我正在尝试将
AppBarLayout的高度设置为0（并返回默认值）。这会导致崩溃，但只在API 21上发生（>=22等正常工作）。
我使用了如下链接中描述的StateListAnimator（因为它是自从support-lib 24.0.0以来设置高度的“官方”方法）：
https://dev59.com/JFoT5IYBdhLWcg3w8jFm#37992366
我的实际方法如下：
public void setAppBarElevation(final boolean visible) {
if (appBar != null && Build.VERSION.SDK_INT >= Build.VERSION_CODES.LOLLIPOP) {
appBar.setStateListAnimator(AnimatorInflater.loadStateListAnimator(this, (visible) ? R.animator.appbar_elevated : R.animator.appbar_not_elevated));
}
}
与两个XML文件一起使用(另一个设置了android:valueTo="0"):
<?xml version="1.0" encoding="utf-8"?>
<selector xmlns:android="http://schemas.android.com/apk/res/android">
<item>
<objectAnimator android:propertyName="elevation"
android:valueTo="@dimen/default_appbar_elevation"
android:valueType="floatType"/>
</item>
</selector>
我已经测试了一些不同Android版本（API 19、21、23、24、25）的设备，但只有在21上崩溃。
日志显示，在设置高度时出现了一些JNI错误（我想这是来自StateListAnimator）：
--------- beginning of system
JNI DETECTED ERROR IN APPLICATION: cant call void android.view.View.setElevation(float) on null object
in call to CallVoidMethodV
from void android.animation.PropertyValuesHolder.nCallFloatMethod(java.lang.Object, long, float)
"main" prio=5 tid=1 Runnable
| group="main" sCount=0 dsCount=0 obj=0x72fc2000 self=0xf421c500
| sysTid=20172 nice=0 cgrp=apps sched=0/0 handle=0xf77de160
| state=R schedstat=( 3803514732 320072004 1563 ) utm=340 stm=40 core=0 HZ=100
| stack=0xff6fb000-0xff6fd000 stackSize=8MB
| held mutexes= "mutator lock"(shared held)
native: #00 pc 00005b13 /system/lib/libbacktrace_libc++.so (UnwindCurrent::Unwind(unsigned int, ucontext*)+83)
native: #01 pc 00002e92 /system/lib/libbacktrace_libc++.so (Backtrace::Unwind(unsigned int, ucontext*)+34)
native: #02 pc 003c8f68 /system/lib/libart.so (art::DumpNativeStack(std::__1::basic_ostream<char, std::__1::char_traits<char> >&, int, char const*, art::mirror::ArtMethod*)+136)
native: #03 pc 00391f8d /system/lib/libart.so (art::Thread::Dump(std::__1::basic_ostream<char, std::__1::char_traits<char> >&) const+285)
native: #04 pc 001006b0 /system/lib/libart.so (art::JniAbort(char const*, char const*)+1024)
native: #05 pc 0010125f /system/lib/libart.so (art::JniAbortF(char const*, char const*, ...)+111)
native: #06 pc 001016b2 /system/lib/libart.so (art::ScopedCheck::CheckVirtualMethod(_jobject*, _jmethodID*)+514)
native: #07 pc 00112340 /system/lib/libart.so (art::CheckJNI::CallVoidMethodV(_JNIEnv*, _jobject*, _jmethodID*, char*)+144)
native: #08 pc 000776ca /system/lib/libandroid_runtime.so (_JNIEnv::CallVoidMethod(_jobject*, _jmethodID*, ...)+42)
native: #09 pc 00123ecb /system/lib/libandroid_runtime.so (???)
native: #10 pc 00089596 /data/dalvik-cache/x86/system@framework@boot.oat (Java_android_animation_PropertyValuesHolder_nCallFloatMethod__Ljava_lang_Object_2JF+174)
at android.animation.PropertyValuesHolder.nCallFloatMethod(Native method)
at android.animation.PropertyValuesHolder.access$400(PropertyValuesHolder.java:38)
at android.animation.PropertyValuesHolder$FloatPropertyValuesHolder.setAnimatedValue(PropertyValuesHolder.java:1296)
at android.animation.ObjectAnimator.animateValue(ObjectAnimator.java:952)
at android.animation.ValueAnimator.animationFrame(ValueAnimator.java:1207)
at android.animation.ValueAnimator.doAnimationFrame(ValueAnimator.java:1248)
at android.animation.ValueAnimator$AnimationHandler.doAnimationFrame(ValueAnimator.java:659)
at android.animation.ValueAnimator$AnimationHandler.run(ValueAnimator.java:682)
at android.view.Choreographer$CallbackRecord.run(Choreographer.java:767)
at android.view.Choreographer.doCallbacks(Choreographer.java:580)
at android.view.Choreographer.doFrame(Choreographer.java:549)
at android.view.Choreographer$FrameDisplayEventReceiver.run(Choreographer.java:753)
at android.os.Handler.handleCallback(Handler.java:739)
at android.os.Handler.dispatchMessage(Handler.java:95)
at android.os.Looper.loop(Looper.java:135)
at android.app.ActivityThread.main(ActivityThread.java:5219)
at java.lang.reflect.Method.invoke!(Native method)
at java.lang.reflect.Method.invoke(Method.java:372)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:899)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:694)
有没有一种方法可以使用当前的Support-Library（我目前正在使用25.0.0，但使用24.x.x会崩溃）来隐藏AppBar的阴影（并重新启用它）？