void main() {
final square = Square(side: 10);
final circle = Circle(radius: 100);
printArea(square);
printArea(circle);
}
void printArea(Shape shape) {
print(shape.area());
}
abstract class Shape {
double area();
}
class Square implements Shape {
Square({this.side});
double side;
double area() => side * side;
}
class Circle implements Shape {
Circle({this.radius});
double radius;
double area() => radius * radius;
}
My question is inside printArea(Shape shape) is that "Shape" type of abstract class that I have created in the code? And does creating objects from a class that implements the abstract class, does those object becomes a type of abstract class "Shape"? Otherwise how is it possible to pass those created Objects as an argument ,assigning to the "Shape shape"?
void printArea(Shape shape) {
print(shape.area());
}
This means you take any object like Shape or an object which implements or extends from Shape. Since objects extending or implementing Shape are going to have the same properties and methods as Shape you can accept any object as long the object will behave like a Shape.
abstract class just means you can't make a object from this class since the class is allowed to specify methods which are not implemented.
When you create a class which extends or implements from an another class (abstract or not) it will be part of a class hierarchy. E.g. your Circle are a Shape but also a Object since all classes automatically will extends from the Object class:
https://api.dart.dev/stable/2.8.2/dart-core/Object-class.html
Related
I want to make a paint game in andengine. There is my codes. How can i use them in andengine? Or is there anything like drawPath in andengine? I tried to add Rects or Lines for drawing but my FPS was 10-15.
import android.content.Context;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Paint;
import android.graphics.Path;
import android.util.AttributeSet;
import android.view.MotionEvent;
import android.view.View;
public class SingleTouchEventView extends View {
private Paint paint = new Paint();
private Path path = new Path();
public SingleTouchEventView(Context context, AttributeSet attrs) {
super(context, attrs);
setBackgroundColor(Color.WHITE);
paint.setAntiAlias(true);
paint.setStrokeWidth(6f);
paint.setColor(Color.BLACK);
paint.setStyle(Paint.Style.STROKE);
paint.setStrokeJoin(Paint.Join.ROUND);
}
#Override
protected void onDraw(Canvas canvas) {
canvas.drawPath(path, paint);
}
#Override
public boolean onTouchEvent(MotionEvent event) {
float eventX = event.getX();
float eventY = event.getY();
switch (event.getAction()) {
case MotionEvent.ACTION_DOWN:
path.moveTo(eventX, eventY);
return true;
case MotionEvent.ACTION_MOVE:
path.lineTo(eventX, eventY);
break;
case MotionEvent.ACTION_UP:
// nothing to do
break;
default:
return false;
}
// Schedules a repaint.
invalidate();
return true;
}
There are several ways to accomplish what you want.
create Rectangles (not lines since they differ from device to device) and add them to the scene to get a path. Use object pools to reuse your objects (Rectangles).
if the first approach doesn't perform well then you could also draw directly on an empty texture using canvas.
there is a class called RenderTexture on which you can draw entities. Use such a RenderTexture and draw your lines to it. create a sprite using this Texture and add it to the scene.
using Microsoft.Xna.Framework.Graphics;
using Microsoft.Xna.Framework.Media;
using Microsoft.Xna.Framework;
using Microsoft.Xna.Framework.Content;
namespace TileEngine
{
class Renderer : DrawableGameComponent
{
SpriteBatch spriteBatch;
public Renderer(Game game)
: base(game)
{
// TODO: Construct any child components here
}
protected override void LoadContent()
{
// base.LoadContent();
}
public override void Draw(GameTime gameTime)
{
base.Draw(gameTime);
}
public override void Update(GameTime gameTime)
{
base.Update(gameTime);
}
public override void Initialize()
{
base.Initialize();
}
public RenderTarget2D new_texture(int width, int height)
{
Texture2D TEX = new Texture2D(GraphicsDevice, width, height); //create the texture to render to
RenderTarget2D Mine = new RenderTarget2D(GraphicsDevice, width, height);
GraphicsDevice.SetRenderTarget(Mine); //set the render device to the reference provided
//maybe base.draw can be used with spritebatch. Idk. We'll see if the order of operation
//works out. Wish I could call base.draw here.
return Mine; //I'm hoping that this returns the same instance and not a copy.
}
public void draw_texture(int width, int height, RenderTarget2D Mine)
{
GraphicsDevice.SetRenderTarget(null); //Set the renderer to render to the backbuffer again
Rectangle drawrect = new Rectangle(0, 0, width, height); //Set the rendering size to what we want
spriteBatch.Begin(); //This uses spritebatch to draw the texture directly to the screen
spriteBatch.Draw(Mine, drawrect, Color.White); //This uses the color white
spriteBatch.End(); //ends the spritebatch
//Call base.draw after this since it doesn't seem to recognize inside the function
//maybe base.draw can be used with spritebatch. Idk. We'll see if the order of operation
//works out. Wish I could call base.draw here.
}
public GraphicsDevice myDevice { get; set; }
}
}
I still can't call this class as an object in XNA
Here is the working code in the initialize function where I try to create it.
But in my draw code it still doesn't let me go:
tileclipping.draw_texture(...);
Here's the full code from game1
using System;
using System.Collections.Generic;
using System.Linq;
using Microsoft.Xna.Framework;
using Microsoft.Xna.Framework.Audio;
using Microsoft.Xna.Framework.Content;
using Microsoft.Xna.Framework.GamerServices;
using Microsoft.Xna.Framework.Graphics;
using Microsoft.Xna.Framework.Input;
using Microsoft.Xna.Framework.Media;
using TileEngine;
namespace TileEngine
{
/// <summary>
/// This is the main type for your game
/// </summary>
public class Game1 : Microsoft.Xna.Framework.Game
{
public GraphicsDeviceManager graphics;
SpriteBatch spriteBatch;
TileMap myMap = new TileMap();
int squaresAcross = 12;
int squaresDown = 12;
public Game1()
{
graphics = new GraphicsDeviceManager(this);
Content.RootDirectory = "Content";
}
/// <summary>
/// Allows the game to perform any initialization it needs to before starting to run.
/// This is where it can query for any required services and load any non-graphic
/// related content. Calling base.Initialize will enumerate through any components
/// and initialize them as well.
/// </summary>
protected override void Initialize()
{
// tileClipping = new Renderer();
// TODO: Add your initialization logic here
Renderer tileclipping = new Renderer(this) ;
//Components.Add(tileclippping);
base.Initialize();
}
/// <summary>
/// LoadContent will be called once per game and is the place to load
/// all of your content.
/// </summary>
protected override void LoadContent()
{
// Create a new SpriteBatch, which can be used to draw textures.
spriteBatch = new SpriteBatch(GraphicsDevice);
Tile.TileSetTexture = Content.Load<Texture2D>(#"Textures\TileSets\part1_tileset");
// TODO: use this.Content to load your game content here
}
/// <summary>
/// UnloadContent will be called once per game and is the place to unload
/// all content.
/// </summary>
protected override void UnloadContent()
{
// TODO: Unload any non ContentManager content here
}
/// <summary>
/// Allows the game to run logic such as updating the world,
/// checking for collisions, gathering input, and playing audio.
/// </summary>
/// <param name="gameTime">Provides a snapshot of timing values.</param>
protected override void Update(GameTime gameTime)
{
// Allows the game to exit
if (GamePad.GetState(PlayerIndex.One).Buttons.Back == ButtonState.Pressed)
this.Exit();
KeyboardState ks = Keyboard.GetState();
if (ks.IsKeyDown(Keys.Left))
{
Camera.Location.X = MathHelper.Clamp(Camera.Location.X - 8, 0, (myMap.MapWidth - squaresAcross) * 32);
}
if (ks.IsKeyDown(Keys.Right))
{
Camera.Location.X = MathHelper.Clamp(Camera.Location.X + 8, 0, (myMap.MapWidth - squaresAcross) * 32);
}
if (ks.IsKeyDown(Keys.Up))
{
Camera.Location.Y = MathHelper.Clamp(Camera.Location.Y - 8, 0, (myMap.MapHeight - squaresDown) * 32);
}
if (ks.IsKeyDown(Keys.Down))
{
Camera.Location.Y = MathHelper.Clamp(Camera.Location.Y + 8, 0, (myMap.MapHeight - squaresDown) * 32);
}
// TODO: Add your update logic here
base.Update(gameTime);
}
/// <summary>
/// This is called when the game should draw itself.
/// </summary>
/// <param name="gameTime">Provides a snapshot of timing values.</param>
protected override void Draw(GameTime gameTime)
{
GraphicsDevice.Clear(Color.CornflowerBlue);
//use the instance of renderer called tileclipping to generate a new texture of a specified size for tiles
//this surface is 200 pixels by 200 pixels for the reason that it's the same as the clipping i'll choose
Texture2D mytexture = new Texture2D(GraphicsDevice, 200, 200);
RenderTarget2D Mine = new RenderTarget2D(graphics.GraphicsDevice, 200, 200);
//Mine = tileclipping.new_texture(200, 200);
spriteBatch.Begin();
Vector2 firstSquare = new Vector2(Camera.Location.X / 32, Camera.Location.Y / 32);
int firstX = (int)firstSquare.X;
int firstY = (int)firstSquare.Y;
Vector2 squareOffset = new Vector2(Camera.Location.X % 32, Camera.Location.Y % 32);
int offsetX = (int)squareOffset.X;
int offsetY = (int)squareOffset.Y;
for (int y = 0; y < squaresDown; y++)
{
for (int x = 0; x < squaresAcross; x++)
{
spriteBatch.Draw(
Tile.TileSetTexture,
new Rectangle((x * 32) - offsetX, (y * 32) - offsetY, 32, 32),
Tile.GetSourceRectangle(myMap.Rows[y + firstY].Columns[x + firstX].TileID),
Color.White);
}
}
spriteBatch.End();
// TODO: Add your drawing code here
//There are two instances of mine
//A new one is made each time tileclipping.new_texture is called
//This function can re use the copy created by new texture
//hopefully this saves on memory
base.Draw(gameTime);
}
public CubeMapFace Tex2d { get; set; }
internal Renderer tileClipping { get; set; }
public IGameComponent tileclippping { get; set; }
}
}
I'm sorry if it isn't clear what i'm trying to do.
I'm trying to capture a 2d texture (or create one) OUTSIDE my game class
I'm trying to use a class as a handler, to pass these texture2d's back and forth between GAME1
and my Renderer
I don't WANT to have all my textures inside my main class.
Also another thing with this is that I'm trying to basically have a generic
texture2d CREATOR.
Aka this isn't for something simple like rendering sprites.
The function of RENDERER is to either create a new TEXTURE2D object with a NEW render target object
based on parameters fed to this function:
public RenderTarget2D new_texture(int width, int height)
{
Texture2D TEX = new Texture2D(GraphicsDevice, width, height); //create the texture to render to
RenderTarget2D Mine = new RenderTarget2D(GraphicsDevice, width, height);
GraphicsDevice.SetRenderTarget(Mine); //set the render device to the reference provided
//maybe base.draw can be used with spritebatch. Idk. We'll see if the order of operation
//works out. Wish I could call base.draw here.
return Mine; //I'm hoping that this returns the same instance and not a copy.
}
I need a way of creating a copy of the renderer class WITHOUT having it in the gamecomponents list.
The reason is because XNA won't let me access Graphics device, which is a required parameter OF a texture2D object.
So basically i'm doing all this stuff as a work around just becuase Texture2D requires graphics device as a parameter and I can't willy nilly pass GraphicsDevice INTO an instance of my renderer class i've already tried that and it fails.
So there will be situations in my game where say
if (Camera_zoom==1){
scaling_texture.dispose();
scaling_texture = tileclipping.new_texture(camera_width*camera_zoom, camera_height*camera_zoom);
// call a refresh command here
this.refresh_scene(...) //Inside here is a ton of sprite batches because the render target is now set to NEW scaling_texture
//after that we do the drawing using spritebatch inside draw function of main game class
//expecting that a render texture is provided for us by these pre requisites.
//then after that we call the render command
//it returns the render target to the screen
//then in the draw command AFTER the sprite batches were drawn TO the target surface called scaling_texture
//We use various parameters to tell it to draw this scaling_texture as a spritebatch.draw() inside the
//game1 draw class
//So basically I want to do things in this order
/// Create new texture of variable size
// use it as render target
// Do all my spritebatch
// call another spritebatch
//draw the contents of said texture on the screen as the rendering target
//Dispose of the texture object
//Check the scaling size of it
//Re create the scaling texture with a NEW resolution (each frame)
//Select it as a render target
//Do the spritebatchy stuff all over again repeat above for all game loop
//BUT I want parts of this, mainly the creation of this Texture2D object, and the drawing of it to the backbuffer
//To all happen inside my Renderer class
//but for all main game spritebatches to happen inside my main game class
//This is a problem for me and XNA doesn't seem to want to let me organize it this way
//Unless i'm missing something which is why i'm making this lengthy post
//ANY and all help is appreciated.
//Thanks again and I hope I explained myself well enough this time IE my intentions.
//PLEASE NOTE I am SET on doing things THIS way. I will NEED a texture 2d rendering target that is NON static
//During MOST of my GAME project.
//That said.. IT HAS TO have function to wrap it inside Renderer. THere is no way in hell I'm going to do this
//In a spaghetti code fashion Inside GAME1 with nested if statements.
//Thanks all
}
I just took the time to read it completely, and if I understand correctly, you want to have all your textures into a manager to be able to acess them from everywhere in your program ?
what I normally do is have a Class like this one :
Class Images
{
public static Texture2d Ball;
public static Texture2d Hero;
public static void loadContent(Content content)
{
Ball = content.load<Texture2d>("/GFX/GameObject/Ball");
Hero = content.load<Texture2d>("/GFX/SpriteSheet/Hero");
}
}
This class allow you to use Image.Hero or Image.Ball from everywhere in your code. All you have to do is to set it in your game loadcontent sub :
protected override void LoadContent()
{
// Create a new SpriteBatch, which can be used to draw textures.
spriteBatch = new SpriteBatch(GraphicsDevice);
Images.LoadContent(GraphicsDeviceManager.Content);
Sounds.LoadContent(GraphicsDeviceManager.Content);
Tile.TileSetTexture = Content.Load<Texture2D>(#"Textures\TileSets\part1_tileset");
// TODO: use this.Content to load your game content here
}
From here, if you need to recreate or reload the texture in your own renderer class, you could set images.ball getter or setter differently and handle it how you want, or just create a new function to clone these texture and do what you need for your renderer class. Edit : I'm not 100% sure about if the class itself is static or not, I dont have the code in front of me and I didnt touch it in a long time.
I'm not home, so I cant find the tutorial I had about splash screen. but it also let you load a delegate instead of an asset, and that delegate lets you do some actions instead : as the 1st item to load, you load all the texture and fonts needed for your splash screen, as well as a background music that you start playing right away. If you want, let me know and I'll add in the link once I get home.
Currently, my game using some pixel detections.
For exemple, for sprites, i retrieve the pixel of its position.
When i move it, the position values have some decimals like :
thePixel = new vector(position.X, position.Y);
//thePixel = (52.2451, 635.2642)
so i have to Round These values
thePixel = new vector((float)Math.Round(position.X, 0), (float)Math.Round(position.Y, 0));
//thePixel = (52, 635)
I would like to know if there are some other ways to get perfect position (means, without decimal) without Rounding them.
Is it maybe a moving method problem ?
Thx for reading, hope you can help.
You can't really get around the need to round your values, but you can make it a lot nicer to code by using an extension method:
public static class Vector2Extensions
{
public static Vector2 Floor(this Vector2 vector)
{
return new Vector2((float)Math.Floor(vector.X), (float)Math.Floor(vector.Y));
}
}
(As you can see, personally I prefer Floor to Round. I also have one for Ceiling.)
Then you can just use it like this:
HandleCollision(position.Floor());
Of course, if you're doing per-pixel collision detection - your collision maths should probably be integer-based (not stored as float in a Vector2). You could use Point. Turns out I have an extension method for that too:
public static class Vector2Extensions
{
public static Point AsXnaPoint(this Vector2 v)
{
return new Point((int)v.X, (int)v.Y);
}
}
Then:
HandleCollision(position.AsXNAPoint());
Or possibly:
HandleCollision(position.Floor().AsXNAPoint());
Why Vector2 (from XNA's library) uses float not int?
Position on computer screen is given in pixels so that cursor position can be defined by two integers. There is no such a thing like half a pixel. Why we use floats then?
In SpriteBatch class I've found 7 overloaded methods called Draw. Two of them:
public void Draw(Texture2D texture, Rectangle destinationRectangle, Color color);
public void Draw(Texture2D texture, Vector2 position, Color color);
So we can see that Draw accepts both int and float coordinates.
I came across this problem when I've been implementing screen coordinates of my game's objects. I assumed that Rectangle is good choice to hold object's size and screen coordinates. But now I'm not sure...
Mathematically, a vector is a motion, not a position. While a position on the screen might not technically be able to be between integers, a motion definitely can. If a vector used ints then the slowest you could move would be (1, 1). With floats you can move (.1, .1), (.001, .001), and so on.
(Notice also that the XNA struct Point does actually use ints.)
You could use both Vector2 and Rectangle to represent your objects coordinates. I usually do it like this:
public class GameObject
{
Texture2D _texture;
public Vector2 Position { get; set; }
public int Width { get; private set; } //doesn't have to be private
public int Height { get; private set; } //but it's nicer when it doesn't change :)
public Rectangle PositionRectangle
{
get
{
return new Rectangle((int)Position.X, (int)Position.Y, Width, Height);
}
}
public GameObject(Texture2D texture)
{
this._texture = texture;
this.Width = texture.Width;
this.Height = texture.Height;
}
}
To move objects, just set their Position property to a new value.
_player.Position = new Vector2(_player.Position.X, 100);
You don't have to worry about the rectangle, as it's value depends directly on Position.
My game objects also usually contain methods to draw themselves, such as
public void Draw(SpriteBatch spriteBatch, GameTime gameTime)
{
spriteBatch.Draw(this._texture, this.Position, Color.White);
}
Collision detection code in your Game.Update() could just use the PositionRectangle to test for collisions
//_player and _enemy are of type GameObject (or one that inherits it)
if(_player.PositionRectangle.Intersects(_enemy.PositionRectangle))
{
_player.Lives--;
_player.InvurnerabilityPeriod = 2000;
//or something along these lines;
}
You could also call the spriteBatch.Draw() with PositionRectangle, you shouldn't notice much difference.
There is such a thing as "half a pixel." Using float coordinates that aren't pixel-aligned will cause your sprites to be rendered at sub-pixel coordinates. This is often necessary to make objects appear to scroll smoothly, but it can also produce an unpleasant shimmering effect in some circumstances.
See here for a summary of the basic idea: Subpixel rendering
I'm building a map editor for a project and need to draw a hexagon and fill it with a solid color. I have the shape correct but for the life of me can't figure out how to fill it. I suspect it may be due to whether the thing is a Shape, Sprite or UIComponent. Here is what I have for the polygon itself:
import com.Polygon;
import mx.core.UIComponent;
public class greenFillOne extends UIComponent {
public var hexWidth:Number = 64;
public var hexLength:Number = 73;
public function greenFillOne() {
var hexPoly:Polygon = new Polygon;
hexPoly.drawPolygon(40,6,27+(hexWidth*.25),37,0x499b0e,1,30);
addChild(hexPoly);
}
}
The Polygon class isn't a standard Adobe library, so I don't know the specifics. However, assuming that it uses the standard flash API, it should be no problem to add some code to extend the function. You just need to make sure you're doing a graphics.beginFill before the graphics.lineTo / graphics.moveTo functions. And then finish with graphics.endFill.
e.g.,
var g:Graphics = someShape.graphics;
g.beginFill(0xFF0000,.4); // red, .4 opacity
g.moveTo(x1,y1);
g.lineTo(x2,y2);
g.lineTo(x3,y3);
g.lineTo(x1,y1);
g.endFill();
This will draw a triangle filled with .4 red.
I'll put this here because answering it as a comment to Glenn goes past the character limit. My actionscript file extends UIComponent. When I created a variable hexPoly:Polygon = new Polygon; it would render the outline of the hex, but would not fill it no matter what I did. I examined polygon.as and duplicated the methods, but as a sprite and it worked. So, I need to figure out how to wrap the polygon as a sprite, or just leave it as is.
var hexPoly:Sprite = new Sprite;
hexPoly.graphics.beginFill(0x4ea50f,1);
hexPoly.graphics.moveTo(xCenter+(hexWidth*.25)+Math.sin(radians(330))*radius,offset+(radius-Math.cos(radians(330))*radius));
hexPoly.graphics.lineTo(xCenter+(hexWidth*.25)+Math.sin(radians(30))*radius,offset+(radius-Math.cos(radians(30))*radius));
hexPoly.graphics.lineTo(xCenter+(hexWidth*.25)+Math.sin(radians(90))*radius,offset+(radius-Math.cos(radians(90))*radius));
hexPoly.graphics.lineTo(xCenter+(hexWidth*.25)+Math.sin(radians(150))*radius,offset+(radius-Math.cos(radians(150))*radius));
hexPoly.graphics.lineTo(xCenter+(hexWidth*.25)+Math.sin(radians(210))*radius,offset+(radius-Math.cos(radians(210))*radius));
hexPoly.graphics.lineTo(xCenter+(hexWidth*.25)+Math.sin(radians(270))*radius,offset+(radius-Math.cos(radians(270))*radius));
hexPoly.graphics.endFill();
addChild(hexPoly);