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為了復(fù)習(xí)一下SurfaceView的使用，在此寫了一個(gè)經(jīng)典的小球碰撞檢測(cè)例子程序，希望能夠夠幫助正在學(xué)習(xí)游戲的人。
先看一下效果圖：
下面我們就來(lái)逐一分析一下它的實(shí)現(xiàn)過(guò)程：
1.啟動(dòng)入口：
import android.os.Bundle;
import android.app.Activity;
import android.view.Window;
import android.view.WindowManager;
public class MainActivity extends Activity {
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
//全屏設(shè)置
requestWindowFeature(Window.FEATURE_NO_TITLE);
this.getWindow().setFlags(WindowManager.LayoutParams.FLAG_FULLSCREEN,
WindowManager.LayoutParams.FLAG_FULLSCREEN);
//將畫布放進(jìn)去
GameView gameView = new GameView(this);
setContentView(gameView);
}
}2.小球類
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Paint;
/**
* 小球?qū)嵗? * @author ZHF
*
*/
public class Ball {
int x, y; //小球的實(shí)時(shí)位置
int startX, startY; //小球的初始位置
float vX, vY; //小球的速度
int r; //小球的半徑
double startTimeX; //開始時(shí)間
double startTimeY; //開始時(shí)間
BallThread ballThread; //小球移動(dòng)線程
Paint paint = new Paint(); //畫筆
public Ball(int x, int y, float vX, float vY, int r) {
this.x = x;
this.y = y;
this.startX = x;
this.startY = y;
this.vX = vX;
this.vY = vY;
this.r = r;
//為每個(gè)小球?qū)嵗粋€(gè)獨(dú)立的線程，在抬手時(shí)開啟線程
ballThread = new BallThread(this);
paint.setColor(Color.RED); //小球?yàn)榧t色實(shí)心
}
/**繪畫方法**/
public void drawSelf(Canvas canvas) {
canvas.drawCircle(x, y, r, paint);
}
}3.障礙物類：
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Paint;
/**
* 障礙物
*
* @author ZHF
*
*/
public class Obstruction {
int x, y;
int hWeight; //寬度和高度一樣
Paint paint = new Paint();
public Obstruction(int x, int y, int hWeight) {
this.x = x;
this.y = y;
this.hWeight = hWeight;
paint.setColor(Color.GREEN); //設(shè)置畫筆顏色
}
public void drawSelf(Canvas canvas) {
canvas.drawRect(x - hWeight, y - hWeight, x + hWeight, y + hWeight, paint);
}
}以上代碼比較簡(jiǎn)單，在此不多做解釋，下面主要來(lái)看一下兩個(gè)主要線程類：
4.小球移動(dòng)線程（碰撞檢測(cè)）：
/**
* 小球移動(dòng)和碰撞檢測(cè)線程
* @author ZHF
*
*/
public class BallThread extends Thread {
boolean flag; //標(biāo)記線程是否開啟
Ball ball; //小球
double currentTime; //當(dāng)前時(shí)間
public BallThread(Ball ball) {
flag = true;
this.ball = ball;
}
@Override
public void run() {
while(flag) {
//調(diào)試：碰撞檢測(cè)開始時(shí)間
long startTime = System.currentTimeMillis();
//計(jì)算出小球移動(dòng)的時(shí)間片：將每次刷新分成若干時(shí)間小片段，用于計(jì)算每次時(shí)間小片段小球移動(dòng)的距離
currentTime = System.nanoTime();
double timeSpanX = (currentTime - ball.startTimeX) /1000 /1000 /1000;
double timeSpanY = (currentTime - ball.startTimeY) /1000 /1000 /1000;
int xBackup = ball.x; //保存小球的碰撞前的位置
int yBackup = ball.y;
ball.x = (int) (ball.startX + ball.vX * timeSpanX);//小球移動(dòng)的距離
ball.y = (int) (ball.startY + ball.vY * timeSpanY);
//邊界碰撞檢測(cè)
if((ball.vX > 0 && (ball.x + ball.r) >= 479) || (ball.vX < 0 && (ball.x - ball.r) <= 0)) {
ball.x = xBackup;
ball.vX = 0 - ball.vX; //速度反向
ball.startTimeX = System.nanoTime(); //重新記錄開始時(shí)間
ball.startX = ball.x; //重新記錄開始位置
}
if((ball.vY > 0 && (ball.y + ball.r) >= 799) || (ball.vY < 0 && (ball.y - ball.r) <= 0)) {
ball.y = yBackup;
ball.vY = 0 - ball.vY; //速度反向
ball.startTimeY = System.nanoTime(); //重新記錄開始時(shí)間
ball.startY = ball.y; //重新記錄開始位置
}
//障礙物碰撞檢測(cè)
for(int i = 0; i < GameView.obstructList.size(); i++) {
Obstruction o = GameView.obstructList.get(i);
if(Math.abs(ball.x - o.x) < (ball.r + o.hWeight) && Math.abs(ball.y - o.y) < (ball.r + o.hWeight)){
if(Math.abs(xBackup - o.x) >= (ball.r + o.hWeight)) {
ball.x = xBackup;
ball.vX = 0 - ball.vX;
ball.startTimeX = System.nanoTime();
ball.startX = ball.x;
}
if(Math.abs(yBackup - o.y) >= (ball.r + o.hWeight)) {
ball.y = yBackup;
ball.vY = 0 - ball.vY;
ball.startTimeY = System.nanoTime();
ball.startY = ball.y;
}
break; //跳出循環(huán)
}
}
//調(diào)試：碰撞檢測(cè)結(jié)束時(shí)間 實(shí)驗(yàn)證明碰撞加測(cè)基本不耗時(shí)間
long endTime = System.currentTimeMillis();
System.out.println(endTime + "----" + startTime + "= " +(endTime - startTime));
try {
Thread.sleep(10);
} catch (Exception e) {
e.printStackTrace();
}
}
}
}分析：
1.我們將刷新時(shí)間分割成：將每次刷新時(shí)間分成若干時(shí)間小片段timeSpanX和timeSpanY，用于計(jì)算每次時(shí)間小片段小球移動(dòng)的距離.
2.我們?cè)谛∏蚺c邊界碰撞之前，記錄一下時(shí)間startTime，在其與邊界碰撞之后，我們將其x軸、y軸方向上做一系列的操作（方向取反，回到碰撞前位置，重新記錄開始時(shí)間）其實(shí)，我通過(guò)調(diào)試發(fā)現(xiàn)碰撞時(shí)間基本可以忽略.
3.我們這里的碰撞檢測(cè)是邊界檢測(cè)，只考慮小球與障礙物、邊界的碰撞，沒(méi)有考慮小球之間的碰撞，有興趣的同學(xué)可以自行研究一下。
5.繪畫線程：
2
import android.graphics.Canvas;
import android.util.Log;
import android.view.SurfaceHolder;
/**
* 繪畫主界面線程
* @author ZHF
*
*/
public class DrawThread extends Thread {
boolean flag; //標(biāo)記線程是否開啟
GameView gameView;
SurfaceHolder holder;
Canvas canvas;
public DrawThread(GameView gameView) {
flag = true;
this.gameView = gameView;
holder = gameView.getHolder(); //獲取畫布鎖
}
@Override
public void run() {
while(flag) {
//獲取當(dāng)前繪畫開始時(shí)間
long startTime = System.currentTimeMillis();
synchronized(holder) {
canvas = holder.lockCanvas(); //獲取當(dāng)前被鎖住的畫布
if(canvas != null) {
gameView.draw(canvas); //對(duì)畫布進(jìn)行操作
holder.unlockCanvasAndPost(canvas); //釋放畫布
}
}
long endTime = System.currentTimeMillis();
int diffTime = (int) (endTime - startTime);
Log.d("DrawTime", diffTime+"");
while(diffTime <= 2) {
diffTime = (int) (System.currentTimeMillis() - startTime);
Thread.yield(); //將線程的所有權(quán)交給另一個(gè)線程
}
}
}
} 分析：
1. 首先，我們將畫布鎖住之后，對(duì)其進(jìn)行繪畫，畫完之后自然要釋放畫布啦
2. 為了優(yōu)化程序，我們計(jì)算出繪畫所用時(shí)間，當(dāng)繪畫時(shí)間過(guò)長(zhǎng)時(shí)，暫停當(dāng)前正在執(zhí)行的線程對(duì)象，通知CPU來(lái)執(zhí)行其他線程（注意：這里的其他也包含當(dāng)前線程）
6.主界面：
import java.util.ArrayList;
import java.util.Random;
import android.content.Context;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Paint;
import android.view.MotionEvent;
import android.view.SurfaceHolder;
import android.view.SurfaceView;
/**
* 游戲主界面
* @author ZHF
*
*/
public class GameView extends SurfaceView implements SurfaceHolder.Callback {
SurfaceHolder holder;
DrawThread drawThread; //繪畫線程
Ball[] ballArray = new Ball[5]; //裝小球的數(shù)組
int ballPointer = 0; //當(dāng)前指向數(shù)組中第幾個(gè)球
static ArrayList<Obstruction> obstructList = new ArrayList<Obstruction>(); //裝障礙物的集合
int xDown, yDown; //記錄手指按下時(shí)的坐標(biāo)
public GameView(Context context) {
super(context);
holder = getHolder(); //獲取畫布鎖
holder.addCallback(this); //添加回調(diào)
//初始化障礙物
Random random = new Random();
for(int i = 0; i < 3; i++) {
Obstruction o = new Obstruction(random.nextInt(380) + 50, random.nextInt(700) + 50, 50);
obstructList.add(o); //將創(chuàng)出的障礙物對(duì)象添加到集合中去
}
}
@Override
public void surfaceCreated(SurfaceHolder holder) {
drawThread = new DrawThread(this);
drawThread.start(); //開啟繪畫線程
}
@Override
public void surfaceChanged(SurfaceHolder holder, int format, int width,
int height) {
//畫布發(fā)生變化，eg:轉(zhuǎn)屏操作,處理畫布操作
}
@Override
public void surfaceDestroyed(SurfaceHolder holder) {
//銷毀畫布操作
drawThread.flag = false; //停掉線程
drawThread = null; //GC會(huì)及時(shí)發(fā)現(xiàn)并處理掉該對(duì)象
}
public void draw(Canvas canvas) {
canvas.drawColor(Color.BLACK); //背景顏色
Paint paint = new Paint();
paint.setTextSize(25);
paint.setColor(Color.WHITE); //文字顏色
canvas.drawText("小球碰撞檢測(cè)", 50, 20, paint);
//畫出小球
for(int i = 0; i < 5; i++) {
if(ballArray[i] != null) {
ballArray[i].drawSelf(canvas); //當(dāng)前小球繪畫出自己
}
}
//畫出障礙物
for(int i = 0; i < obstructList.size(); i++) {
obstructList.get(i).drawSelf(canvas);
}
}
@Override
public boolean onTouchEvent(MotionEvent event) {
int x = (int) event.getX();
int y = (int) event.getY();
if(event.getAction() == 0) { //按下
//記錄按下時(shí)X，Y的坐標(biāo)
xDown = x;
yDown = y;
//生成第一個(gè)球
Ball ball = new Ball(x, y, 0, 0, 20);
if(ballArray[ballPointer] != null) {
ballArray[ballPointer].ballThread.flag = false; //關(guān)閉小球移動(dòng)線程
ballArray[ballPointer].ballThread = null;
}
ballArray[ballPointer] = ball;
} else if(event.getAction() == 1) { //抬起
int xOffset = x - xDown;
int yOffset = y - yDown;
double sin = yOffset / Math.sqrt(xOffset * xOffset + yOffset * yOffset);
double cos = xOffset / Math.sqrt(xOffset * xOffset + yOffset * yOffset);
ballArray[ballPointer].startTimeX = System.nanoTime(); //當(dāng)前小球開始時(shí)間
ballArray[ballPointer].startTimeY = System.nanoTime();
ballArray[ballPointer].vX = (float) (500 * cos); //當(dāng)前小球的速度
ballArray[ballPointer].vY = (float) (500 * sin);
ballArray[ballPointer].ballThread.start(); //開啟小球移動(dòng)線程
ballPointer ++; //下一個(gè)小球
if(ballPointer >= 5) {
ballPointer = 0;
}
}
return true;
}
}分析：
1.這里我們啟動(dòng)小球移動(dòng)線程方式：采用手指觸屏滑動(dòng)，記錄按下、抬起位置，通過(guò)計(jì)算角度得出算出發(fā)射方向。
2.每次發(fā)出小球后下標(biāo)ballPointer ++指向下一個(gè)小球，當(dāng)?shù)竭_(dá)數(shù)組上限后，重新返回到下標(biāo)0.
ok! 到此功能已經(jīng)實(shí)現(xiàn)，想要完整源碼在此下載：http://download.csdn.net/detail/zhf651555765/5775035
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