安卓如何在Java画布中绘制JSON文本？

Question

如何在Android Canvas中编写格式非常好的JSON对象/字符串

比如说,

val jsonText = "{"profile":{"name": "Robert","account_id": "31"}}"

将被绘制到一个Canvas中，如下所示：

Answer 1

Canvas functions have some limitations as it draws all text in single line. If the width of the text exceeds the width of the Canvas, the text will be clipped. hence we use staticLayout for the same to show text in paragraph or multi-line approach.

下面的代码用于在画布中显示json格式的文本，其中json是从资产文件加载的

fun drawTextOnCanvas(activity: FragmentActivity) {
var canvas = Canvas(bitmap)
var textPaint=TextPaint()
textPaint.density=20f
textPaint.bgColor=Color.BLACK

val jsonText = activity.loadJSONFromAsset("demo.json")
val jsonObject = JSONObject(jsonText);
val text=jsonObject.toString(1)
val staticLayout=StaticLayout.Builder.obtain(text,0,text.length,textPaint,150)

staticLayout.build().draw(canvas)}

希望这有帮助

Answer 2

生成PDF

import android.graphics.Color
import android.graphics.Paint
import android.graphics.pdf.PdfDocument
import com.google.gson.GsonBuilder    

class PdfGeneratorService(){

    private val ROW_INC = 20F
    private val COL_INC = 15F
    
    fun jsonFormat(jsonStr: String): String {

        var indentCount = 0

        val builder = StringBuilder()
        for (c in jsonStr) {
            if (indentCount > 0 && '\n' == builder.last()) {
                for (x in 0..indentCount) builder.append("    ")
            }
            when (c) {
                '{', '[' -> {
                    builder.append(c).append("\n")
                    indentCount++
                }
                ',' -> builder.append(c).append("\n")
                '}', ']' -> {
                    builder.append("\n")
                    indentCount 
                    for (x in 0..indentCount) builder.append("    ")
                    builder.append(c)
                }
                else -> builder.append(c)
            }
        }

        return builder.toString()
    }

    private fun createPdf(textToPdf: String) {
        try {
            val gSon = GsonBuilder().setPrettyPrinting().create()
            val text = gSon.toJson(jsonFormat(textToPdf))

            val rawLines = text.split("\\n")
            val jsonLines = rawLines.map { it.replace("\\", "") }
            val maxLengthString = jsonLines.maxBy { it.length }

            val paint = Paint()
            paint.color = Color.BLACK
            paint.fontSpacing

            val pageWidth = paint.measureText(maxLengthString).toInt() + 2 * COL_INC.toInt() // 2, two side padding
            val pageHeight = (ROW_INC * rawLines.size + ROW_INC).toInt()

            val document = PdfDocument()
            val pageInfo: PdfDocument.PageInfo = PdfDocument.PageInfo.Builder(pageWidth, pageHeight, 1).create()
            val page: PdfDocument.Page = document.startPage(pageInfo)
            val canvas = page.canvas

            for (line in jsonLines) {
                canvas.drawText(line, column, row, paint)
                row += ROW_INC
            }

            document.finishPage(page)
            document.writeTo(FileOutputStream(File(PATH_TO_PDF_FILE)))
            document.close()
        }catch (e: java.lang.Exception){
            Log.e("classTag", e)
        }
    }
}

您可以找到关于如何使用Gson的文章