packages/SystemUI/src/com/android/systemui/statusbar/phone/PanelView.java - platform/frameworks/base - Git at Google

 /*
  * Copyright (C) 2012 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 com.android.systemui.statusbar.phone;

 import java.util.ArrayDeque;
 import java.util.ArrayList;
 import java.util.Iterator;

 import android.animation.ObjectAnimator;
 import android.animation.TimeAnimator;
 import android.animation.TimeAnimator.TimeListener;
 import android.content.Context;
 import android.content.res.Resources;
 import android.util.AttributeSet;
 import android.util.Slog;
 import android.view.MotionEvent;
 import android.view.VelocityTracker;
 import android.view.View;
 import android.widget.FrameLayout;

 import com.android.systemui.R;

 public class PanelView extends FrameLayout {
     public static final boolean DEBUG = PanelBar.DEBUG;
     public static final String TAG = PanelView.class.getSimpleName();
     public final void LOG(String fmt, Object... args) {
         if (!DEBUG) return;
         Slog.v(TAG, (mViewName != null ? (mViewName + ": ") : "") + String.format(fmt, args));
     }

     public static final boolean BRAKES = false;
     private boolean mRubberbandingEnabled = true;

     private float mSelfExpandVelocityPx; // classic value: 2000px/s
     private float mSelfCollapseVelocityPx; // classic value: 2000px/s (will be negated to collapse "up")
     private float mFlingExpandMinVelocityPx; // classic value: 200px/s
     private float mFlingCollapseMinVelocityPx; // classic value: 200px/s
     private float mCollapseMinDisplayFraction; // classic value: 0.08 (25px/min(320px,480px) on G1)
     private float mExpandMinDisplayFraction; // classic value: 0.5 (drag open halfway to expand)
     private float mFlingGestureMaxXVelocityPx; // classic value: 150px/s

     private float mFlingGestureMinDistPx;

     private float mExpandAccelPx; // classic value: 2000px/s/s
     private float mCollapseAccelPx; // classic value: 2000px/s/s (will be negated to collapse "up")

     private float mFlingGestureMaxOutputVelocityPx; // how fast can it really go? (should be a little
                                                     // faster than mSelfCollapseVelocityPx)

     private float mCollapseBrakingDistancePx = 200; // XXX Resource
     private float mExpandBrakingDistancePx = 150; // XXX Resource
     private float mBrakingSpeedPx = 150; // XXX Resource

     private View mHandleView;
     private float mPeekHeight;
     private float mTouchOffset;
     private float mExpandedFraction = 0;
     private float mExpandedHeight = 0;
     private boolean mJustPeeked;
     private boolean mClosing;
     private boolean mRubberbanding;
     private boolean mTracking;

     private TimeAnimator mTimeAnimator;
     private ObjectAnimator mPeekAnimator;
     private FlingTracker mVelocityTracker;

     /**
      * A very simple low-pass velocity filter for motion events; not nearly as sophisticated as
      * VelocityTracker but optimized for the kinds of gestures we expect to see in status bar
      * panels.
      */
     private static class FlingTracker {
         static final boolean DEBUG = false;
         final int MAX_EVENTS = 8;
         final float DECAY = 0.75f;
         ArrayDeque<MotionEventCopy> mEventBuf = new ArrayDeque<MotionEventCopy>(MAX_EVENTS);
         float mVX, mVY = 0;
         private static class MotionEventCopy {
             public MotionEventCopy(float x2, float y2, long eventTime) {
                 this.x = x2;
                 this.y = y2;
                 this.t = eventTime;
             }
             public float x, y;
             public long t;
         }
         public FlingTracker() {
         }
         public void addMovement(MotionEvent event) {
             if (mEventBuf.size() == MAX_EVENTS) {
                 mEventBuf.remove();
             }
             mEventBuf.add(new MotionEventCopy(event.getX(), event.getY(), event.getEventTime()));
         }
         public void computeCurrentVelocity(long timebase) {
             if (FlingTracker.DEBUG) {
                 Slog.v("FlingTracker", "computing velocities for " + mEventBuf.size() + " events");
             }
             mVX = mVY = 0;
             MotionEventCopy last = null;
             int i = 0;
             float totalweight = 0f;
             float weight = 10f;
             for (final Iterator<MotionEventCopy> iter = mEventBuf.descendingIterator();
                     iter.hasNext();) {
                 final MotionEventCopy event = iter.next();
                 if (last != null) {
                     final float dt = (float) (event.t - last.t) / timebase;
                     final float dx = (event.x - last.x);
                     final float dy = (event.y - last.y);
                     if (FlingTracker.DEBUG) {
                         Slog.v("FlingTracker", String.format("   [%d] dx=%.1f dy=%.1f dt=%.0f vx=%.1f vy=%.1f",
                                 i,
                                 dx, dy, dt,
                                 (dx/dt),
                                 (dy/dt)
                                 ));
                     }
                     mVX += weight * dx / dt;
                     mVY += weight * dy / dt;
                     totalweight += weight;
                     weight *= DECAY;
                 }
                 last = event;
                 i++;
             }
             mVX /= totalweight;
             mVY /= totalweight;

             if (FlingTracker.DEBUG) {
                 Slog.v("FlingTracker", "computed: vx=" + mVX + " vy=" + mVY);
             }
         }
         public float getXVelocity() {
             return mVX;
         }
         public float getYVelocity() {
             return mVY;
         }
         public void recycle() {
             mEventBuf.clear();
         }

         static FlingTracker sTracker;
         static FlingTracker obtain() {
             if (sTracker == null) {
                 sTracker = new FlingTracker();
             }
             return sTracker;
         }
     }

     private int[] mAbsPos = new int[2];
     PanelBar mBar;

     private final TimeListener mAnimationCallback = new TimeListener() {
         @Override
         public void onTimeUpdate(TimeAnimator animation, long totalTime, long deltaTime) {
             animationTick(deltaTime);
         }
     };

     private final Runnable mStopAnimator = new Runnable() {
         @Override
         public void run() {
             if (mTimeAnimator != null && mTimeAnimator.isStarted()) {
                 mTimeAnimator.end();
                 mRubberbanding = false;
                 mClosing = false;
             }
         }
     };

     private float mVel, mAccel;
     private int mFullHeight = 0;
     private String mViewName;
     protected float mInitialTouchY;
     protected float mFinalTouchY;

     public void setRubberbandingEnabled(boolean enable) {
         mRubberbandingEnabled = enable;
     }

     private void runPeekAnimation() {
         if (DEBUG) LOG("peek to height=%.1f", mPeekHeight);
         if (mTimeAnimator.isStarted()) {
             return;
         }
         if (mPeekAnimator == null) {
             mPeekAnimator = ObjectAnimator.ofFloat(this,
                     "expandedHeight", mPeekHeight)
                 .setDuration(250);
         }
         mPeekAnimator.start();
     }

     private void animationTick(long dtms) {
         if (!mTimeAnimator.isStarted()) {
             // XXX HAX to work around bug in TimeAnimator.end() not resetting its last time
             mTimeAnimator = new TimeAnimator();
             mTimeAnimator.setTimeListener(mAnimationCallback);

             if (mPeekAnimator != null) mPeekAnimator.cancel();

             mTimeAnimator.start();

             mRubberbanding = mRubberbandingEnabled // is it enabled at all?
                     && mExpandedHeight > getFullHeight() // are we past the end?
                     && mVel >= -mFlingGestureMinDistPx; // was this not possibly a "close" gesture?
             if (mRubberbanding) {
                 mClosing = true;
             } else if (mVel == 0) {
                 // if the panel is less than halfway open, close it
                 mClosing = (mFinalTouchY / getFullHeight()) < 0.5f;
             } else {
                 mClosing = mExpandedHeight > 0 && mVel < 0;
             }
         } else if (dtms > 0) {
             final float dt = dtms * 0.001f;                  // ms -> s
             if (DEBUG) LOG("tick: v=%.2fpx/s dt=%.4fs", mVel, dt);
             if (DEBUG) LOG("tick: before: h=%d", (int) mExpandedHeight);

             final float fh = getFullHeight();
             boolean braking = false;
             if (BRAKES) {
                 if (mClosing) {
                     braking = mExpandedHeight <= mCollapseBrakingDistancePx;
                     mAccel = braking ? 10*mCollapseAccelPx : -mCollapseAccelPx;
                 } else {
                     braking = mExpandedHeight >= (fh-mExpandBrakingDistancePx);
                     mAccel = braking ? 10*-mExpandAccelPx : mExpandAccelPx;
                 }
             } else {
                 mAccel = mClosing ? -mCollapseAccelPx : mExpandAccelPx;
             }

             mVel += mAccel * dt;

             if (braking) {
                 if (mClosing && mVel > -mBrakingSpeedPx) {
                     mVel = -mBrakingSpeedPx;
                 } else if (!mClosing && mVel < mBrakingSpeedPx) {
                     mVel = mBrakingSpeedPx;
                 }
             } else {
                 if (mClosing && mVel > -mFlingCollapseMinVelocityPx) {
                     mVel = -mFlingCollapseMinVelocityPx;
                 } else if (!mClosing && mVel > mFlingGestureMaxOutputVelocityPx) {
                     mVel = mFlingGestureMaxOutputVelocityPx;
                 }
             }

             float h = mExpandedHeight + mVel * dt;

             if (mRubberbanding && h < fh) {
                 h = fh;
             }

             if (DEBUG) LOG("tick: new h=%d closing=%s", (int) h, mClosing?"true":"false");

             setExpandedHeightInternal(h);

             mBar.panelExpansionChanged(PanelView.this, mExpandedFraction);

             if (mVel == 0
                     || (mClosing && mExpandedHeight == 0)
                     || ((mRubberbanding || !mClosing) && mExpandedHeight == fh)) {
                 post(mStopAnimator);
             }
         }
     }

     public PanelView(Context context, AttributeSet attrs) {
         super(context, attrs);

         mTimeAnimator = new TimeAnimator();
         mTimeAnimator.setTimeListener(mAnimationCallback);
     }

     private void loadDimens() {
         final Resources res = getContext().getResources();

         mSelfExpandVelocityPx = res.getDimension(R.dimen.self_expand_velocity);
         mSelfCollapseVelocityPx = res.getDimension(R.dimen.self_collapse_velocity);
         mFlingExpandMinVelocityPx = res.getDimension(R.dimen.fling_expand_min_velocity);
         mFlingCollapseMinVelocityPx = res.getDimension(R.dimen.fling_collapse_min_velocity);

         mFlingGestureMinDistPx = res.getDimension(R.dimen.fling_gesture_min_dist);

         mCollapseMinDisplayFraction = res.getFraction(R.dimen.collapse_min_display_fraction, 1, 1);
         mExpandMinDisplayFraction = res.getFraction(R.dimen.expand_min_display_fraction, 1, 1);

         mExpandAccelPx = res.getDimension(R.dimen.expand_accel);
         mCollapseAccelPx = res.getDimension(R.dimen.collapse_accel);

         mFlingGestureMaxXVelocityPx = res.getDimension(R.dimen.fling_gesture_max_x_velocity);

         mFlingGestureMaxOutputVelocityPx = res.getDimension(R.dimen.fling_gesture_max_output_velocity);

         mPeekHeight = res.getDimension(R.dimen.peek_height)
             + getPaddingBottom() // our window might have a dropshadow
             - (mHandleView == null ? 0 : mHandleView.getPaddingTop()); // the handle might have a topshadow
     }

     private void trackMovement(MotionEvent event) {
         // Add movement to velocity tracker using raw screen X and Y coordinates instead
         // of window coordinates because the window frame may be moving at the same time.
         float deltaX = event.getRawX() - event.getX();
         float deltaY = event.getRawY() - event.getY();
         event.offsetLocation(deltaX, deltaY);
         if (mVelocityTracker != null) mVelocityTracker.addMovement(event);
         event.offsetLocation(-deltaX, -deltaY);
     }

     // Pass all touches along to the handle, allowing the user to drag the panel closed from its interior
     @Override
     public boolean onTouchEvent(MotionEvent event) {
         return mHandleView.dispatchTouchEvent(event);
     }

     @Override
     protected void onFinishInflate() {
         super.onFinishInflate();
         mHandleView = findViewById(R.id.handle);

         loadDimens();

         if (DEBUG) LOG("handle view: " + mHandleView);
         if (mHandleView != null) {
             mHandleView.setOnTouchListener(new View.OnTouchListener() {
                 @Override
                 public boolean onTouch(View v, MotionEvent event) {
                     final float y = event.getY();
                     final float rawY = event.getRawY();
                     if (DEBUG) LOG("handle.onTouch: a=%s y=%.1f rawY=%.1f off=%.1f",
                             MotionEvent.actionToString(event.getAction()),
                             y, rawY, mTouchOffset);
                     PanelView.this.getLocationOnScreen(mAbsPos);

                     switch (event.getAction()) {
                         case MotionEvent.ACTION_DOWN:
                             mTracking = true;
                             mHandleView.setPressed(true);
                             postInvalidate(); // catch the press state change
                             mInitialTouchY = y;
                             mVelocityTracker = FlingTracker.obtain();
                             trackMovement(event);
                             mTimeAnimator.cancel(); // end any outstanding animations
                             mBar.onTrackingStarted(PanelView.this);
                             mTouchOffset = (rawY - mAbsPos[1]) - PanelView.this.getExpandedHeight();
                             if (mExpandedHeight == 0) {
                                 mJustPeeked = true;
                                 runPeekAnimation();
                             }
                             break;

                         case MotionEvent.ACTION_MOVE:
                             final float h = rawY - mAbsPos[1] - mTouchOffset;
                             if (h > mPeekHeight) {
                                 if (mPeekAnimator != null && mPeekAnimator.isRunning()) {
                                     mPeekAnimator.cancel();
                                 }
                                 mJustPeeked = false;
                             }
                             if (!mJustPeeked) {
                                 PanelView.this.setExpandedHeightInternal(h);
                                 mBar.panelExpansionChanged(PanelView.this, mExpandedFraction);
                             }

                             trackMovement(event);
                             break;

                         case MotionEvent.ACTION_UP:
                         case MotionEvent.ACTION_CANCEL:
                             mFinalTouchY = y;
                             mTracking = false;
                             mHandleView.setPressed(false);
                             postInvalidate(); // catch the press state change
                             mBar.onTrackingStopped(PanelView.this);
                             trackMovement(event);

                             float vel = 0, yVel = 0, xVel = 0;
                             boolean negative = false;

                             if (mVelocityTracker != null) {
                                 // the velocitytracker might be null if we got a bad input stream
                                 mVelocityTracker.computeCurrentVelocity(1000);

                                 yVel = mVelocityTracker.getYVelocity();
                                 negative = yVel < 0;

                                 xVel = mVelocityTracker.getXVelocity();
                                 if (xVel < 0) {
                                     xVel = -xVel;
                                 }
                                 if (xVel > mFlingGestureMaxXVelocityPx) {
                                     xVel = mFlingGestureMaxXVelocityPx; // limit how much we care about the x axis
                                 }

                                 vel = (float)Math.hypot(yVel, xVel);
                                 if (vel > mFlingGestureMaxOutputVelocityPx) {
                                     vel = mFlingGestureMaxOutputVelocityPx;
                                 }

                                 mVelocityTracker.recycle();
                                 mVelocityTracker = null;
                             }

                             // if you've barely moved your finger, we treat the velocity as 0
                             // preventing spurious flings due to touch screen jitter
                             final float deltaY = Math.abs(mFinalTouchY - mInitialTouchY);
                             if (deltaY < mFlingGestureMinDistPx
                                     || vel < mFlingExpandMinVelocityPx
                                     ) {
                                 vel = 0;
                             }

                             if (negative) {
                                 vel = -vel;
                             }

                             if (DEBUG) LOG("gesture: dy=%f vel=(%f,%f) vlinear=%f",
                                     deltaY,
                                     xVel, yVel,
                                     vel);

                             fling(vel, true);

                             break;
                     }
                     return true;
                 }});
         }
     }

     public void fling(float vel, boolean always) {
         if (DEBUG) LOG("fling: vel=%.3f, this=%s", vel, this);
         mVel = vel;

         if (always||mVel != 0) {
             animationTick(0); // begin the animation
         }
     }

     @Override
     protected void onAttachedToWindow() {
         super.onAttachedToWindow();
         mViewName = getResources().getResourceName(getId());
     }

     public String getName() {
         return mViewName;
     }

     @Override
     protected void onViewAdded(View child) {
         if (DEBUG) LOG("onViewAdded: " + child);
     }

     public View getHandle() {
         return mHandleView;
     }

     // Rubberbands the panel to hold its contents.
     @Override
     protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
         super.onMeasure(widthMeasureSpec, heightMeasureSpec);

         if (DEBUG) LOG("onMeasure(%d, %d) -> (%d, %d)",
                 widthMeasureSpec, heightMeasureSpec, getMeasuredWidth(), getMeasuredHeight());

         // Did one of our children change size?
         int newHeight = getMeasuredHeight();
         if (newHeight != mFullHeight) {
             mFullHeight = newHeight;
             // If the user isn't actively poking us, let's rubberband to the content
             if (!mTracking && !mRubberbanding && !mTimeAnimator.isStarted()
                     && mExpandedHeight > 0 && mExpandedHeight != mFullHeight) {
                 mExpandedHeight = mFullHeight;
             }
         }
         heightMeasureSpec = MeasureSpec.makeMeasureSpec(
                     (int) mExpandedHeight, MeasureSpec.AT_MOST); // MeasureSpec.getMode(heightMeasureSpec));
         setMeasuredDimension(widthMeasureSpec, heightMeasureSpec);
     }


     public void setExpandedHeight(float height) {
         if (DEBUG) LOG("setExpandedHeight(%.1f)", height);
         mRubberbanding = false;
         if (mTimeAnimator.isRunning()) {
             post(mStopAnimator);
         }
         setExpandedHeightInternal(height);
         mBar.panelExpansionChanged(PanelView.this, mExpandedFraction);
     }

     @Override
     protected void onLayout (boolean changed, int left, int top, int right, int bottom) {
         if (DEBUG) LOG("onLayout: changed=%s, bottom=%d eh=%d fh=%d", changed?"T":"f", bottom, (int)mExpandedHeight, mFullHeight);
         super.onLayout(changed, left, top, right, bottom);
     }

     public void setExpandedHeightInternal(float h) {
         float fh = getFullHeight();
         if (fh == 0) {
             // Hmm, full height hasn't been computed yet
         }

         if (h < 0) h = 0;
         if (!(mRubberbandingEnabled && (mTracking || mRubberbanding)) && h > fh) h = fh;
         mExpandedHeight = h;

         if (DEBUG) LOG("setExpansion: height=%.1f fh=%.1f tracking=%s rubber=%s", h, fh, mTracking?"T":"f", mRubberbanding?"T":"f");

         requestLayout();
 //        FrameLayout.LayoutParams lp = (FrameLayout.LayoutParams) getLayoutParams();
 //        lp.height = (int) mExpandedHeight;
 //        setLayoutParams(lp);

         mExpandedFraction = Math.min(1f, (fh == 0) ? 0 : h / fh);
     }

     private float getFullHeight() {
         if (mFullHeight <= 0) {
             if (DEBUG) LOG("Forcing measure() since fullHeight=" + mFullHeight);
             measure(MeasureSpec.makeMeasureSpec(android.view.ViewGroup.LayoutParams.WRAP_CONTENT, MeasureSpec.EXACTLY),
                     MeasureSpec.makeMeasureSpec(android.view.ViewGroup.LayoutParams.WRAP_CONTENT, MeasureSpec.EXACTLY));
         }
         return mFullHeight;
     }

     public void setExpandedFraction(float frac) {
         setExpandedHeight(getFullHeight() * frac);
     }

     public float getExpandedHeight() {
         return mExpandedHeight;
     }

     public float getExpandedFraction() {
         return mExpandedFraction;
     }

     public boolean isFullyExpanded() {
         return mExpandedHeight >= getFullHeight();
     }

     public boolean isFullyCollapsed() {
         return mExpandedHeight <= 0;
     }

     public boolean isCollapsing() {
         return mClosing;
     }

     public void setBar(PanelBar panelBar) {
         mBar = panelBar;
     }

     public void collapse() {
         // TODO: abort animation or ongoing touch
         if (DEBUG) LOG("collapse: " + this);
         if (!isFullyCollapsed()) {
             mTimeAnimator.cancel();
             mClosing = true;
             // collapse() should never be a rubberband, even if an animation is already running
             mRubberbanding = false;
             fling(-mSelfCollapseVelocityPx, /*always=*/ true);
         }
     }

     public void expand() {
         if (DEBUG) LOG("expand: " + this);
         if (isFullyCollapsed()) {
             mBar.startOpeningPanel(this);
             fling(mSelfExpandVelocityPx, /*always=*/ true);
         } else if (DEBUG) {
             if (DEBUG) LOG("skipping expansion: is expanded");
         }
     }
 }
	/*
	* Copyright (C) 2012 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 com.android.systemui.statusbar.phone;

	import java.util.ArrayDeque;
	import java.util.ArrayList;
	import java.util.Iterator;

	import android.animation.ObjectAnimator;
	import android.animation.TimeAnimator;
	import android.animation.TimeAnimator.TimeListener;
	import android.content.Context;
	import android.content.res.Resources;
	import android.util.AttributeSet;
	import android.util.Slog;
	import android.view.MotionEvent;
	import android.view.VelocityTracker;
	import android.view.View;
	import android.widget.FrameLayout;

	import com.android.systemui.R;

	public class PanelView extends FrameLayout {
	public static final boolean DEBUG = PanelBar.DEBUG;
	public static final String TAG = PanelView.class.getSimpleName();
	public final void LOG(String fmt, Object... args) {
	if (!DEBUG) return;
	Slog.v(TAG, (mViewName != null ? (mViewName + ": ") : "") + String.format(fmt, args));
	}

	public static final boolean BRAKES = false;
	private boolean mRubberbandingEnabled = true;

	private float mSelfExpandVelocityPx; // classic value: 2000px/s
	private float mSelfCollapseVelocityPx; // classic value: 2000px/s (will be negated to collapse "up")
	private float mFlingExpandMinVelocityPx; // classic value: 200px/s
	private float mFlingCollapseMinVelocityPx; // classic value: 200px/s
	private float mCollapseMinDisplayFraction; // classic value: 0.08 (25px/min(320px,480px) on G1)
	private float mExpandMinDisplayFraction; // classic value: 0.5 (drag open halfway to expand)
	private float mFlingGestureMaxXVelocityPx; // classic value: 150px/s

	private float mFlingGestureMinDistPx;

	private float mExpandAccelPx; // classic value: 2000px/s/s
	private float mCollapseAccelPx; // classic value: 2000px/s/s (will be negated to collapse "up")

	private float mFlingGestureMaxOutputVelocityPx; // how fast can it really go? (should be a little
	// faster than mSelfCollapseVelocityPx)

	private float mCollapseBrakingDistancePx = 200; // XXX Resource
	private float mExpandBrakingDistancePx = 150; // XXX Resource
	private float mBrakingSpeedPx = 150; // XXX Resource

	private View mHandleView;
	private float mPeekHeight;
	private float mTouchOffset;
	private float mExpandedFraction = 0;
	private float mExpandedHeight = 0;
	private boolean mJustPeeked;
	private boolean mClosing;
	private boolean mRubberbanding;
	private boolean mTracking;

	private TimeAnimator mTimeAnimator;
	private ObjectAnimator mPeekAnimator;
	private FlingTracker mVelocityTracker;

	/**
	* A very simple low-pass velocity filter for motion events; not nearly as sophisticated as
	* VelocityTracker but optimized for the kinds of gestures we expect to see in status bar
	* panels.
	*/
	private static class FlingTracker {
	static final boolean DEBUG = false;
	final int MAX_EVENTS = 8;
	final float DECAY = 0.75f;
	ArrayDeque<MotionEventCopy> mEventBuf = new ArrayDeque<MotionEventCopy>(MAX_EVENTS);
	float mVX, mVY = 0;
	private static class MotionEventCopy {
	public MotionEventCopy(float x2, float y2, long eventTime) {
	this.x = x2;
	this.y = y2;
	this.t = eventTime;
	}
	public float x, y;
	public long t;
	}
	public FlingTracker() {
	}
	public void addMovement(MotionEvent event) {
	if (mEventBuf.size() == MAX_EVENTS) {
	mEventBuf.remove();
	}
	mEventBuf.add(new MotionEventCopy(event.getX(), event.getY(), event.getEventTime()));
	}
	public void computeCurrentVelocity(long timebase) {
	if (FlingTracker.DEBUG) {
	Slog.v("FlingTracker", "computing velocities for " + mEventBuf.size() + " events");
	}
	mVX = mVY = 0;
	MotionEventCopy last = null;
	int i = 0;
	float totalweight = 0f;
	float weight = 10f;
	for (final Iterator<MotionEventCopy> iter = mEventBuf.descendingIterator();
	iter.hasNext();) {
	final MotionEventCopy event = iter.next();
	if (last != null) {
	final float dt = (float) (event.t - last.t) / timebase;
	final float dx = (event.x - last.x);
	final float dy = (event.y - last.y);
	if (FlingTracker.DEBUG) {
	Slog.v("FlingTracker", String.format(" [%d] dx=%.1f dy=%.1f dt=%.0f vx=%.1f vy=%.1f",
	i,
	dx, dy, dt,
	(dx/dt),
	(dy/dt)
	));
	}
	mVX += weight * dx / dt;
	mVY += weight * dy / dt;
	totalweight += weight;
	weight *= DECAY;
	}
	last = event;
	i++;
	}
	mVX /= totalweight;
	mVY /= totalweight;

	if (FlingTracker.DEBUG) {
	Slog.v("FlingTracker", "computed: vx=" + mVX + " vy=" + mVY);
	}
	}
	public float getXVelocity() {
	return mVX;
	}
	public float getYVelocity() {
	return mVY;
	}
	public void recycle() {
	mEventBuf.clear();
	}

	static FlingTracker sTracker;
	static FlingTracker obtain() {
	if (sTracker == null) {
	sTracker = new FlingTracker();
	}
	return sTracker;
	}
	}

	private int[] mAbsPos = new int[2];
	PanelBar mBar;

	private final TimeListener mAnimationCallback = new TimeListener() {
	@Override
	public void onTimeUpdate(TimeAnimator animation, long totalTime, long deltaTime) {
	animationTick(deltaTime);
	}
	};

	private final Runnable mStopAnimator = new Runnable() {
	@Override
	public void run() {
	if (mTimeAnimator != null && mTimeAnimator.isStarted()) {
	mTimeAnimator.end();
	mRubberbanding = false;
	mClosing = false;
	}
	}
	};

	private float mVel, mAccel;
	private int mFullHeight = 0;
	private String mViewName;
	protected float mInitialTouchY;
	protected float mFinalTouchY;

	public void setRubberbandingEnabled(boolean enable) {
	mRubberbandingEnabled = enable;
	}

	private void runPeekAnimation() {
	if (DEBUG) LOG("peek to height=%.1f", mPeekHeight);
	if (mTimeAnimator.isStarted()) {
	return;
	}
	if (mPeekAnimator == null) {
	mPeekAnimator = ObjectAnimator.ofFloat(this,
	"expandedHeight", mPeekHeight)
	.setDuration(250);
	}
	mPeekAnimator.start();
	}

	private void animationTick(long dtms) {
	if (!mTimeAnimator.isStarted()) {
	// XXX HAX to work around bug in TimeAnimator.end() not resetting its last time
	mTimeAnimator = new TimeAnimator();
	mTimeAnimator.setTimeListener(mAnimationCallback);

	if (mPeekAnimator != null) mPeekAnimator.cancel();

	mTimeAnimator.start();

	mRubberbanding = mRubberbandingEnabled // is it enabled at all?
	&& mExpandedHeight > getFullHeight() // are we past the end?
	&& mVel >= -mFlingGestureMinDistPx; // was this not possibly a "close" gesture?
	if (mRubberbanding) {
	mClosing = true;
	} else if (mVel == 0) {
	// if the panel is less than halfway open, close it
	mClosing = (mFinalTouchY / getFullHeight()) < 0.5f;
	} else {
	mClosing = mExpandedHeight > 0 && mVel < 0;
	}
	} else if (dtms > 0) {
	final float dt = dtms * 0.001f; // ms -> s
	if (DEBUG) LOG("tick: v=%.2fpx/s dt=%.4fs", mVel, dt);
	if (DEBUG) LOG("tick: before: h=%d", (int) mExpandedHeight);

	final float fh = getFullHeight();
	boolean braking = false;
	if (BRAKES) {
	if (mClosing) {
	braking = mExpandedHeight <= mCollapseBrakingDistancePx;
	mAccel = braking ? 10*mCollapseAccelPx : -mCollapseAccelPx;
	} else {
	braking = mExpandedHeight >= (fh-mExpandBrakingDistancePx);
	mAccel = braking ? 10*-mExpandAccelPx : mExpandAccelPx;
	}
	} else {
	mAccel = mClosing ? -mCollapseAccelPx : mExpandAccelPx;
	}

	mVel += mAccel * dt;

	if (braking) {
	if (mClosing && mVel > -mBrakingSpeedPx) {
	mVel = -mBrakingSpeedPx;
	} else if (!mClosing && mVel < mBrakingSpeedPx) {
	mVel = mBrakingSpeedPx;
	}
	} else {
	if (mClosing && mVel > -mFlingCollapseMinVelocityPx) {
	mVel = -mFlingCollapseMinVelocityPx;
	} else if (!mClosing && mVel > mFlingGestureMaxOutputVelocityPx) {
	mVel = mFlingGestureMaxOutputVelocityPx;
	}
	}

	float h = mExpandedHeight + mVel * dt;

	if (mRubberbanding && h < fh) {
	h = fh;
	}

	if (DEBUG) LOG("tick: new h=%d closing=%s", (int) h, mClosing?"true":"false");

	setExpandedHeightInternal(h);

	mBar.panelExpansionChanged(PanelView.this, mExpandedFraction);

	if (mVel == 0
	\|\| (mClosing && mExpandedHeight == 0)
	\|\| ((mRubberbanding \|\| !mClosing) && mExpandedHeight == fh)) {
	post(mStopAnimator);
	}
	}
	}

	public PanelView(Context context, AttributeSet attrs) {
	super(context, attrs);

	mTimeAnimator = new TimeAnimator();
	mTimeAnimator.setTimeListener(mAnimationCallback);
	}

	private void loadDimens() {
	final Resources res = getContext().getResources();

	mSelfExpandVelocityPx = res.getDimension(R.dimen.self_expand_velocity);
	mSelfCollapseVelocityPx = res.getDimension(R.dimen.self_collapse_velocity);
	mFlingExpandMinVelocityPx = res.getDimension(R.dimen.fling_expand_min_velocity);
	mFlingCollapseMinVelocityPx = res.getDimension(R.dimen.fling_collapse_min_velocity);

	mFlingGestureMinDistPx = res.getDimension(R.dimen.fling_gesture_min_dist);

	mCollapseMinDisplayFraction = res.getFraction(R.dimen.collapse_min_display_fraction, 1, 1);
	mExpandMinDisplayFraction = res.getFraction(R.dimen.expand_min_display_fraction, 1, 1);

	mExpandAccelPx = res.getDimension(R.dimen.expand_accel);
	mCollapseAccelPx = res.getDimension(R.dimen.collapse_accel);

	mFlingGestureMaxXVelocityPx = res.getDimension(R.dimen.fling_gesture_max_x_velocity);

	mFlingGestureMaxOutputVelocityPx = res.getDimension(R.dimen.fling_gesture_max_output_velocity);

	mPeekHeight = res.getDimension(R.dimen.peek_height)
	+ getPaddingBottom() // our window might have a dropshadow
	- (mHandleView == null ? 0 : mHandleView.getPaddingTop()); // the handle might have a topshadow
	}

	private void trackMovement(MotionEvent event) {
	// Add movement to velocity tracker using raw screen X and Y coordinates instead
	// of window coordinates because the window frame may be moving at the same time.
	float deltaX = event.getRawX() - event.getX();
	float deltaY = event.getRawY() - event.getY();
	event.offsetLocation(deltaX, deltaY);
	if (mVelocityTracker != null) mVelocityTracker.addMovement(event);
	event.offsetLocation(-deltaX, -deltaY);
	}

	// Pass all touches along to the handle, allowing the user to drag the panel closed from its interior
	@Override
	public boolean onTouchEvent(MotionEvent event) {
	return mHandleView.dispatchTouchEvent(event);
	}

	@Override
	protected void onFinishInflate() {
	super.onFinishInflate();
	mHandleView = findViewById(R.id.handle);

	loadDimens();

	if (DEBUG) LOG("handle view: " + mHandleView);
	if (mHandleView != null) {
	mHandleView.setOnTouchListener(new View.OnTouchListener() {
	@Override
	public boolean onTouch(View v, MotionEvent event) {
	final float y = event.getY();
	final float rawY = event.getRawY();
	if (DEBUG) LOG("handle.onTouch: a=%s y=%.1f rawY=%.1f off=%.1f",
	MotionEvent.actionToString(event.getAction()),
	y, rawY, mTouchOffset);
	PanelView.this.getLocationOnScreen(mAbsPos);

	switch (event.getAction()) {
	case MotionEvent.ACTION_DOWN:
	mTracking = true;
	mHandleView.setPressed(true);
	postInvalidate(); // catch the press state change
	mInitialTouchY = y;
	mVelocityTracker = FlingTracker.obtain();
	trackMovement(event);
	mTimeAnimator.cancel(); // end any outstanding animations
	mBar.onTrackingStarted(PanelView.this);
	mTouchOffset = (rawY - mAbsPos[1]) - PanelView.this.getExpandedHeight();
	if (mExpandedHeight == 0) {
	mJustPeeked = true;
	runPeekAnimation();
	}
	break;

	case MotionEvent.ACTION_MOVE:
	final float h = rawY - mAbsPos[1] - mTouchOffset;
	if (h > mPeekHeight) {
	if (mPeekAnimator != null && mPeekAnimator.isRunning()) {
	mPeekAnimator.cancel();
	}
	mJustPeeked = false;
	}
	if (!mJustPeeked) {
	PanelView.this.setExpandedHeightInternal(h);
	mBar.panelExpansionChanged(PanelView.this, mExpandedFraction);
	}

	trackMovement(event);
	break;

	case MotionEvent.ACTION_UP:
	case MotionEvent.ACTION_CANCEL:
	mFinalTouchY = y;
	mTracking = false;
	mHandleView.setPressed(false);
	postInvalidate(); // catch the press state change
	mBar.onTrackingStopped(PanelView.this);
	trackMovement(event);

	float vel = 0, yVel = 0, xVel = 0;
	boolean negative = false;

	if (mVelocityTracker != null) {
	// the velocitytracker might be null if we got a bad input stream
	mVelocityTracker.computeCurrentVelocity(1000);

	yVel = mVelocityTracker.getYVelocity();
	negative = yVel < 0;

	xVel = mVelocityTracker.getXVelocity();
	if (xVel < 0) {
	xVel = -xVel;
	}
	if (xVel > mFlingGestureMaxXVelocityPx) {
	xVel = mFlingGestureMaxXVelocityPx; // limit how much we care about the x axis
	}

	vel = (float)Math.hypot(yVel, xVel);
	if (vel > mFlingGestureMaxOutputVelocityPx) {
	vel = mFlingGestureMaxOutputVelocityPx;
	}

	mVelocityTracker.recycle();
	mVelocityTracker = null;
	}

	// if you've barely moved your finger, we treat the velocity as 0
	// preventing spurious flings due to touch screen jitter
	final float deltaY = Math.abs(mFinalTouchY - mInitialTouchY);
	if (deltaY < mFlingGestureMinDistPx
	\|\| vel < mFlingExpandMinVelocityPx
	) {
	vel = 0;
	}

	if (negative) {
	vel = -vel;
	}

	if (DEBUG) LOG("gesture: dy=%f vel=(%f,%f) vlinear=%f",
	deltaY,
	xVel, yVel,
	vel);

	fling(vel, true);

	break;
	}
	return true;
	}});
	}
	}

	public void fling(float vel, boolean always) {
	if (DEBUG) LOG("fling: vel=%.3f, this=%s", vel, this);
	mVel = vel;

	if (always\|\|mVel != 0) {
	animationTick(0); // begin the animation
	}
	}

	@Override
	protected void onAttachedToWindow() {
	super.onAttachedToWindow();
	mViewName = getResources().getResourceName(getId());
	}

	public String getName() {
	return mViewName;
	}

	@Override
	protected void onViewAdded(View child) {
	if (DEBUG) LOG("onViewAdded: " + child);
	}

	public View getHandle() {
	return mHandleView;
	}

	// Rubberbands the panel to hold its contents.
	@Override
	protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
	super.onMeasure(widthMeasureSpec, heightMeasureSpec);

	if (DEBUG) LOG("onMeasure(%d, %d) -> (%d, %d)",
	widthMeasureSpec, heightMeasureSpec, getMeasuredWidth(), getMeasuredHeight());

	// Did one of our children change size?
	int newHeight = getMeasuredHeight();
	if (newHeight != mFullHeight) {
	mFullHeight = newHeight;
	// If the user isn't actively poking us, let's rubberband to the content
	if (!mTracking && !mRubberbanding && !mTimeAnimator.isStarted()
	&& mExpandedHeight > 0 && mExpandedHeight != mFullHeight) {
	mExpandedHeight = mFullHeight;
	}
	}
	heightMeasureSpec = MeasureSpec.makeMeasureSpec(
	(int) mExpandedHeight, MeasureSpec.AT_MOST); // MeasureSpec.getMode(heightMeasureSpec));
	setMeasuredDimension(widthMeasureSpec, heightMeasureSpec);
	}


	public void setExpandedHeight(float height) {
	if (DEBUG) LOG("setExpandedHeight(%.1f)", height);
	mRubberbanding = false;
	if (mTimeAnimator.isRunning()) {
	post(mStopAnimator);
	}
	setExpandedHeightInternal(height);
	mBar.panelExpansionChanged(PanelView.this, mExpandedFraction);
	}

	@Override
	protected void onLayout (boolean changed, int left, int top, int right, int bottom) {
	if (DEBUG) LOG("onLayout: changed=%s, bottom=%d eh=%d fh=%d", changed?"T":"f", bottom, (int)mExpandedHeight, mFullHeight);
	super.onLayout(changed, left, top, right, bottom);
	}

	public void setExpandedHeightInternal(float h) {
	float fh = getFullHeight();
	if (fh == 0) {
	// Hmm, full height hasn't been computed yet
	}

	if (h < 0) h = 0;
	if (!(mRubberbandingEnabled && (mTracking \|\| mRubberbanding)) && h > fh) h = fh;
	mExpandedHeight = h;

	if (DEBUG) LOG("setExpansion: height=%.1f fh=%.1f tracking=%s rubber=%s", h, fh, mTracking?"T":"f", mRubberbanding?"T":"f");

	requestLayout();
	// FrameLayout.LayoutParams lp = (FrameLayout.LayoutParams) getLayoutParams();
	// lp.height = (int) mExpandedHeight;
	// setLayoutParams(lp);

	mExpandedFraction = Math.min(1f, (fh == 0) ? 0 : h / fh);
	}

	private float getFullHeight() {
	if (mFullHeight <= 0) {
	if (DEBUG) LOG("Forcing measure() since fullHeight=" + mFullHeight);
	measure(MeasureSpec.makeMeasureSpec(android.view.ViewGroup.LayoutParams.WRAP_CONTENT, MeasureSpec.EXACTLY),
	MeasureSpec.makeMeasureSpec(android.view.ViewGroup.LayoutParams.WRAP_CONTENT, MeasureSpec.EXACTLY));
	}
	return mFullHeight;
	}

	public void setExpandedFraction(float frac) {
	setExpandedHeight(getFullHeight() * frac);
	}

	public float getExpandedHeight() {
	return mExpandedHeight;
	}

	public float getExpandedFraction() {
	return mExpandedFraction;
	}

	public boolean isFullyExpanded() {
	return mExpandedHeight >= getFullHeight();
	}

	public boolean isFullyCollapsed() {
	return mExpandedHeight <= 0;
	}

	public boolean isCollapsing() {
	return mClosing;
	}

	public void setBar(PanelBar panelBar) {
	mBar = panelBar;
	}

	public void collapse() {
	// TODO: abort animation or ongoing touch
	if (DEBUG) LOG("collapse: " + this);
	if (!isFullyCollapsed()) {
	mTimeAnimator.cancel();
	mClosing = true;
	// collapse() should never be a rubberband, even if an animation is already running
	mRubberbanding = false;
	fling(-mSelfCollapseVelocityPx, /always=/ true);
	}
	}

	public void expand() {
	if (DEBUG) LOG("expand: " + this);
	if (isFullyCollapsed()) {
	mBar.startOpeningPanel(this);
	fling(mSelfExpandVelocityPx, /always=/ true);
	} else if (DEBUG) {
	if (DEBUG) LOG("skipping expansion: is expanded");
	}
	}
	}