TextInputLayout中的错误文本由键盘覆盖

Question

TextInputLayout包含一个EditText,后者又接收来自用户的输入.使用Android设计支持库中引入的TextInputLayout,我们应该将错误设置为持有EditText而不是EditText本身的TextInputLayout.编写UI时,将只关注EditText而不是整个TextInputLayout,这可能导致键盘覆盖错误.在以下GIF通知中,用户必须先删除键盘才能看到错误消息.这与设置IME动作以使用键盘继续前进相结合会导致真正令人困惑的结果.

布局xml代码:

<android.support.design.widget.TextInputLayout
    android:id="@+id/uid_text_input_layout"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    app:errorEnabled="true"
    android:layout_marginTop="8dp">

    <EditText
        android:id="@+id/uid_edit_text"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:singleLine="true"
        android:hint="Cardnumber"
        android:imeOptions="actionDone"/>

</android.support.design.widget.TextInputLayout>

Java代码将错误设置为TextInputLayout:

uidTextInputLayout.setError("Incorrect cardnumber");

如何在用户没有看到错误消息的情况下确保错误消息可见？有可能移动焦点吗？

Answer 1

为了确保错误消息在用户没有看到它的情况下可见,我TextInputLayout将其子类化并放入一个ScrollView.这使我可以在需要时向下滚动以显示错误消息,在每次设置错误消息时.使用它的activity/fragment类中不需要进行任何更改.

import androidx.core.view.postDelayed

/**
 * [TextInputLayout] subclass that handles error messages properly.
 */
class SmartTextInputLayout @JvmOverloads constructor(
        context: Context, attrs: AttributeSet? = null, defStyleAttr: Int = 0
) : TextInputLayout(context, attrs, defStyleAttr) {

    private val scrollView by lazy(LazyThreadSafetyMode.NONE) {
        findParentOfType<ScrollView>() ?: findParentOfType<NestedScrollView>()
    }

    private fun scrollIfNeeded() {
        // Wait a bit (like 10 frames) for other UI changes to happen
        scrollView?.postDelayed(160) {
            scrollView?.scrollDownTo(this)
        }
    }

    override fun setError(value: CharSequence?) {
        val changed = error != value

        super.setError(value)

        // work around https://stackoverflow.com/q/34242902/1916449
        if (value == null) isErrorEnabled = false

        // work around https://stackoverflow.com/q/31047449/1916449
        if (changed) scrollIfNeeded()
    }
}

以下是帮助方法:

/**
 * Find the closest ancestor of the given type.
 */
inline fun <reified T> View.findParentOfType(): T? {
    var p = parent
    while (p != null && p !is T) p = p.parent
    return p as T?
}

/**
 * Scroll down the minimum needed amount to show [descendant] in full. More
 * precisely, reveal its bottom.
 */
fun ViewGroup.scrollDownTo(descendant: View) {
    // Could use smoothScrollBy, but it sometimes over-scrolled a lot
    howFarDownIs(descendant)?.let { scrollBy(0, it) }
}

/**
 * Calculate how many pixels below the visible portion of this [ViewGroup] is the
 * bottom of [descendant].
 *
 * In other words, how much you need to scroll down, to make [descendant]'s bottom
 * visible.
 */
fun ViewGroup.howFarDownIs(descendant: View): Int? {
    val bottom = Rect().also {
        // See https://stackoverflow.com/a/36740277/1916449
        descendant.getDrawingRect(it)
        offsetDescendantRectToMyCoords(descendant, it)
    }.bottom
    return (bottom - height - scrollY).takeIf { it > 0 }
}

我还修复了TextInputLayout.setError()在清除同一类中的错误后留下空白空间.

Answer 2

这实际上是 Google 的一个已知问题。

https://issuetracker.google.com/issues/37051832

他们提出的解决方案是创建一个自定义 TextInputEditText 类

class MyTextInputEditText : TextInputEditText {
    @JvmOverloads
    constructor(
        context: Context,
        attrs: AttributeSet? = null,
        defStyleAttr: Int = android.R.attr.editTextStyle
    ) : super(context, attrs, defStyleAttr) {
    }

    private val parentRect = Rect()

    override fun getFocusedRect(rect: Rect?) {
        super.getFocusedRect(rect)
        rect?.let {
            getMyParent().getFocusedRect(parentRect)
            rect.bottom = parentRect.bottom
        }
    }

    override fun getGlobalVisibleRect(rect: Rect?, globalOffset: Point?): Boolean {
        val result = super.getGlobalVisibleRect(rect, globalOffset)
        rect?.let {
            getMyParent().getGlobalVisibleRect(parentRect, globalOffset)
            rect.bottom = parentRect.bottom
        }
        return result
    }

    override fun requestRectangleOnScreen(rect: Rect?): Boolean {
        val result = super.requestRectangleOnScreen(rect)
        val parent = getMyParent()
        // 10 is a random magic number to define a rectangle height.
        parentRect.set(0, parent.height - 10, parent.right, parent.height)
        parent.requestRectangleOnScreen(parentRect, true /*immediate*/)
        return result;
    }

    private fun getMyParent(): View {
        var myParent: ViewParent? = parent;
        while (!(myParent is TextInputLayout) && myParent != null) {
            myParent = myParent.parent
        }
        return if (myParent == null) this else myParent as View
    }
}```