popupwindow实现按钮下方阴影

popupwindow弹窗实现点击按钮，下方弹出popwindow，并且只是按钮下方有阴影，按钮以及上方没有阴影

/**
 * Automatically generated file. DO NOT MODIFY
 */
package com.example.wpl.popdemo;

public final class BuildConfig {
  public static final boolean DEBUG = Boolean.parseBoolean（“true“）;
  public static final String APPLICATION_ID = “com.example.wpl.popdemo“;
  public static final String BUILD_TYPE = “debug“;
  public static final String FLAVOR = ““;
  public static final int VERSION_CODE = 1;
  public static final String VERSION_NAME = “1.0“;
}

 属性            大小     日期    时间   名称
----------- ---------  ---------- -----  ----

     文件        147  2018-09-07 08:36  popDemo\.gitignore

     文件          1  2018-09-07 09:57  popDemo\.gradle\4.4\fileChanges\last-build.bin

     文件         17  2018-09-07 09:57  popDemo\.gradle\4.4\fileContent\fileContent.lock

     文件     261569  2018-09-07 09:56  popDemo\.gradle\4.4\fileHashes\fileHashes.bin

     文件         17  2018-09-07 09:57  popDemo\.gradle\4.4\fileHashes\fileHashes.lock

     文件      20809  2018-09-07 09:56  popDemo\.gradle\4.4\fileHashes\resourceHashesCache.bin

     文件     760471  2018-09-07 09:56  popDemo\.gradle\4.4\javaCompile\classAnalysis.bin

     文件     312679  2018-09-07 09:56  popDemo\.gradle\4.4\javaCompile\jarAnalysis.bin

     文件         17  2018-09-07 09:56  popDemo\.gradle\4.4\javaCompile\javaCompile.lock

     文件     198808  2018-09-07 09:56  popDemo\.gradle\4.4\javaCompile\taskHistory.bin

     文件      28538  2018-09-07 09:56  popDemo\.gradle\4.4\javaCompile\taskJars.bin

     文件    2425818  2018-09-07 09:57  popDemo\.gradle\4.4\taskHistory\taskHistory.bin

     文件         17  2018-09-07 09:57  popDemo\.gradle\4.4\taskHistory\taskHistory.lock

     文件         17  2018-09-07 09:57  popDemo\.gradle\buildOutputCleanup\buildOutputCleanup.lock

     文件         51  2018-09-07 08:36  popDemo\.gradle\buildOutputCleanup\cache.properties

     文件      20819  2018-09-07 09:57  popDemo\.gradle\buildOutputCleanup\outputFiles.bin

     文件        535  2018-09-07 09:56  popDemo\.idea\caches\build_file_checksums.ser

     文件       1803  2018-09-07 08:36  popDemo\.idea\codestyles\Project.xml

     文件        626  2018-09-07 08:36  popDemo\.idea\gradle.xml

     文件        541  2018-09-07 08:36  popDemo\.idea\libraries\Gradle__android_arch_core_common_1_1_1_jar.xml

     文件        655  2018-09-07 08:36  popDemo\.idea\libraries\Gradle__android_arch_core_runtime_1_1_1.xml

     文件        556  2018-09-07 08:36  popDemo\.idea\libraries\Gradle__android_arch_lifecycle_common_1_1_1_jar.xml

     文件        695  2018-09-07 08:36  popDemo\.idea\libraries\Gradle__android_arch_lifecycle_livedata_core_1_1_1.xml

     文件        666  2018-09-07 08:36  popDemo\.idea\libraries\Gradle__android_arch_lifecycle_runtime_1_1_1.xml

     文件        676  2018-09-07 08:36  popDemo\.idea\libraries\Gradle__android_arch_lifecycle_viewmodel_1_1_1.xml

     文件        537  2018-09-07 08:36  popDemo\.idea\libraries\Gradle__com_android_support_animated_vector_drawable_28_0_0_rc02.xml

     文件        501  2018-09-07 08:36  popDemo\.idea\libraries\Gradle__com_android_support_appcompat_v7_28_0_0_rc02.xml

     文件        522  2018-09-07 08:36  popDemo\.idea\libraries\Gradle__com_android_support_asynclayoutinflater_28_0_0_rc02.xml

     文件        390  2018-09-07 08:36  popDemo\.idea\libraries\Gradle__com_android_support_collections_28_0_0_rc02_jar.xml

     文件        509  2018-09-07 08:36  popDemo\.idea\libraries\Gradle__com_android_support_constraint_constraint_layout_1_1_3.xml

............此处省略2998个文件信息