第三方开源控件ExplosionField源码解析
笑谈风云，一语定乾坤。今天和大伙分享一个有意思的开源控件。
简介
先上一张图，大家感受下。
是不是酷炫？是不是似曾相识？在小米系统MIUI中的删除APK功能也是有上面这种粒子炸裂的效果的。下面给出github地址 https://github.com/tyrantgit/ExplosionField
如果无法访问的话，就直接在下面下载源码： 源码点我
集成和使用
首先导入explosionfield做为library，并在gradle中添加好依赖。（也可以将library打包成aar文件，直接放入到libs目录中）。 做完以上步骤后，在Activity的onCreate方法中实例化ExplosionField。 private ExplosionField mExplosionField;@Overrideprotected void onCreate(Bundle savedInstanceState) {super.onCreate(savedInstanceState);setContentView(R.layout.activity_main);mExplosionField = ExplosionField.attach2Window(this);}
源码分析
集成和使用是比较简单，那么再看看具体是如何实现的：
首先，将ExplosionField依附到activity上。
ExplosionField.java
public static ExplosionField attach2Window(Activity activity) {ViewGroup rootView = (ViewGroup) activity.findViewById(Window.ID_ANDROID_CONTENT);ExplosionField explosionField = new ExplosionField(activity);rootView.addView(explosionField, new ViewGroup.LayoutParams(ViewGroup.LayoutParams.MATCH_PARENT, ViewGroup.LayoutParams.MATCH_PARENT));return explosionField;} public static final int ID_ANDROID_CONTENT = com.android.internal.R.id.content; private int[] mExpandInset = new int[2];public ExplosionField(Context context) {super(context);init();}public ExplosionField(Context context, AttributeSet attrs) {super(context, attrs);init();}public ExplosionField(Context context, AttributeSet attrs, int defStyleAttr) {super(context, attrs, defStyleAttr);init();}private void init() {Arrays.fill(mExpandInset, Utils.dp2Px(32));} private static final float DENSITY = Resources.getSystem().getDisplayMetrics().density;private static final Canvas sCanvas = new Canvas();public static int dp2Px(int dp) {return Math.round(dp * DENSITY);} public void explode(final View view) {Rect r = new Rect();view.getGlobalVisibleRect(r);int[] location = new int[2];getLocationOnScreen(location);r.offset(-location[0], -location[1]);r.inset(-mExpandInset[0], -mExpandInset[1]);int startDelay = 100;ValueAnimator animator = ValueAnimator.ofFloat(0f, 1f).setDuration(150);animator.addUpdateListener(new ValueAnimator.AnimatorUpdateListener() {//抖动效果Random random = new Random();@Overridepublic void onAnimationUpdate(ValueAnimator animation) {view.setTranslationX((random.nextFloat() - 0.5f) * view.getWidth() * 0.05f);view.setTranslationY((random.nextFloat() - 0.5f) * view.getHeight() * 0.05f);}});animator.start();view.animate().setDuration(150).setStartDelay(startDelay).scaleX(0f).scaleY(0f).alpha(0f).start();explode(Utils.createBitmapFromView(view), r, startDelay, ExplosionAnimator.DEFAULT_DURATION);} public void offset(int dx, int dy) {left += dx;top += dy;right += dx;bottom += dy;} public void inset(int dx, int dy) {left += dx;top += dy;right -= dx;bottom -= dy;} public void explode(Bitmap bitmap, Rect bound, long startDelay, long duration) {final ExplosionAnimator explosion = new ExplosionAnimator(this, bitmap, bound);explosion.addListener(new AnimatorListenerAdapter() {@Overridepublic void onAnimationEnd(Animator animation) {mExplosions.remove(animation);}});explosion.setStartDelay(startDelay);explosion.setDuration(duration);mExplosions.add(explosion);explosion.start();} public static Bitmap createBitmapFromView(View view) {if (view instanceof ImageView) {//从图片中创建BitmapDrawable drawable = ((ImageView) view).getDrawable();if (drawable != null && drawable instanceof BitmapDrawable) {return ((BitmapDrawable) drawable).getBitmap();}}view.clearFocus();Bitmap bitmap = createBitmapSafely(view.getWidth(),view.getHeight(), Bitmap.Config.ARGB_8888, 1);if (bitmap != null) {synchronized (sCanvas) {Canvas canvas = sCanvas;canvas.setBitmap(bitmap);view.draw(canvas);canvas.setBitmap(null);}}return bitmap;}/*** 创建Bitmap 如果在创建Bitmap过程中内存不足，则手动触发一次GC，然后再尝试创建* @param width* @param height* @param config* @param retryCount* @return*/public static Bitmap createBitmapSafely(int width, int height, Bitmap.Config config, int retryCount) {try {return Bitmap.createBitmap(width, height, config);} catch (OutOfMemoryError e) {e.printStackTrace();if (retryCount > 0) {System.gc();return createBitmapSafely(width, height, config, retryCount - 1);}return null;}} static long DEFAULT_DURATION = 0x400;private static final Interpolator DEFAULT_INTERPOLATOR = new AccelerateInterpolator(0.6f);private static final float END_VALUE = 1.4f;private static final float X = Utils.dp2Px(5);private static final float Y = Utils.dp2Px(20);private static final float V = Utils.dp2Px(2);private static final float W = Utils.dp2Px(1);private Paint mPaint;//画笔private Particle[] mParticles;//粒子集合private Rect mBound;//区域矩阵private View mContainer;//视图Viewpublic ExplosionAnimator(View container, Bitmap bitmap, Rect bound) {mPaint = new Paint();mBound = new Rect(bound);int partLen = 15;mParticles = new Particle[partLen * partLen];Random random = new Random(System.currentTimeMillis());int w = bitmap.getWidth() / (partLen + 2);int h = bitmap.getHeight() / (partLen + 2);for (int i = 0; i < partLen; i++) {for (int j = 0; j < partLen; j++) {mParticles[(i * partLen) + j] = generateParticle(bitmap.getPixel((j + 1) * w, (i + 1) * h), random);}}mContainer = container;setFloatValues(0f, END_VALUE);//设置动画起点终点setInterpolator(DEFAULT_INTERPOLATOR);//设置变速器setDuration(DEFAULT_DURATION);//设置动画运行时间} private Particle generateParticle(int color, Random random) {Particle particle = new Particle();particle.color = color;particle.radius = V;if (random.nextFloat() < 0.2f) {particle.baseRadius = V + ((X - V) * random.nextFloat());} else {particle.baseRadius = W + ((V - W) * random.nextFloat());}float nextFloat = random.nextFloat();particle.top = mBound.height() * ((0.18f * random.nextFloat()) + 0.2f);particle.top = nextFloat < 0.2f ? particle.top : particle.top + ((particle.top * 0.2f) * random.nextFloat());particle.bottom = (mBound.height() * (random.nextFloat() - 0.5f)) * 1.8f;float f = nextFloat < 0.2f ? particle.bottom : nextFloat < 0.8f ? particle.bottom * 0.6f : particle.bottom * 0.3f;//particle.bottom = f;particle.mag = 4.0f * particle.top / particle.bottom;particle.neg = (-particle.mag) / particle.bottom;f = mBound.centerX() + (Y * (random.nextFloat() - 0.5f));particle.baseCx = f;particle.cx = f;f = mBound.centerY() + (Y * (random.nextFloat() - 0.5f));particle.baseCy = f;particle.cy = f;particle.life = END_VALUE / 10 * random.nextFloat();//0-0.14particle.overflow = 0.4f * random.nextFloat();//0-0.4particle.alpha = 1f;return particle;} private class Particle {//粒子透明度float alpha;//粒子颜色int color;//圆心x坐标float cx;//圆心y坐标float cy;//圆半径float radius;//起点x坐标float baseCx;//起点Y坐标float baseCy;//初始圆半径float baseRadius;//高部float top;//底部float bottom;float mag;float neg;float life;float overflow;public void advance(float factor) {float f = 0f;float normalization = factor / END_VALUE;if (normalization < life || normalization > 1f - overflow) {alpha = 0f;return;}normalization = (normalization - life) / (1f - life - overflow);float f2 = normalization * END_VALUE;if (normalization >= 0.7f) {f = (normalization - 0.7f) / 0.3f;}alpha = 1f - f;f = bottom * f2;cx = baseCx + f;cy = (float) (baseCy - this.neg * Math.pow(f, 2.0)) - f * mag;radius = V + (baseRadius - V) * f2;}} @Overridepublic void start() {super.start();mContainer.invalidate(mBound);} @Overrideprotected void onDraw(Canvas canvas) {super.onDraw(canvas);for (ExplosionAnimator explosion : mExplosions) {explosion.draw(canvas);}} public boolean draw(Canvas canvas) {if (!isStarted()) {return false;}for (Particle particle : mParticles) {particle.advance((float) getAnimatedValue());if (particle.alpha > 0f) {mPaint.setColor(particle.color);mPaint.setAlpha((int) (Color.alpha(particle.color) * particle.alpha));canvas.drawCircle(particle.cx, particle.cy, particle.radius, mPaint);}}mContainer.invalidate();return true;}整个View涉及到的代码量不大，但是读起来让人觉得酣畅淋漓。
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