Computational aircraft games in the bullets are essential, they are numerous and full of the entire screen, these random or have a certain AI small objects, it is not always easy to achieve, sometimes you have to consider a lot of problems related to effectiveness. We defined the Gameobject, to a large extent, to facilitate the reuse of Sprite, because we have a lot of bullets, it is impossible not to add a bullet is a sprite, I need to share the same sprite. We implement it by inheriting Gameobject.
Here's an analysis of this bullet:
It will inherit from Gameobject;
Record the number of bullets;
An array of the states of a bullet, recording the type of each bullet, position x,y, speed vx,vy, survival alive, and so on.
Initialize Bullets
A drawing method that draws the bullet to the screen.
A collision detection method.
All right, here's the definition of our bullets, and note that this idea--reusing sprite--is important. (This is a reference to Tony's many designs)
public class Bullets extends Gameobject {
Private int[][] bullets;//Bullet State Array
Length of the private int bulletstotal;//array
Private Random rnd;//Random number
public static final int bullet_type_left=0;//Bullet initialization location type
public static final int bullet_type_right=1;//divided into about four kinds
public static final int bullet_type_top=2;
public static final int bullet_type_bottom=3;
private int width,height;//screen with high and wide, for random bullet position
Public Bullets (Image img,int picwidth,int picheight,int bulletstotal,int height) {
Super (Img,picwidth,picheight);
This.bulletstotal=bulletstotal;
Bullets=new Int[bulletstotal][6];
Rnd=new Random ();
This.width=width;
This.height=height;
}
public void Initbullets () {//Init Bullet State Array
for (int i = 0; i < bullets.length; i++) {
Initbullet (i);
}
}
private void Initbullet (int i) {//Initialize index bullet
Bullets[i][0] = (Rnd.nextint () & 0x7fffffff)% 4; Type
BULLETS[I][5] = 1; Alive 1 means surviving, and 0 means dead.
if (Math.Abs (Planexcenter-bulletxcenter) < range) {
if (Math.Abs (Planeycenter-bulletycenter) < range) {
result = true;
}
}
return result;
}
private void Updataspritepos (int i) {//update sprite to position of I bullet
Sprite.setposition (bullets[i][1],bullets[i][2]);
}
/* No use now
public void Resetdeadbullet () {
for (int i = 0; i < bullets.length; i++) {
if (bullets[i][5]==0) {//dead bullet
Initbullet (i);
}
}
}
*/
public void Killbullets (Sprite planesprite,int range) {kills bullets in a certain area
for (int i = 0; i < bullets.length; i++) {
if (bullets[i][5]!=0) {//alive bullets
if (Iscollision (Planesprite, I, range)) {
bullets[i][5]=0;
Initbullet (i);
}
}
}
}
}
How does the bullet represent?
First we use a two-dimensional array to record the bullet information:
Bullets[i][0] The type of bullet, there are up, down, left and right four, respectively, the bullet flew into the screen before the four kinds of positions;
BULLETS[I][1] represents the x-coordinate of a bullet;
Bullets[i][2] represents the y-coordinate of a bullet.
BULLETS[I][3] represents the X-directional velocity of a bullet;
Bullets[i][4] Indicates the y-direction velocity of the bullet;
BULLETS[I][5] Indicates the survival status of the bullet;
How does the bullet initialize?
We first write a method to initialize a single bullet, and then facilitate the array to invoke Initbullet (i), to update the entire state array.
How does a bullet draw?
We first wrote a method of drawing a single bullet, and then facilitated the array call Paint (g,i), to draw the entire state array.
How does a bullet collide?
There are a number of ways in which sprite itself provides border collision detection and pixel based collision detection. The former is not very suitable for our game, our aircraft is irregular objects, and the flight game is sensitive to collisions, and the latter is not the efficiency of our trust, so we are using a radius detection, the aircraft approximation as a circle, select the appropriate radius, Math.Abs ( Planexcenter-bulletxcenter) < range indicates collision.
The collision seems to be simple, in fact, is very complex problem, thankfully, two-dimensional collision is much simpler than three-dimensional collision. One trick is to make the expansion detection radius smaller and not to be big--the leak detection is better than false detection.
Bullets updated?
We use Refreshbullets to update, which is the main logical part. This method is responsible for facilitating the array detection collision, if the collision will be in the collision position of the bullet killed, and the corresponding treatment, here is the end of the game and explosion of the aircraft, otherwise update the position of the bullet.
We just linearly traverse the entire array, collision detection, followed by the update location; but there is a premise that collision detection is simple and the processing part is simple: In this game, collision detection is only the bullets and aircraft detection, collision detection at the end of the game is not executed (through the control Boolean Needcollision), and the process is simpler--it ends the game directly. If not, for example, after the process is not simply to end the game, we have to design a bit more complex. It might not be a simple plane-centric collision. We need to design good game events and design a collision system.
If the collision itself is more complex, or the number of bullets, the type of increase, our linear traversal of the array can not always detect all the bullets, the screen may need to partition, not in one area of the unit does not detect.
Anyway, when you think about your 1934, you're not going to be imagining bullets, airplanes or anything, you have to think about a system.
To sum up the public interface of the Bullet class:
N Bullets (Image img,int picwidth,int picheight,int bulletstotal,int height) constructor
n public void Initbullets () initialization Bullets Array
n public void Paint (Graphics g) Paint Bullets Array
n public void Refreshbullets (Sprite planesprite, boolean needcollision) update Bullet array state, collision detection, processing and other logic work synthesis
n public void Killbullets (Sprite planesprite,int Range)//later explained
So far, our game has begun to take shape, the next step is to add effect class, hey, a little meaning ...
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