After switch to webview context i am unable to click child button ellement in ios app web view page

Hai,
Can any one please help me to solve out,in my ios application i have to test web view page,i am able switch web view context in my case,after switch the web view context i am unable to click child button element.can any one please help me

below is the html code

below is my code please correct it:

List el = d.findElements(By.xpath("//div[@class=‘stxt resizable draggable txtblock book0 ui-resizable ui-draggable uneblock ui-draggable-disabled ui-state-disabled’]//*"));
for(int i =0;i<el.size();i++){
WebElement webele = (WebElement) el.get(i);

			   String bookname=webele.getAttribute("class");

System.out.println(bookname);
if(bookname.contains(“stxt edit-button ui-unconvert-btn”)) {
webele.click();

        break;
        }
        
        }

when i trie with above code i am getting selenium.webdriver exception