Hello Circle

kellbot · by **kellbot** » Sat Jun 27, 2009 5:21 pm

Sort of a graphical version of "hello world" I put this "hello circle" mini tutorial together, mostly as a way of documenting my own work for future use.

The program places a red dot on the screen wherever you touch.

I'm sure there are a number of things I could be doing better, but it can at least serve as a starting point for folks. Any feedback is appreciated.

http://www.kellbot.com/2009/06/android-hello-circle/

smbody · by **smbody** » Tue Jul 21, 2009 1:37 pm

nice tutorial! TNX!

feduza · by **feduza** » Fri Oct 23, 2009 12:12 am

Thank you for your tutor!

But in the emulator this works very slow. Will it works the same on the real device?

Can I use this tutor to make simple game?

rmcdonal · by **rmcdonal** » Thu Nov 12, 2009 5:43 am

I'm pretty new, but this has been the best tutorial I've seen yet. In other words, it's very easy, direct, and gratifying. Thanks!

rmcdonal · by **rmcdonal** » Thu Nov 12, 2009 5:48 am

I forgot to mention, there were a couple of things I added. An import to the main class:

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import android.view.MotionEvent;
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A return to the onTouch method:

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        main.setOnTouchListener(new OnTouchListener() {
 
                public boolean onTouch(View v, MotionEvent e) {
 
                        float x = e.getX();
 
                        float y = e.getY();
 
                        FrameLayout flView = (FrameLayout) v;
 
                        flView.addView(new Ball(getParent(), x, y, 25));
 
                        return true;
 
                }
 
        });
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And, I added an extra circle as a test in the Ball class (for fun and test):

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import android.content.Context;
 
import android.graphics.Canvas;
 
import android.graphics.Color;
 
import android.graphics.Paint;
 
import android.view.View;
 
public class Ball extends View {
 
        private final float x;
 
        private final float y;
 
        private final int r;
 
        private final Paint mRed = new Paint(Paint.ANTI_ALIAS_FLAG);
 
        private final Paint mBlack = new Paint(Paint.ANTI_ALIAS_FLAG);
 
        public Ball(Context context, float x, float y, int r) {
 
                super(context);
 
                this.x = x;
 
                this.y = y;
 
                this.r = r;
 
                mRed.setColor(Color.RED);
 
                mBlack.setColor(Color.BLACK);           
 
        }
 
        @Override
 
        protected void onDraw(Canvas canvas) {
 
                super.onDraw(canvas);
 
                canvas.drawCircle(x, y, r, mRed);
 
                canvas.drawCircle(x, y, r/2, mBlack);
 
        }
 
}
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Jadis · by **Jadis** » Thu Nov 12, 2009 3:13 pm

Hah, hello! I found your tutorial about a week ago and have been reading and reading to try and figure out how to clear the canvas each time Ball() is called. Do you have any ideas? I'm still very new to Java, and even moreso to android :shock:

Cyphic · by **Cyphic** » Fri Nov 13, 2009 9:04 pm

First tutorial I've tried on anddev.org. Got it working with the comments on the post. Also did some changes to it, only having one circle which moves etc. Thanks!

Hello Circle

Hello Circle

Re: Hello Circle

missing..

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