| /* |
| * Copyright (C) 2010 The Android Open Source Project |
| * |
| * Licensed under the Apache License, Version 2.0 (the "License"); |
| * you may not use this file except in compliance with the License. |
| * You may obtain a copy of the License at |
| * |
| * http://www.apache.org/licenses/LICENSE-2.0 |
| * |
| * Unless required by applicable law or agreed to in writing, software |
| * distributed under the License is distributed on an "AS IS" BASIS, |
| * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
| * See the License for the specific language governing permissions and |
| * limitations under the License. |
| */ |
| |
| package android.widget; |
| |
| import android.graphics.Canvas; |
| import android.graphics.drawable.Drawable; |
| import android.view.animation.AnimationUtils; |
| import android.view.animation.DecelerateInterpolator; |
| import android.view.animation.Interpolator; |
| |
| /** |
| * This class performs the glow effect used at the edges of scrollable widgets. |
| * @hide |
| */ |
| public class EdgeGlow { |
| private static final String TAG = "EdgeGlow"; |
| |
| // Time it will take the effect to fully recede in ms |
| private static final int RECEDE_TIME = 1000; |
| |
| // Time it will take before a pulled glow begins receding |
| private static final int PULL_TIME = 250; |
| |
| // Time it will take for a pulled glow to decay to partial strength before release |
| private static final int PULL_DECAY_TIME = 10000; |
| |
| private static final float MAX_ALPHA = 1.f; |
| private static final float HELD_EDGE_ALPHA = 0.7f; |
| private static final float HELD_EDGE_SCALE_Y = 0.5f; |
| private static final float HELD_GLOW_ALPHA = 0.5f; |
| private static final float HELD_GLOW_SCALE_Y = 0.5f; |
| |
| private static final float MAX_GLOW_HEIGHT = 3.f; |
| |
| private static final float PULL_GLOW_BEGIN = 1.f; |
| private static final float PULL_EDGE_BEGIN = 0.6f; |
| |
| // Minimum velocity that will be absorbed |
| private static final int MIN_VELOCITY = 100; |
| |
| private static final float EPSILON = 0.001f; |
| |
| private final Drawable mEdge; |
| private final Drawable mGlow; |
| private int mWidth; |
| private int mHeight; |
| |
| private float mEdgeAlpha; |
| private float mEdgeScaleY; |
| private float mGlowAlpha; |
| private float mGlowScaleY; |
| |
| private float mEdgeAlphaStart; |
| private float mEdgeAlphaFinish; |
| private float mEdgeScaleYStart; |
| private float mEdgeScaleYFinish; |
| private float mGlowAlphaStart; |
| private float mGlowAlphaFinish; |
| private float mGlowScaleYStart; |
| private float mGlowScaleYFinish; |
| |
| private long mStartTime; |
| private float mDuration; |
| |
| private final Interpolator mInterpolator; |
| |
| private static final int STATE_IDLE = 0; |
| private static final int STATE_PULL = 1; |
| private static final int STATE_ABSORB = 2; |
| private static final int STATE_RECEDE = 3; |
| private static final int STATE_PULL_DECAY = 4; |
| |
| // How much dragging should effect the height of the edge image. |
| // Number determined by user testing. |
| private static final int PULL_DISTANCE_EDGE_FACTOR = 5; |
| |
| // How much dragging should effect the height of the glow image. |
| // Number determined by user testing. |
| private static final int PULL_DISTANCE_GLOW_FACTOR = 5; |
| private static final float PULL_DISTANCE_ALPHA_GLOW_FACTOR = 0.8f; |
| |
| private static final int VELOCITY_EDGE_FACTOR = 8; |
| private static final int VELOCITY_GLOW_FACTOR = 16; |
| |
| private int mState = STATE_IDLE; |
| |
| private float mPullDistance; |
| |
| public EdgeGlow(Drawable edge, Drawable glow) { |
| mEdge = edge; |
| mGlow = glow; |
| |
| mInterpolator = new DecelerateInterpolator(); |
| } |
| |
| public void setSize(int width, int height) { |
| mWidth = width; |
| mHeight = height; |
| } |
| |
| public boolean isFinished() { |
| return mState == STATE_IDLE; |
| } |
| |
| public void finish() { |
| mState = STATE_IDLE; |
| } |
| |
| /** |
| * Call when the object is pulled by the user. |
| * |
| * @param deltaDistance Change in distance since the last call |
| */ |
| public void onPull(float deltaDistance) { |
| final long now = AnimationUtils.currentAnimationTimeMillis(); |
| if (mState == STATE_PULL_DECAY && now - mStartTime < mDuration) { |
| return; |
| } |
| if (mState != STATE_PULL) { |
| mGlowScaleY = PULL_GLOW_BEGIN; |
| } |
| mState = STATE_PULL; |
| |
| mStartTime = now; |
| mDuration = PULL_TIME; |
| |
| mPullDistance += deltaDistance; |
| float distance = Math.abs(mPullDistance); |
| |
| mEdgeAlpha = mEdgeAlphaStart = Math.max(PULL_EDGE_BEGIN, Math.min(distance, MAX_ALPHA)); |
| mEdgeScaleY = mEdgeScaleYStart = Math.max( |
| HELD_EDGE_SCALE_Y, Math.min(distance * PULL_DISTANCE_EDGE_FACTOR, 1.f)); |
| |
| mGlowAlpha = mGlowAlphaStart = Math.min(MAX_ALPHA, |
| mGlowAlpha + |
| (Math.abs(deltaDistance) * PULL_DISTANCE_ALPHA_GLOW_FACTOR)); |
| |
| float glowChange = Math.abs(deltaDistance); |
| if (deltaDistance > 0 && mPullDistance < 0) { |
| glowChange = -glowChange; |
| } |
| if (mPullDistance == 0) { |
| mGlowScaleY = 0; |
| } |
| |
| // Do not allow glow to get larger than MAX_GLOW_HEIGHT. |
| mGlowScaleY = mGlowScaleYStart = Math.min(MAX_GLOW_HEIGHT, Math.max( |
| 0, mGlowScaleY + glowChange * PULL_DISTANCE_GLOW_FACTOR)); |
| |
| mEdgeAlphaFinish = mEdgeAlpha; |
| mEdgeScaleYFinish = mEdgeScaleY; |
| mGlowAlphaFinish = mGlowAlpha; |
| mGlowScaleYFinish = mGlowScaleY; |
| } |
| |
| /** |
| * Call when the object is released after being pulled. |
| */ |
| public void onRelease() { |
| mPullDistance = 0; |
| |
| if (mState != STATE_PULL && mState != STATE_PULL_DECAY) { |
| return; |
| } |
| |
| mState = STATE_RECEDE; |
| mEdgeAlphaStart = mEdgeAlpha; |
| mEdgeScaleYStart = mEdgeScaleY; |
| mGlowAlphaStart = mGlowAlpha; |
| mGlowScaleYStart = mGlowScaleY; |
| |
| mEdgeAlphaFinish = 0.f; |
| mEdgeScaleYFinish = 0.f; |
| mGlowAlphaFinish = 0.f; |
| mGlowScaleYFinish = 0.f; |
| |
| mStartTime = AnimationUtils.currentAnimationTimeMillis(); |
| mDuration = RECEDE_TIME; |
| } |
| |
| /** |
| * Call when the effect absorbs an impact at the given velocity. |
| * |
| * @param velocity Velocity at impact in pixels per second. |
| */ |
| public void onAbsorb(int velocity) { |
| mState = STATE_ABSORB; |
| velocity = Math.max(MIN_VELOCITY, Math.abs(velocity)); |
| |
| mStartTime = AnimationUtils.currentAnimationTimeMillis(); |
| mDuration = 0.1f + (velocity * 0.03f); |
| |
| // The edge should always be at least partially visible, regardless |
| // of velocity. |
| mEdgeAlphaStart = 0.f; |
| mEdgeScaleY = mEdgeScaleYStart = 0.f; |
| // The glow depends more on the velocity, and therefore starts out |
| // nearly invisible. |
| mGlowAlphaStart = 0.5f; |
| mGlowScaleYStart = 0.f; |
| |
| // Factor the velocity by 8. Testing on device shows this works best to |
| // reflect the strength of the user's scrolling. |
| mEdgeAlphaFinish = Math.max(0, Math.min(velocity * VELOCITY_EDGE_FACTOR, 1)); |
| // Edge should never get larger than the size of its asset. |
| mEdgeScaleYFinish = Math.max( |
| HELD_EDGE_SCALE_Y, Math.min(velocity * VELOCITY_EDGE_FACTOR, 1.f)); |
| |
| // Growth for the size of the glow should be quadratic to properly |
| // respond |
| // to a user's scrolling speed. The faster the scrolling speed, the more |
| // intense the effect should be for both the size and the saturation. |
| mGlowScaleYFinish = Math.min(0.025f + (velocity * (velocity / 100) * 0.00015f), 1.75f); |
| // Alpha should change for the glow as well as size. |
| mGlowAlphaFinish = Math.max( |
| mGlowAlphaStart, Math.min(velocity * VELOCITY_GLOW_FACTOR * .00001f, MAX_ALPHA)); |
| } |
| |
| |
| /** |
| * Draw into the provided canvas. Assumes that the canvas has been rotated |
| * accordingly and the size has been set. The effect will be drawn the full |
| * width of X=0 to X=width, emitting from Y=0 and extending to some factor < |
| * 1.f of height. |
| * |
| * @param canvas Canvas to draw into |
| * @return true if drawing should continue beyond this frame to continue the |
| * animation |
| */ |
| public boolean draw(Canvas canvas) { |
| update(); |
| |
| final int edgeHeight = mEdge.getIntrinsicHeight(); |
| final int glowHeight = mGlow.getIntrinsicHeight(); |
| |
| final float distScale = (float) mHeight / mWidth; |
| |
| mGlow.setAlpha((int) (Math.max(0, Math.min(mGlowAlpha, 1)) * 255)); |
| // Width of the image should be 3 * the width of the screen. |
| // Should start off screen to the left. |
| mGlow.setBounds(-mWidth, 0, mWidth * 2, (int) Math.min( |
| glowHeight * mGlowScaleY * distScale * 0.6f, mHeight * MAX_GLOW_HEIGHT)); |
| mGlow.draw(canvas); |
| |
| mEdge.setAlpha((int) (Math.max(0, Math.min(mEdgeAlpha, 1)) * 255)); |
| mEdge.setBounds(0, 0, mWidth, (int) (edgeHeight * mEdgeScaleY)); |
| mEdge.draw(canvas); |
| |
| return mState != STATE_IDLE; |
| } |
| |
| private void update() { |
| final long time = AnimationUtils.currentAnimationTimeMillis(); |
| final float t = Math.min((time - mStartTime) / mDuration, 1.f); |
| |
| final float interp = mInterpolator.getInterpolation(t); |
| |
| mEdgeAlpha = mEdgeAlphaStart + (mEdgeAlphaFinish - mEdgeAlphaStart) * interp; |
| mEdgeScaleY = mEdgeScaleYStart + (mEdgeScaleYFinish - mEdgeScaleYStart) * interp; |
| mGlowAlpha = mGlowAlphaStart + (mGlowAlphaFinish - mGlowAlphaStart) * interp; |
| mGlowScaleY = mGlowScaleYStart + (mGlowScaleYFinish - mGlowScaleYStart) * interp; |
| |
| if (t >= 1.f - EPSILON) { |
| switch (mState) { |
| case STATE_ABSORB: |
| mState = STATE_RECEDE; |
| mStartTime = AnimationUtils.currentAnimationTimeMillis(); |
| mDuration = RECEDE_TIME; |
| |
| mEdgeAlphaStart = mEdgeAlpha; |
| mEdgeScaleYStart = mEdgeScaleY; |
| mGlowAlphaStart = mGlowAlpha; |
| mGlowScaleYStart = mGlowScaleY; |
| |
| // After absorb, the glow and edge should fade to nothing. |
| mEdgeAlphaFinish = 0.f; |
| mEdgeScaleYFinish = 0.f; |
| mGlowAlphaFinish = 0.f; |
| mGlowScaleYFinish = 0.f; |
| break; |
| case STATE_PULL: |
| mState = STATE_PULL_DECAY; |
| mStartTime = AnimationUtils.currentAnimationTimeMillis(); |
| mDuration = PULL_DECAY_TIME; |
| |
| mEdgeAlphaStart = mEdgeAlpha; |
| mEdgeScaleYStart = mEdgeScaleY; |
| mGlowAlphaStart = mGlowAlpha; |
| mGlowScaleYStart = mGlowScaleY; |
| |
| // After pull, the glow and edge should fade to nothing. |
| mEdgeAlphaFinish = 0.f; |
| mEdgeScaleYFinish = 0.f; |
| mGlowAlphaFinish = 0.f; |
| mGlowScaleYFinish = 0.f; |
| break; |
| case STATE_PULL_DECAY: |
| // When receding, we want edge to decrease more slowly |
| // than the glow. |
| float factor = mGlowScaleYFinish != 0 ? 1 |
| / (mGlowScaleYFinish * mGlowScaleYFinish) |
| : Float.MAX_VALUE; |
| mEdgeScaleY = mEdgeScaleYStart + |
| (mEdgeScaleYFinish - mEdgeScaleYStart) * |
| interp * factor; |
| break; |
| case STATE_RECEDE: |
| mState = STATE_IDLE; |
| break; |
| } |
| } |
| } |
| } |