Initial commit:

- Particles spray upwards.

.gitignore

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+bin/
+gen/
+.classpath
+.project
+.swp
+

AndroidManifest.xml

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+<?xml version="1.0" encoding="utf-8"?>
+<manifest xmlns:android="http://schemas.android.com/apk/res/android"
+      package="com.timwu.Particles"
+      android:versionCode="1"
+      android:versionName="1.0">
+    <application android:icon="@drawable/icon" android:label="@string/app_name">
+        <activity android:name=".ParticleSimulator"
+                  android:label="@string/app_name">
+            <intent-filter>
+                <action android:name="android.intent.action.MAIN" />
+                <category android:name="android.intent.category.LAUNCHER" />
+            </intent-filter>
+        </activity>
+
+    </application>
+
+
+</manifest> 

default.properties

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+# This file is automatically generated by Android Tools.
+# Do not modify this file -- YOUR CHANGES WILL BE ERASED!
+#
+# This file must be checked in Version Control Systems.
+#
+# To customize properties used by the Ant build system use,
+# "build.properties", and override values to adapt the script to your
+# project structure.
+
+# Project target.
+target=android-9

proguard.cfg

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+-optimizationpasses 5
+-dontusemixedcaseclassnames
+-dontskipnonpubliclibraryclasses
+-dontpreverify
+-verbose
+-optimizations !code/simplification/arithmetic,!field/*,!class/merging/*
+
+-keep public class * extends android.app.Activity
+-keep public class * extends android.app.Application
+-keep public class * extends android.app.Service
+-keep public class * extends android.content.BroadcastReceiver
+-keep public class * extends android.content.ContentProvider
+-keep public class com.android.vending.licensing.ILicensingService
+
+-keepclasseswithmembernames class * {
+    native <methods>;
+}
+
+-keepclasseswithmembernames class * {
+    public <init>(android.content.Context, android.util.AttributeSet);
+}
+
+-keepclasseswithmembernames class * {
+    public <init>(android.content.Context, android.util.AttributeSet, int);
+}
+
+-keepclassmembers enum * {
+    public static **[] values();
+    public static ** valueOf(java.lang.String);
+}
+
+-keep class * implements android.os.Parcelable {
+  public static final android.os.Parcelable$Creator *;
+}

res/layout/main.xml

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+<?xml version="1.0" encoding="utf-8"?>
+<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
+    android:orientation="vertical"
+    android:layout_width="fill_parent"
+    android:layout_height="fill_parent"
+    >
+    <com.timwu.Particles.ParticleView
+    	android:id="@+id/particle_view"
+    	android:layout_width="fill_parent"
+    	android:layout_height="fill_parent"/>
+</LinearLayout>

res/values/strings.xml

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+<?xml version="1.0" encoding="utf-8"?>
+<resources>
+    <string name="hello">Hello World, ParticleSimulator!</string>
+    <string name="app_name">Particles</string>
+</resources>

src/com/timwu/Particles/ParticleSimulator.java

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+package com.timwu.Particles;
+
+import android.app.Activity;
+import android.os.Bundle;
+
+public class ParticleSimulator extends Activity {
+    /** Called when the activity is first created. */
+    @Override
+    public void onCreate(Bundle savedInstanceState) {
+        super.onCreate(savedInstanceState);
+        setContentView(R.layout.main);
+    }
+}

src/com/timwu/Particles/ParticleView.java

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+package com.timwu.Particles;
+
+import java.util.ArrayList;
+import java.util.Calendar;
+import java.util.Collections;
+import java.util.Iterator;
+import java.util.List;
+import java.util.Random;
+
+import android.content.Context;
+import android.graphics.Canvas;
+import android.graphics.Color;
+import android.graphics.Paint;
+import android.util.AttributeSet;
+import android.util.Log;
+import android.view.SurfaceHolder;
+import android.view.SurfaceView;
+
+public class ParticleView extends SurfaceView implements SurfaceHolder.Callback {
+	private static final String TAG = "ParticleView";
+	private static final float NANO_SECONDS_PER_SECOND = 1000000000.0f;
+
+	private ParticleViewLoop loop;
+
+	public ParticleView(Context context, AttributeSet attrs) {
+		super(context, attrs);
+		loop = new ParticleViewLoop();
+		getHolder().addCallback(this);
+	}
+
+	private class ParticleViewLoop extends Thread {
+		private List<Particle> particles = Collections.synchronizedList(new ArrayList<Particle>());
+		private long prevTick;
+
+		@Override
+		public void run() {
+			Log.i(TAG, "Starting particle simulator.");
+//			Log.i(TAG, "Generating particles.");
+//			addRandomParticles();
+
+			prevTick = System.nanoTime();
+			Log.i(TAG, "Starting with tick " + prevTick);
+			while(!isInterrupted()) {
+				doPhysics();
+				doAnimation();
+				doDraw();
+			}
+		}
+
+		private void doPhysics() {
+			// Add a particle each time around
+			sprayParticles(1, getWidth() / 2.0f, getHeight() * 0.1f, 10.0f, 
+					(float) (3 * Math.PI / 2), (float) Math.PI / 4);
+
+			// Physics states that any particle outside of the view, should be annihilated. I think.
+			Iterator<Particle> pit = particles.iterator();
+			while(pit.hasNext()) {
+				Particle p = pit.next();
+				if (p.x < 0 || p.x > getWidth() || p.y < 0 || p.y > getHeight()) {
+					pit.remove();
+				}
+			}
+		}
+
+		private void doAnimation() {
+			long curTick = System.nanoTime();
+			float dt = (curTick - prevTick) / NANO_SECONDS_PER_SECOND;
+			for(Particle p : particles) {
+				p.tick(dt);
+			}
+			prevTick = curTick;
+		}
+
+		private void doDraw() {
+			Canvas c = getHolder().lockCanvas();
+			synchronized (getHolder()) {
+				c.clipRect(0, 0, getWidth(), getHeight());
+				c.drawColor(Color.BLACK);
+				Paint paint = new Paint();
+				paint.setStyle(Paint.Style.FILL_AND_STROKE);
+				for (Particle p : particles) {
+					paint.setColor(p.color);
+					c.drawCircle(p.x, p.y, p.r, paint);
+				}
+			}
+			getHolder().unlockCanvasAndPost(c);
+		}
+
+		private void addRandomParticles() {
+			Random r = new Random();
+			for (int i = 0; i < 1000; i++) {
+				Particle p = new Particle();
+				p.x = r.nextInt(getWidth());
+				p.y = r.nextInt(getHeight());
+				p.r = 2.0f;
+				p.color = Color.CYAN;
+				p.vx = r.nextFloat() * 10.0f;
+				p.vy = r.nextFloat() * 10.0f;
+				particles.add(p);
+			}
+		}
+
+		private void sprayParticles(int n, float x, float y, float vMax, float angle, float angleWindow) {
+			Random r = new Random();
+			for (;n > 0; n--) {
+				Particle p = new Particle();
+				float v = vMax * r.nextFloat();
+				float a = angle + (r.nextFloat() - 0.5f) * angleWindow;
+				p.x = x;
+				p.y = y;
+				p.vx = (float) (Math.cos(a) * v);
+				p.vy = (float) (Math.sin(a) * v);
+				p.color = Color.CYAN;
+				p.r = 2.0f;
+				Log.i(TAG, "p " + p);
+				particles.add(p);
+			}
+		}
+	}
+
+	private class Particle {
+		private float x, y;
+		private float vx, vy;
+		private float r;
+		private int color;
+
+		private void tick(float dt) {
+			// Just doing a naive implementation where velocity will be
+			// constant over the timeslice. Probably not too bad an approximation.
+			x += vx * dt;
+			y += vy * dt;
+		}
+
+		public String toString() {
+			return "(" + x + ", " + y + ") <" + vx + ", " + vy + ">";
+		}
+	}
+
+	@Override
+	public void surfaceChanged(SurfaceHolder holder, int fmt, int width, int height) {
+		Log.i(TAG, "Surface changed.");
+	}
+
+	@Override
+	public void surfaceCreated(SurfaceHolder holder) {
+		Log.i(TAG, "Starting drawing loop.");
+		loop.start();
+	}
+
+	@Override
+	public void surfaceDestroyed(SurfaceHolder holder) {
+		Log.i(TAG, "Stopping drawing loop.");
+		loop.interrupt();
+	}
+}