ConstraintLayout：以编程方式更改约束

Question

我需要ConstraintSet的帮助。我的目标是在代码中更改视图的约束，但我无法弄清楚如何正确执行此操作。

我有4个TextViews和一个ImageView。我需要将ImageView约束设置为其中一个TextViews。

check_answer4 = (TextView) findViewById(R.id.check_answer4);
check_answer1 = (TextView) findViewById(R.id.check_answer1);
check_answer2 = (TextView) findViewById(R.id.check_answer2);
check_answer3 = (TextView) findViewById(R.id.check_answer3);

correct_answer_icon = (ImageView) findViewById(R.id.correct_answer_icon);

如果第一个答案是正确的，我需要设置ImageView的约束

app:layout_constraintRight_toRightOf="@+id/check_answer1"
app:layout_constraintTop_toTopOf="@+id/check_answer1"

如果第二个答案是正确的，我需要设置ImageView的约束

app:layout_constraintRight_toRightOf="@+id/check_answer2"
app:layout_constraintTop_toTopOf="@+id/check_answer2"

等等。

Answer 1

1. 要将图像视图的约束设置为：

   app:layout_constraintRight_toRightOf="@+id/check_answer1"
   app:layout_constraintTop_toTopOf="@+id/check_answer1"

   使用：

   ConstraintSet constraintSet = new ConstraintSet();
   constraintSet.clone(constraintLayout);
   constraintSet.connect(R.id.imageView,ConstraintSet.RIGHT,R.id.check_answer1,ConstraintSet.RIGHT,0);
   constraintSet.connect(R.id.imageView,ConstraintSet.TOP,R.id.check_answer1,ConstraintSet.TOP,0);
   constraintSet.applyTo(constraintLayout);

2. 要将图像视图的约束设置为：

   app:layout_constraintRight_toRightOf="@+id/check_answer2"
   app:layout_constraintTop_toTopOf="@+id/check_answer2"

   使用：

   ConstraintSet constraintSet = new ConstraintSet();
   constraintSet.clone(constraintLayout); 
   constraintSet.connect(R.id.imageView,ConstraintSet.RIGHT,R.id.check_answer2,ConstraintSet.RIGHT,0);      
   constraintSet.connect(R.id.imageView,ConstraintSet.TOP,R.id.check_answer2,ConstraintSet.TOP,0);
   constraintSet.applyTo(constraintLayout);

Answer 2

假设我们想在运行时更改约束，使button1在单击时与button2对齐：

然后，有这个布局：

<android.support.constraint.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:id="@+id/root"
    android:paddingBottom="@dimen/activity_vertical_margin"
    android:paddingLeft="@dimen/activity_horizontal_margin"
    android:paddingRight="@dimen/activity_horizontal_margin"
    android:paddingTop="@dimen/activity_vertical_margin">


    <Button
        android:id="@+id/button1"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Button 1"
        app:layout_constraintTop_toTopOf="@+id/button3"
        app:layout_constraintBottom_toBottomOf="@+id/button3"
        app:layout_constraintStart_toEndOf="@+id/button3"
        android:layout_marginStart="0dp"
        app:layout_constraintEnd_toEndOf="parent"
        android:layout_marginEnd="0dp" />

    <Button
        android:id="@+id/button2"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginLeft="16dp"
        android:text="Button 2"
        app:layout_constraintLeft_toLeftOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        android:layout_marginStart="8dp"
        app:layout_constraintEnd_toEndOf="parent"
        android:layout_marginEnd="8dp"
        app:layout_constraintBottom_toBottomOf="parent"
        android:layout_marginBottom="8dp"
        app:layout_constraintTop_toTopOf="parent"
        android:layout_marginTop="8dp"
        app:layout_constraintHorizontal_bias="0.0"
        app:layout_constraintVertical_bias="0.5" />

    <Button
        android:id="@+id/button3"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginLeft="16dp"
        android:text="Button 3"
        app:layout_constraintLeft_toLeftOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        android:layout_marginStart="8dp"
        app:layout_constraintEnd_toEndOf="parent"
        android:layout_marginEnd="8dp"
        app:layout_constraintTop_toTopOf="parent"
        android:layout_marginTop="8dp"
        app:layout_constraintBottom_toBottomOf="parent"
        android:layout_marginBottom="8dp"
        app:layout_constraintHorizontal_bias="0.0"
        app:layout_constraintVertical_bias="0.223" />
</android.support.constraint.ConstraintLayout>

我们可以做以下事情：

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)

        button1.setOnClickListener {
            val params = button1.layoutParams as ConstraintLayout.LayoutParams
            params.leftToRight = button2.id
            params.topToTop = button2.id
            params.bottomToBottom = button2.id
            button1.requestLayout()
        }
    }