android - 如何在 android 自定义 View 的 Canvas 上绘制段落

Question

我要在 Canvas 上绘制大量文本。我可以设置文本，但所有文本都显示在一行中。所以我无法阅读所有文本。我想设置文本作为 Canvas 上的一段。谁能告诉我实现此功能的方法。

我尝试使用 getLineCount()、getLineBound() 但它在这些行上提示错误，因为我的 View 不包含这些方法。

Answer 1

您可能必须找到可以容纳在您的 Canvas 宽度内的最长子字符串并重复此操作，直到您的整个“冗长”字符串被分解成更小的字符串。递归在这里有帮助

你可以尝试这样的事情:

class Font
{
    private TextPaint tp = new TextPaint();
    private Paint p = new Paint();

    int getCharWidth(char ch, int fontSize)
    {
        tp.setTextSize(fontSize);
        Rect r = new Rect();
        tp.getTextBounds(String.valueOf(ch), 0, 1, r);
        return r.width();
    }

    int getHeight(int fontSize)
    {
        tp.setTextSize(fontSize);
        Rect r = new Rect();
        tp.getTextBounds(String.valueOf('A'), 0, 1, r);
        return r.height();
    }

    int getStringWidth(String str, int fontSize)
    {
        p.setTextSize(fontSize);
        tp.setTextSize(fontSize);
        Rect r = new Rect();
        tp.getTextBounds(str, 0, str.length(), r);          
        return r.width();//you may also try p.measureText(str);
    }
}

public String getLongestSubString(int width, int fontSize, String text)
{   
    int maxCharPerLine = width / (new Font()).getCharWidth('A', fontSize);
    int stringWidth = (new Font()).getStringWidth(text, fontSize);
    int posOfSpace = text.lastIndexOf(' ');
    if( stringWidth <= width || maxCharPerLine >= text.length())
        return text;
    String temp = text.substring(0, (posOfSpace == -1) ? (maxCharPerLine > text.length() ? text.length() : maxCharPerLine) : posOfSpace);
    return getLongestSubString(width, fontSize, temp);
}

public ArrayList<String> breakTextToLines(int width, int fontSize, String text)
{
    if(text == null)
        return null;
    ArrayList<String> lines = new ArrayList<String>();

    text = text.replace("\n", " ");

    int length = -1;
    String tempText = "";

    do
    {
        if( !tempText.endsWith(" ") && tempText.length() > 0)
            length += tempText.length();
        else
            length += tempText.length() + 1;

        if( length >= text.length())
            break;

        tempText = getLongestSubString(width, fontSize, text.substring(length));
        lines.add(tempText);
    }
    while(length < text.length());

    return lines;
}

现在，一旦您将字符串列表(使用 breakTextToLines(int,int,String) 方法)分解为现在可以适合 Canvas 的更小的字符串，您就可以开始您的绘图过程了如下图

int fontSize = 20;
float lineSpaceFactor = 0.5f;
int lineHeight = (new Font()).getHeight(fontSize);
int lineSpace = (int)(lineSpaceFactor * lineHeight);

int width = 256;//your canvas width can go here
int height = 256;//your canvas height can go here
String string = "Need a lengthy string? why not Dr Zoidberg maybe? woop woop woop!!!";//your lengthy string can go here
Canvas canvas = new Canvas(bitmap);//your canvas or bitmap source goes here
Paint paint = new Paint(Paint.ANTI_ALIAS_FLAG);
paint.setTextAlign(Align.CENTER);
paint.setTextSize(fontSize);

ArrayList<String> lines = breakTextToLines(width, fontSize, string);
int numOfLines = lines.size();
int overallHeight = numOfLines * (lineHeight + lineSpace);

int yLoc = (height - overallHeight) / 2;
yLoc += lineSpace;

for(String line : lines)
{
    int xLoc = textureWidth /2 ;       
    canvas.drawText(text, xLoc, yLoc, paint);

    yLoc += (lineHeight + lineSpace);       
}
//your canvas would now be drawn with the paragraph broken into lines and centre aligned 

希望这对您有所帮助。