Chih-Chung Chang | 7c3c938 | 2012-07-03 12:49:45 +0800 | [diff] [blame^] | 1 | /* |
| 2 | * Copyright (C) 2006 The Android Open Source Project |
| 3 | * |
| 4 | * Licensed under the Apache License, Version 2.0 (the "License"); |
| 5 | * you may not use this file except in compliance with the License. |
| 6 | * You may obtain a copy of the License at |
| 7 | * |
| 8 | * http://www.apache.org/licenses/LICENSE-2.0 |
| 9 | * |
| 10 | * Unless required by applicable law or agreed to in writing, software |
| 11 | * distributed under the License is distributed on an "AS IS" BASIS, |
| 12 | * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
| 13 | * See the License for the specific language governing permissions and |
| 14 | * limitations under the License. |
| 15 | */ |
| 16 | |
| 17 | package com.android.gallery3d.common; |
| 18 | |
| 19 | import android.content.Context; |
| 20 | import android.hardware.SensorManager; |
| 21 | import android.os.Build; |
| 22 | import android.util.FloatMath; |
| 23 | import android.view.ViewConfiguration; |
| 24 | import android.view.animation.AnimationUtils; |
| 25 | import android.view.animation.Interpolator; |
| 26 | |
| 27 | |
| 28 | /** |
| 29 | * This class encapsulates scrolling. The duration of the scroll |
| 30 | * can be passed in the constructor and specifies the maximum time that |
| 31 | * the scrolling animation should take. Past this time, the scrolling is |
| 32 | * automatically moved to its final stage and computeScrollOffset() |
| 33 | * will always return false to indicate that scrolling is over. |
| 34 | */ |
| 35 | public class Scroller { |
| 36 | private int mMode; |
| 37 | |
| 38 | private int mStartX; |
| 39 | private int mStartY; |
| 40 | private int mFinalX; |
| 41 | private int mFinalY; |
| 42 | |
| 43 | private int mMinX; |
| 44 | private int mMaxX; |
| 45 | private int mMinY; |
| 46 | private int mMaxY; |
| 47 | |
| 48 | private int mCurrX; |
| 49 | private int mCurrY; |
| 50 | private long mStartTime; |
| 51 | private int mDuration; |
| 52 | private float mDurationReciprocal; |
| 53 | private float mDeltaX; |
| 54 | private float mDeltaY; |
| 55 | private boolean mFinished; |
| 56 | private Interpolator mInterpolator; |
| 57 | private boolean mFlywheel; |
| 58 | |
| 59 | private float mVelocity; |
| 60 | |
| 61 | private static final int DEFAULT_DURATION = 250; |
| 62 | private static final int SCROLL_MODE = 0; |
| 63 | private static final int FLING_MODE = 1; |
| 64 | |
| 65 | private static float DECELERATION_RATE = (float) (Math.log(0.75) / Math.log(0.9)); |
| 66 | private static float ALPHA = 800; // pixels / seconds |
| 67 | private static float START_TENSION = 0.4f; // Tension at start: (0.4 * total T, 1.0 * Distance) |
| 68 | private static float END_TENSION = 1.0f - START_TENSION; |
| 69 | private static final int NB_SAMPLES = 100; |
| 70 | private static final float[] SPLINE = new float[NB_SAMPLES + 1]; |
| 71 | |
| 72 | private float mDeceleration; |
| 73 | private final float mPpi; |
| 74 | |
| 75 | static { |
| 76 | float x_min = 0.0f; |
| 77 | for (int i = 0; i <= NB_SAMPLES; i++) { |
| 78 | final float t = (float) i / NB_SAMPLES; |
| 79 | float x_max = 1.0f; |
| 80 | float x, tx, coef; |
| 81 | while (true) { |
| 82 | x = x_min + (x_max - x_min) / 2.0f; |
| 83 | coef = 3.0f * x * (1.0f - x); |
| 84 | tx = coef * ((1.0f - x) * START_TENSION + x * END_TENSION) + x * x * x; |
| 85 | if (Math.abs(tx - t) < 1E-5) break; |
| 86 | if (tx > t) x_max = x; |
| 87 | else x_min = x; |
| 88 | } |
| 89 | final float d = coef + x * x * x; |
| 90 | SPLINE[i] = d; |
| 91 | } |
| 92 | SPLINE[NB_SAMPLES] = 1.0f; |
| 93 | |
| 94 | // This controls the viscous fluid effect (how much of it) |
| 95 | sViscousFluidScale = 8.0f; |
| 96 | // must be set to 1.0 (used in viscousFluid()) |
| 97 | sViscousFluidNormalize = 1.0f; |
| 98 | sViscousFluidNormalize = 1.0f / viscousFluid(1.0f); |
| 99 | } |
| 100 | |
| 101 | private static float sViscousFluidScale; |
| 102 | private static float sViscousFluidNormalize; |
| 103 | |
| 104 | /** |
| 105 | * Create a Scroller with the default duration and interpolator. |
| 106 | */ |
| 107 | public Scroller(Context context) { |
| 108 | this(context, null); |
| 109 | } |
| 110 | |
| 111 | /** |
| 112 | * Create a Scroller with the specified interpolator. If the interpolator is |
| 113 | * null, the default (viscous) interpolator will be used. "Flywheel" behavior will |
| 114 | * be in effect for apps targeting Honeycomb or newer. |
| 115 | */ |
| 116 | public Scroller(Context context, Interpolator interpolator) { |
| 117 | this(context, interpolator, |
| 118 | context.getApplicationInfo().targetSdkVersion >= Build.VERSION_CODES.HONEYCOMB); |
| 119 | } |
| 120 | |
| 121 | /** |
| 122 | * Create a Scroller with the specified interpolator. If the interpolator is |
| 123 | * null, the default (viscous) interpolator will be used. Specify whether or |
| 124 | * not to support progressive "flywheel" behavior in flinging. |
| 125 | */ |
| 126 | public Scroller(Context context, Interpolator interpolator, boolean flywheel) { |
| 127 | mFinished = true; |
| 128 | mInterpolator = interpolator; |
| 129 | mPpi = context.getResources().getDisplayMetrics().density * 160.0f; |
| 130 | mDeceleration = computeDeceleration(ViewConfiguration.getScrollFriction()); |
| 131 | mFlywheel = flywheel; |
| 132 | } |
| 133 | |
| 134 | /** |
| 135 | * The amount of friction applied to flings. The default value |
| 136 | * is {@link ViewConfiguration#getScrollFriction}. |
| 137 | * |
| 138 | * @param friction A scalar dimension-less value representing the coefficient of |
| 139 | * friction. |
| 140 | */ |
| 141 | public final void setFriction(float friction) { |
| 142 | mDeceleration = computeDeceleration(friction); |
| 143 | } |
| 144 | |
| 145 | private float computeDeceleration(float friction) { |
| 146 | return SensorManager.GRAVITY_EARTH // g (m/s^2) |
| 147 | * 39.37f // inch/meter |
| 148 | * mPpi // pixels per inch |
| 149 | * friction; |
| 150 | } |
| 151 | |
| 152 | /** |
| 153 | * |
| 154 | * Returns whether the scroller has finished scrolling. |
| 155 | * |
| 156 | * @return True if the scroller has finished scrolling, false otherwise. |
| 157 | */ |
| 158 | public final boolean isFinished() { |
| 159 | return mFinished; |
| 160 | } |
| 161 | |
| 162 | /** |
| 163 | * Force the finished field to a particular value. |
| 164 | * |
| 165 | * @param finished The new finished value. |
| 166 | */ |
| 167 | public final void forceFinished(boolean finished) { |
| 168 | mFinished = finished; |
| 169 | } |
| 170 | |
| 171 | /** |
| 172 | * Returns how long the scroll event will take, in milliseconds. |
| 173 | * |
| 174 | * @return The duration of the scroll in milliseconds. |
| 175 | */ |
| 176 | public final int getDuration() { |
| 177 | return mDuration; |
| 178 | } |
| 179 | |
| 180 | /** |
| 181 | * Returns the current X offset in the scroll. |
| 182 | * |
| 183 | * @return The new X offset as an absolute distance from the origin. |
| 184 | */ |
| 185 | public final int getCurrX() { |
| 186 | return mCurrX; |
| 187 | } |
| 188 | |
| 189 | /** |
| 190 | * Returns the current Y offset in the scroll. |
| 191 | * |
| 192 | * @return The new Y offset as an absolute distance from the origin. |
| 193 | */ |
| 194 | public final int getCurrY() { |
| 195 | return mCurrY; |
| 196 | } |
| 197 | |
| 198 | /** |
| 199 | * Returns the current velocity. |
| 200 | * |
| 201 | * @return The original velocity less the deceleration. Result may be |
| 202 | * negative. |
| 203 | */ |
| 204 | public float getCurrVelocity() { |
| 205 | return mVelocity - mDeceleration * timePassed() / 2000.0f; |
| 206 | } |
| 207 | |
| 208 | /** |
| 209 | * Returns the start X offset in the scroll. |
| 210 | * |
| 211 | * @return The start X offset as an absolute distance from the origin. |
| 212 | */ |
| 213 | public final int getStartX() { |
| 214 | return mStartX; |
| 215 | } |
| 216 | |
| 217 | /** |
| 218 | * Returns the start Y offset in the scroll. |
| 219 | * |
| 220 | * @return The start Y offset as an absolute distance from the origin. |
| 221 | */ |
| 222 | public final int getStartY() { |
| 223 | return mStartY; |
| 224 | } |
| 225 | |
| 226 | /** |
| 227 | * Returns where the scroll will end. Valid only for "fling" scrolls. |
| 228 | * |
| 229 | * @return The final X offset as an absolute distance from the origin. |
| 230 | */ |
| 231 | public final int getFinalX() { |
| 232 | return mFinalX; |
| 233 | } |
| 234 | |
| 235 | /** |
| 236 | * Returns where the scroll will end. Valid only for "fling" scrolls. |
| 237 | * |
| 238 | * @return The final Y offset as an absolute distance from the origin. |
| 239 | */ |
| 240 | public final int getFinalY() { |
| 241 | return mFinalY; |
| 242 | } |
| 243 | |
| 244 | /** |
| 245 | * Call this when you want to know the new location. If it returns true, |
| 246 | * the animation is not yet finished. loc will be altered to provide the |
| 247 | * new location. |
| 248 | */ |
| 249 | public boolean computeScrollOffset() { |
| 250 | if (mFinished) { |
| 251 | return false; |
| 252 | } |
| 253 | |
| 254 | int timePassed = (int)(AnimationUtils.currentAnimationTimeMillis() - mStartTime); |
| 255 | |
| 256 | if (timePassed < mDuration) { |
| 257 | switch (mMode) { |
| 258 | case SCROLL_MODE: |
| 259 | float x = timePassed * mDurationReciprocal; |
| 260 | |
| 261 | if (mInterpolator == null) |
| 262 | x = viscousFluid(x); |
| 263 | else |
| 264 | x = mInterpolator.getInterpolation(x); |
| 265 | |
| 266 | mCurrX = mStartX + Math.round(x * mDeltaX); |
| 267 | mCurrY = mStartY + Math.round(x * mDeltaY); |
| 268 | break; |
| 269 | case FLING_MODE: |
| 270 | final float t = (float) timePassed / mDuration; |
| 271 | final int index = (int) (NB_SAMPLES * t); |
| 272 | final float t_inf = (float) index / NB_SAMPLES; |
| 273 | final float t_sup = (float) (index + 1) / NB_SAMPLES; |
| 274 | final float d_inf = SPLINE[index]; |
| 275 | final float d_sup = SPLINE[index + 1]; |
| 276 | final float distanceCoef = d_inf + (t - t_inf) / (t_sup - t_inf) * (d_sup - d_inf); |
| 277 | |
| 278 | mCurrX = mStartX + Math.round(distanceCoef * (mFinalX - mStartX)); |
| 279 | // Pin to mMinX <= mCurrX <= mMaxX |
| 280 | mCurrX = Math.min(mCurrX, mMaxX); |
| 281 | mCurrX = Math.max(mCurrX, mMinX); |
| 282 | |
| 283 | mCurrY = mStartY + Math.round(distanceCoef * (mFinalY - mStartY)); |
| 284 | // Pin to mMinY <= mCurrY <= mMaxY |
| 285 | mCurrY = Math.min(mCurrY, mMaxY); |
| 286 | mCurrY = Math.max(mCurrY, mMinY); |
| 287 | |
| 288 | if (mCurrX == mFinalX && mCurrY == mFinalY) { |
| 289 | mFinished = true; |
| 290 | } |
| 291 | |
| 292 | break; |
| 293 | } |
| 294 | } |
| 295 | else { |
| 296 | mCurrX = mFinalX; |
| 297 | mCurrY = mFinalY; |
| 298 | mFinished = true; |
| 299 | } |
| 300 | return true; |
| 301 | } |
| 302 | |
| 303 | /** |
| 304 | * Start scrolling by providing a starting point and the distance to travel. |
| 305 | * The scroll will use the default value of 250 milliseconds for the |
| 306 | * duration. |
| 307 | * |
| 308 | * @param startX Starting horizontal scroll offset in pixels. Positive |
| 309 | * numbers will scroll the content to the left. |
| 310 | * @param startY Starting vertical scroll offset in pixels. Positive numbers |
| 311 | * will scroll the content up. |
| 312 | * @param dx Horizontal distance to travel. Positive numbers will scroll the |
| 313 | * content to the left. |
| 314 | * @param dy Vertical distance to travel. Positive numbers will scroll the |
| 315 | * content up. |
| 316 | */ |
| 317 | public void startScroll(int startX, int startY, int dx, int dy) { |
| 318 | startScroll(startX, startY, dx, dy, DEFAULT_DURATION); |
| 319 | } |
| 320 | |
| 321 | /** |
| 322 | * Start scrolling by providing a starting point and the distance to travel. |
| 323 | * |
| 324 | * @param startX Starting horizontal scroll offset in pixels. Positive |
| 325 | * numbers will scroll the content to the left. |
| 326 | * @param startY Starting vertical scroll offset in pixels. Positive numbers |
| 327 | * will scroll the content up. |
| 328 | * @param dx Horizontal distance to travel. Positive numbers will scroll the |
| 329 | * content to the left. |
| 330 | * @param dy Vertical distance to travel. Positive numbers will scroll the |
| 331 | * content up. |
| 332 | * @param duration Duration of the scroll in milliseconds. |
| 333 | */ |
| 334 | public void startScroll(int startX, int startY, int dx, int dy, int duration) { |
| 335 | mMode = SCROLL_MODE; |
| 336 | mFinished = false; |
| 337 | mDuration = duration; |
| 338 | mStartTime = AnimationUtils.currentAnimationTimeMillis(); |
| 339 | mStartX = startX; |
| 340 | mStartY = startY; |
| 341 | mFinalX = startX + dx; |
| 342 | mFinalY = startY + dy; |
| 343 | mDeltaX = dx; |
| 344 | mDeltaY = dy; |
| 345 | mDurationReciprocal = 1.0f / (float) mDuration; |
| 346 | } |
| 347 | |
| 348 | /** |
| 349 | * Start scrolling based on a fling gesture. The distance travelled will |
| 350 | * depend on the initial velocity of the fling. |
| 351 | * |
| 352 | * @param startX Starting point of the scroll (X) |
| 353 | * @param startY Starting point of the scroll (Y) |
| 354 | * @param velocityX Initial velocity of the fling (X) measured in pixels per |
| 355 | * second. |
| 356 | * @param velocityY Initial velocity of the fling (Y) measured in pixels per |
| 357 | * second |
| 358 | * @param minX Minimum X value. The scroller will not scroll past this |
| 359 | * point. |
| 360 | * @param maxX Maximum X value. The scroller will not scroll past this |
| 361 | * point. |
| 362 | * @param minY Minimum Y value. The scroller will not scroll past this |
| 363 | * point. |
| 364 | * @param maxY Maximum Y value. The scroller will not scroll past this |
| 365 | * point. |
| 366 | */ |
| 367 | public void fling(int startX, int startY, int velocityX, int velocityY, |
| 368 | int minX, int maxX, int minY, int maxY) { |
| 369 | // Continue a scroll or fling in progress |
| 370 | if (mFlywheel && !mFinished) { |
| 371 | float oldVel = getCurrVelocity(); |
| 372 | |
| 373 | float dx = (float) (mFinalX - mStartX); |
| 374 | float dy = (float) (mFinalY - mStartY); |
| 375 | float hyp = FloatMath.sqrt(dx * dx + dy * dy); |
| 376 | |
| 377 | float ndx = dx / hyp; |
| 378 | float ndy = dy / hyp; |
| 379 | |
| 380 | float oldVelocityX = ndx * oldVel; |
| 381 | float oldVelocityY = ndy * oldVel; |
| 382 | if (Math.signum(velocityX) == Math.signum(oldVelocityX) && |
| 383 | Math.signum(velocityY) == Math.signum(oldVelocityY)) { |
| 384 | velocityX += oldVelocityX; |
| 385 | velocityY += oldVelocityY; |
| 386 | } |
| 387 | } |
| 388 | |
| 389 | mMode = FLING_MODE; |
| 390 | mFinished = false; |
| 391 | |
| 392 | float velocity = FloatMath.sqrt(velocityX * velocityX + velocityY * velocityY); |
| 393 | |
| 394 | mVelocity = velocity; |
| 395 | final double l = Math.log(START_TENSION * velocity / ALPHA); |
| 396 | mDuration = (int) (1000.0 * Math.exp(l / (DECELERATION_RATE - 1.0))); |
| 397 | mStartTime = AnimationUtils.currentAnimationTimeMillis(); |
| 398 | mStartX = startX; |
| 399 | mStartY = startY; |
| 400 | |
| 401 | float coeffX = velocity == 0 ? 1.0f : velocityX / velocity; |
| 402 | float coeffY = velocity == 0 ? 1.0f : velocityY / velocity; |
| 403 | |
| 404 | int totalDistance = |
| 405 | (int) (ALPHA * Math.exp(DECELERATION_RATE / (DECELERATION_RATE - 1.0) * l)); |
| 406 | |
| 407 | mMinX = minX; |
| 408 | mMaxX = maxX; |
| 409 | mMinY = minY; |
| 410 | mMaxY = maxY; |
| 411 | |
| 412 | mFinalX = startX + Math.round(totalDistance * coeffX); |
| 413 | // Pin to mMinX <= mFinalX <= mMaxX |
| 414 | mFinalX = Math.min(mFinalX, mMaxX); |
| 415 | mFinalX = Math.max(mFinalX, mMinX); |
| 416 | |
| 417 | mFinalY = startY + Math.round(totalDistance * coeffY); |
| 418 | // Pin to mMinY <= mFinalY <= mMaxY |
| 419 | mFinalY = Math.min(mFinalY, mMaxY); |
| 420 | mFinalY = Math.max(mFinalY, mMinY); |
| 421 | } |
| 422 | |
| 423 | static float viscousFluid(float x) |
| 424 | { |
| 425 | x *= sViscousFluidScale; |
| 426 | if (x < 1.0f) { |
| 427 | x -= (1.0f - (float)Math.exp(-x)); |
| 428 | } else { |
| 429 | float start = 0.36787944117f; // 1/e == exp(-1) |
| 430 | x = 1.0f - (float)Math.exp(1.0f - x); |
| 431 | x = start + x * (1.0f - start); |
| 432 | } |
| 433 | x *= sViscousFluidNormalize; |
| 434 | return x; |
| 435 | } |
| 436 | |
| 437 | /** |
| 438 | * Stops the animation. Contrary to {@link #forceFinished(boolean)}, |
| 439 | * aborting the animating cause the scroller to move to the final x and y |
| 440 | * position |
| 441 | * |
| 442 | * @see #forceFinished(boolean) |
| 443 | */ |
| 444 | public void abortAnimation() { |
| 445 | mCurrX = mFinalX; |
| 446 | mCurrY = mFinalY; |
| 447 | mFinished = true; |
| 448 | } |
| 449 | |
| 450 | /** |
| 451 | * Extend the scroll animation. This allows a running animation to scroll |
| 452 | * further and longer, when used with {@link #setFinalX(int)} or {@link #setFinalY(int)}. |
| 453 | * |
| 454 | * @param extend Additional time to scroll in milliseconds. |
| 455 | * @see #setFinalX(int) |
| 456 | * @see #setFinalY(int) |
| 457 | */ |
| 458 | public void extendDuration(int extend) { |
| 459 | int passed = timePassed(); |
| 460 | mDuration = passed + extend; |
| 461 | mDurationReciprocal = 1.0f / mDuration; |
| 462 | mFinished = false; |
| 463 | } |
| 464 | |
| 465 | /** |
| 466 | * Returns the time elapsed since the beginning of the scrolling. |
| 467 | * |
| 468 | * @return The elapsed time in milliseconds. |
| 469 | */ |
| 470 | public int timePassed() { |
| 471 | return (int)(AnimationUtils.currentAnimationTimeMillis() - mStartTime); |
| 472 | } |
| 473 | |
| 474 | /** |
| 475 | * Sets the final position (X) for this scroller. |
| 476 | * |
| 477 | * @param newX The new X offset as an absolute distance from the origin. |
| 478 | * @see #extendDuration(int) |
| 479 | * @see #setFinalY(int) |
| 480 | */ |
| 481 | public void setFinalX(int newX) { |
| 482 | mFinalX = newX; |
| 483 | mDeltaX = mFinalX - mStartX; |
| 484 | mFinished = false; |
| 485 | } |
| 486 | |
| 487 | /** |
| 488 | * Sets the final position (Y) for this scroller. |
| 489 | * |
| 490 | * @param newY The new Y offset as an absolute distance from the origin. |
| 491 | * @see #extendDuration(int) |
| 492 | * @see #setFinalX(int) |
| 493 | */ |
| 494 | public void setFinalY(int newY) { |
| 495 | mFinalY = newY; |
| 496 | mDeltaY = mFinalY - mStartY; |
| 497 | mFinished = false; |
| 498 | } |
| 499 | |
| 500 | /** |
| 501 | * @hide |
| 502 | */ |
| 503 | public boolean isScrollingInDirection(float xvel, float yvel) { |
| 504 | return !mFinished && Math.signum(xvel) == Math.signum(mFinalX - mStartX) && |
| 505 | Math.signum(yvel) == Math.signum(mFinalY - mStartY); |
| 506 | } |
| 507 | } |