android - 如何在TextView中用与文本不同的颜色对文本加下划线？

我知道如何在textview中给文本加下划线。但是，如何在带有不同颜色的文本下划线呢？
下划线可以通过以下方式完成:

TextView t = (TextView) findViewById(R.id.textview);
t.setPaintFlags(t.getPaintFlags() | Paint.UNDERLINE_TEXT_FLAG);
t.setText("Underline Text");

假设我的textcolor是黑色的，而我想在蓝色下划线，怎么做？
提前致谢。

最佳答案

我有同样的问题，在阅读其他关于EditText的文章时，我偶然发现了Layout类。它通过使用 Canvas 手动绘制下划线来提供实现此目标所需的一切。
首先，我定义了自定义属性，以便在XML布局文件中轻松自定义

<declare-styleable name="UnderlinedTextView" >
    <attr name="underlineHeight" format="dimension" />
    <attr name="underlineOffset" format="dimension" />
    <attr name="underlineColor" format="color" />
    <attr name="underLinePosition" format="enum">
        <enum name="baseline" value="0" />
        <enum name="below" value="1" />
    </attr>
</declare-styleable>

还有一个自定义的TextView类

   class UnderlinedTextView @JvmOverloads constructor(
    context: Context, attrs: AttributeSet? = null, defStyleAttr: Int = 0
) : androidx.appcompat.widget.AppCompatTextView(context, attrs, defStyleAttr) {

    @Retention(AnnotationRetention.SOURCE)
    @IntDef(POSITION_BASELINE, POSITION_BELOW)
    annotation class UnderLinePosition {
        companion object {
            const val POSITION_BASELINE = 0
            const val POSITION_BELOW = 1
        }
    }

    private val linePaint = Paint(Paint.ANTI_ALIAS_FLAG).apply {
        style = Paint.Style.FILL
    }

    var lineColor: Int
        get() = linePaint.color
        set(value) {
            if (linePaint.color != value) {
                linePaint.color = value
                invalidate()
            }
        }

    var lineHeight: Float
        get() = linePaint.strokeWidth
        set(value) {
            if (linePaint.strokeWidth != value) {
                linePaint.strokeWidth = value
                updateSpacing()
            }
        }

    var lineTopOffset = 0F
        set(value) {
            if (field != value) {
                field = value
                updateSpacing()
            }
        }

    @UnderLinePosition
    var linePosition = POSITION_BASELINE

    private val rect = Rect()

    private var internalAdd: Float = lineSpacingExtra

    private inline val extraSpace
        get() = lineTopOffset + lineHeight

    init {
        val density = context.resources.displayMetrics.density

        val typedArray = context.obtainStyledAttributes(attrs, R.styleable.UnderlinedTextView, defStyleAttr, 0)
        lineColor = typedArray.getColor(R.styleable.UnderlinedTextView_underlineColor, currentTextColor)
        lineTopOffset = typedArray.getDimension(R.styleable.UnderlinedTextView_underlineOffset, 0f)
        lineHeight = typedArray.getDimension(R.styleable.UnderlinedTextView_underlineHeight, density * 1)
        linePosition = typedArray.getInt(R.styleable.UnderlinedTextView_underLinePosition, POSITION_BASELINE)
        typedArray.recycle()
    }

    override fun onMeasure(widthMeasureSpec: Int, heightMeasureSpec: Int) {
        super.onMeasure(widthMeasureSpec, heightMeasureSpec)
        setMeasuredDimension(measuredWidth, measuredHeight + (extraSpace + 0.5f).toInt())
    }

    override fun onDraw(canvas: Canvas?) {
        canvas?.takeIf { !text.isNullOrEmpty() }?.let {
            val count = lineCount
            val layout = layout
            var xStart: Float
            var xStop: Float
            var yStart: Float
            var firstCharInLine: Int
            var lastCharInLine: Int
            var lastLine: Boolean
            var offset: Int
            val lineSpacing = lineSpacingExtra * lineSpacingMultiplier
            for (i in 0 until count) {
                val baseline = getLineBounds(i, rect)
                lastLine = i == count - 1
                offset = if (lastLine) 0 else 1
                firstCharInLine = layout.getLineStart(i)
                lastCharInLine = layout.getLineEnd(i)
                xStart = layout.getPrimaryHorizontal(firstCharInLine)
                xStop = layout.getPrimaryHorizontal(lastCharInLine - offset)
                yStart = when (linePosition) {
                    POSITION_BASELINE -> baseline + lineTopOffset
                    POSITION_BELOW -> (rect.bottom + lineTopOffset) - if (lastLine) 0F else lineSpacing
                    else -> throw NotImplementedError("")
                }
                canvas.drawRect(xStart, yStart, xStop, yStart + lineHeight, linePaint)
            }
        }
        super.onDraw(canvas)
    }

    private fun updateSpacing() {
        setLineSpacing(internalAdd, 1f)
    }

    override fun setLineSpacing(add: Float, mult: Float) {
        internalAdd = add
        super.setLineSpacing(add + extraSpace, 1f)
    }
}

然后它的用法很简单

<some.package.UnderlinedTextView
    android:id="@+id/tvTest"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:layout_alignParentBottom="true"
    android:layout_marginBottom="10dp"
    android:layout_marginLeft="20dp"
    android:layout_marginRight="20dp"
    android:gravity="center"
    android:text="This is a demo text"
    android:textSize="16sp"
    app:underlineColor="#ffc112ef"
    app:underlineHeight="3dp"/>

最终结果

多行

单行

关于android - 如何在TextView中用与文本不同的颜色对文本加下划线？，我们在Stack Overflow上找到一个类似的问题：https://stackoverflow.com/questions/19046614/