在使用espresso进行测试的时候，点击一个横向列表的时候会在点击的项目下出现对应的横线。
实现方式是在FrameLayout下放两个TextView,
一个TextView包含下划线，默认是FrameLayout的第一个元素；
一个TextView不包含下划线，默认是FrameLayout的第二个元素；
两个元素大小一致，当选中时，切换1,2两个TextView的属性。
espresso使用的matcher为：
Matcher<View> viewLabel = allOf(withClassName(endsWith("TextView")), isNotCoveredByBothers(), withAlpha(1.0f), isDisplayed(), isDescendantOfA(withId(TABS)));
TABS是列表的祖先元素。
查看代码发现 两个TextView 区别就是 Alpha 值不一样，有下划线的 Alpha 值为1.0.（设置这个值为什么会有这样的下划线）。
/**
* isNotCoveredByBothers
* @return
*/
public static Matcher<View> isNotCoveredByBothers() {
return new TypeSafeMatcher<View>() {
@Override
public void describeTo(Description description) {
description.appendText("is displayed on the screen to the user");
} @Override
public boolean matchesSafely(View view) {
return view.getGlobalVisibleRect(new Rect())
&& !isViewCoveredBybrothers(view);
}
};
} /**
* 检查一个包含父控件的view是否被后面的兄弟遮挡
* 检查一个包含父控件的view是否被后面的兄弟遮挡
* @param view
* @return
*/
public static boolean isViewCoveredBybrothers(final View view) {
View currentView = view;
if (currentView.getParent() == null) {
//无父控件,当作未遮挡
return false;
}
if (currentView.getParent() instanceof ViewGroup) {
ViewGroup currentParent = (ViewGroup) currentView.getParent();
// if the parent of view is not visible,return true
if (currentParent.getVisibility() != View.VISIBLE) {
//父控件不可见
return true;
} int start = indexOfViewInParent(currentView, currentParent);
for (int i = start + 1; i < currentParent.getChildCount(); i++) {
Rect viewRect = new Rect();
view.getGlobalVisibleRect(viewRect);
View otherView = currentParent.getChildAt(i);
Rect otherViewRect = new Rect();
otherView.getGlobalVisibleRect(otherViewRect);
// if view intersects its older brother(covered),return true
if (Rect.intersects(viewRect, otherViewRect)) {
return true;
}
}
}
return false;
} /**
* view在parent的index
* @param view
* @param parent
* @return
*/
private static int indexOfViewInParent(View view, ViewGroup parent) {
int index;
for (index = 0; index < parent.getChildCount(); index++) {
if (parent.getChildAt(index) == view) {
break;
}
}
return index;
}