UIAutomator2.0详解（UIDevice篇----waitForWindowUpdate）

书接上文（waitForIdle），我们继续UIDevice的wait方式总结。本篇将着重讲说waitForWindowUpdate方法。

public boolean waitForWindowUpdate(final String packageName, long timeout) 

我们还以上文滑动的测试案例为实验对象。这里只是将相应的waitForIdle换成waitForWindowUpdate方法。

修改后，代码如下：

    String packageName="com.breakloop.test";
    int timeOut=1000;

    @Test
    public void FunctionKeyTest4(){
        Log.i(TAG, "Start Test");
        mDevice.waitForIdle(timeOut);

        int h=mDevice.getDisplayHeight();
        int w=mDevice.getDisplayWidth();

        int left=200;
        int right=w-200;
        int step=50;
        Log.i(TAG, "left = "+left+" Right = "+right);

        //(1)From Right to Left
        Log.i(TAG, "from ("+right+","+h/2+") to ("+left+","+h/2+")");
        result=mDevice.swipe(right, h/2, left, h/2, step);
        Log.i(TAG, "Swipe result (Right to Left) = "+result);
        result = mDevice.waitForWindowUpdate(packageName, timeOut);
        Log.i(TAG, "wait For Window Update, result = " + result);

        //(2)From Left to Right
        Log.i(TAG, "from ("+left+","+h/2+") to ("+right+","+h/2+")");
        result=mDevice.swipe(left, h/2, right, h/2, step);
        Log.i(TAG, "Swipe result (Left to Right) = "+result);
        result = mDevice.waitForWindowUpdate(packageName, timeOut);
        Log.i(TAG, "wait For Window Update, result = " + result);

        //(3)Click
        Log.i(TAG, "Click(300,1000)");
        result=mDevice.click(300, 1000);
        Log.i(TAG, "Click = "+result);
        result = mDevice.waitForWindowUpdate(packageName, timeOut);
        Log.i(TAG, "wait For Window Update, result = " + result);

    }

执行结果如下：

11-08 20:01:42.199 I/com.breakloop.u2demo.uidevice.FingerTest: Start Test
11-08 20:01:42.839 I/com.breakloop.u2demo.uidevice.FingerTest: left = 200 Right = 880
11-08 20:01:42.839 I/com.breakloop.u2demo.uidevice.FingerTest: from (880,906) to (200,906)
11-08 20:01:43.836 I/com.breakloop.u2demo.uidevice.FingerTest: Swipe result (Right to Left) = true
11-08 20:01:45.391 I/com.breakloop.u2demo.uidevice.FingerTest: wait For Window Update, result = false
11-08 20:01:45.391 I/com.breakloop.u2demo.uidevice.FingerTest: from (200,906) to (880,906)
11-08 20:01:46.227 I/com.breakloop.u2demo.uidevice.FingerTest: Swipe result (Left to Right) = true
11-08 20:01:48.400 I/com.breakloop.u2demo.uidevice.FingerTest: wait For Window Update, result = false
11-08 20:01:48.400 I/com.breakloop.u2demo.uidevice.FingerTest: Click(300,1000)
11-08 20:01:48.511 I/com.breakloop.u2demo.uidevice.FingerTest: Click = true

执行效果如下图：

从效果看，与之前采用waitForIdle的效果相同。但从日志里，可以发现，waitForWindowUpdate返回了False。原因在于，packageName与当前运行的App的packageName不相等。这一点可以从方法的源码中得到结论。

那么，如果packageName为null呢？官方文档中给出了说明，即，任何APP的window content update event都会结束等待。

我们将packageName改为null，看一下效果。

运行结果如下：

11-09 23:23:36.709 I/TestRunner: started: FunctionKeyTest4(com.breakloop.u2demo.uidevice.FingerTest)
11-09 23:23:36.711 I/MonitoringInstrumentation: Activities that are still in CREATED to STOPPED: 0
11-09 23:23:36.712 I/com.breakloop.u2demo.uidevice.FingerTest: Start Test
11-09 23:23:37.214 I/com.breakloop.u2demo.uidevice.FingerTest: left = 200 Right = 880
11-09 23:23:37.215 I/com.breakloop.u2demo.uidevice.FingerTest: from (880,906) to (200,906)
11-09 23:23:38.046 I/com.breakloop.u2demo.uidevice.FingerTest: Swipe result (Right to Left) = true
11-09 23:23:38.071 I/com.breakloop.u2demo.uidevice.FingerTest: wait For Window Update, result = true
11-09 23:23:38.071 I/com.breakloop.u2demo.uidevice.FingerTest: from (200,906) to (880,906)
11-09 23:23:38.908 I/com.breakloop.u2demo.uidevice.FingerTest: Swipe result (Left to Right) = true
11-09 23:23:38.981 I/com.breakloop.u2demo.uidevice.FingerTest: wait For Window Update, result = true
11-09 23:23:38.981 I/com.breakloop.u2demo.uidevice.FingerTest: Click(300,1000)
11-09 23:23:39.093 I/com.breakloop.u2demo.uidevice.FingerTest: Click = true
11-09 23:23:39.111 I/com.breakloop.u2demo.uidevice.FingerTest: wait For Window Update, result = true
11-09 23:23:39.112 I/TestRunner: finished: FunctionKeyTest4(com.breakloop.u2demo.uidevice.FingerTest)

从日志里，可以发现，方法返回了true。
从效果上看，第一个滑动动作并没有完成，便开始第二个滑动动作了。因此，waitForWindowUpdate不会像waitForIdle一样，即使出现Idle也等待动作完成，而是只要出现WindowContentUpdate事件便停止等待。

那么，如果出现超时，方法是否会抛出异常呢？我们缩短Timeout的时间，为10毫秒。

效果如下：

执行结果如下：

11-09 23:46:46.690 I/TestRunner: started: FunctionKeyTest4(com.breakloop.u2demo.uidevice.FingerTest)
11-09 23:46:46.693 I/MonitoringInstrumentation: Activities that are still in CREATED to STOPPED: 0
11-09 23:46:46.693 I/com.breakloop.u2demo.uidevice.FingerTest: Start Test
11-09 23:46:47.194 I/com.breakloop.u2demo.uidevice.FingerTest: left = 200 Right = 880
11-09 23:46:47.195 I/com.breakloop.u2demo.uidevice.FingerTest: from (880,906) to (200,906)
11-09 23:46:48.014 I/com.breakloop.u2demo.uidevice.FingerTest: Swipe result (Right to Left) = true
11-09 23:46:48.025 I/com.breakloop.u2demo.uidevice.FingerTest: wait For Window Update, result = false
11-09 23:46:48.025 I/com.breakloop.u2demo.uidevice.FingerTest: from (200,906) to (880,906)
11-09 23:46:48.840 I/com.breakloop.u2demo.uidevice.FingerTest: Swipe result (Left to Right) = true
11-09 23:46:48.851 I/com.breakloop.u2demo.uidevice.FingerTest: wait For Window Update, result = false
11-09 23:46:48.851 I/com.breakloop.u2demo.uidevice.FingerTest: Click(300,1000)
11-09 23:46:48.963 I/com.breakloop.u2demo.uidevice.FingerTest: Click = true
11-09 23:46:48.974 I/com.breakloop.u2demo.uidevice.FingerTest: wait For Window Update, result = false
11-09 23:46:48.975 I/TestRunner: finished: FunctionKeyTest4(com.breakloop.u2demo.uidevice.FingerTest)

从执行效果看，第一个滑动未完成，最后点击操作未完成。点击之所以未完成，是因为测试案例执行结束。

从日志可看，waitForWindowUpdate在超时的情况下，并未抛出异常，而是返回false。但不论返回true或false，都立即执行后面的动作。

最后，再来解决一个核心问题：什么是windowUpdate？
查看方法的源码，可以发现，方法是对AccessibilityEvent.TYPE_WINDOW_CONTENT_CHANGED事件的监听。

而对AccessibilityEvent.TYPE_WINDOW_CONTENT_CHANGED的官方解释是：

represents the event of change in the content of a window. This change can be adding/removing view, changing a view size, etc

即view的添加，移除或大小的改变等。

那么TextView中内容的变化，是否会引发该事件呢？

答案是不会。内容变化应属于控件的状态变化。此前，我们在博文UIAutomator2.0详解（UIDevice篇—-触屏操作2）的实例中，使用过该方法，在输入数据后，可以从执行结果中看到，方法返回值为false，即在未超时的情况下，未发现AccessibilityEvent.TYPE_WINDOW_CONTENT_CHANGED事件。

对于AccessibilityEvent.TYPE_WINDOW_CONTENT_CHANGED的官方解释可参照：
https://developer.android.google.cn/reference/android/view/accessibility/AccessibilityEvent.html