Android小程序

Android小程序--模擬焰火粒子和瀑布粒子
   需要注意的是，粒子系統和前面開發的物理小球之間有類似的地方，其都是通過數學方法和物理公式模擬客觀世界中物體的運動軌跡。不同的是物理小球更強調個體運動，而焰火粒子系統更注重整體感覺，這點區別在代碼中也能體現。
   1、開發粒子對象Particle類：

package xiao.fuyan.particle;

/**
 * Created by xiao on 2017/2/10.
 */
public class Particle {
    //粒子半徑
    int r;
    //粒子顏色
    int color;
    //垂直速度
    double v_v;
    //水平速度
    double h_v;
    //初始坐標
    int startX;
    int startY;
    //實時坐標
    int x, y;
    //起始時間
    double startTime;

    //構造器
    public Particle(int color, int r, double v_v, double h_v, int x, int y, double startTime){
        //初始化各個變量
        this.color = color;
        this.r = r;
        this.v_v = v_v;
        this.h_v = h_v;
        this.startX = x;
        this.startY = y;
        this.x = x;
        this.y = y;
        this.startTime = startTime;
    }
}

   2、開發粒子集合ParticleSet類：

package xiao.fuyan.particle;

import android.graphics.Color;

import java.util.ArrayList;

/**
 * Created by xiao on 2017/2/10.
 */
public class ParticleSet {
    //用於存放Particle對象的集合
    ArrayList<Particle> particleSet;
    //構造器，
    public ParticleSet(){
        particleSet = new ArrayList<Particle>();
    }

    //向粒子集合中添加指定個數的粒子對象
    public void add(int count, double startTime){
        for(int i =0; i < count; i++){
            
            //該段代碼是開發焰火粒子
            //獲取粒子對象的顏色
            int tempColor = this.getColor(i);
            //設置粒子半徑
            int tempR = 3;
            //隨機產生粒子豎直方向上的速度
            double tempv_v = -30 + 10 * (Math.random());
            //同上獲取水平方向上的速度
            double temph_v = 10 - 20 * (Math.random());

            //粒子的X坐標是固定的
            int tempX = 160;
            //隨機產生Y坐標，90 - 100之間
            int tempY = (int) (100 - 10 * (Math.random()));

            Particle particle = new Particle(tempColor, tempR, tempv_v, temph_v, tempX, tempY, startTime);
            //將創建好的Particle對象添加到列表中
            particleSet.add(particle);

            //下面代碼是將焰火粒子變為瀑布粒子
//            int tempColor = this.getColor(i);
//            //粒子半徑
//            int tempR = 3;
//            //豎直方向速度為零
//            double tempv_v = 0;
//            double temph_v = 20 + 10 * (Math.random());
//
//            int tempX = 50;
//            int tempY = (int) (50 - 10 * (Math.random()));
//
//            //創建Particle對象
//            Particle particle = new Particle(tempColor, tempR, tempv_v, temph_v, tempX, tempY, startTime);
//            //將創建好的Particle對象加入列表
//            particleSet.add(particle);
        }
    }

    //獲取指定索引的顏色
    public int getColor(int i){
        int color = Color.RED;
        switch (i % 8){
            case 0:
                color = Color.RED;
                break;
            case 1:
                color = Color.BLUE;
                break;
            case 2:
                color = Color.GRAY;
                break;
            case 3:
                color = Color.GREEN;
                break;
            case 4:
                color = Color.CYAN;
                break;
            case 5:
                color = Color.YELLOW;
                break;
            case 6:
                color = Color.MAGENTA;
                break;
            case 7:
                color = Color.LTGRAY;
                break;
        }
        return color;
    }
}

   3、開發物理引擎ParticleThread類：

package xiao.fuyan.particle;

import java.util.ArrayList;

/**
 * Created by xiao on 2017/2/10.
 */
public class ParticleThread extends Thread {

    //線程執行標志位
    boolean flag;
    //ParticleView對象的引用
    ParticleView father;
    //線程休眠的時間
    int sleepSpan = 80;
    //物理引擎的時間軸
    double time = 0;
    //每次計算粒子的位移時采用的時間間隔
    double span = 0.15;

    //構造器
    public ParticleThread(ParticleView father){
        this.father = father;
        this.flag = true;
    }

    //線程執行的方法
    @Override
    public void run() {
        while(flag){
            //每次添加五個粒子
            father.ps.add(15, time);
            //獲取粒子集合
            ArrayList<Particle> tempSet = father.ps.particleSet;
            //記錄粒子集合的大小
            int count = tempSet.size();
            for(int i = 0; i < count; i++){   //遍歷粒子集合，修改其軌跡
                Particle particle = tempSet.get(i);
                //計算從程序開始到現在的時間
                double timeSpan = time - particle.startTime;
                //計算出粒子的X坐標
                int tempX = (int) (particle.startX + particle.h_v * timeSpan);
                //計算Y坐標
                int tempY = (int) (particle.startY + 4.9 * timeSpan * timeSpan + particle.v_v * timeSpan);

                //如果粒子超出屏幕下邊沿
                if(tempY > 1920){
                    tempSet.remove(particle);
                    //重新設置粒子的個數
                    count = tempSet.size();
                }

                //修改粒子的坐標
                particle.x = tempX;
                particle.y = tempY;
            }

            //將時間延長
            time += span;
            try{
                Thread.sleep(sleepSpan);//休眠一段時間
            }catch (Exception e){
                e.printStackTrace();
            }
        }
    }
}

   4、開發視圖ParticleView類：

package xiao.fuyan.particle;

import android.content.Context;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Paint;
import android.graphics.RectF;
import android.view.SurfaceHolder;
import android.view.SurfaceView;

import java.util.ArrayList;

/**
 * Created by xiao on 2017/2/10.
 */
public class ParticleView extends SurfaceView implements SurfaceHolder.Callback {
    //粒子的Y坐標超過該值就會從粒子集合中移出
    public static final int DIE_OUT_LINE = 1920;
    //後台刷新屏幕的線程
    DrawThread dt = null;
    //ParticleSet對象的引用
    ParticleSet ps;
    //ParticleThread對象的引用
    ParticleThread pt;
    //聲明幀速率字符串
    String fps = "FPS:N/A";

    //構造器
    public ParticleView(Context context){
        super(context);
        //添加callback接口
        this.getHolder().addCallback(this);
        //創建DrawThread對象
        dt = new DrawThread(this, getHolder());
        //創建ParticleSet對象
        ps = new ParticleSet();
        //創建ParticleThread對象
        pt = new ParticleThread(this);
    }

    //繪制屏幕
    public void doDraw(Canvas canvas){
        //清除屏幕
        canvas.drawColor(Color.BLACK);
        //獲取ParticleSet對象中的粒子
        ArrayList<Particle> particleSet = ps.particleSet;

        Paint paint = new Paint();
        for(int i = 0; i < particleSet.size(); i++){
            Particle p = particleSet.get(i);
            paint.setColor(p.color);
            //獲取粒子坐標和半徑
            int tempX = p.x;
            int tempY = p.y;
            int tempR = p.r;
            //繪制該粒子
            RectF oval = new RectF(tempX, tempY, tempX + 2 * tempR, tempY + 2 * tempR);
            canvas.drawOval(oval, paint);
        }

        //設置畫筆顏色
        paint.setColor(Color.WHITE);
        paint.setTextSize(60);
        paint.setAntiAlias(true);
        //畫出幀速率字符串
        canvas.drawText(fps, 900, 80, paint);
    }

    @Override
    public void surfaceChanged(SurfaceHolder holder, int format, int width, int height) {

    }

    @Override
    public void surfaceCreated(SurfaceHolder holder) {
        //啟動線程
        if(!dt.isAlive()){
            dt.start();
        }
        if(!pt.isAlive()){
            pt.start();
        }
    }

    @Override
    public void surfaceDestroyed(SurfaceHolder holder) {
        //停止線程
        dt.flag = false;
        dt = null;
        pt.flag = false;
        pt = null;
    }
}

   5、開發DrawThread類：

package xiao.fuyan.particle;

import android.graphics.Canvas;
import android.view.SurfaceHolder;

/**
 * Created by xiao on 2017/2/10.
 */
public class DrawThread extends Thread {
    //ParticleView對象
    ParticleView particleView;
    //SurfaceHolder對象的引用
    SurfaceHolder surfaceHolder;
    //線程執行的標志位
    boolean flag = false;
    //休眠時間
    int sleepSpan = 30;
    //記錄起始時間，用於計算幀速率
    long start = System.nanoTime();
    //記錄幀數，
    int count = 0;

    //構造器
    public DrawThread(ParticleView particleView, SurfaceHolder surfaceHolder){
        this.particleView = particleView;
        this.surfaceHolder = surfaceHolder;
        this.flag = true;
    }

    @Override
    //線程執行的方法，用於重繪屏幕和計算幀速率
    public void run() {
        Canvas canvas = null;
        while(flag){
            try{
                //獲取ParticleView的畫布
                canvas = surfaceHolder.lockCanvas(null);
                //加鎖並且繪制
                synchronized (surfaceHolder){
                    particleView.doDraw(canvas);
                }
            }catch (Exception e){
                e.printStackTrace();
            }finally {
                if(canvas != null){   //如果canvas不為空
                    //surfaceHolder解鎖，並將畫布對象傳回
                    surfaceHolder.unlockCanvasAndPost(canvas);
                }
            }

            //如果計滿20幀，計算幀速率
            this.count++;
            if(count == 20){
                count = 0;
                //獲取當前時間
                long tempStamp = System.nanoTime();
                //獲取時間間隔
                long span = tempStamp - start;;
                //為start重新賦值
                start = tempStamp;
                //計算幀速率
                double fps = Math.round(10000000000.0 / span * 20) / 100.0;
                //設置實時幀速率
                particleView.fps = "FPS" + fps;
            }
        }

        try{
            Thread.sleep(sleepSpan);
        }catch (Exception e){
            e.printStackTrace();
        }
    }
}

   6、開發程序MainActivity類：

package xiao.fuyan.particle;

import android.app.Activity;
import android.os.Bundle;
import android.view.Window;
import android.view.WindowManager;


public class MainActivity extends Activity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        //設置不顯示標題
        requestWindowFeature(Window.FEATURE_NO_TITLE);
        //設置全屏顯示模式
        getWindow().setFlags(WindowManager.LayoutParams.FLAG_FULLSCREEN,
                WindowManager.LayoutParams.FLAG_FULLSCREEN);

        //創建一個ParticleView對象
        ParticleView particleView = new ParticleView(this);
        setContentView(particleView);

    }
}