Draw dash line on a Canvas

Question

How can i draw dash line on a canvas. I already tried this:

Paint dashPaint = new Paint(); dashPaint.setARGB(255, 0, 0, 0); dashPaint.setStyle(Paint.Style.STROKE); dashPaint.setPathEffect(new DashPathEffect(new float[]{5, 10, 15, 20}, 0)); canvas.drawLine(0, canvas.getHeight() / 2, canvas.getWidth(), canvas.getHeight() / 2, dashPaint); 

And it gave me not dash line but a simple one.

Answer 1

You are drawing a line, as per documentation, drawLine function will:

Draw a line segment with the specified start and stop x,y coordinates, using the specified paint.

Note that since a line is always "framed", the Style is ignored in the paint.

Degenerate lines (length is 0) will not be drawn.

 canvas.drawLine(0, canvas.getHeight() / 2, canvas.getWidth(), canvas.getHeight() / 2, dashPaint)  

To draw a dashed line, a suggestion is to use the Path primitive

       private Path    mPath;        mPath = new Path();        mPath.moveTo(0, h / 2);        mPath.quadTo(w/2, h/2, w, h/2);         // h and w are height and width of the screen          Paint mPaint = new Paint();        mPaint.setARGB(255, 0, 0, 0);        mPaint.setStyle(Paint.Style.STROKE);        mPaint.setPathEffect(new DashPathEffect(new float[]{5, 10, 15, 20}, 0)); 

In onDraw()

       canvas.drawPath(mPath, mPaint);  

Snap shot

I have background and dashed line drew over it.

Example

public class FingerPaintActivity extends Activity {     MyView mv;      @Override     protected void onCreate(Bundle savedInstanceState) {         super.onCreate(savedInstanceState);         mv = new MyView(this);         setContentView(mv);         mPaint = new Paint();         mPaint.setAntiAlias(true);         mPaint.setDither(true);         mPaint.setColor(0xFFFF0000);         mPaint.setARGB(255, 0, 0, 0);         mPaint.setStyle(Paint.Style.STROKE);         mPaint.setPathEffect(new DashPathEffect(new float[]{10, 40,}, 0));         mPaint.setStrokeWidth(12);     }      private Paint mPaint;      public class MyView extends View {         private Bitmap mBitmap;         private Canvas mCanvas;         private Path mPath;         private Paint mBitmapPaint;         Context context;          public MyView(Context c) {             super(c);             context = c;             mPath = new Path();             mBitmapPaint = new Paint(Paint.DITHER_FLAG);         }          @Override         protected void onSizeChanged(int w, int h, int oldw, int oldh) {             super.onSizeChanged(w, h, oldw, oldh);             mBitmap = Bitmap.createBitmap(w, h, Bitmap.Config.ARGB_8888);             mCanvas = new Canvas(mBitmap);             mPath.moveTo(0, h / 2);             mPath.quadTo(w / 2, h / 2, w, h / 2);         }          @Override         protected void onDraw(Canvas canvas) {             super.onDraw(canvas);             canvas.drawBitmap(mBitmap, 0, 0, mBitmapPaint);             canvas.drawPath(mPath, mPaint);         }     } } 

Modify the above according to your needs.