iOS UI中元素的lastSnapshot中子元素的屬性測試始終爲空，爲什麼？

Question

我正在研究UI測試框架WebDriverAgent來自facebook。這非常棒，樂於助人。它幾乎包含iOS UI測試的所有知識。

XCTest有許多未公開的類和屬性。例如，XCUIElement有一個名爲lastSnapshot屬性，lastSnapshot還具有許多有用的特性，如標籤，標識符，幀，父，孩子，pathDescription，等。問題如下：

孩子屬性用於從某個元素中獲取所有子元素，就像從視圖中的子視圖一樣。但是，當我試圖從元素的lastSnapshot中獲取子項的值時，它始終爲空。雖然我可以正確地得到其他屬性的值，如標籤，標識符，父母等，這讓我困擾了好幾天。這裏的exapmle代碼：

- (void)testExample { 
    XCUIApplication *app = [[XCUIApplication alloc] init]; 
    XCUIElement *windowElement = [app.windows elementBoundByIndex:2]; 
    XCUIElement *statusBarElement = [windowElement.query elementBoundByIndex:0]; 
    XCUIElement *otherElement = [statusBarElement.query elementBoundByIndex:1]; 
    XCUIElement *timeElement = [otherElement.query elementBoundByIndex:2]; 

    [timeElement query]; 
    [timeElement resolve]; 
    NSLog(@"lastSnapshot = %@", timeElement.lastSnapshot); 
    NSLog(@"children = %@", timeElement.lastSnapshot.children); 
} 

Answer 1

STUDING WebDriverAgent之前，我用XCUIElement的一類遞歸元素樹：

- (XCUIElementNode *)recursiveUIElementsWithLevel:(NSInteger)elementLevel { 
    XCUIElementNode *node = [XCUIElementNode new]; 
    node.elementLevel = elementLevel; 
    node.elementValue = self; 
    NSArray *arrayNotIncludeSelf = [self recursiveUIElementsNotIncludeSelfWithLevel:elementLevel]; 
    node.subNodes = [NSMutableArray arrayWithArray:arrayNotIncludeSelf]; 

    return node; 
} 

- (NSArray *)recursiveUIElementsNotIncludeSelfWithLevel:(NSInteger)elementLevel { 
    NSMutableArray *elementArray = [NSMutableArray new]; 

    XCUIElementQuery *childrenQuery = [self childrenMatchingType:XCUIElementTypeAny]; 

    for (NSUInteger elementIndex = 0; elementIndex < childrenQuery.count; elementIndex ++) { 
     XCUIElement *element = [childrenQuery elementBoundByIndex:elementIndex]; 
     XCUIElementNode *subNode = [XCUIElementNode new]; 
     subNode.elementLevel = elementLevel + 1; 
     subNode.elementValue = element; 
     subNode.subNodes = [NSMutableArray arrayWithArray:[element recursiveUIElementsNotIncludeSelfWithLevel:subNode.elementLevel]]; 
     [elementArray addObject:subNode]; 
    } 

    return [NSArray arrayWithArray:elementArray]; 
} 

它通過這種方式doese工作，但遞歸遍歷經驗需要很多時間不能被接受。