ShadowCountDownTimer not work

[WingsII]

Description

If CountDownTimer is used in the code, robolectric will automatically use ShadowCountDownTimer, I found that it cannot trigger onTick() callback. And its internal data (mHandler, etc.) are empty.

If I use the original CountDownTimer object, or a custom empty Shadow object, this problem does not occur. Member variables are also normal.

Steps to Reproduce

Create a CountDownTimer in the Test case and run timer.start(), its member variables are empty, and will not trigger onTick.

Robolectric & Android Version

Robolectric : 4.2.1
JDK 1.8.0_332

Link to a public git repo demonstrating the problem:

NA

[utzcoz]

Hi @WingsII , 4.2.1 is old in a sense. Could you try latest 4.8.1 to check whether this problem was fixed? I remember there are some fixes were checked in for time. Looking forward your feedback. Thanks.

[WingsII]

Hi @WingsII , 4.2.1 is old in a sense. Could you try latest 4.8.1 to check whether this problem was fixed? I remember there are some fixes were checked in for time. Looking forward your feedback. Thanks.

After testing, this problem still exists on the latest version.

Robolectric & Android Version

Robolectric : 4.8.1
JDK 11.0.11

[hoisie]

Ah good catch. I notice that ShadowCountDownTimer's __constructor__ shadow method does not invoke the original constructor. This ruins the normal object initialization process and leaves a lot of the members uninitialized. It should have a call to Shadow.invokeConstructor.

https://github.com/robolectric/robolectric/blob/master/shadows/framework/src/main/java/org/robolectric/shadows/ShadowCountDownTimer.java

[hoisie]

@WingsII from the shadow API it appears thata you have to call ShadowCountDownTimer.invokeTick:

https://github.com/robolectric/robolectric/blob/master/shadows/framework/src/main/java/org/robolectric/shadows/ShadowCountDownTimer.java#L34-L36

[hoisie]

Looks like the real code uses SystemClock.elapsedRealtime(), which gives a virtual/fake time in Robolectric. However, it should be possible to idle the scheduler to invoke the ticks.

[WingsII]

Looks like the real code uses SystemClock.elapsedRealtime(), which gives a virtual/fake time in Robolectric. However, it should be possible to idle the scheduler to invoke the ticks.

There are several points:

1. In the real environment, CountDownTimer is a local variable and cannot be called directly.

2. I tried to write ShadowLooper.idleMainLooper(*) but it still doesn't work actually, because the internal variable mHandler is null.

3. According to the source code, if it is initialized correctly, CountDownTimer::onTick() will be called once when start() is used.

4. Why doesn't ShadowCountDownTimer invoke the original constructor when it initializes. Is this a bug or is there some reason? Will it be fixed later?

[hoisie]

Why doesn't ShadowCountDownTimer invoke the original constructor when it initializes. Is this a bug or is there some reason? Will it be fixed later?

It is because the constructor of CountDownTimer is shadowed in ShadowCountDownTimer (the __constructor__ method). I would agree that this is a bug. The __constructor__ method should call the original constructor as well.

[hoisie]

Specifically, the constructor should probably be doing this:

  @Implementation
  protected void __constructor__(long millisInFuture, long countDownInterval) {
    this.countDownInterval = countDownInterval;
    this.millisInFuture = millisInFuture;
    this.started = false;
    // call the original constructor
    Shadow.invokeConstructor(
        CountDownTimer.class,
        countDownTimer,
        ClassParameter.from(long.class, millisInFuture),
        ClassParameter.from(long.class, countDownInterval));
  }

[WingsII]

Specifically, the constructor should probably be doing this:

  @Implementation
  protected void __constructor__(long millisInFuture, long countDownInterval) {
    this.countDownInterval = countDownInterval;
    this.millisInFuture = millisInFuture;
    this.started = false;
    // call the original constructor
    Shadow.invokeConstructor(
        CountDownTimer.class,
        countDownTimer,
        ClassParameter.from(long.class, millisInFuture),
        ClassParameter.from(long.class, countDownInterval));
  }

It works, great!