Android : Drawing View with shapes plotted in r theta (r,θ) relation

r = 0.875*width/2+0.125cos(12θ)

r - width/2*cos(4θ)

r - width/2

Say you want to create views which contains shares as shown above. In those each circle drawn in (r,θ) relation. I implemented following onDraw method with possible two options.

Option 1. Rotating canvas and drawing circles - this is direct use of (r , θ)

Option 2. Converting points into x,y plan coordinate and drawing the circle.

@Override
protected void onDraw(Canvas canvas) {
float width = getWidth()/2;
float height = getHeight()/2;
Paint paint = new Paint();
paint.setColor(Color.RED);
        //Option 1
long time = System.currentTimeMillis();
canvas.save();
canvas.translate(width, height);
for(int i = 0 ; i < 13;i++){
canvas.drawCircle(width, 0, width*0.2f, paint);
canvas.rotate(-15);
}
canvas.restore();
Log.i(TAG, "::onDraw:" + "time 1 = " + (System.currentTimeMillis()-time));
        //Option 2
long time1 = System.currentTimeMillis();
canvas.save();
canvas.translate(width, height);
float angle = 0;
for(int i = 0 ; i < 13;i++){
float radian = (float) (Math.PI*angle/180.0f);
canvas.drawCircle((float) (width*Math.cos(radian)),
(float) (width*Math.sin(radian)), width*0.2f, paint);
angle+=15;
}
canvas.restore();
Log.i(TAG, "::onDraw:" + "time 2 = " + (System.currentTimeMillis()-time1));
}

Since above coding draw only 13 circles, I couldn't find a clear different in execution time for both options. So I change the code to draw 180 circle as follows:

@Override
protected void onDraw(Canvas canvas) {
float width = getWidth()/2;
float height = getHeight()/2;
Paint paint = new Paint();
paint.setColor(Color.RED);
long time1 = System.currentTimeMillis();
canvas.save();
canvas.translate(width, height);
for(int i = 0 ; i < 180;i++){
float radius = width;
canvas.drawCircle(radius, 0, 2.0f, paint);
canvas.rotate(-1);
}
canvas.restore();
time1 = System.currentTimeMillis()-time1;
long time2 = System.currentTimeMillis();
canvas.save();
canvas.translate(width, height);
for(int i = 0 ; i < 180;i++){
float radian = (float) (Math.PI*i/180.0f);
float radius = width;
canvas.drawCircle((float) (radius*Math.cos(radian)),
(float) (radius*Math.sin(radian)), 2.0f, paint);
}
canvas.restore();
time2 = System.currentTimeMillis()-time2;
Log.i(TAG, "::onDraw:" + "time1,time2, (time1-time2) = "
+ time1 + ","+time2+","+(time1-time2));
}

Now i could see clear different and Option 2 is faster than Option 1.



INFO/demo.theta.DemoRTheta(5302): ::onDraw:time1,time2, (time1-time2) = 62,35,27
INFO/demo.theta.DemoRTheta(5302): ::onDraw:time1,time2, (time1-time2) = 66,36,30
INFO/demo.theta.DemoRTheta(5302): ::onDraw:time1,time2, (time1-time2) = 66,37,29
INFO/demo.theta.DemoRTheta(5302): ::onDraw:time1,time2, (time1-time2) = 63,35,28
INFO/demo.theta.DemoRTheta(5302): ::onDraw:time1,time2, (time1-time2) = 68,34,34
INFO/demo.theta.DemoRTheta(5302): ::onDraw:time1,time2, (time1-time2) = 63,35,28
INFO/demo.theta.DemoRTheta(5302): ::onDraw:time1,time2, (time1-time2) = 61,35,26
INFO/demo.theta.DemoRTheta(5302): ::onDraw:time1,time2, (time1-time2) = 59,35,24
INFO/demo.theta.DemoRTheta(5302): ::onDraw:time1,time2, (time1-time2) = 68,40,28
INFO/demo.theta.DemoRTheta(5302): ::onDraw:time1,time2, (time1-time2) = 75,32,43
INFO/demo.theta.DemoRTheta(5302): ::onDraw:time1,time2, (time1-time2) = 65,32,33
INFO/demo.theta.DemoRTheta(5302): ::onDraw:time1,time2, (time1-time2) = 52,36,16

Here you have expresions for other above graphs. 

float radian = (float) (Math.PI*i/180.0f);

float radius = width;

float radius = (float) (width*Math.cos(4*radian));

float radius = (float) (0.875f*width+0.125f*width*Math.cos(12*radian));

But Option 2 needs some extra calculation to translate  (r , θ) into (x, y), in above examples we needed to determine only center of the circle.
Let see some of the view as follows.

canvas.save();
canvas.translate(width, height);
for(int i = 0 ; i < 72;i++){
canvas.drawLine(width*0.8F, 0, width*1.0f, 0, paint);
canvas.rotate(5);
}
canvas.restore();

Now we have to find start x,y and end x,y that need extra calculation and extra analysis effect to come up with that expresion.
Next one is more interesting need to use Path.

canvas.save();
canvas.translate(width, height);
for(int i = 0 ; i < 18;i++){
Path path = new Path();
path.moveTo(width*0.8F, 0);
path.lineTo(width, width*0.1F);
path.lineTo(width, -width*0.1F);
path.lineTo(width*0.8F, 0);
canvas.drawPath(path, paint);
canvas.rotate(20);
}
canvas.restore();

Now you can find translation expression and can find out which one is faster in each cases.
Enjoy!

Android: Aligning Custom Views at Base Line

Have you ever try to align a non-symmetric custom view at a custom base line as follows?

I tried it using base line attribute of Relative Layout.

First adjust the size of view:

@Override

protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {

super.onMeasure(widthMeasureSpec, heightMeasureSpec);

//Height should be always width * 7 / 12

setMeasuredDimension(getMeasuredWidth(), getMeasuredWidth()*7/12);

}

Then Override the getBaseLine method:

@Override

public int getBaseline() {

//base line is from bottom to width/12 (radius of the blue circle)

return getMeasuredHeight()-getMeasuredWidth()/12;

}

Following onDraw method would explain the reason for the above calculation:

@Override

protected void onDraw(Canvas canvas) {

Paint paint = new Paint();

paint.setAntiAlias(true);

//Draw the half circle

paint.setColor(Color.GRAY);

float width = getWidth();

float height = getHeight();

canvas.save();

canvas.translate(width/2, height-width/12);

canvas.drawArc(new RectF(-width/3, -width/3, +width/3, width/3), 0, -180, true, paint);

//Draw small circles

paint.setColor(Color.DKGRAY);

RectF rectF = new RectF(-width/2+width/24, -width/12+width/24, -width/3-width/24,                +width/12-width/24);

canvas.drawOval(rectF, paint);

for(int i = 0 ; i < 15 ;i++){

canvas.rotate(12f);

canvas.drawOval(rectF, paint);

}

//Draw blue circle

paint.setColor(Color.BLUE);

canvas.rotate(-180+30);

canvas.drawOval(new RectF(-width/2, -width/12, -width/3, +width/12), paint);

//Draw red arrow

paint.setColor(Color.RED);

Path path = new Path();

path.moveTo(-width*5/12, 0);

path.lineTo(10, -width/12);

path.lineTo(0, 0);

path.lineTo(10, +width/12);

path.close();

canvas.drawPath(path, paint);

canvas.restore();

}

Finally, create a layout xml as following:

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:orientation="vertical" android:layout_width="fill_parent"
android:layout_height="fill_parent">
<demo.ui.testing.DemoUITesting
android:layout_height="fill_parent" android:layout_width="fill_parent"
android:layout_alignBaseline="@+id/radioButton1"
android:layout_toRightOf="@+id/radioButton1">
<RadioButton android:layout_width="wrap_content"
android:layout_height="wrap_content" android:id="@+id/radioButton1"
android:layout_centerVertical="true">
</RelativeLayout>

Enjoy!.