Dfind the center of canvas android how to#
Dfind the center of canvas android android#

We would be adding a button to the bottom of our Custom View, and on-click, we change the colours of the shapes drawn in our custom View. invalidate instructs the View to redraw its state. When this method is called, we tell the View that some View properties have changed and the current rendering is not valid and needs to be changed. On the other hand, we are given a handy dandy utility called invalidate().

When working with custom views, a way of telling the view that its state need to change is by redrawing the views with the changed properties.įollowing this line of thought, we might think of invoking onDraw when changes have been made to the View, but the View itself calls the onDraw when it’s ready - so we can’t do this. We might want it to react or animate by changing some of its properties, or for some detail to change based on user interaction (touch, hold, drag e.t.c.). For example, you can use a BitmapShader to define a bitmap as a texture to.

Dfind the center of canvas android android#

Android defines several subclasses of Shader for Paint to use, such as BitmapShader, ComposeShader, LinearGradient, RadialGradient, and SweepGradient. Most times, we would want to change the state of our custom view. In Android, Shader defines the color (s) or the texture with which the Paint object should draw (other than a bitmap).

Dfind the center of canvas android how to#

Now that we’ve learnt how to draw rectangles and circles, let’s try to make them dynamic by changing the state of the shapes. To understand this concept better, let’s draw another set of shapes by shifting the origin of our canvas. The x and y parameters indicate the point the canvas origin should be moved to - our new origin (where our draw calls would start from). Now that we understand why we could want to translate the canvas, how then do we do it? We can boycott all that by moving the canvas origin to the area of the next draw call when required. This largely helps in eliminating unnecessary and repeated calculations from the actual origin of the canvas when drawing a lot of shapes. Once here, all we need to do is to draw the triangle using the new origin.įinally, we translate one last time to another position on the canvas and this serves as the center of a circle, then we draw the circle using the radius. After that, we translate the whole origin to the top of the triangle. Instead of re-calculating the points from the origin for every single draw operation, we only use the actual origin (top-left) to draw the rectangle. to draw a line canvas.In this “translated” version, we see something different. Its Canvas width minus text width divided by 2. Radius: The radius of the cirle to be drawn How to center my text on a canvas The formula for horizontal centering is easy. to draw a circle canvas.drawCircle (float cx, float cy, float radius, Paint paint)Ĭx: The x-coordinate of the center of the cirle to be drawnĬy: The y-coordinate of the center of the cirle to be drawn to draw a oval canvas.drawOval (float left, float top, float right, float bottom, Paint paint) Height: The bottom side of the rectangle to be drawn

Width: The right side of the rectangle to be drawn StartY: The top side of the rectangle to be drawn StartX: The left side of the rectangle to be drawn to draw a rectangle canvas.drawRect(startX, startY, width, height, paint) Paint paint = new Paint() Įxample of some of the methods of Canvas class Canvas class provide us many method which help us to draw any time of shape.įor draw anything via Canvas class we need the object of Paint class. We can give any shape to a custom view by overriding onDraw(Canvas canvas) method.

The most important part of custom view is its appearance. We can create custom view by extending View class.