How to draw circle by canvas in Android?

Question

I want to draw circle by canvas. Here is my code:

[MyActivity.java]:

public class MyActivity extends Activity  {  public void onCreate(Bundle savedInstanceState)     {       ...       setContentView(new View(this,w,h));    }          } 

[View.java]:

public class View extends SurfaceView {     public View(Context context, int w, int h)     {         super(context);         Canvas grid = new Canvas(Bitmap.createBitmap(h,w, Bitmap.Config.ARGB_8888));         grid. drawColor(Color.WHITE);         Paint paint = new Paint();         paint.setStyle(Paint.Style.FILL);         grid.drawCircle(w/2, h/2 , w/2, paint);     } } 

So I have just black screen without circle. Why it does not work? How to fix it?

Answer 1

You can override the onDraw method of your view and draw the circle.

protected void onDraw(Canvas canvas) {  super.onDraw(canvas);   canvas.drawCircle(x, y, radius, paint);  } 

For a better reference on drawing custom views check out the official Android documentation.

http://developer.android.com/training/custom-views/custom-drawing.html

Answer 2

import android.app.Activity; import android.content.Context; import android.graphics.Canvas; import android.graphics.Color; import android.graphics.Paint; import android.os.Bundle; import android.view.View;  public class MainActivity extends Activity  {       @Override      public void onCreate(Bundle savedInstanceState)      {          super.onCreate(savedInstanceState);          setContentView(new MyView(this));      }       public class MyView extends View      {          Paint paint = null;          public MyView(Context context)           {               super(context);               paint = new Paint();          }           @Override          protected void onDraw(Canvas canvas)           {             super.onDraw(canvas);             int x = getWidth();             int y = getHeight();             int radius;             radius = 100;             paint.setStyle(Paint.Style.FILL);             paint.setColor(Color.WHITE);             canvas.drawPaint(paint);             // Use Color.parseColor to define HTML colors             paint.setColor(Color.parseColor("#CD5C5C"));             canvas.drawCircle(x / 2, y / 2, radius, paint);         }      } } 

Edit if you want to draw circle at centre. You could also translate your entire canvas to center then draw circle at center.using

canvas.translate(getWidth()/2f,getHeight()/2f); canvas.drawCircle(0,0, radius, paint); 

These two link also help

http://www.compiletimeerror.com/2013/09/introduction-to-2d-drawing-in-android.html#.VIg_A5SSy9o

http://android-coding.blogspot.com/2012/04/draw-circle-on-canvas-canvasdrawcirclet.html