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以编程方式创建UI时,不会显示回收项目

android-recyclerview kotlin android

J. Doe · 技术社区 · 2 年前

出于某种原因,我不想使用XML,我只想以编程方式创建我的UI。我现在的问题是,无论我提供多少元素,我的视图都不会显示在屏幕上。这是我的屏幕:

我不明白为什么它没有显示出来。我使用以下命令将一个非常简单的视图添加到父视图的上下文中 ConstraintLayout 我甚至提供了一个固定的高度。

请注意,我正在使用 AndroidView 因为我想在Jetpack Compose中使用这个RecyclerView。但我不认为这会导致这个问题。

我添加了下面的代码,我也在这里上传了项目(运行应用程序会立即显示问题): https://github.com/Jasperav/RecyclerView/tree/main

fun createChat(context: Context): ConstraintLayout {
    val recyclerView = createRecyclerView(context)

    return recyclerView
}

fun createRecyclerView(context: Context): ConstraintLayout {
    val constraintLayout = createConstraintLayout(context)
    val parent = applyDefaults(constraintLayout.constraintLayout, View(context), MATCH_PARENT, MATCH_PARENT)

    parent.setBackgroundColor(context.getColor(R.color.yellow))

    constraintLayout.fill(parent, constraintLayout.constraintLayout)

    val recyclerView = applyDefaults(constraintLayout.constraintLayout, RecyclerView(context), MATCH_PARENT, MATCH_PARENT)

    recyclerView.setBackgroundColor(context.getColor(R.color.purple_500))

    constraintLayout.fill(recyclerView, parent)

    val shapeDrawable = MaterialShapeDrawable()

    shapeDrawable.fillColor = ColorStateList.valueOf(context.getColor(R.color.teal_200))
    shapeDrawable.setStroke(5f, context.getColor(R.color.red))

    recyclerView.background = shapeDrawable
    recyclerView.adapter = ChatAdapter()
    recyclerView.layoutManager = LinearLayoutManager(context, RecyclerView.VERTICAL, false)

    return constraintLayout.constraintLayout
}

class ChatCell : View {
    private val textView: TextView

    constructor(parent: ViewGroup) : super(parent.context) {
        println("Created")

        val constraintLayout = createConstraintLayout(context)

        textView = applyDefaults(constraintLayout.constraintLayout, TextView(context), MATCH_PARENT, MATCH_PARENT)

        constraintLayout.constraintSet.constrainHeight(textView.id, 100)
        constraintLayout.constraintSet.applyTo(constraintLayout.constraintLayout)

        constraintLayout.fill(textView, constraintLayout.constraintLayout)

        textView.text = "test"
        textView.setBackgroundColor(context.getColor(R.color.red))
        setBackgroundColor(context.getColor(R.color.red))
    }

    fun x() {
    }
}

class ViewHolderTemp : RecyclerView.ViewHolder {
    val chatCell: ChatCell

    constructor(chatCell: ChatCell) : super(chatCell) {
        this.chatCell = chatCell
    }
}

class ChatAdapter : RecyclerView.Adapter<ViewHolderTemp>() {
    override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): ViewHolderTemp {
        val chatCell = ChatCell(parent)

        return ViewHolderTemp(chatCell)
    }

    override fun getItemCount() = 2

    override fun onBindViewHolder(holder: ViewHolderTemp, position: Int) {
        holder.chatCell.x()
    }
}

class Layout(val constraintLayout: ConstraintLayout, val constraintSet: ConstraintSet)

fun createConstraintLayout(context: Context): Layout {
    val c = ConstraintLayout(context).apply {
        id = View.generateViewId()
        layoutParams = ViewGroup.LayoutParams(
            MATCH_PARENT,
            MATCH_PARENT,
        )
    }

    val set = ConstraintSet()

    set.clone(c)

    return Layout(c, set)
}


fun <T: View> applyDefaults(constraintLayout: ConstraintLayout, view: T, width: Int, height: Int): T {
    view.id = View.generateViewId()
    view.layoutParams = ConstraintLayout.LayoutParams(
        width,
        height,
    )

    constraintLayout.addView(view)

    return view
}

fun Layout.fill(view: View, inView: View) {
    val constraintSet = ConstraintSet()

    constraintSet.clone(constraintLayout)

    constraintSet.connect(view.id, ConstraintSet.LEFT, inView.id, ConstraintSet.LEFT);
    constraintSet.connect(view.id, ConstraintSet.TOP, inView.id, ConstraintSet.TOP);
    constraintSet.connect(view.id, ConstraintSet.RIGHT, inView.id, ConstraintSet.RIGHT);
    constraintSet.connect(view.id, ConstraintSet.BOTTOM, inView.id, ConstraintSet.BOTTOM);

    constraintSet.applyTo(constraintLayout)
}

@Composable
fun GreetingX() {
    AndroidView(factory = { context ->
        createChat(context)
    })
}

@Preview(showBackground = true)
@Composable
fun DefaultPreviewX() {
    RecyclverTestTheme {
        GreetingX()
    }
}

0 回复 | 直到 2 年前

Cheticamp 2 年前

你的班级 ChatCell 不是做你想做的事。下面是一个版本,我认为,它做了你想要的事。我加入了评论来解释正在发生的事情。

class ChatCell(parent: ViewGroup) : ConstraintLayout(parent.context) {
    private val textView: TextView

    init {
        // LayoutParams for ConstraintLayout within the RecyclerView
        layoutParams = LayoutParams(MATCH_PARENT, WRAP_CONTENT)

        // Create the TextView within the ConstraintLayout and add it to the layout.
        textView = TextView(parent.context).apply {
            id = View.generateViewId()
            // Always use ConstraintSet.MATCH_CONSTRAINT (size = 0) with appropriate constraints
            // for MATCH_PARENT within a ConstraintLayout.
            layoutParams = LayoutParams(ConstraintSet.MATCH_CONSTRAINT, 100)
            setBackgroundColor(context.getColor(R.color.white))
        }
        addView(textView)

        // Now that the TextView is added to the ConstraintLayout, we can constrain it.
        // Note that the TextView MUST be added to the ConstraintLayout before we create
        // the ConstraintSet.
        val cs = ConstraintSet()
        cs.clone(this)
        cs.connect(
            textView.id,
            ConstraintSet.START,
            ConstraintSet.PARENT_ID,
            ConstraintSet.START
        )
        cs.connect(textView.id, ConstraintSet.END, ConstraintSet.PARENT_ID, ConstraintSet.END)
        cs.applyTo(this)

        // Our item view is now created and will be drawn appropriately within the RecyclerView.
    }

    // Here is where we bind the text to the item view's TextView.
    fun x(text: String) {
        textView.text = text
    }
}

这个 onBindViewHolder() 函数与新代码一起工作时看起来像下面这样:

override fun onBindViewHolder(holder: ViewHolderTemp, position: Int) {
    holder.chatCell.x("Text at position $position")
}

这是模拟器上的应用程序:

更好的函数声明 ChatCell 自定义视图将是

class ChatCell @JvmOverloads constructor(
    context: Context, attrs: AttributeSet? = null
) : ConstraintLayout(context, attrs)

这将允许在XML中使用该类,并消除Android Studio对类声明方式的抱怨。