cannot find symbol unityplayeractivity while building WebViewPlugin-*.aar.tmpl

Hi,
I'm trying to build the WebViewPlugin-*.aar.tmpl. But I'm running into this build error.
Would it be possible to help me fix this ?

Thank you in advance.

> Task :webview:compileReleaseJavaWithJavac FAILED
F:\unity-webview\plugins\Android\webview\src\main\java\net\gree\unitywebview\CUnityPlayerActivity.java:7: error: cannot find symbol
    extends UnityPlayerActivity
            ^
  symbol: class UnityPlayerActivity
F:\unity-webview\plugins\Android\webview\src\main\java\net\gree\unitywebview\CUnityPlayerActivity.java:9: error: method does not override or implement a method from a supertype
    @Override
    ^
F:\unity-webview\plugins\Android\webview\src\main\java\net\gree\unitywebview\CUnityPlayerActivity.java:11: error: cannot find symbol
        requestWindowFeature(1);
        ^
  symbol:   method requestWindowFeature(int)
  location: class CUnityPlayerActivity
F:\unity-webview\plugins\Android\webview\src\main\java\net\gree\unitywebview\CUnityPlayerActivity.java:12: error: cannot find symbol
        super.onCreate(bundle);
        ^
  symbol:   variable super
  location: class CUnityPlayerActivity
F:\unity-webview\plugins\Android\webview\src\main\java\net\gree\unitywebview\CUnityPlayerActivity.java:13: error: cannot find symbol
        getWindow().setFormat(2);
        ^
  symbol:   method getWindow()
  location: class CUnityPlayerActivity
F:\unity-webview\plugins\Android\webview\src\main\java\net\gree\unitywebview\CUnityPlayerActivity.java:14: error: cannot find symbol
        mUnityPlayer = new CUnityPlayer(this);
        ^
  symbol:   variable mUnityPlayer
  location: class CUnityPlayerActivity
F:\unity-webview\plugins\Android\webview\src\main\java\net\gree\unitywebview\CUnityPlayerActivity.java:14: error: incompatible types: CUnityPlayerActivity cannot be converted to ContextWrapper
        mUnityPlayer = new CUnityPlayer(this);
                                        ^
F:\unity-webview\plugins\Android\webview\src\main\java\net\gree\unitywebview\CUnityPlayerActivity.java:15: error: cannot find symbol
        setContentView(mUnityPlayer);
                       ^
  symbol:   variable mUnityPlayer
  location: class CUnityPlayerActivity
F:\unity-webview\plugins\Android\webview\src\main\java\net\gree\unitywebview\CUnityPlayerActivity.java:16: error: cannot find symbol
        mUnityPlayer.requestFocus();
        ^
  symbol:   variable mUnityPlayer
  location: class CUnityPlayerActivity
Note: F:\unity-webview\plugins\Android\webview\src\main\java\net\gree\unitywebview\CWebViewPlugin.java uses or overrides a deprecated API.
Note: Recompile with -Xlint:deprecation for details.
Note: Some messages have been simplified; recompile with -Xdiags:verbose to get full output
9 errors

FAILURE: Build failed with an exception.

* What went wrong:
Execution failed for task ':webview:compileReleaseJavaWithJavac'.
> Compilation failed; see the compiler error output for details.

* Try:
Run with --stacktrace option to get the stack trace. Run with --info or --debug option to get more log output. Run with --scan to get full insights.

* Get more help at https://help.gradle.org

Start with plugins/Android/webview/src/main/java/net/gree/unitywebview/CUnityPlayerActivity.java and the :webview:compileReleaseJavaWithJavac failure shown in the report. Inspect how UnityPlayerActivity is supplied during the WebViewPlugin build, then rerun the release compilation. Done means the WebViewPlugin AAR template builds without the missing-symbol errors.