以编程方式修改 ConstraintSet 链未按预期工作

Question

出于某种原因，当以编程方式修改 ConstraintLayout 的 ConstraintSet 以更改视图位置（属于链）时，结果与预期不同。

在下面的示例中，我构建了一个 带有图标视图的按钮，其中图像可以放置在按钮的开头或结尾。当图标位于末尾时，一切都很好。但是当它被设置为位于按钮的开头时，它的内容无缘无故地向左对齐。

我不知道如何解决这个问题。我已经在代码中尝试了几次修改，但是 none 成功了。

如何解决？

将图标设置为位于按钮开头时的错误行为。它以某种方式与按钮的左侧对齐

ButtonWithIconView.kt

package com.example.buttonwithimageexample

import android.content.Context
import android.content.res.Resources
import android.graphics.Color
import android.util.AttributeSet
import android.util.TypedValue
import android.view.Gravity
import android.view.View
import android.widget.ImageView
import android.widget.TextView
import androidx.constraintlayout.widget.ConstraintLayout
import androidx.constraintlayout.widget.ConstraintSet
import androidx.core.content.res.getIntOrThrow

class ButtonWithIconView : ConstraintLayout {

    private val iconView by lazy { findViewById<ImageView>(R.id.icon) }
    private val textView by lazy { findViewById<TextView>(R.id.text) }

    /**
     * Acceptable values: Gravity.START and Gravity.END
     */
    private var iconGravity = Gravity.START

    constructor(context: Context?) : super(context) {
        commonInit(context, null)
    }

    constructor(context: Context?, attrs: AttributeSet?) : super(context, attrs) {
        commonInit(context, attrs)
    }

    constructor(
        context: Context?,
        attrs: AttributeSet?,
        defStyleAttr: Int
    ) : super(context, attrs, defStyleAttr) {
        commonInit(context, attrs)
    }

    private fun commonInit(context: Context?, attrs: AttributeSet?) {
        if (context == null) {
            return
        }

        this.setBackgroundColor(Color.LTGRAY)
        this.setPadding(
            BUTTON_PADDING,
            BUTTON_PADDING,
            BUTTON_PADDING,
            BUTTON_PADDING
        )

        View.inflate(context, R.layout.button_with_icon_view, this)

        if (attrs != null) {
            applyAttrs(attrs)
        }

        if (isInEditMode) {
            return
        }
    }

    private fun applyAttrs(attrs: AttributeSet) {
        val typedArray = context.obtainStyledAttributes(
            attrs,
            R.styleable.ButtonWithIconView,
            0,
            0
        )

        if (typedArray.hasValue(R.styleable.ButtonWithIconView_button_text)) {
            textView.text = typedArray.getText(R.styleable.ButtonWithIconView_button_text)
        }

        if (typedArray.hasValue(R.styleable.ButtonWithIconView_button_icon_position)) {
            when (typedArray.getIntOrThrow(R.styleable.ButtonWithIconView_button_icon_position)) {
                ATTR_BUTTON_ICON_POS_START -> setIconPosition(Gravity.START)
                ATTR_BUTTON_ICON_POS_END -> setIconPosition(Gravity.END)
            }
        }

        typedArray.recycle()
    }

    private fun getACopyOfTheCurrentConstraintSet(): ConstraintSet {
        return ConstraintSet().apply {
            this.clone(this@ButtonWithIconView)
        }
    }

    private fun onBeforeMovingIcon(constrainSet: ConstraintSet) {
        constrainSet.removeFromHorizontalChain(textView.id)
        constrainSet.removeFromHorizontalChain(iconView.id)

        constrainSet.clear(iconView.id, ConstraintSet.LEFT)
        constrainSet.clear(iconView.id, ConstraintSet.TOP)
        constrainSet.clear(iconView.id, ConstraintSet.RIGHT)
        constrainSet.clear(iconView.id, ConstraintSet.BOTTOM)
        constrainSet.clear(iconView.id, ConstraintSet.START)
        constrainSet.clear(iconView.id, ConstraintSet.END)

        when (iconGravity) {
            Gravity.START -> {
                constrainSet.clear(
                    textView.id,
                    ConstraintSet.START
                )

                constrainSet.connect(
                    textView.id,
                    ConstraintSet.START,
                    ConstraintSet.PARENT_ID,
                    ConstraintSet.START,
                    0
                )
            }
            Gravity.END -> {
                constrainSet.clear(
                    textView.id,
                    ConstraintSet.END
                )

                constrainSet.connect(
                    textView.id,
                    ConstraintSet.END,
                    ConstraintSet.PARENT_ID,
                    ConstraintSet.END,
                    0
                )
            }
        }
    }

    private fun moveIconToLeftOfTheText() {
        val newConstraintSet = getACopyOfTheCurrentConstraintSet()

        onBeforeMovingIcon(newConstraintSet)

        newConstraintSet.clear(
            textView.id,
            ConstraintSet.START
        )

        newConstraintSet.connect(
            iconView.id,
            ConstraintSet.END,
            textView.id,
            ConstraintSet.START,
            HALF_DISTANCE_BETWEEN_ICON_AND_TEXT
        )

        /**
         *  When this line is set, the resulting layout becomes bugged. Instead of the chain
         * being centralized in the parent, it is to the start of it =,/.
         *  Without that function call, everything works as expected, but it shouldn't, because
         * it as a chain (<left to right of> and <right to left of> are required).
         */
        newConstraintSet.connect(
            textView.id,
            ConstraintSet.START,
            iconView.id,
            ConstraintSet.END,
            HALF_DISTANCE_BETWEEN_ICON_AND_TEXT
        )

        newConstraintSet.connect(
            iconView.id,
            ConstraintSet.START,
            ConstraintSet.PARENT_ID,
            ConstraintSet.START,
            0
        )

        newConstraintSet.connect(
            iconView.id,
            ConstraintSet.TOP,
            ConstraintSet.PARENT_ID,
            ConstraintSet.TOP,
            0
        )

        newConstraintSet.connect(
            iconView.id,
            ConstraintSet.BOTTOM,
            ConstraintSet.PARENT_ID,
            ConstraintSet.BOTTOM,
            0
        )

        newConstraintSet.createHorizontalChain(
            ConstraintSet.PARENT_ID,
            ConstraintSet.LEFT,
            ConstraintSet.PARENT_ID,
            ConstraintSet.RIGHT,
            intArrayOf(
                iconView.id,
                textView.id
            ),
            null,
            ConstraintSet.CHAIN_PACKED
        )

        newConstraintSet.applyTo(this)
        iconGravity = Gravity.START
    }

    private fun moveIconToTheRightOfTheText() {
        val newConstraintSet = getACopyOfTheCurrentConstraintSet()

        onBeforeMovingIcon(newConstraintSet)

        newConstraintSet.clear(
            textView.id,
            ConstraintSet.END
        )

        newConstraintSet.connect(
            iconView.id,
            ConstraintSet.START,
            textView.id,
            ConstraintSet.END,
            HALF_DISTANCE_BETWEEN_ICON_AND_TEXT
        )

        newConstraintSet.connect(
            textView.id,
            ConstraintSet.END,
            iconView.id,
            ConstraintSet.START,
            HALF_DISTANCE_BETWEEN_ICON_AND_TEXT
        )

        newConstraintSet.connect(
            iconView.id,
            ConstraintSet.TOP,
            ConstraintSet.PARENT_ID,
            ConstraintSet.TOP,
            0
        )

        newConstraintSet.connect(
            iconView.id,
            ConstraintSet.END,
            ConstraintSet.PARENT_ID,
            ConstraintSet.END,
            0
        )

        newConstraintSet.connect(
            iconView.id,
            ConstraintSet.BOTTOM,
            ConstraintSet.PARENT_ID,
            ConstraintSet.BOTTOM,
            0
        )

        newConstraintSet.createHorizontalChain(
            ConstraintSet.PARENT_ID,
            ConstraintSet.LEFT,
            ConstraintSet.PARENT_ID,
            ConstraintSet.RIGHT,
            intArrayOf(
                textView.id,
                iconView.id
            ),
            null,
            ConstraintSet.CHAIN_PACKED
        )

        newConstraintSet.applyTo(this)
        iconGravity = Gravity.END
    }

    /**
     * @param gravity may be Gravity.START or Gravity.END (from the text)
     */
    fun setIconPosition(gravity: Int) {
        when (gravity) {
            Gravity.START -> moveIconToLeftOfTheText()
            Gravity.END -> moveIconToTheRightOfTheText()
            else -> throw IllegalArgumentException("Invalid gravity: $gravity")
        }
    }

    companion object {
        private val BUTTON_PADDING = TypedValue.applyDimension(
            TypedValue.COMPLEX_UNIT_DIP,
            16f,
            Resources.getSystem().displayMetrics
        ).toInt()
        private val HALF_DISTANCE_BETWEEN_ICON_AND_TEXT = TypedValue.applyDimension(
            TypedValue.COMPLEX_UNIT_DIP,
            4f,
            Resources.getSystem().displayMetrics
        ).toInt()

        private const val ATTR_BUTTON_ICON_POS_START = 0
        private const val ATTR_BUTTON_ICON_POS_END = 1
    }
}

button_with_icon_view.xml

<?xml version="1.0" encoding="utf-8"?>
<merge 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:orientation="vertical"
    tools:background="#CCCCCC"
    tools:layout_height="wrap_content"
    tools:layout_width="wrap_content"
    tools:padding="8dp"
    tools:parentTag="androidx.constraintlayout.widget.ConstraintLayout">

    <ImageView
        android:id="@+id/icon"
        android:layout_width="16dp"
        android:layout_height="16dp"
        android:layout_marginRight="4dp"
        android:background="#FF0000"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintEnd_toStartOf="@+id/text"
        app:layout_constraintHorizontal_chainStyle="packed"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent" />

    <TextView
        android:id="@+id/text"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginLeft="4dp"
        android:includeFontPadding="false"
        android:text="Clicker"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toEndOf="@+id/icon"
        app:layout_constraintTop_toTopOf="parent" />

</merge>

attrs.xml

<?xml version="1.0" encoding="utf-8"?>
<resources>
    <declare-styleable name="ButtonWithIconView">
        <attr name="button_text" />
        <attr name="button_icon_position" format="enum">
            <enum name="start" value="0" />
            <enum name="end" value="1" />
        </attr>
    </declare-styleable>
</resources>

activity_main.xml

<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.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"
    tools:context=".MainActivity">

    <com.example.buttonwithimageexample.ButtonWithIconView
        android:id="@+id/left_button"
        android:layout_width="170dp"
        android:layout_height="wrap_content"
        app:button_icon_position="start"
        app:button_text="Left Button"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintEnd_toStartOf="@+id/right_button"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent" />

    <com.example.buttonwithimageexample.ButtonWithIconView
        android:id="@+id/right_button"
        android:layout_width="170dp"
        android:layout_height="wrap_content"
        app:button_icon_position="end"
        app:button_text="Right Button"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toEndOf="@+id/left_button"
        app:layout_constraintTop_toTopOf="parent" />

</androidx.constraintlayout.widget.ConstraintLayout>

Answer 1

您有更好的选择，而不是以编程方式从头开始重新创建约束集。您的解决方案很难阅读且不易修改。

1 - 为 start/end gravity 创建布局文件并将其应用到 setGravity 方法中：

fun setIconPosition(gravity: Int) {
    val cs = ConstraintSet()
    cs.clone(context, when (gravity) {
        Gravity.START -> R.layout.button_with_icon_view_start
        Gravity.END -> R.layout.button_with_icon_view_end
        else -> throw IllegalArgumentException("Invalid gravity: $gravity")
    })
    setConstraintSet(cs)
}

现在您不再需要难以理解的代码块。但是，如果您想修改布局，则必须同时维护两个布局文件。所以我推荐以下方法：

2 - 使用 Placeholders 设置约束并简单地交换它们的内容：

button_with_icon_view.xml

<?xml version="1.0" encoding="utf-8"?>
<merge xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    tools:parentTag="androidx.constraintlayout.widget.ConstraintLayout">

    <androidx.constraintlayout.widget.Placeholder
        android:id="@+id/placeHolderStart"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginEnd="4dp"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintEnd_toStartOf="@+id/placeHolderEnd"
        app:layout_constraintHorizontal_chainStyle="packed"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent"
        tools:content="@+id/icon"/>

    <androidx.constraintlayout.widget.Placeholder
        android:id="@+id/placeHolderEnd"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginStart="4dp"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toEndOf="@+id/placeHolderStart"
        app:layout_constraintTop_toTopOf="parent"
        tools:content="@+id/text"/>

    <ImageView
        android:id="@+id/icon"
        android:layout_width="16dp"
        android:layout_height="16dp"
        android:background="#FF0000" />

    <TextView
        android:id="@+id/text"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:includeFontPadding="false"
        android:text="Clicker" />
</merge>

替换视图：

fun setIconPosition(gravity : Int){
    when(gravity){
        Gravity.START -> {
            placeHolderStart.setContentId(iconView.id)
            placeHolderEnd.setContentId(textView.id)
        }
        Gravity.END -> {
            placeHolderStart.setContentId(textView.id)
            placeHolderEnd.setContentId(iconView.id)
        }
    }
    this.iconGravity = gravity
}

以编程方式修改 ConstraintSet 链未按预期工作

Modifying ConstraintSet chains programmatically not working as expected

android

android-constraintlayout

constraint-layout-chains

constraintset