android setVisibility(LinearLayout.VISIBLE)在WebView @JavascriptInterface函数中不起作用

Handler handler = new Handler(Looper.getMainLooper()) {
    @Override
    public void handleMessage(Message msg) {
        // 在这里进行UI操作
        if (msg.what == 1) {
            LinearLayout layout = findViewById(R.id.layout);
            layout.setVisibility(View.VISIBLE);
        }
    }
};

@JavascriptInterface
public void showLayout() {
    Message message = new Message();
    message.what = 1;
    handler.sendMessage(message);
}

webView.addJavascriptInterface(new JavaScriptInterface(), "Android");

<script>
    function showLayout() {
        Android.showLayout();
    }
</script>