Android TextView 中的 Markdown 支持

Question

有没有办法让 TextView 检测降价标签并相应地呈现文本？更具体地说，我的应用程序包含一个 TextView ，用户可以在其中提供描述，并且他们通常会使用 markdown 来格式化他们的描述。不幸的是，文本没有呈现，而是我们看到了写在 textview 中的所有标签。

Answer 1

看看 commonmark-java 库。我自己还没有尝试过，但我认为你可以让它在你的情况下工作

Answer 2

Android SDK 中没有对 Markdown 的内置支持。你必须使用像 markdown4j or CommonMark.

这样的库

Answer 3

如果要渲染 HTML，可以使用 Html.fromHtml("your string")，有关 Android 中字符串的更多资源，请查看此 link

Answer 4

在 textview 中没有对 markdown 的继承支持，但是如果你只需要通过简单的 "regexp" 匹配实现简单的 markdown-lite，这部分来自我的 "load readme from project root folder" in https://github.com/mofosyne/instantReadmeApp 会有帮助。

请注意，这不会删除文本中的标记，只会以不同的方式设置行的样式。这可能是好事也可能是坏事，具体取决于您的应用程序。

哦，好东西？它在本机文本视图中设置样式，因此文本仍然可以像普通文本一样选择。

特别是这一行：https://github.com/mofosyne/instantReadmeApp/blob/master/app/src/main/java/com/github/mofosyne/instantreadme/ReadMe.java#L137

下面略作修改：private void updateMainDisplay(String text) 到 private void style_psudomarkdown_TextView(String text, TextView textview_input)，因此您可以对不同的文本视图使用相同的函数

```

/*
    Text Styler
    A crappy psudo markdown styler. Could do with a total revamp.
 */

/*
* Styling the textview for easier readability
* */
private void style_psudomarkdown_TextView(String text, TextView textview_input) {
    //TextView mTextView = (TextView) findViewById(R.id.readme_info);
    TextView mTextView = textview_input;

    // Let's update the main display
    // Needs to set as spannable otherwise http://whosebug.com/questions/16340681/fatal-exception-string-cant-be-cast-to-spannable
    mTextView.setText(text, TextView.BufferType.SPANNABLE);
    // Let's prettify it!
    changeLineinView_TITLESTYLE(mTextView, "# ", 0xfff4585d, 2f); // Primary Header
    changeLineinView(mTextView, "\n# ", 0xFFF4A158, 1.5f); // Secondary Header
    changeLineinView(mTextView, "\n## ", 0xFFF4A158, 1.2f); // Secondary Header
    changeLineinView(mTextView, "\n---", 0xFFF4A158, 1.2f); // Horizontal Rule
    changeLineinView(mTextView, "\n>",   0xFF89e24d, 0.9f); // Block Quotes
    changeLineinView(mTextView, "\n - ", 0xFFA74DE3, 1f);   // Classic Markdown List
    changeLineinView(mTextView, "\n- ", 0xFFA74DE3, 1f);   // NonStandard List

    //spanSetterInView(String startTarget, String endTarget, int typefaceStyle, String fontFamily,TextView tv, int colour, float size)
    // Limitation of spanSetterInView. Well its not a regular expression... so can't exactly have * list, and *bold* at the same time.
    spanSetterInView(mTextView, "\n```\n", "\n```\n",   Typeface.BOLD,        "monospace",  0xFF45c152,  0.8f, false); // fenced code Blocks ( endAtLineBreak=false since this is a multiline block operator)
    spanSetterInView(mTextView,   " **"  ,     "** ",   Typeface.BOLD,        "",  0xFF89e24d,  1f, true); // Bolding
    spanSetterInView(mTextView,    " *"  ,      "* ",   Typeface.ITALIC,      "",  0xFF4dd8e2,  1f, true); // Italic
    spanSetterInView(mTextView,  " ***"  ,    "*** ",   Typeface.BOLD_ITALIC, "",  0xFF4de25c,  1f, true); // Bold and Italic
    spanSetterInView(mTextView,    " `"  ,      "` ",   Typeface.BOLD,        "monospace",  0xFF45c152,  0.8f, true); // inline code
    spanSetterInView(mTextView, "\n    " ,      "\n",   Typeface.BOLD,        "monospace",  0xFF45c152,  0.7f, true); // classic indented code
}

private void changeLineinView(TextView tv, String target, int colour, float size) {
    String vString = (String) tv.getText().toString();
    int startSpan = 0, endSpan = 0;
    //Spannable spanRange = new SpannableString(vString);
    Spannable spanRange = (Spannable) tv.getText();
    while (true) {
        startSpan = vString.indexOf(target, endSpan-1);     // (!@#$%) I want to check a character behind in case it is a newline
        endSpan = vString.indexOf("\n", startSpan+1);       // But at the same time, I do not want to read the point found by startSpan. This is since startSpan may point to a initial newline.
        ForegroundColorSpan foreColour = new ForegroundColorSpan(colour);
        // Need a NEW span object every loop, else it just moves the span
        // Fix: -1 in startSpan or endSpan, indicates that the indexOf has already searched the entire string with not valid match (Lack of endspan check, occoured because of the inclusion of endTarget, which added extra complications)
        if ( (startSpan < 0) || ( endSpan < 0 ) ) break;// Need a NEW span object every loop, else it just moves the span
        // Need to make sure that start range is always smaller than end range. (Solved! Refer to few lines above with (!@#$%) )
        if (endSpan > startSpan) {
            //endSpan = startSpan + target.length();
            spanRange.setSpan(foreColour, startSpan, endSpan, Spannable.SPAN_EXCLUSIVE_EXCLUSIVE);
            // Also wannna bold the span too
            spanRange.setSpan(new RelativeSizeSpan(size), startSpan, endSpan, Spannable.SPAN_EXCLUSIVE_EXCLUSIVE);
            spanRange.setSpan(new StyleSpan(Typeface.BOLD), startSpan, endSpan, Spannable.SPAN_EXCLUSIVE_EXCLUSIVE);
        }
    }
    tv.setText(spanRange);
}

private void changeLineinView_TITLESTYLE(TextView tv, String target, int colour, float size) {
    String vString = (String) tv.getText().toString();
    int startSpan = 0, endSpan = 0;
    //Spannable spanRange = new SpannableString(vString);
    Spannable spanRange = (Spannable) tv.getText();
    /*
    * Had to do this, since there is something wrong with this overlapping the "##" detection routine
    * Plus you only really need one title.
     */
    //while (true) {
    startSpan = vString.substring(0,target.length()).indexOf(target, endSpan-1); //substring(target.length()) since we only want the first line
    endSpan = vString.indexOf("\n", startSpan+1);
    ForegroundColorSpan foreColour = new ForegroundColorSpan(colour);
    // Need a NEW span object every loop, else it just moves the span
        /*
        if (startSpan < 0)
            break;
            */
    if ( !(startSpan < 0) ) { // hacky I know, but its to cater to the case where there is no header text
        // Need to make sure that start range is always smaller than end range.
        if (endSpan > startSpan) {
            //endSpan = startSpan + target.length();
            spanRange.setSpan(foreColour, startSpan, endSpan, Spannable.SPAN_EXCLUSIVE_EXCLUSIVE);
            // Also wannna bold the span too
            spanRange.setSpan(new RelativeSizeSpan(size), startSpan, endSpan, Spannable.SPAN_EXCLUSIVE_EXCLUSIVE);
            spanRange.setSpan(new StyleSpan(Typeface.BOLD_ITALIC), startSpan, endSpan, Spannable.SPAN_EXCLUSIVE_EXCLUSIVE);
        }
    }
    //}
    tv.setText(spanRange);
}


private void spanSetterInView(TextView tv, String startTarget, String endTarget, int typefaceStyle, String fontFamily, int colour, float size, boolean endAtLineBreak) {
    String vString = (String) tv.getText().toString();
    int startSpan = 0, endSpan = 0;
    //Spannable spanRange = new SpannableString(vString);
    Spannable spanRange = (Spannable) tv.getText();
    while (true) {
        startSpan = vString.indexOf(startTarget, endSpan-1);     // (!@#$%) I want to check a character behind in case it is a newline
        endSpan = vString.indexOf(endTarget, startSpan+1+startTarget.length());     // But at the same time, I do not want to read the point found by startSpan. This is since startSpan may point to a initial newline. We also need to avoid the first patten matching a token from the second pattern.
        // Since this is pretty powerful, we really want to avoid overmatching it, and limit any problems to a single line. Especially if people forget to type in the closing symbol (e.g. * in bold)
        if (endAtLineBreak){
            int endSpan_linebreak = vString.indexOf("\n", startSpan+1+startTarget.length());
            if ( endSpan_linebreak < endSpan ) { endSpan = endSpan_linebreak; }
        }
        // Fix: -1 in startSpan or endSpan, indicates that the indexOf has already searched the entire string with not valid match (Lack of endspan check, occoured because of the inclusion of endTarget, which added extra complications)
        if ( (startSpan < 0) || ( endSpan < 0 ) ) break;// Need a NEW span object every loop, else it just moves the span
        // We want to also include the end "** " characters
        endSpan += endTarget.length();
        // If all is well, we shall set the styles and etc...
        if (endSpan > startSpan) {// Need to make sure that start range is always smaller than end range. (Solved! Refer to few lines above with (!@#$%) )
            spanRange.setSpan(new ForegroundColorSpan(colour), startSpan, endSpan, Spannable.SPAN_EXCLUSIVE_EXCLUSIVE);
            spanRange.setSpan(new RelativeSizeSpan(size), startSpan, endSpan, Spannable.SPAN_EXCLUSIVE_EXCLUSIVE);
            spanRange.setSpan(new StyleSpan(typefaceStyle), startSpan, endSpan, Spannable.SPAN_EXCLUSIVE_EXCLUSIVE);
            // Default to normal font family if settings is empty
            if( !fontFamily.equals("") )  spanRange.setSpan(new TypefaceSpan(fontFamily), startSpan, endSpan, Spannable.SPAN_EXCLUSIVE_EXCLUSIVE);
        }
    }
    tv.setText(spanRange);
}

```

上面的实现最多只支持2个headers（但是你可以很容易地修改正则表达式来支持超过2个headers）。

这是一系列基于正则表达式的文本视图，由两个正则表达式函数组成，始终匹配一行 changeLineinView() 和 changeLineinView_TITLESTYLE()

对于多行跨越 spanSetterInView() 函数处理它。

因此，只要您有一个不与任何其他语法冲突的正则表达式，就可以扩展它以满足您的目的。

Markdownish 语法：

这是支持的语法。不能支持完整的降价，因为这只是一个精简的 hacky 实现。但对于易于在移动设备 phone 键盘上键入的简洁显示来说非常方便。

# H1 only in first line (Due to technical hacks used)

## H2 headers as usual

## Styling
Like: *italic* **bold** ***bold_italic***

## Classic List
 - list item 1
 - list item 2

## Nonstandard List Syntax
- list item 1
- list item 2

## Block Quotes
> Quoted stuff

## codes
here is inline `literal` codes. Must have space around it.

    ```
    codeblocks
    Good for ascii art
    ```

    Or 4 space code indent like classic markdown.

Answer 5

我了解到您想将包含 Markdown 标记的 String 转换为可在 TextView 中使用的格式化 CharSequence。我知道的两个选项是：

Bypass ：使用本机 C 库来解析文本。不幸的是，这个项目似乎已经死了。
commonmark-spannable-android：纯java，基于非常好的commonmark-java 图书馆。

我都用过，在我看来，第二个更好：不需要处理原生架构，更小的 APK，而且性能相当好（在我的情况下慢了 2 倍，超过了够好了）

更新：找到另一个选项（这是我现在使用的选项）：

Markwon：纯 java，也使用 commonmark-java 作为解析器，可选择支持图像和表格

Answer 6

我可以推荐MarkdownView。我用它来从资产文件夹加载降价文件。

如果它对任何人有帮助，这是我的实现...

在我的布局中：

<us.feras.mdv.MarkdownView
    android:id="@+id/descriptionMarkdownView"
    android:layout_width="0dp"
    android:layout_height="wrap_content"
    android:layout_marginTop="10dp"
    app:layout_constraintTop_toBottomOf="@id/thumbnailImageView"
    app:layout_constraintStart_toEndOf="@id/guidelineStart"
    app:layout_constraintEnd_toEndOf="@id/guidelineEnd"
    app:layout_constraintBottom_toTopOf="@id/parent"/>

在我的 Activity:

val cssPath = "file:///android_asset/markdown.css"
val markdownPath = "file:///android_asset/markdown/filename.md"
descriptionMarkdownView.loadMarkdownFile(markdownPath, cssPath)

Answer 7

我从上周五开始关注这个 post 并测试了这里建议的许多 Markdown 库 - 这个问题和这些答案基本上是我可以在网上找到的关于该主题的最佳来源。

其中有两个最引起我的注意，MarkdownView and Markwon, but the former was easier to deal with than the latter and so I used it to empower a Room note taking app 通过 Markdown 格式（这是我的主要个人目标）。

如果你想要一个Markdown实时预览，你可以使用this sample activity provided by the library itself and, among other options，如果你需要自己适配activity，我建议你添加以下代码您的项目：

build.gradle

implementation 'us.feras.mdv:markdownview:1.1.0'

private MarkdownView markdownView;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    this.markdownView = findViewById(R.id.markdownView);
    this.udateMarkdownView();
}

private void updateMarkdownView() {
    markdownView.loadMarkdown(note_content.getText().toString());
}

Here 你会发现我在 GitHub 上提供的示例，你可以在其中看到一个工作项目，除了图书馆本身给我们的示例。

Android TextView 中的 Markdown 支持

Markdown support in Android TextView

android

markdown

textview

Markdownish 语法：