TextAppearanceSpan的使用

SpannableStringBuilder可以用来实现富文本样式。
TextAppearanceSpan是系统提供的用来修改文本简单样式：

• 设置不同的文字大小
• 设置不同的文字颜色
• 设置文字的字体
• 设置文字粗体
• 超链接颜色

    fun testSpan() {
        var builder = SpannableStringBuilder()
        var price = "10,837"
        var note = "当前价"
        builder.append("¥")
        builder.append("${price} ")
        builder.append(note)

        //默认字体，粗体，文字大小：60，红色
        var yuanSpan = TextAppearanceSpan(
            null, Typeface.BOLD, 60,
            ColorStateList.valueOf(resources.getColor(R.color._C6100E)), null
        )
        builder.setSpan(yuanSpan, 0, 1, SpannableStringBuilder.SPAN_EXCLUSIVE_EXCLUSIVE)

        //默认字体，粗体，文字大小：80，红色
        var priceSpan = TextAppearanceSpan(
            null, Typeface.BOLD, 80,
            ColorStateList.valueOf(resources.getColor(R.color._C6100E)), null
        )
        builder.setSpan(
            priceSpan,
            1,
            price.length + 1,
            SpannableStringBuilder.SPAN_EXCLUSIVE_EXCLUSIVE
        )

        //serif字体，正常，文字大小：60，灰色
        var noteSpan = TextAppearanceSpan(
            "sans", Typeface.NORMAL, 60,
            ColorStateList.valueOf(resources.getColor(R.color._888888)), null
        )
        builder.setSpan(
            noteSpan,
            builder.length - note.length,
            builder.length,
            SpannableStringBuilder.SPAN_EXCLUSIVE_EXCLUSIVE
        )

        findViewById(R.id.tv_app).setText(builder)
    }

效果如图：

¥10,837当前价.jpg

!

TextAppearanceSpan支持的属性，可以从源码中获得：

    /**
     * Uses the specified TextAppearance resource to determine the
     * text appearance, and the specified text color resource
     * to determine the color.  The appearance should be,
     * for example, android.R.style.TextAppearance_Small,
     * and the colorList should be, for example,
     * android.R.styleable.Theme_textColorPrimary.
     */
    public TextAppearanceSpan(Context context, int appearance, int colorList) {
        ColorStateList textColor;

        TypedArray a =
            context.obtainStyledAttributes(appearance,
                                           com.android.internal.R.styleable.TextAppearance);
        //字体颜色
        textColor = a.getColorStateList(com.android.internal.R.styleable.
                                        TextAppearance_textColor);
       //超链接颜色
        mTextColorLink = a.getColorStateList(com.android.internal.R.styleable.
                                        TextAppearance_textColorLink);
       //字体大小
        mTextSize = a.getDimensionPixelSize(com.android.internal.R.styleable.
                                        TextAppearance_textSize, -1);
        //风格：粗体、斜体、正常
        mStyle = a.getInt(com.android.internal.R.styleable.TextAppearance_textStyle, 0);

        //字体
        if (!context.isRestricted() && context.canLoadUnsafeResources()) {
            mTypeface = a.getFont(com.android.internal.R.styleable.TextAppearance_fontFamily);
        } else {
            mTypeface = null;
        }
        if (mTypeface != null) {
            mFamilyName = null;
        } else {
            String family = a.getString(com.android.internal.R.styleable.TextAppearance_fontFamily);
            if (family != null) {
                mFamilyName = family;
            } else {
                int tf = a.getInt(com.android.internal.R.styleable.TextAppearance_typeface, 0);

                switch (tf) {
                    case 1:
                        mFamilyName = "sans";
                        break;

                    case 2:
                        mFamilyName = "serif";
                        break;

                    case 3:
                        mFamilyName = "monospace";
                        break;

                    default:
                        mFamilyName = null;
                        break;
                }
            }
        }

        mTextFontWeight = a.getInt(com.android.internal.R.styleable
                .TextAppearance_textFontWeight, -1);

        final String localeString = a.getString(com.android.internal.R.styleable
                .TextAppearance_textLocale);
        if (localeString != null) {
            LocaleList localeList = LocaleList.forLanguageTags(localeString);
            if (!localeList.isEmpty()) {
                mTextLocales = localeList;
            } else {
                mTextLocales = null;
            }
        } else {
            mTextLocales = null;
        }

         //文字投影
        mShadowRadius = a.getFloat(com.android.internal.R.styleable
                .TextAppearance_shadowRadius, 0.0f);
        mShadowDx = a.getFloat(com.android.internal.R.styleable
                .TextAppearance_shadowDx, 0.0f);
        mShadowDy = a.getFloat(com.android.internal.R.styleable
                .TextAppearance_shadowDy, 0.0f);
        mShadowColor = a.getInt(com.android.internal.R.styleable
                .TextAppearance_shadowColor, 0);

        mHasElegantTextHeight = a.hasValue(com.android.internal.R.styleable
                .TextAppearance_elegantTextHeight);
        mElegantTextHeight = a.getBoolean(com.android.internal.R.styleable
                .TextAppearance_elegantTextHeight, false);

        mHasLetterSpacing = a.hasValue(com.android.internal.R.styleable
                .TextAppearance_letterSpacing);
        mLetterSpacing = a.getFloat(com.android.internal.R.styleable
                .TextAppearance_letterSpacing, 0.0f);

        mFontFeatureSettings = a.getString(com.android.internal.R.styleable
                .TextAppearance_fontFeatureSettings);

        mFontVariationSettings = a.getString(com.android.internal.R.styleable
                .TextAppearance_fontVariationSettings);

        a.recycle();

        if (colorList >= 0) {
            a = context.obtainStyledAttributes(com.android.internal.R.style.Theme,
                                            com.android.internal.R.styleable.Theme);

            textColor = a.getColorStateList(colorList);
            a.recycle();
        }

        mTextColor = textColor;
    }