TextView加载html文本字体颜色无法解析的问题

我们知道Android中显示html网页一般使用WebView加载，有的时候我们只需要查看简略的信息或者只是显示html的一部分内容就需要使用TextView了。而Android中使用TextView加载html的一般方式为：

textview.setText(Html.fromHtml(htmlString))；

这种方式能够在大部分情况下较好地显示html标签中指定的字体、样式等。但是对于字体的背景色和前景色来说，如果后端返回给你的格式为：#ff0000 16进制的代码是解析是没有问题的。如果后端给你返回：rgb(255,0,0) 以rgb表示的颜色时是没有办法解析的。
当然这种情况最好的解决方式是让后端给你改一下。
下面给出我的解决方案：

textView.setText(Html.fromHtml(htmlString,null, new CustomTagHandler(context, textView.getTextColors())));

我的测试文本中字体的颜色和背景色都写在span标签里面，这里我以span标签为例，其他标签类似。

package com.hemashequ.hmc.util;

import android.content.Context;
import android.content.res.ColorStateList;
import android.content.res.Resources;
import android.graphics.Color;
import android.text.Editable;
import android.text.Html;
import android.text.Spannable;
import android.text.Spanned;
import android.text.TextUtils;
import android.text.style.AbsoluteSizeSpan;
import android.text.style.BackgroundColorSpan;
import android.text.style.ForegroundColorSpan;
import android.text.style.TextAppearanceSpan;
import android.util.Log;

import com.hemashequ.hmccommon.util.DensityUtil;

import org.xml.sax.XMLReader;

import java.lang.reflect.Field;
import java.util.HashMap;
import java.util.Map;

/**
 * @author: hmc
 * @project: laifenyong-android-as
 * @package: com.hemashequ.hmc.util
 * @time: 2019/8/29 17:37
 * @description:
 */
public class CustomTagHandler implements Html.TagHandler {

    final HashMap attributes = new HashMap();
    private final String TAG = "CustomTagHandler";
    private int startIndex = 0;
    private int stopIndex = 0;
    private ColorStateList mOriginColors;
    private Context mContext;

    public CustomTagHandler(Context context, ColorStateList originColors) {
        mContext = context;
        mOriginColors = originColors;
    }

    @Override
    public void handleTag(boolean opening, String tag, Editable output, XMLReader xmlReader) {
        processAttributes(xmlReader);

        if (tag.equalsIgnoreCase("span")) {
            if (opening) {
                startSpan(tag, output, xmlReader);
            } else {
                endSpan(tag, output, xmlReader);
                attributes.clear();
            }
        }
    }

    private void processAttributes(final XMLReader xmlReader) {
        try {
            Field elementField = xmlReader.getClass().getDeclaredField("theNewElement");
            elementField.setAccessible(true);
            Object element = elementField.get(xmlReader);
            Field attsField = element.getClass().getDeclaredField("theAtts");
            attsField.setAccessible(true);
            Object atts = attsField.get(element);
            Field dataField = atts.getClass().getDeclaredField("data");
            dataField.setAccessible(true);
            String[] data = (String[]) dataField.get(atts);
            Field lengthField = atts.getClass().getDeclaredField("length");
            lengthField.setAccessible(true);
            int len = (Integer) lengthField.get(atts);

            /**
             * MSH: Look for supported attributes and add to hash map.
             * This is as tight as things can get :)
             * The data index is "just" where the keys and values are stored.
             */
            for (int i = 0; i < len; i++) {
                attributes.put(data[i * 5 + 1], data[i * 5 + 4]);
            }
        } catch (Exception e) {
        }
    }

    public void startSpan(String tag, Editable output, XMLReader xmlReader) {
        startIndex = output.length();
    }

    public void endSpan(String tag, Editable output, XMLReader xmlReader) {
        stopIndex = output.length();

        String color = attributes.get("color");
        String bacgroundColor  = attributes.get("background-color");
        String size = attributes.get("size");
        String style = attributes.get("style");
        if (!TextUtils.isEmpty(style)) {
            analysisStyle(startIndex, stopIndex, output, style);
        }
        if (!TextUtils.isEmpty(size)) {
            size = size.split("px")[0];
        }
        if (!TextUtils.isEmpty(bacgroundColor)) {
            if (bacgroundColor.startsWith("@")) {
                Resources res = Resources.getSystem();
                String name = bacgroundColor.substring(1);
                int colorRes = res.getIdentifier(name, "color", "android");
                if (colorRes != 0) {
                    output.setSpan(new BackgroundColorSpan(colorRes), startIndex, stopIndex, Spanned.SPAN_EXCLUSIVE_EXCLUSIVE);
                }
            } else {
                if (bacgroundColor.startsWith("rgb")) {
                    bacgroundColor = bacgroundColor.replace("rgb(", "");
                    bacgroundColor = bacgroundColor.replace(")", "");
                    String[] rgbs = bacgroundColor.split(", ");
                    bacgroundColor = toHex(Integer.parseInt(rgbs[0]), Integer.parseInt(rgbs[1]), Integer.parseInt(rgbs[2]));
                }
                try {
                    output.setSpan(new BackgroundColorSpan(Color.parseColor(bacgroundColor)), startIndex, stopIndex, Spanned.SPAN_EXCLUSIVE_EXCLUSIVE);
                } catch (Exception e) {
                    e.printStackTrace();
                    reductionFontColor(startIndex, stopIndex, output);
                }
            }
        }
        if (!TextUtils.isEmpty(color)) {
            if (color.startsWith("@")) {
                Resources res = Resources.getSystem();
                String name = color.substring(1);
                int colorRes = res.getIdentifier(name, "color", "android");
                if (colorRes != 0) {
                    output.setSpan(new ForegroundColorSpan(colorRes), startIndex, stopIndex, Spanned.SPAN_EXCLUSIVE_EXCLUSIVE);
                }
            } else {
                try {
                    output.setSpan(new ForegroundColorSpan(Color.parseColor(color)), startIndex, stopIndex, Spanned.SPAN_EXCLUSIVE_EXCLUSIVE);
                } catch (Exception e) {
                    e.printStackTrace();
                    reductionFontColor(startIndex, stopIndex, output);
                }
            }
        }
        if (!TextUtils.isEmpty(size)) {
            int fontSizePx = 16;
            if (null != mContext) {
                fontSizePx = DensityUtil.sp2px(mContext, Integer.parseInt(size));
            }
            output.setSpan(new AbsoluteSizeSpan(fontSizePx), startIndex, stopIndex, Spanned.SPAN_EXCLUSIVE_EXCLUSIVE);
        }
    }

    /**
     * 解析style属性
     *
     * @param startIndex
     * @param stopIndex
     * @param editable
     * @param style
     */
    private void analysisStyle(int startIndex, int stopIndex, Editable editable, String style) {
        Log.e(TAG, "style：" + style);
        String[] attrArray = style.split(";");
        Map attrMap = new HashMap<>();
        if (null != attrArray) {
            for (String attr : attrArray) {
                String[] keyValueArray = attr.split(":");
                if (null != keyValueArray && keyValueArray.length == 2) {
                    // 记住要去除前后空格
                    attrMap.put(keyValueArray[0].trim(), keyValueArray[1].trim());
                }
            }
        }
        String color = attrMap.get("color");
        String bacgroundColor  = attrMap.get("background-color");
        String fontSize = attrMap.get("font-size");
        if (!TextUtils.isEmpty(fontSize)) {
            fontSize = fontSize.split("px")[0];
        }
        if (!TextUtils.isEmpty(bacgroundColor)) {
            if (bacgroundColor.startsWith("@")) {
                Resources res = Resources.getSystem();
                String name = bacgroundColor.substring(1);
                int colorRes = res.getIdentifier(name, "color", "android");
                if (colorRes != 0) {
                    editable.setSpan(new BackgroundColorSpan(colorRes), startIndex, stopIndex, Spanned.SPAN_EXCLUSIVE_EXCLUSIVE);
                }
            } else {
                if (bacgroundColor.startsWith("rgb")) {
                    bacgroundColor = bacgroundColor.replace("rgb(", "");
                    bacgroundColor = bacgroundColor.replace(")", "");
                    String[] rgbs = bacgroundColor.split(", ");
                    bacgroundColor = toHex(Integer.parseInt(rgbs[0]), Integer.parseInt(rgbs[1]), Integer.parseInt(rgbs[2]));
                }
                try {
                    editable.setSpan(new BackgroundColorSpan(Color.parseColor(bacgroundColor)), startIndex, stopIndex, Spanned.SPAN_EXCLUSIVE_EXCLUSIVE);
                } catch (Exception e) {
                    e.printStackTrace();
                    reductionFontColor(startIndex, stopIndex, editable);
                }
            }
        }
        if (!TextUtils.isEmpty(color)) {
            if (color.startsWith("@")) {
                Resources res = Resources.getSystem();
                String name = color.substring(1);
                int colorRes = res.getIdentifier(name, "color", "android");
                if (colorRes != 0) {
                    editable.setSpan(new ForegroundColorSpan(colorRes), startIndex, stopIndex, Spanned.SPAN_EXCLUSIVE_EXCLUSIVE);
                }
            } else {
                if (color.startsWith("rgb")) {
                    color = color.replace("rgb(", "");
                    color = color.replace(")", "");
                    String[] rgbs = color.split(", ");
                    color = toHex(Integer.parseInt(rgbs[0]), Integer.parseInt(rgbs[1]), Integer.parseInt(rgbs[2]));
                }

                try {
                    editable.setSpan(new ForegroundColorSpan(Color.parseColor(color)), startIndex, stopIndex, Spanned.SPAN_EXCLUSIVE_EXCLUSIVE);
                } catch (Exception e) {
                    e.printStackTrace();
                    reductionFontColor(startIndex, stopIndex, editable);
                }
            }
        }
        if (!TextUtils.isEmpty(fontSize)) {
            int fontSizePx = 14;
            if (null != mContext) {
                fontSizePx = DensityUtil.sp2px(mContext, Integer.parseInt(fontSize));
            }
            editable.setSpan(new AbsoluteSizeSpan(fontSizePx), startIndex, stopIndex, Spanned.SPAN_EXCLUSIVE_EXCLUSIVE);
        }
    }

    /**
     * 还原为原来的颜色
     *
     * @param startIndex
     * @param stopIndex
     * @param editable
     */
    private void reductionFontColor(int startIndex, int stopIndex, Editable editable) {
        if (null != mOriginColors) {
            editable.setSpan(new TextAppearanceSpan(null, 0, 0, mOriginColors, null),
                    startIndex, stopIndex,
                    Spannable.SPAN_EXCLUSIVE_EXCLUSIVE);
        } else {
            editable.setSpan(new ForegroundColorSpan(0xff2b2b2b), startIndex, stopIndex, Spanned.SPAN_EXCLUSIVE_EXCLUSIVE);
        }
    }

    public static String toHex(int r, int g, int b) {
        return "#" + toBrowserHexValue(r) + toBrowserHexValue(g)
                + toBrowserHexValue(b);
    }

    private static String toBrowserHexValue(int number) {
        StringBuilder builder = new StringBuilder(
                Integer.toHexString(number & 0xff));
        while (builder.length() < 2) {
            builder.append("0");
        }
        return builder.toString().toUpperCase();
    }
}

由于Android 8.0使用TextView加载html文本时会自动解析文本中的span标签，因此可以使用自定义标签来代替span标签，例如：“fontstyle”。如果要对多标签解析，只需要在handleTag方法中增加即可，方式如下：

@Override
    public void handleTag(boolean opening, String tag, Editable output, XMLReader xmlReader) {
        processAttributes(xmlReader);

        if (tag.equalsIgnoreCase("fontstyle")) {
            if (opening) {
                startSpan(tag, output, xmlReader);
            } else {
                endSpan(tag, output, xmlReader);
                attributes.clear();
            }
        }

        if (tag.equalsIgnoreCase("p")) {
            if (opening) {
                startSpan(tag, output, xmlReader);
            } else {
                endSpan(tag, output, xmlReader);
                attributes.clear();
            }
        }
    }

上面的代码解析了替代后的span标签和p标签。