边做游戏边学android—5（飞机大战④子弹发射和碰撞检测）

飞机是要发射子弹的，子弹也不止一种，先创建子弹的基类。代码如下：

package com.example.object;

import android.content.res.Resources;
import android.graphics.Canvas;

public class Bullet extends GameObject {
protected int harm;

public Bullet(Resources resources) {
super(resources);
// TODO Auto-generated constructor stub
}

@Override
protected void initBitmap() {
// TODO Auto-generated method stub

}

@Override
public void drawSelf(Canvas canvas) {
// TODO Auto-generated method stub

}

@Override
public void release() {
// TODO Auto-generated method stub

}

public boolean isCollide(GameObject obj) {
if(object_x + object_width <= obj.getObject_x()){
return false;
}
else if(obj.getObject_x() + obj.getObject_width() <= object_x){
return false;
}
else if(object_y + object_height <= obj.getObject_y()){
return false;
}
else if(obj.getObject_y() + obj.getObject_height() <=object_y){
return false;
}
return true;
}

public int getHarm() {
return harm;
}

public void setHarm(int harm) {
this.harm = harm;
}

}

再创建子弹类：

package com.example.object;

import android.content.res.Resources;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.graphics.Canvas;

import com.example.planewars.R;

public class MyBullet extends Bullet {
private Bitmap bullet;
private int sum=3;
private int current=0;

public MyBullet(Resources resources) {
super(resources);
// TODO Auto-generated constructor stub
initBitmap();

this.harm =1;
}

public void initial(int arg0,float arg1,float arg2) {
if(current< sum){
isAlive = true;
speed = 10;
object_x = arg1 - object_width/2;
object_y = arg2 - object_height;
current++;
}
}

public void initBitmap(){
bullet = BitmapFactory.decodeResource(resources, R.drawable.bullet);
object_width = bullet.getWidth();
object_height = bullet.getHeight();
}

public void drawSelf(Canvas canvas){
if(isAlive){
canvas.save();
canvas.clipRect(object_x, object_y, object_x + object_width, object_y + object_height);
canvas.drawBitmap(bullet, object_x, object_y,paint);
canvas.restore();
logic();
}
}

public void release(){
if(!bullet.isRecycled()){
bullet.recycle();
}
}

public void logic(){
//      if(object_y >=0) {
//          object_y -= speed;
//      } else {
//          isAlive = false;
//      }
object_y -= speed;
}

public boolean isCollide(GameObject obj){
return super.isCollide(obj);
}

}

子弹是在飞机里发射出来的，修改一下myplane的代码。修改后如下：

package com.example.object;

import java.util.ArrayList;
import java.util.List;

import android.content.res.Resources;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.graphics.Canvas;

import com.example.planewars.R;
import com.example.view.MainView;

import com.example.factory.GameObjectFactory;
import com.example.interfaces.IMyPlane;

public class MyPlane extends GameObject implements IMyPlane {
private float middle_x;
private float middle_y;
private Bitmap myplane;
private Bitmap myplaneexplosion;
private MainView mainView;
private GameObjectFactory factory;
private List<Bullet> bullets;
private Bitmap bullet;

public MyPlane(Resources resources) {
super(resources);
// TODO Auto-generated constructor stub
initBitmap();
factory = new GameObjectFactory();
bullets = new ArrayList<Bullet>();
//createBullet();
this.speed = 8;
}

public void setMainView(MainView mainView) {
this.mainView = mainView;
}

public void setScreenWH(float screen_width, float screen_height) {
super.setScreenWH(screen_width, screen_height);
object_x = screen_width/2 - object_width/2;
object_y = screen_height - object_height;
middle_x = object_x + object_width/2;
middle_y = object_y + object_height/2;
}

@Override
protected void initBitmap() {
// TODO Auto-generated method stub
myplane = BitmapFactory.decodeResource(resources, R.drawable.myplane);
myplaneexplosion = BitmapFactory.decodeResource(resources, R.drawable.myplaneexplosion);
object_width = myplane.getWidth()/2;
object_height = myplane.getHeight();
}

@Override
public void drawSelf(Canvas canvas) {
// TODO Auto-generated method stub
if(isAlive){
int x = (int) (currentFrame * object_width);
canvas.save();
canvas.clipRect(object_x, object_y,object_x + object_width, object_y + object_height);
canvas.drawBitmap(myplane, object_x -x, object_y, paint);
canvas.restore();
currentFrame++;
if(currentFrame >= 2){
currentFrame = 0;
}
} else {
int x = (int) (currentFrame * object_width);
canvas.save();
canvas.clipRect(object_x, object_y,object_x + object_width, object_y + object_height);
canvas.drawBitmap(myplaneexplosion, object_x -x, object_y, paint);
canvas.restore();
currentFrame++;
if(currentFrame >= 2){
currentFrame = 1;
}
}

}

public void shoot(Canvas canvas,List<EnemyPlane> planes){
for(Bullet obj:bullets){
if(obj.isAlive()){
for(EnemyPlane pobj:planes){
if(pobj.isCanCollide()){
if(obj.isCollide(pobj)){
pobj.attacked(obj.getHarm());
}
}
}
obj.drawSelf(canvas);
//          bullet = BitmapFactory.decodeResource(resources, R.drawable.bullet);
//          canvas.save();
//          canvas.clipRect(object_x, object_y, object_x + object_width, object_y + object_height);
//          canvas.drawBitmap(bullet, object_x, object_y,paint);
//          canvas.restore();
}
}
}

public void createBullet(){
for(int i=0;i<5;i++){
MyBullet bullet =(MyBullet) factory.createBullet(resources);
bullets.add(bullet);
}
}

public void initBullet(){
for(Bullet obj:bullets){
//          if(obj.isAlive()){
obj.initial(0, middle_x, middle_y);
//              break;
//          }
}
}

public void isBulletoverTime(){
createBullet();
}

@Override
public void release() {
// TODO Auto-generated method stub
if(!myplane.isRecycled()){
myplane.recycle();
}
if(!myplaneexplosion.isRecycled()){
myplaneexplosion.recycle();
}
}

public float getMiddle_x() {
return middle_x;
}

public void setMiddle_x(float middle_x) {
this.middle_x = middle_x;
this.object_x =  middle_x - object_width/2;
}

public float getMiddle_y() {
return middle_y;
}

public void setMiddle_y(float middle_y) {
this.middle_y = middle_y;
this.object_y = middle_y - object_height/2;
}

}

当然也还要在mianview里初始化视图和draw里加上创建子弹的代码。修改之后的代码如下：

public void initObject(){
myPlane.isBulletoverTime();
myPlane.initBullet();
for(EnemyPlane obj:enemyPlanes){
if(obj instanceof SmallPlane){
obj.initial(speedTime, 0, 0);
continue;
}
}
}

public void release(){
for(GameObject obj:enemyPlanes){
obj.release();
}
myPlane.release();
}

public void drawSelf(){
try{
canvas = sfh.lockCanvas();
canvas.drawColor(Color.WHITE);
//canvas.scale(scalex, scaley, 0, 0);
myPlane.drawSelf(canvas);
myPlane.shoot(canvas, enemyPlanes);
for(EnemyPlane obj:enemyPlanes){
obj.drawSelf(canvas);
if(obj.isCanCollide() && myPlane.isAlive()){
if(obj.isCollide(myPlane)){
myPlane.setAlive(false);
}
}
}
} catch(Exception err){
err.printStackTrace();
}finally{
if(canvas != null);
sfh.unlockCanvasAndPost(canvas);
}
}

游戏运行截图：



再加上游戏分数。主界面，和游戏结束界面，飞机大战就基本完成了，当然，为了使游戏内容丰富一点，也可以添加多种子弹和敌机。然后还有游戏里添加物品。