I want to learn, how to create custom view. I have gone through multiple tutorial and didn't get what i want(I mean concept).
What i have learned
I am sharing my concept,if i am wrong please correct me.
If you want to make a minor change to the standard view then inherit itself(e.g extends seekbar) and customize it.
But if you want to make difficult or multifunction view, We should inherit View Class
When we inherit a View.
Two methods are neccessary
onDraw(Canvas canvas) // it call each time it and also can be call using invalidate.
onMeasure // it measure the actual width and size and set our viewit accordingly
Whatever you want to draw on View can be done using canvas;(Am i right).
To define additional attributes create an attrs.xml file in your res/values folder. and add <declare-styleable name="YourCustomView"> and add attributes to it.
get these attribute in the constructor of the View using TypedArray call recyle method.
My Confusions
can we draw something without using Canvas
can we draw ImageView without converting it to bitmap.
I simply want to create a custom imageView which can be rotated like
a dialView but it should rotate half(semi-circle) and also want to
draw its progress outside it. using canvas.drawArc()
What i want to achieve
I want to create my own custom knob, I have searched our google but didn't find what i want see my questions here
First Question
Second Question
Thanks in Advance....
1)You can use openGL. Otherwise you need a canvas. The canvas defines where you're drawing to, without it (or the openGL equivalent) we don't know where to draw. You might not want to draw directly to the screen, its common to draw to bitmaps in many cases.
2)Your question doesn't make a lot of sense. Why would you want to draw an ImageView, other than by letting it draw itself?
3)Easiest way to do that is to use a normal image view and call setRotation to rotate it as needed.
Related
I've recently started building my second android app and I've hit a wall. What I want to know in general is this. In almost all other programming languages that I've used there is a simple way of drawing arbitrarily on screen. Usually there is some sort of Scene or Canvas type class and another GraphicObject type class. So If, say, I want to draw a car, I create a class that descends from GraphicObject and define they it draws itself and then add an instantiation of the Car class (the object) to the Scene. If I want a second car, you just instantiate another and put it wherever you like, by setting some kind of coordinate function. If this is a program where what is drawn depends on user input, everything must be done programatically and hence it does not depend on anything other than the code written.
How do you achieve this in Android? As far as I can muster the only object which you can define the way it is drawn is a View. However I have not been able to simply take my custom view (that draws a rectangle in my case) and instantiate two of them a put them in the screen where I want them, and do this in a programtic simple way....
Thank you for any advice.
Well if I want to draw lets say 10 rectangles then I wont instantiate my custom View 10 times. Instead I will add logic in my custom View to be able to draw 10 or more rectangles. Anyway if you want to draw again what was drawn in a View then you can call setDrawingCacheEnabled(true); on your View and then call getDrawingCache() to get Bitmap to draw it somewhere else.
Its almost same in android also,
All the widgets are inherited from class View, by extending this class you can actually create whatever you want limiting by only yours imagination, you have access to canvas here, use it along with touch controls exposed from class itself to override all the behaviours you want as per your need,.
http://developer.android.com/reference/android/view/View.html
http://developer.android.com/reference/android/graphics/Canvas.html
I want to draw a bitmap to the canvas.
However, I am an inexperienced programmer and don't know how to make the canvas the main screen.
Basically, I want to draw a bitmap to the main activity using a canvas. I know how to draw bitmaps to canvases but it doesn't show up anywhere that I can see (with only one activity). I want the bitmap to show up on the main activity. Any tips?
Sorry if the wording is confusing, thanks for any help.
see these links. might think they may be helpful.
https://www.linux.com/learn/tutorials/707993-how-to-draw-2d-object-in-android-with-a-canvas
http://www.linux.com/learn/tutorials/703911-2d-drawing-with-android-motion-sensors
you can try searching online..
some example
http://www.edu4java.com/en/androidgame/androidgame2.html
or some game engine which will help you to develop game with proper memory management.
https://stackoverflow.com/questions/17163446/what-is-the-best-2d-game-engine-for-android
What you are trying to do is create your own CustomView. When you are putting a button or anything in your layout file that is actually a view. Android does allow you to create your own view to manually handle things on the screen. Games are usually implemented that way. They use customview by extending SurfaceView/GLSurfaceView.
As for the solution of your problem:
create a custom view by extending the View.
add all the constructor from superclass.
override onDraw method
onDraw method will pass you a canvas for you to draw
draw whatever you like(Bitmap, line ,....) using canvas
In your layout file include the customview you just created.
<my.packagename.MyCustomView android:width .... > </my.packagename.MyCustomView>
Hope this helps.
Also you will find lots good resources on how you can create your own customview.
I've been working on this for a while but can't find anything that exactly addresses my question (at least not something easy to understand).
I have a main layout XML file where I define various layout objects like a Button or a TextView (and I know I can add SurfaceView, View, and view and other things too). I want to draw a shape (in my case it's an arc) in just one of these objects so it doesn't take up the whole screen and so I can position it relative to other things.
(In my case it will ultimately re-draw the arc kind of like a circle with a gap in a different position every time I call a method depending on a value I pass to the method, but that's separate from my basic question.)
I know the answer will have something to do with a canvas, an onDraw method, maybe Paint, probably a view. I have been able to draw a circle from a custom View object by setting the main java file's layout as that View (as opposed to R.layouts.main), but that takes up the whole screen, and I'm unsure how I might be able to have that dynamically draw with modifications.
A really clear explanation or better yet an actual example would just be awesome.
As i see it u need to draw a specific shape on widget and not on complete screen. Try using layer List.
you can refer this link for sample Link
I am writing an App that need to render an image if a user selects an option. The image will read a data file and according to the contents of the data file render an appropriate amount of rectangles, lines and text (I'm visualizing data). I read this site Drawables or Canavs and if I understood it correctly it says I should use drawables. But what I don't understand (haven't found where or missed it) is where I define the space to draw shapes in. As I do not know the number of shapes and thus the size of the entire visualization until I read the data file, i do not know how large of a composite image (size required to render all of the shapes and lines) I need.
So I have three questions.
Should I use drawables to accomplish what I need to do?
Does the mDrawable.setBounds method define the 'size' of the visualization I am working in
Can I draw lines and insert text with drawables?
To show a Drawable you would use an ImageView with the source set to a drawable, or some other UI component with the background set to the drawable, or override the onDraw method of a custom UI View of your own and use the Drawable#draw(Canvas) call to draw the Drawable to the canvas and thus the view that is using that canvas to draw itself. The Drawable#setBounds method defines where on the canvas the Drawable#draw method draws to.
Generally, in your situation, Drawable wouldn't be used at all. Rather you would just subclass View, override onDraw(Canvas), and make your drawing calls directly on the Canvas object. This object has drawBitmap, drawLines, drawText, etc. methods:
http://developer.android.com/reference/android/graphics/Canvas.html#drawText(java.lang.String,%20float,%20float,%20android.graphics.Paint)
I am always confused about this and I need a pointer on how you would do it. If create a an xml layout with multiple imagesview and text view. And Lets say I want to draw line between two images and move an image along this line. How do I draw this line? I know I can get location of both images view so I have x1,y1 and x2,y2. My problem is with drawing.
Do I need surface view to have the drawing capabilities and loading bitmaps on the screen along the line?
If yes, then I guess I should always surface view to fill the screen and views on top just incase I need to draw which seems kinda wrong?
IF no (I hope thats the answer), then how do I draw lines, or load bitmaps on screen using only X,Y values?
I hope I was able to explain my confusion
Thanks
EDIT: Actually I thougth of a way of explaining my confusion better.
When you create an activity with xml layout you have something like
onCreate (){
setContentView(R.id.layout)
}
but when you have activity with drawing view you have something like
onCreate (){
SurfaceView v = new Surfaceview(this);
setContentView(v)
}
My problem is that we have to set the content layout to EITHER xml layout or to be drawing area . What if I want to set it to my xml layout and at the same time I can draw anywhere on the screen (over images view, empty areas, TextViews ..etc)
See my question?
That depends on what your desired result is and how much flexibility you need. You can have a look at this android Animations tutorial (the site is down at the time of posting but google has it cached).
If you don't need flexibility, then for your line, you might be able to create a View in your xml with an android:background fill color and a size that makes it look as you wish. You could then use an Animation on your bitmap's ImageView to translate it along the line, and use a listener on said Animation to show/hide the various Views as necessary at the beginning or end of your Animation.
If you need flexibility, the SurfaceView is probably your best bet.