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android – Draw multi-line text to Canvas

Posted by: admin March 11, 2020 Leave a comment

Questions:

A hopefully quick question, but I can’t seem to find any examples… I’d like to write multi-line text to a custom View via a Canvas, and in onDraw() I have:

...
String text = "This is\nmulti-line\ntext";
canvas.drawText(text, 100, 100, mTextPaint);
...

I was hoping this would result in line breaks, but instead I am seeing cryptic characters where the \n would be.

Any pointers appreciated.

Paul

How to&Answers:

Unfortunately Android doesn’t know what \n is. What you have to do is strip the \n and then offset the Y to get your text on the next line. So something like this:

canvas.drawText("This is", 100, 100, mTextPaint);
canvas.drawText("multi-line", 100, 150, mTextPaint);
canvas.drawText("text", 100, 200, mTextPaint);

Answer:

I found another way using static layouts. The code is here for anyone to refer to:

TextPaint mTextPaint=new TextPaint();
StaticLayout mTextLayout = new StaticLayout(mText, mTextPaint, canvas.getWidth(), Alignment.ALIGN_NORMAL, 1.0f, 0.0f, false);

canvas.save();
// calculate x and y position where your text will be placed

textX = ...
textY = ...

canvas.translate(textX, textY);
mTextLayout.draw(canvas);
canvas.restore();

Answer:

Just iterate through each line:

int x = 100, y = 100;
for (String line: text.split("\n")) {
      canvas.drawText(line, x, y, mTextPaint);
      y += mTextPaint.descent() - mTextPaint.ascent();
}

Answer:

I have written complete example

enter image description here

colors.xml

  <color name="transparentBlack">#64000000</color>

java class

 public class MainActivity extends AppCompatActivity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        Bitmap bm = BitmapFactory.decodeResource(getResources(), R.drawable.amit);
        ImageView imageView = (ImageView)findViewById(R.id.imageView);
        imageView.setImageBitmap(drawTextToBitmap(this, bm, "Name: Kolala\nDate: Dec 23 2016 12:47 PM, \nLocation: 440 Banquets & Restaurents"));

    }

  public Bitmap drawTextToBitmap(Context gContext,
                                   Bitmap bitmap,
                                   String gText) {
        Resources resources = gContext.getResources();
        float scale = resources.getDisplayMetrics().density;

        android.graphics.Bitmap.Config bitmapConfig =
                bitmap.getConfig();
        // set default bitmap config if none
        if(bitmapConfig == null) {
            bitmapConfig = android.graphics.Bitmap.Config.ARGB_8888;
        }
        // resource bitmaps are imutable,
        // so we need to convert it to mutable one
        bitmap = bitmap.copy(bitmapConfig, true);

        Canvas canvas = new Canvas(bitmap);
        // new antialised Paint
        Paint paint = new Paint(Paint.ANTI_ALIAS_FLAG);

        // text color - #3D3D3D
        paint.setColor(Color.WHITE);
        // text size in pixels
        paint.setTextSize((int) (25 * scale));
        // text shadow
        paint.setShadowLayer(1f, 0f, 1f, Color.WHITE);

        // draw text to the Canvas center
        Rect bounds = new Rect();

        int noOfLines = 0;
        for (String line: gText.split("\n")) {
           noOfLines++;
        }

        paint.getTextBounds(gText, 0, gText.length(), bounds);
        int x = 20;
        int y = (bitmap.getHeight() - bounds.height()*noOfLines);

        Paint mPaint = new Paint();
        mPaint.setColor(getResources().getColor(R.color.transparentBlack));
        int left = 0;
        int top = (bitmap.getHeight() - bounds.height()*(noOfLines+1));
        int right = bitmap.getWidth();
        int bottom = bitmap.getHeight();
        canvas.drawRect(left, top, right, bottom, mPaint);

        for (String line: gText.split("\n")) {
            canvas.drawText(line, x, y, paint);
            y += paint.descent() - paint.ascent();
        }

        return bitmap;
    }
}

Answer:

This is my solution that is based on @Dave’s answer (thanks btw 😉 )

import android.graphics.Canvas;
import android.graphics.Paint;

public class mdCanvas
{
    private Canvas m_canvas;

    public mdCanvas(Canvas canvas)
    {
        m_canvas = canvas;
    }

    public void drawMultiline(String str, int x, int y, Paint paint)
    {
        for (String line: str.split("\n"))
        {
              m_canvas.drawText(line, x, y, paint);
              y += -paint.ascent() + paint.descent();
        }
    }
}

I tried to inherit Canvas, but it doesn’t really let you. So this is an in-between class!

Answer:

I have to add here my version which considers STROKE WIDTH as well.

void drawMultiLineText(String str, float x, float y, Paint paint, Canvas canvas) {
   String[] lines = str.split("\n");
   float txtSize = -paint.ascent() + paint.descent();       

   if (paint.getStyle() == Style.FILL_AND_STROKE || paint.getStyle() == Style.STROKE){
      txtSize += paint.getStrokeWidth(); //add stroke width to the text size
   }
   float lineSpace = txtSize * 0.2f;  //default line spacing

   for (int i = 0; i < lines.length; ++i) {
      canvas.drawText(lines[i], x, y + (txtSize + lineSpace) * i, paint);
   }
}

Answer:

Yes. Use canvas.getFontSpacing() as the increment. I’ve tried it myself out of curiosity and it works for any font-size.

Answer:

try this

Paint paint1 = new Paint();
paint1.setStyle(Paint.Style.FILL);
paint1.setAntiAlias(true);
paint1.setColor(Color.BLACK);
paint1.setTextSize(15);


TextView tv = new TextView(context);
tv.setTextColor(Color.BLACK);
LinearLayout.LayoutParams llp = new LinearLayout.LayoutParams(LayoutParams.WRAP_CONTENT, LayoutParams.WRAP_CONTENT);
llp.setMargins(5, 2, 0, 0); // llp.setMargins(left, top, right, bottom);
tv.setLayoutParams(llp);
tv.setTextSize(10);
String text="this is good to see you , i am the king of the team";

tv.setText(text);
tv.setDrawingCacheEnabled(true);
tv.measure(MeasureSpec.makeMeasureSpec(canvas.getWidth(), MeasureSpec.EXACTLY), MeasureSpec.makeMeasureSpec(canvas.getHeight(), MeasureSpec.EXACTLY));
tv.layout(0, 0, tv.getMeasuredWidth(), tv.getMeasuredHeight());
canvas.drawBitmap(tv.getDrawingCache(), 5, 10, paint1);
tv.setDrawingCacheEnabled(false);

Answer:

it will work. i tested

 public Bitmap drawMultilineTextToBitmap(Context gContext,
                                       int gResId,
                                       String gText) {    
      // prepare canvas
      Resources resources = gContext.getResources();
      float scale = resources.getDisplayMetrics().density;
      Bitmap bitmap = BitmapFactory.decodeResource(resources, gResId);

      android.graphics.Bitmap.Config bitmapConfig = bitmap.getConfig();
      // set default bitmap config if none
      if(bitmapConfig == null) {
        bitmapConfig = android.graphics.Bitmap.Config.ARGB_8888;
      }
      // resource bitmaps are imutable,
      // so we need to convert it to mutable one
      bitmap = bitmap.copy(bitmapConfig, true);

      Canvas canvas = new Canvas(bitmap);

      // new antialiased Paint
      TextPaint paint=new TextPaint(Paint.ANTI_ALIAS_FLAG);
      // text color - #3D3D3D
      paint.setColor(Color.rgb(61, 61, 61));
      // text size in pixels
      paint.setTextSize((int) (14 * scale));
      // text shadow
      paint.setShadowLayer(1f, 0f, 1f, Color.WHITE);

      // set text width to canvas width minus 16dp padding
      int textWidth = canvas.getWidth() - (int) (16 * scale);

      // init StaticLayout for text
      StaticLayout textLayout = new StaticLayout(
        gText, paint, textWidth, Layout.Alignment.ALIGN_CENTER, 1.0f, 0.0f, false);

      // get height of multiline text
      int textHeight = textLayout.getHeight();

      // get position of text's top left corner
      float x = (bitmap.getWidth() - textWidth)/2;
      float y = (bitmap.getHeight() - textHeight)/2;

      // draw text to the Canvas center
      canvas.save();
      canvas.translate(x, y);
      textLayout.draw(canvas);
      canvas.restore();

      return bitmap;
    }

Source : http://www.skoumal.net/en/android-drawing-multiline-text-on-bitmap/

Answer:

I re-used the solution proposed by GreenBee and made a function to draw some multi line text into specified bounds with the “…” at the end if a truncate happened:

public static void drawMultiLineEllipsizedText(final Canvas _canvas, final TextPaint _textPaint, final float _left,
            final float _top, final float _right, final float _bottom, final String _text) {
        final float height = _bottom - _top;

        final StaticLayout measuringTextLayout = new StaticLayout(_text, _textPaint, (int) Math.abs(_right - _left),
                Alignment.ALIGN_NORMAL, 1.0f, 0.0f, false);

        int line = 0;
        final int totalLineCount = measuringTextLayout.getLineCount();
        for (line = 0; line < totalLineCount; line++) {
            final int lineBottom = measuringTextLayout.getLineBottom(line);
            if (lineBottom > height) {
                break;
            }
        }
        line--;

        if (line < 0) {
            return;
        }

        int lineEnd;
        try {
            lineEnd = measuringTextLayout.getLineEnd(line);
        } catch (Throwable t) {
            lineEnd = _text.length();
        }
        String truncatedText = _text.substring(0, Math.max(0, lineEnd));

        if (truncatedText.length() < 3) {
            return;
        }

        if (truncatedText.length() < _text.length()) {
            truncatedText = truncatedText.substring(0, Math.max(0, truncatedText.length() - 3));
            truncatedText += "...";
        }
        final StaticLayout drawingTextLayout = new StaticLayout(truncatedText, _textPaint, (int) Math.abs(_right
                - _left), Alignment.ALIGN_NORMAL, 1.0f, 0.0f, false);

        _canvas.save();
        _canvas.translate(_left, _top);
        drawingTextLayout.draw(_canvas);
        _canvas.restore();
    }

Answer:

Solution without StaticLayout

//Get post text
    String text = post.getText();

    //Get weight of space character in px
    float spaceWeight = paint.measureText(" ");

    //Start main algorithm of drawing words on canvas
    //Split text to words
    for (String line : text.split(" ")) {
        //If we had empty space just continue
        if (line.equals("")) continue;
        //Get weight of the line
        float lineWeight = paint.measureText(line);
        //If our word(line) doesn't have any '\n' we do next
        if (line.indexOf('\n') == -1) {
            //If word can fit into current line
            if (cnv.getWidth() - pxx - defaultMargin >= lineWeight) {
                //Draw text
                cnv.drawText(line, pxx, pxy, paint);
                //Move start x point to word weight + space weight
                pxx += lineWeight + spaceWeight;
            } else {
                //If word can't fit into current line
                //Move x point to start
                //Move y point to the next line
                pxx = defaultMargin;
                pxy += paint.descent() - paint.ascent();
                //Draw
                cnv.drawText(line, pxx, pxy, paint);
                //Move x point to word weight + space weight
                pxx += lineWeight + spaceWeight;
            }
            //If line contains '\n'
        } else {
            //If '\n' is on the start of the line
            if (line.indexOf('\n') == 0) {
                pxx = defaultMargin;
                pxy += paint.descent() - paint.ascent();
                cnv.drawText(line.replaceAll("\n", ""), pxx, pxy, paint);
                pxx += lineWeight + spaceWeight;
            } else {
                //If '\n' is somewhere in the middle
                //and it also can contain few '\n'
                //Split line to sublines
                String[] subline = line.split("\n");
                for (int i = 0; i < subline.length; i++) {
                    //Get weight of new word
                    lineWeight = paint.measureText(subline[i]);
                    //If it's empty subline that's mean that we have '\n'
                    if (subline[i].equals("")) {
                        pxx = defaultMargin;
                        pxy += paint.descent() - paint.ascent();
                        cnv.drawText(subline[i], pxx, pxy, paint);
                        continue;
                    }
                    //If we have only one word
                    if (subline.length == 1 && i == 0) {
                        if (cnv.getWidth() - pxx >= lineWeight) {
                            cnv.drawText(subline[0], pxx, pxy, paint);
                            pxx = defaultMargin;
                            pxy += paint.descent() - paint.ascent();
                        } else {
                            pxx = defaultMargin;
                            pxy += paint.descent() - paint.ascent();
                            cnv.drawText(subline[0], pxx, pxy, paint);
                            pxx = defaultMargin;
                            pxy += paint.descent() - paint.ascent();
                        }
                        continue;
                    }
                    //If we have set of words separated with '\n'
                    //it is the first word
                    //Make sure we can put it into current line
                    if (i == 0) {
                        if (cnv.getWidth() - pxx >= lineWeight) {
                            cnv.drawText(subline[0], pxx, pxy, paint);
                            pxx = defaultMargin;
                        } else {
                            pxx = defaultMargin;
                            pxy += paint.descent() - paint.ascent();
                            cnv.drawText(subline[0], pxx, pxy, paint);
                            pxx = defaultMargin;
                        }
                    } else {
                        pxx = defaultMargin;
                        pxy += paint.descent() - paint.ascent();
                        cnv.drawText(subline[i], pxx, pxy, paint);
                        pxx += lineWeight + spaceWeight;
                    }
                }

            }
        }
    }

Answer:

I worked with what I had, which already converted single lines to canvases, and I worked off Lumis’s answer, and I ended up with this. The 1.3 and 1.3f are meant as padding between lines, relative to the size of the font.

public static Bitmap getBitmapFromString(final String text, final String font, int textSize, final int textColor)
{
    String lines[] = text.split("\n");
    textSize = getRelX(textSize);  //a method in my app that adjusts the font size relative to the screen size
    Paint paint = new Paint(Paint.ANTI_ALIAS_FLAG);
    paint.setTextSize(textSize);
    paint.setColor(textColor);
    paint.setTextAlign(Paint.Align.LEFT);
    Typeface face = Typeface.createFromAsset(GameActivity.getContext().getAssets(),GameActivity.getContext().getString(R.string.font) + font + GameActivity.getContext().getString(R.string.font_ttf));
    paint.setTypeface(face);
    float baseline = -paint.ascent(); // ascent() is negative
    int width = (int) (paint.measureText(text) + 0.5f); // round
    int height = (int) (baseline + paint.descent() + 0.5f);
    Bitmap image = Bitmap.createBitmap(width, (int)(height * 1.3 * lines.length), Bitmap.Config.ARGB_8888);
    Canvas canvas = new Canvas(image);
    for (int i = 0; i < lines.length; ++i)
    {
        canvas.drawText(lines[i], 0, baseline + textSize * 1.3f * i, paint);
    }
    return image;
}

Answer:

My example with Dynamic Text Sizing and spacing, Works great for me…

public Bitmap fontTexture(String string, final Context context) {
    float text_x = 512;
    float text_y = 512;
    final float scale = context.getResources().getDisplayMetrics().density;

    int mThreshold = (int) (THRESHOLD_DIP * scale + 0.5f);

    String[] splited = string.split("\s+");
    double longest = 0;
    for(String s:splited){
        if (s.length() > longest) {
            longest = s.length();
        }
    }
    if(longest > MAX_STRING_LENGTH) {
        double ratio = (double) MAX_STRING_LENGTH / longest;
        mThreshold = (int) ((THRESHOLD_DIP * ((float) ratio)) * scale + 0.5f);
    }

    Bitmap bitmap = Bitmap.createBitmap(1024, 1024, Bitmap.Config.ARGB_8888);

    Canvas canvas = new Canvas(bitmap);

    Typeface font = Typeface.createFromAsset(context.getAssets(),
            "fonts/dotted_font.ttf");

    TextPaint mTextPaint=new TextPaint();
    mTextPaint.setColor(Color.YELLOW);
    mTextPaint.setTextAlign(Paint.Align.CENTER);
    mTextPaint.setTextSize(mThreshold);
    mTextPaint.setTypeface(font);
    StaticLayout mTextLayout = new StaticLayout(string, mTextPaint, canvas.getWidth(), Layout.Alignment.ALIGN_NORMAL, 1.0f, 0.0f, false);

    canvas.save();

    canvas.translate(text_x, text_y);
    mTextLayout.draw(canvas);
    canvas.restore();


    return bitmap;
}