Hello,

I must draw Button ( or any component View ) on canvas.
Anyone know, it is posible and what i must do??

I trying solution:
mybutton.draw(canvas) in override method onDraw but my button isn't drawn

Hi,

Your Button must have passed measurement and layout before drawing. Just call measure() and layout() methods before draw().

Thanks for your Replay but this solution doesn't work. Maybe I doing something wrong.
This is my code:

Code: Select all

public class Game extends View {
   Button _button;
   
   public Game(Context context) {
      super(context);
   
      _button = new Button(context);      
      _button.measure(50, 50);
      _button.layout(20,20,20,20);
}
   @Override
   protected void onDraw(Canvas canvas) {;
      _button.draw(canvas);
      postInvalidate();
   }

}


Hi,

You missed to read the documentation how to use the measure() call. It takes arguments, generated by MeasureSpec (http://developer.android.com/reference/android/view/View.MeasureSpec.html).

Also, you shouldn't call layout() with hardcoded values, use getMeasuredWidth() and getMeasuredHeight() instead.

Edit: Performance tip:
calling postInvalidate() from onDraw() is unnecessary overhead. A simple invalidate() or it's variants with dirty rectangle will be better.

thanks, its work great:)
Now I have another trouble, i can't change/set position my button.
I trying this method but doesn't work, my button stay on position (0,0):

Code: Select all

int width = _button.getMeasuredWidth();
int height = _button.getMeasuredHeight();
int left = 60;
int top = 60;
      
_button.layout(left, top, left + width, top + height);


I'm glad it helped!

Offset the Button by setting some padding before layout():
http://developer.android.com/reference/ ... ,%20int%29

Hello

this helped me. got succeeded in creating button on canvas but it is not supporting click event.

plz tell me

hey, has there been a solution to registering button clicks for buttons made in java code for canvas/custom views? Cause I'm having this same problem and I've really hit a wall in app development :/

Dear All,
I'm trying to the same thing as timothymilla did.
But when I call setPadding(150, 100, 0, 0) only the text in button locate, I really need locate the button at the center of the canvas. How can I do?
Thanks for your help.

I'm also experiencing the same problem as above. Please teach us how to set the button position on canvan. tnx!

Hi all,

I know this post is outdated but if some of you are still searching how to draw a view in a canvas setting a margin, here is a solution :

Code: Select all

           //We use a layout to contain the button (or any view you want to draw)
           LinearLayout ll = new LinearLayout(getApplicationContext());
           ll.setOrientation(LinearLayout.VERTICAL);

           //We set the layout parameters
           LinearLayout.LayoutParams layoutParams = new LinearLayout.LayoutParams(
                LinearLayout.LayoutParams.FILL_PARENT, LinearLayout.LayoutParams.WRAP_CONTENT);

           //SET THE MARGIN HERE
           layoutParams.setMargins(150, 150, 0, 0);

           //Declare a new view (here a button)
           Button button=new Button(getApplicationContext());
           button.setText("some text");
          
           //Add it to our linear layout
           ll.addView(button, layoutParams);
          
           //Measure and layout the linear layout before drawing it
           ll.measure(MeasureSpec.getSize(ll.getMeasuredWidth()), MeasureSpec.getSize(ll.getMeasuredHeight()));
           ll.layout(0, 0, MeasureSpec.getSize(button.getMeasuredWidth()), MeasureSpec.getSize(button.getMeasuredHeight()));
           //Finally draw the linear layout on the canvas
           ll.draw(canvas);

As you can see margin is not set directly in the button view because it doesn't support margins operations (only ViewGroup subclasses do : http://developer.android.com/reference/android/view/View.html).
Hope that'll help !

Sorry for reviewing an old thread. But I feel that the topic is not properly discussed and clearly understood. I've used the techniques described in the previous posts along with a SurfaceView, but was unable to render any standard controls including buttons or text boxes. I think this could not be done since the canvas is meant for pixel based drawing while controls are not. Described here: http://developer.android.com/guide/topics/graphics/2d-graphics.html

or... have I got everything terribly wrong?