多行“ReplacementSpan”绘图问题

Question

只要文本不太长，我的自定义替换跨度就可以工作，但一旦文本长于一行，跨度图就会完全分开。我的理解是 draw() 在这种情况下被调用两次导致 span 绘制两次。无法将第二次绘制调用与第一次绘制调用区分开来，让您可以控制要绘制的内容和绘制位置。 start 和 end 变得无用，因为它们报告了错误的值。

ReplacementSpan 应该也适用于多行文本吗？如果能帮助解决此问题，我将不胜感激。

当我将所选文本更改为 CustomReplacementSpan:

时会发生这种情况

CustomReplacementSpan.kt

import android.graphics.Canvas
import android.graphics.Paint
import android.os.Build
import android.text.Layout
import android.text.StaticLayout
import android.text.TextPaint
import android.text.TextUtils
import android.text.style.ReplacementSpan
import androidx.core.graphics.withTranslation

class CustomReplacementSpan(val spanText: String, val color: Int) : ReplacementSpan() {

    override fun getSize(paint: Paint, text: CharSequence?, start: Int, end: Int, fm: Paint.FontMetricsInt?): Int {
        return paint.measureText(spanText).toInt()
    }

    override fun draw(
        canvas: Canvas,
        text: CharSequence?,
        start: Int,
        end: Int,
        x: Float,
        top: Int,
        y: Int,
        bottom: Int,
        paint: Paint
    ) {
        paint.color = color

        canvas.drawMultilineText(
            text = spanText,
            textPaint = paint as TextPaint,
            width = canvas.width,
            x = x,
            y = top.toFloat()
        )
    }


}

fun Canvas.drawMultilineText(
    text: CharSequence,
    textPaint: TextPaint,
    width: Int,
    x: Float,
    y: Float,
    start: Int = 0,
    end: Int = text.length,
    alignment: Layout.Alignment = Layout.Alignment.ALIGN_NORMAL,
    spacingMult: Float = 1f,
    spacingAdd: Float = 0f,
    includePad: Boolean = true,
    ellipsizedWidth: Int = width,
    ellipsize: TextUtils.TruncateAt? = null
) {
    val staticLayout =
        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.M) {
            StaticLayout.Builder.obtain(text, start, end, textPaint, width)
                .setAlignment(alignment)
                .setLineSpacing(spacingAdd, spacingMult)
                .setIncludePad(includePad)
                .setEllipsizedWidth(ellipsizedWidth)
                .setEllipsize(ellipsize)
                .build()
        } else {
            StaticLayout(
                text, start, end, textPaint, width, alignment,
                spacingMult, spacingAdd, includePad, ellipsize, ellipsizedWidth
            )
        }

    staticLayout.draw(this, x, y)
}

private fun StaticLayout.draw(canvas: Canvas, x: Float, y: Float) {
    canvas.withTranslation(x, y) {
        draw(this)
    }
}

MainActivity.kt

import android.os.Bundle
import android.text.Spannable
import android.view.View
import android.widget.EditText
import androidx.appcompat.app.AppCompatActivity
import androidx.core.content.ContextCompat


class MainActivity : AppCompatActivity() {

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

    fun applySpan(view: View) {
        val editText = findViewById<EditText>(R.id.edit)
        if (editText.selectionStart < 0 || editText.selectionEnd < 0) {
            return
        }
        val fullText = editText.text
        val text = fullText.subSequence(editText.selectionStart, editText.selectionEnd)
        val span = CustomReplacementSpan(text.toString(), ContextCompat.getColor(this, android.R.color.holo_blue_dark))
        editText.text.setSpan(span, editText.selectionStart, editText.selectionEnd, Spannable.SPAN_EXCLUSIVE_EXCLUSIVE)
    }
}

activity_main.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout 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:orientation="vertical"
    tools:context=".MainActivity">

    <EditText
        android:id="@+id/edit"
        style="@style/Widget.AppCompat.EditText"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:textSize="20sp" />

    <Button
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:onClick="applySpan"
        android:text="Make it span" />

</LinearLayout>

Answer 1

换行显然是ReplacementSpan做不到的。这是 Florina Muntenescu 发表的一篇文章 Drawing a rounded corner background on text 中的引述，她在博客中介绍了 spans 等内容。（以下引用中的重点是我的。）

We need to draw a drawable together with the text. We can implement a custom ReplacementSpan to draw the background and the text ourselves. However ReplacementSpans cannot flow into the next line, therefore we will not be able to support a multi-line background. They would rather look like Chip, the Material Design component, where every element must fit on a single line.

这就是您遇到的问题。本文继续介绍您可能想要研究的可能解决方案。例如，可以使用本文中概述的一些技术来定义多个 ReplacementSpans 取决于换行符，就像对背景可绘制对象所做的那样。

还有其他跨度类型可能更适合您的目的。 Here 是它们的列表。

多行“ReplacementSpan”绘图问题

Multiline `ReplacementSpan` drawing issue

android

android-edittext

spannablestring