如何使用 WebDriver 检查警报是否存在？

public boolean isAlertPresent()
{
try
{
driver.switchTo().alert();
return true;
}   // try
catch (NoAlertPresentException Ex)
{
return false;
}   // catch
}   // isAlertPresent()

check the link here https://groups.google.com/forum/?fromgroups#!topic/webdriver/1GaSXFK76zY

I would suggest to use ExpectedConditions and alertIsPresent(). ExpectedConditions is a wrapper class that implements useful conditions defined in ExpectedCondition interface.

WebDriverWait wait = new WebDriverWait(driver, 300 /*timeout in seconds*/);
if(wait.until(ExpectedConditions.alertIsPresent())==null)
System.out.println("alert was not present");
else
System.out.println("alert was present");

I found catching exception of driver.switchTo().alert(); is so slow in Firefox (FF V20 & selenium-java-2.32.0).`

So I choose another way:

    private static boolean isDialogPresent(WebDriver driver) {
try {
driver.getTitle();
return false;
} catch (UnhandledAlertException e) {
// Modal dialog showed
return true;
}
}

And it's a better way when most of your test cases is NO dialog present (throwing exception is expensive).

The following (C# implementation, but similar in Java) allows you to determine if there is an alert without exceptions and without creating the WebDriverWait object.

boolean isDialogPresent(WebDriver driver) {
IAlert alert = ExpectedConditions.AlertIsPresent().Invoke(driver);
return (alert != null);
}

I would suggest to use ExpectedConditions and alertIsPresent(). ExpectedConditions is a wrapper class that implements useful conditions defined in ExpectedCondition interface.

public boolean isAlertPresent(){
boolean foundAlert = false;
WebDriverWait wait = new WebDriverWait(driver, 0 /*timeout in seconds*/);
try {
wait.until(ExpectedConditions.alertIsPresent());
foundAlert = true;
} catch (TimeoutException eTO) {
foundAlert = false;
}
return foundAlert;
}

Note: this is based on the answer by nilesh, but adapted to catch the TimeoutException which is thrown by the wait.until() method.

public boolean isAlertPresent() {

try
{
driver.switchTo().alert();
system.out.println(" Alert Present");
}
catch (NoAlertPresentException e)
{
system.out.println("No Alert Present");
}

}

public static void handleAlert(){
if(isAlertPresent()){
Alert alert = driver.switchTo().alert();
System.out.println(alert.getText());
alert.accept();
}
}
public static boolean isAlertPresent(){
try{
driver.switchTo().alert();
return true;
}catch(NoAlertPresentException ex){
return false;
}
}

This code will check whether the alert is present or not.

public static void isAlertPresent(){
try{
Alert alert = driver.switchTo().alert();
System.out.println(alert.getText()+" Alert is Displayed");
}
catch(NoAlertPresentException ex){
System.out.println("Alert is NOT Displayed");
}
}

ExpectedConditions is obsolete, so:

        WebDriverWait wait = new WebDriverWait(driver, TimeSpan.FromSeconds(15));
wait.Until(SeleniumExtras.WaitHelpers.ExpectedConditions.AlertIsPresent());

C# Selenium 'ExpectedConditions is obsolete'