item>
  <item name="android:textColor" >#ffffff</item>
  <item name="android:gravity" >center</item>
  <item name="android:layout_margin" >3dp</item>
  <item name="android:textSize" >30dp</item>
  <item name="android:textStyle" >bold</item>
  <item name="android:shadowColor" >#000000</item>
  <item name="android:shadowDx" >1</item>
  <item name="android:shadowDy" >1</item>
  <item name="android:shadowRadius" >2</item>
</style>

错误：

java.lang.NullPointerException
at com.android.layoutlib.bridge.impl.RenderSessionImpl.isThemeAppCompat(RenderSessionImpl.java:1203)
at com.android.layoutlib.bridge.impl.RenderSessionImpl.findStatusBar(RenderSessionImpl.java:1066)
at com.android.layoutlib.bridge.impl.RenderSessionImpl.init(RenderSessionImpl.java:209)
at com.android.layoutlib.bridge.Bridge.createSession(Bridge.java:319)
at com.android.ide.common.rendering.LayoutLibrary.createSession(LayoutLibrary.java:350)
at com.android.tools.idea.rendering.RenderTask$2.compute(RenderTask.java:497)
at com.android.tools.idea.rendering.RenderTask$2.compute(RenderTask.java:485)
at com.intellij.openapi.application.impl.ApplicationImpl.runReadAction(ApplicationImpl.java:894)
at com.android.tools.idea.rendering.RenderTask.createRenderSession(RenderTask.java:485)
at com.android.tools.idea.rendering.RenderTask.render(RenderTask.java:590)
at org.jetbrains.android.uipreview.AndroidLayoutPreviewToolWindowManager.doRender(AndroidLayoutPreviewToolWindowManager.java:644)
at org.jetbrains.android.uipreview.AndroidLayoutPreviewToolWindowManager.access$1700(AndroidLayoutPreviewToolWindowManager.java:79)
at org.jetbrains.android.uipreview.AndroidLayoutPreviewToolWindowManager$7$1.run(AndroidLayoutPreviewToolWindowManager.java:586)
at com.intellij.openapi.progress.impl.CoreProgressManager$2.run(CoreProgressManager.java:152)
at com.intellij.openapi.progress.impl.CoreProgressManager.registerIndicatorAndRun(CoreProgressManager.java:452)
at com.intellij.openapi.progress.impl.CoreProgressManager.executeProcessUnderProgress(CoreProgressManager.java:402)
at com.intellij.openapi.progress.impl.ProgressManagerImpl.executeProcessUnderProgress(ProgressManagerImpl.java:54)
at com.intellij.openapi.progress.impl.CoreProgressManager.runProcess(CoreProgressManager.java:137)
at org.jetbrains.android.uipreview.AndroidLayoutPreviewToolWindowManager$7.run(AndroidLayoutPreviewToolWindowManager.java:581)
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$1.run(Alarm.java:351)
at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:511)
at java.util.concurrent.FutureTask.run(FutureTask.java:266)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
at java.lang.Thread.run(Thread.java:745)

Answer 1

您可以切换渲染目标版本＆lt; 22。

尝试一次。

您可以从这些步骤安装Android版本，如屏幕截图所示。