将进度手动设置为MotionLayout时，它将清除所有约束

问题描述

我的MotionLayout有两个小部件，一个在MotionLayout中描述，第二个在场景文件中.

I have MotionLayout with two widgets, one is described in MotionLayout, second - in scene file.

布局文件:

<android.support.constraint.motion.MotionLayout 
    xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    android:id="@+id/motion_layout"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    app:layoutDescription="@xml/scene_test">

    <View
        android:id="@+id/test_view_static"
        android:layout_width="40dp"
        android:layout_height="40dp"
        android:background="#ff0000"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintLeft_toLeftOf="parent"
        app:layout_constraintRight_toRightOf="parent"
        app:layout_constraintTop_toTopOf="parent" />

    <View
        android:id="@+id/test_view_dynamic"
        android:layout_width="40dp"
        android:layout_height="40dp"
        android:background="#00ff11" />

</android.support.constraint.motion.MotionLayout>

场景文件:

<MotionScene xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:android="http://schemas.android.com/apk/res/android">

    <Transition
        app:constraintSetStart="@+id/start"
        app:constraintSetEnd="@+id/end"/>

    <ConstraintSet android:id="@id/start">

        <Constraint
            android:id="@+id/test_view_dynamic"
            android:layout_width="40dp"
            android:layout_height="40dp"
            app:layout_constraintRight_toRightOf="parent"
            app:layout_constraintTop_toTopOf="parent" />

    </ConstraintSet>

    <ConstraintSet android:id="@id/end">

        <Constraint
            android:id="@id/test_view_dynamic"
            android:layout_width="40dp"
            android:layout_height="40dp"
            app:layout_constraintRight_toRightOf="parent"
            app:layout_constraintBottom_toBottomOf="parent" />

    </ConstraintSet>

</MotionScene>

然后在活动中我设定进度:

Then in activity i set progress:

//onCreate, etc..
MotionLayout motionLayout = findViewById(R.id.motion_layout);
motionLayout.setProgress(0.5f);

动态视图位于正确的位置，但是静态视图失去了所有约束，但不受场景的影响，如在这里，仅场景文件中描述的窗口小部件应受到影响.

Dynamic view is on right position, but static view loses all constraints, but it is not affected by scene, as described here, only the widget described in the scene file should be affected.

库版本:

implementation 'com.android.support:appcompat-v7:27.1.1'
implementation 'com.android.support.constraint:constraint-layout:2.0.0-alpha2'

此处的示例项目: https://github.com/Anrimian/MotionLayoutIssueTest

更新:感谢Kélian的回答我找到了解决方法:

Upd: Thanks for Kélian's answer I found solution:

public static void setProgress(MotionLayout motionLayout, float progress) {
    if (ViewCompat.isLaidOut(motionLayout)) {
        motionLayout.setProgress(progress);
    } else {
        motionLayout.post(() -> motionLayout.setProgress(progress));
    }
}

推荐答案

这很奇怪，布局检查器显示 test_view_static size:宽度= 0和高度= 0.

This is weird, layout inspector show test_view_static size : width = 0 and height = 0.

我对您的代码进行了一些更新:在onCreate中，在 test_view_static 上添加一个点击侦听器以执行进度，并且效果很好.

I updated a bit your code : in onCreate add a click listener on test_view_static to perform the progress and it worked fine.

我尝试了另一件事:在我放入的onStart()方法中:

I tried another thing : in onStart() method i put :

Handler handler = new Handler();
handler.postDelayed(new Runnable() {
    public void run() {
        MotionLayout motionLayout = findViewById(R.id.motion_layout);
        motionLayout.setProgress(0.5f);
    }
}, 1000);

和MotionLayout的行为符合预期.就像您必须等待MotionLayout初始化之后才能更新进度一样.

and the MotionLayout behave expectedely. It's like you have to wait the MotionLayout to be initialized before updating it's progress.

实际上，您想要具有您在场景中描述的另一种开始布局.您可以执行以下操作，而无需使用:

In fact you want to have another start layout that the one you discribed in the scene. You could do this without updating the progress with :

<ConstraintSet android:id="@id/start">
    <Constraint
        android:id="@+id/test_view_dynamic"
        android:layout_width="40dp"
        android:layout_height="40dp"
        motion:layout_constraintRight_toRightOf="parent"
        motion:layout_constraintTop_toTopOf="parent"
        motion:layout_constraintBottom_toBottomOf="parent" />
</ConstraintSet>

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