Comments on Tutorial For Android: Drawing with Canvas in Android

Thanks a lot i have solve my

2012-02-17T18:53:58.109+08:00

Thanks a lot i have solve my

Excellent tutorials. Thanks!

2012-01-16T21:41:57.224+08:00

Excellent tutorials. Thanks!

I really appreciate the shedding of light on this....

2011-11-28T04:45:15.784+08:00

I really appreciate the shedding of light on this. I too am new to the workflow of Android applications, so this really helped out a lot for me to be able to look at how it should be done, and implement the same fundamentals.

However, I have a couple of things to point out:

1. With your code, if you just tap on the screen before anything is drawn, it will throw an IndexOutOfRangeException, and cause a force close. You can remedy that by adding a try/catch block to the MouseEvent.ACTION_UP conditions.

2. If you change the background colour of the DrawingPanel, you are no longer able to draw (no matter the combination of pen/background colours chosen). This, of course, may have something to do with my newness to the API, and not calling the background changing method in the proper area. If you had any ideas on this one, that would be greatly appreciated :)

Hi All, I basically want to draw a map on the scr...

2011-10-24T18:46:40.813+08:00

Hi All,

I basically want to draw a map on the screen, this will all be done using draw on canvas (this i can do).

However the problem I am having is my overall map is 1000 x 1000, however I only ever want the user to see 10x10. Then every time the user moves (arrows or touch & drag) the app automatically draws the next bitmap within the 1000 x 1000 sequence until they reach the end.

I would also like to add a birdseye view where the view is zoomed in filling up 70% of the Android Screen.

Can anyone point me in the right direction to solve this?

Thanks

For those who want to paint while moving without m...

2011-09-23T05:43:45.079+08:00

For those who want to paint while moving without making it slow, check this code modification at onTouchEvent. @Rolli, take a look if you didn't get it working:

@Override
public boolean onTouchEvent(MotionEvent event) {
synchronized (_thread.getSurfaceHolder()) {
if(event.getAction() == MotionEvent.ACTION_DOWN){
path = new Path();
path.moveTo(event.getX(), event.getY());
path.lineTo(event.getX(), event.getY());
}else if(event.getAction() == MotionEvent.ACTION_MOVE){
path.lineTo(event.getX(), event.getY());
if(_graphics.size() > 0) {
_graphics.remove(_graphics.size() - 1);
}
_graphics.add(path);
}else if(event.getAction() == MotionEvent.ACTION_UP){
path.lineTo(event.getX(), event.getY());
_graphics.remove(_graphics.size() - 1);
_graphics.add(path);
}
return true;
}
}

Hi Sir, how do I make the canvas background as an ...

2011-09-20T15:06:29.346+08:00

Hi Sir, how do I make the canvas background as an image? Thank you very much :)

Excellent post - thanks for spelling out some of t...

2011-09-05T10:23:20.990+08:00

Excellent post - thanks for spelling out some of the options for Paint and adding this fun bit of functionality. It got me going quickly on my newest prototype!

I'll get working on the rest of your Canvas series shortly.

-ProjectJourneyman

see the undo and redo tutorial

2011-06-21T21:37:10.712+08:00

see the undo and redo tutorial

HI How do i erase or clear the canvas after draw ...

2011-06-21T21:28:18.652+08:00

HI
How do i erase or clear the canvas after draw the the line

to create button and listener you should see the u...

2011-06-21T19:57:01.340+08:00

to create button and listener you should see the updated tutorial, see above, it would use the extended SurfaceView in an xml thus you can use core android stuff

Thanks, Nice tutorial How can i add a button and ...

2011-06-21T19:54:14.116+08:00

Thanks, Nice tutorial

How can i add a button and listener to it?

Anybody know why this code crashes onResume? Works...

2011-05-28T11:33:08.363+08:00

Anybody know why this code crashes onResume? Works fine until you back out and try to reopen

This is using view only , define this activity in...

2011-05-10T13:56:01.630+08:00

This is using view only , define this activity in your manifest

public class DrawingActivity extends Activity {
private ArrayList _graphics = new ArrayList();
private Paint mPaint;
Handler myHandler = new Handler() {

public void handleMessage(android.os.Message msg) {
myview.invalidate();

};
};
Myview myview;

@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
// setContentView(new DrawingPanel(this));
mPaint = new Paint();
mPaint.setDither(true);
mPaint.setColor(0xFFFFFF00);
mPaint.setStyle(Paint.Style.STROKE);
mPaint.setStrokeJoin(Paint.Join.ROUND);
mPaint.setStrokeCap(Paint.Cap.ROUND);
mPaint.setStrokeWidth(3);
myview = new Myview(this);
myview.setLayoutParams(new LayoutParams(LayoutParams.FILL_PARENT,
LayoutParams.FILL_PARENT));
setContentView(myview);
myHandler = new Handler();

}

class Myview extends View {

public Myview(Context context) {
super(context);

}

Path path;

@Override
public boolean onTouchEvent(MotionEvent event) {
if (event.getAction() == MotionEvent.ACTION_DOWN) {
path = new Path();
path.moveTo(event.getX(), event.getY());
path.lineTo(event.getX(), event.getY());
_graphics.add(path);
} else if (event.getAction() == MotionEvent.ACTION_MOVE) {
path.lineTo(event.getX(), event.getY());
} else if (event.getAction() == MotionEvent.ACTION_UP) {
path.lineTo(event.getX(), event.getY());
}
invalidate();
return true;
}

@Override
protected void onDraw(Canvas canvas) {
for (Path path : _graphics) {
// canvas.drawPoint(graphic.x, graphic.y, mPaint);
canvas.drawPath(path, mPaint);
}
}
}

}

Thanks for the tip android that's what I neede...

2011-05-07T11:54:53.768+08:00

Thanks for the tip android that's what I needed to speed up my app.

Gread Post. I also have a android canvas example. ...

2011-04-30T13:58:01.370+08:00

Gread Post. I also have a android canvas example. Mine is to draw a bitmap from image. Share with u:

Android Canvas Example

Thanks, great tutorial. iam trying save the path b...

2011-02-17T13:21:50.792+08:00

Thanks, great tutorial. iam trying save the path but i couldnt. how to handle change orientation, when we change orientation i want to draw same path again. how can i achieve this

thanks in advance

As i was trying to play around with Android graphi...

2011-01-21T21:48:40.691+08:00

As i was trying to play around with Android graphics, i got this reference. Then i created the AndroidPaint freeware app. Please have a look at it at AndroidPaint

The preview of the line u draw/drawing are part of...

2010-12-06T19:26:24.564+08:00

The preview of the line u draw/drawing are part of the drawing in canvas series, i had already prepared all the codes, just dont have time right now to blog about it but ill commit ill do it within this week, so stay posted ;-)

There is a problem... the path is shown only when ...

2010-12-06T18:51:08.130+08:00

There is a problem... the path is shown only when we leave the touch from the screen. It should be shown along the finger moving on screen. Other wise we would have no idea from where the lines are originating if we have to draw something continuously. It will just be a wild guess.

@anonymous if you have been following the drawing ...

2010-12-05T16:10:38.742+08:00

@anonymous if you have been following the drawing in android series the last one is one http://www.tutorialforandroid.com/2010/11/drawing-with-canvas-in-android-saving.html, on the first code block you can insert something like isDrawing or hasDrawn boolean variable (before the try catch, inside the while) on where the paths would only be drawn when an event is trigger, which would make the whole experience smooth.

andrea: I attempted to do this but in a different ...

2010-12-05T16:01:42.498+08:00

andrea: I attempted to do this but in a different way. at the end of my onDraw method, i cleared the array (_graphics), but for some reason I cannot draw anything

i think it loses performance because at every onDr...

2010-11-18T06:03:49.069+08:00

i think it loses performance because at every onDraw all the old paths are redrawn. i tried with this:
if(_graphics.size() >= 1)
canvas.drawPath(_graphics.get(_graphics.size()-1), mPaint);

and it keeps smooth.

andrea

Thank you Almond and Zingo, this is most helpfull....

2010-09-02T04:01:24.226+08:00

Thank you Almond and Zingo, this is most helpfull.

I to change position of object. I set new position to my rectangle when user "drags it".

However for some reason, I can see all old positions of retangle.

How could I show only current position?

Can't get this to work at all. My screen stays...

2010-08-09T21:43:42.314+08:00

Can't get this to work at all. My screen stays black with nothing ever changing, even though I do c.drawARGB(255, 255, 255, 255); in onDraw().

There are a lot of ways to delete or reset the can...

2010-05-31T22:59:00.055+08:00

There are a lot of ways to delete or reset the canvas but the reset is kinda not directly clear it. If your canvas came with bitmap, you could recycle the bitmap and redraw the bitmap. If you canvas is purely a background color, then you could just drawColor on your canvas. Hope this link helps http://stackoverflow.com/questions/2423327/android-view-ondraw-always-has-a-clean-canvas