android - NullPointerException 上下文兼容错误

Question

我创建了一个自定义组件，将其添加到布局时出现以下错误

错误如下

java.lang.NullPointerException
    at android.support.v4.content.ContextCompatApi21.getDrawable(ContextCompatApi21.java:26)
    at android.support.v4.content.ContextCompat.getDrawable(ContextCompat.java:321)
    at com.test.digitalexperience.widget.testTicketLoaderWidget.createDrawables(testTicketLoaderWidget.java:101)
    at com.test.digitalexperience.widget.testTicketLoaderWidget.init(testTicketLoaderWidget.java:69)
    at com.test.digitalexperience.widget.testTicketLoaderWidget.<init>(testTicketLoaderWidget.java:52)
    at com.test.digitalexperience.widget.testTicketLoaderWidget.<init>(testTicketLoaderWidget.java:44)
    at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
    at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:57)
    at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45)
    at java.lang.reflect.Constructor.newInstance(Constructor.java:526)
    at org.jetbrains.android.uipreview.ViewLoader.createNewInstance(ViewLoader.java:465)
    at org.jetbrains.android.uipreview.ViewLoader.loadClass(ViewLoader.java:172)
    at org.jetbrains.android.uipreview.ViewLoader.loadView(ViewLoader.java:105)
    at com.android.tools.idea.rendering.LayoutlibCallbackImpl.loadView(LayoutlibCallbackImpl.java:170)
    at android.view.BridgeInflater.loadCustomView(BridgeInflater.java:247)
    at android.view.BridgeInflater.createViewFromTag(BridgeInflater.java:171)
    at android.view.LayoutInflater.createViewFromTag(LayoutInflater.java:704)
    at android.view.LayoutInflater.rInflate_Original(LayoutInflater.java:835)
    at android.view.LayoutInflater_Delegate.rInflate(LayoutInflater_Delegate.java:70)
    at android.view.LayoutInflater.rInflate(LayoutInflater.java:811)
    at android.view.LayoutInflater.rInflateChildren(LayoutInflater.java:798)
    at android.view.LayoutInflater.inflate(LayoutInflater.java:515)
    at android.view.LayoutInflater.inflate(LayoutInflater.java:394)
    at com.android.layoutlib.bridge.impl.RenderSessionImpl.inflate(RenderSessionImpl.java:223)
    at com.android.layoutlib.bridge.Bridge.createSession(Bridge.java:426)
    at com.android.ide.common.rendering.LayoutLibrary.createSession(LayoutLibrary.java:350)
    at com.android.tools.idea.rendering.RenderTask$2.compute(RenderTask.java:510)
    at com.android.tools.idea.rendering.RenderTask$2.compute(RenderTask.java:498)
    at com.intellij.openapi.application.impl.ApplicationImpl.runReadAction(ApplicationImpl.java:967)
    at com.android.tools.idea.rendering.RenderTask.createRenderSession(RenderTask.java:498)
    at com.android.tools.idea.rendering.RenderTask.access$600(RenderTask.java:72)
    at com.android.tools.idea.rendering.RenderTask$3.call(RenderTask.java:610)
    at com.android.tools.idea.rendering.RenderTask$3.call(RenderTask.java:607)
    at com.android.tools.idea.rendering.RenderService.runRenderAction(RenderService.java:359)
    at com.android.tools.idea.rendering.RenderTask.render(RenderTask.java:607)
    at com.android.tools.idea.rendering.RenderTask.render(RenderTask.java:629)
    at org.jetbrains.android.uipreview.AndroidLayoutPreviewToolWindowManager.doRender(AndroidLayoutPreviewToolWindowManager.java:652)
    at org.jetbrains.android.uipreview.AndroidLayoutPreviewToolWindowManager.access$1700(AndroidLayoutPreviewToolWindowManager.java:80)
    at org.jetbrains.android.uipreview.AndroidLayoutPreviewToolWindowManager$7$1.run(AndroidLayoutPreviewToolWindowManager.java:594)
    at com.intellij.openapi.progress.impl.CoreProgressManager$2.run(CoreProgressManager.java:142)
    at com.intellij.openapi.progress.impl.CoreProgressManager.registerIndicatorAndRun(CoreProgressManager.java:446)
    at com.intellij.openapi.progress.impl.CoreProgressManager.executeProcessUnderProgress(CoreProgressManager.java:392)
    at com.intellij.openapi.progress.impl.ProgressManagerImpl.executeProcessUnderProgress(ProgressManagerImpl.java:54)
    at com.intellij.openapi.progress.impl.CoreProgressManager.runProcess(CoreProgressManager.java:127)
    at org.jetbrains.android.uipreview.AndroidLayoutPreviewToolWindowManager$7.run(AndroidLayoutPreviewToolWindowManager.java:589)
    at com.intellij.util.ui.update.MergingUpdateQueue.execute(MergingUpdateQueue.java:337)
    at com.intellij.util.ui.update.MergingUpdateQueue.execute(MergingUpdateQueue.java:327)
    at com.intellij.util.ui.update.MergingUpdateQueue$3.run(MergingUpdateQueue.java:271)
    at com.intellij.util.ui.update.MergingUpdateQueue.flush(MergingUpdateQueue.java:286)
    at com.intellij.util.ui.update.MergingUpdateQueue.flush(MergingUpdateQueue.java:244)
    at com.intellij.util.ui.update.MergingUpdateQueue.run(MergingUpdateQueue.java:234)
    at com.intellij.util.concurrency.QueueProcessor.runSafely(QueueProcessor.java:238)
    at com.intellij.util.Alarm$Request$1.run(Alarm.java:352)
    at java.util.concurrent.Executors$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)

在我的 java 类中我导入了

android.support.v4.content.ContextCompat;

在我添加的依赖项中

dependencies {
    compile 'com.android.support:appcompat-v7:23.1.0'    
}

我用的是gradle版本

com.android.tools.build:gradle:2.0.0

自定义组件小部件代码

http://pastebin.com/nWn46qA3

Answer 1

在构造函数中初始化 mContext 之前调用了 init(Context context, AttributeSet attributeSet) 方法。