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Diffstat (limited to '')
-rw-r--r-- | android/source/src/java/org/mozilla/gecko/gfx/SimpleScaleGestureDetector.java | 322 |
1 files changed, 322 insertions, 0 deletions
diff --git a/android/source/src/java/org/mozilla/gecko/gfx/SimpleScaleGestureDetector.java b/android/source/src/java/org/mozilla/gecko/gfx/SimpleScaleGestureDetector.java new file mode 100644 index 000000000..1d901a02a --- /dev/null +++ b/android/source/src/java/org/mozilla/gecko/gfx/SimpleScaleGestureDetector.java @@ -0,0 +1,322 @@ +/* -*- Mode: Java; c-basic-offset: 4; tab-width: 20; indent-tabs-mode: nil; -*- + * This Source Code Form is subject to the terms of the Mozilla Public + * License, v. 2.0. If a copy of the MPL was not distributed with this + * file, You can obtain one at http://mozilla.org/MPL/2.0/. */ + +package org.mozilla.gecko.gfx; + +import android.graphics.PointF; +import android.util.Log; +import android.view.MotionEvent; + +import org.json.JSONException; + +import java.util.LinkedList; +import java.util.ListIterator; +import java.util.Stack; + +/** + * A less buggy, and smoother, replacement for the built-in Android ScaleGestureDetector. + * + * This gesture detector is more reliable than the built-in ScaleGestureDetector because: + * + * - It doesn't assume that pointer IDs are numbered 0 and 1. + * + * - It doesn't attempt to correct for "slop" when resting one's hand on the device. On some + * devices (e.g. the Droid X) this can cause the ScaleGestureDetector to lose track of how many + * pointers are down, with disastrous results (bug 706684). + * + * - Cancelling a zoom into a pan is handled correctly. + * + * - Starting with three or more fingers down, releasing fingers so that only two are down, and + * then performing a scale gesture is handled correctly. + * + * - It doesn't take pressure into account, which results in smoother scaling. + */ +public class SimpleScaleGestureDetector { + private static final String LOGTAG = "GeckoSimpleScaleGestureDetector"; + + private SimpleScaleGestureListener mListener; + private long mLastEventTime; + private boolean mScaleResult; + + /* Information about all pointers that are down. */ + private LinkedList<PointerInfo> mPointerInfo; + + /** Creates a new gesture detector with the given listener. */ + public SimpleScaleGestureDetector(SimpleScaleGestureListener listener) { + mListener = listener; + mPointerInfo = new LinkedList<PointerInfo>(); + } + + /** Forward touch events to this function. */ + public void onTouchEvent(MotionEvent event) { + switch (event.getAction() & MotionEvent.ACTION_MASK) { + case MotionEvent.ACTION_DOWN: + // If we get ACTION_DOWN while still tracking any pointers, + // something is wrong. Cancel the current gesture and start over. + if (getPointersDown() > 0) + onTouchEnd(event); + onTouchStart(event); + break; + case MotionEvent.ACTION_POINTER_DOWN: + onTouchStart(event); + break; + case MotionEvent.ACTION_MOVE: + onTouchMove(event); + break; + case MotionEvent.ACTION_POINTER_UP: + case MotionEvent.ACTION_UP: + case MotionEvent.ACTION_CANCEL: + onTouchEnd(event); + break; + } + } + + private int getPointersDown() { + return mPointerInfo.size(); + } + + private int getActionIndex(MotionEvent event) { + return (event.getAction() & MotionEvent.ACTION_POINTER_INDEX_MASK) + >> MotionEvent.ACTION_POINTER_INDEX_SHIFT; + } + + private void onTouchStart(MotionEvent event) { + mLastEventTime = event.getEventTime(); + mPointerInfo.addFirst(PointerInfo.create(event, getActionIndex(event))); + if (getPointersDown() == 2) { + sendScaleGesture(EventType.BEGIN); + } + } + + private void onTouchMove(MotionEvent event) { + mLastEventTime = event.getEventTime(); + for (int i = 0; i < event.getPointerCount(); i++) { + PointerInfo pointerInfo = pointerInfoForEventIndex(event, i); + if (pointerInfo != null) { + pointerInfo.populate(event, i); + } + } + + if (getPointersDown() == 2) { + sendScaleGesture(EventType.CONTINUE); + } + } + + private void onTouchEnd(MotionEvent event) { + mLastEventTime = event.getEventTime(); + + int action = event.getAction() & MotionEvent.ACTION_MASK; + boolean isCancel = (action == MotionEvent.ACTION_CANCEL || + action == MotionEvent.ACTION_DOWN); + + int id = event.getPointerId(getActionIndex(event)); + ListIterator<PointerInfo> iterator = mPointerInfo.listIterator(); + while (iterator.hasNext()) { + PointerInfo pointerInfo = iterator.next(); + if (!(isCancel || pointerInfo.getId() == id)) { + continue; + } + + // One of the pointers we were tracking was lifted. Remove its info object from the + // list, recycle it to avoid GC pauses, and send an onScaleEnd() notification if this + // ended the gesture. + iterator.remove(); + pointerInfo.recycle(); + if (getPointersDown() == 1) { + sendScaleGesture(EventType.END); + } + } + } + + /** + * Returns the X coordinate of the focus location (the midpoint of the two fingers). If only + * one finger is down, returns the location of that finger. + */ + public float getFocusX() { + switch (getPointersDown()) { + case 1: + return mPointerInfo.getFirst().getCurrent().x; + case 2: + PointerInfo pointerA = mPointerInfo.getFirst(), pointerB = mPointerInfo.getLast(); + return (pointerA.getCurrent().x + pointerB.getCurrent().x) / 2.0f; + } + + Log.e(LOGTAG, "No gesture taking place in getFocusX()!"); + return 0.0f; + } + + /** + * Returns the Y coordinate of the focus location (the midpoint of the two fingers). If only + * one finger is down, returns the location of that finger. + */ + public float getFocusY() { + switch (getPointersDown()) { + case 1: + return mPointerInfo.getFirst().getCurrent().y; + case 2: + PointerInfo pointerA = mPointerInfo.getFirst(), pointerB = mPointerInfo.getLast(); + return (pointerA.getCurrent().y + pointerB.getCurrent().y) / 2.0f; + } + + Log.e(LOGTAG, "No gesture taking place in getFocusY()!"); + return 0.0f; + } + + /** Returns the most recent distance between the two pointers. */ + public float getCurrentSpan() { + if (getPointersDown() != 2) { + Log.e(LOGTAG, "No gesture taking place in getCurrentSpan()!"); + return 0.0f; + } + + PointerInfo pointerA = mPointerInfo.getFirst(), pointerB = mPointerInfo.getLast(); + return PointUtils.distance(pointerA.getCurrent(), pointerB.getCurrent()); + } + + /** Returns the second most recent distance between the two pointers. */ + public float getPreviousSpan() { + if (getPointersDown() != 2) { + Log.e(LOGTAG, "No gesture taking place in getPreviousSpan()!"); + return 0.0f; + } + + PointerInfo pointerA = mPointerInfo.getFirst(), pointerB = mPointerInfo.getLast(); + PointF a = pointerA.getPrevious(), b = pointerB.getPrevious(); + if (a == null || b == null) { + a = pointerA.getCurrent(); + b = pointerB.getCurrent(); + } + + return PointUtils.distance(a, b); + } + + /** Returns the time of the last event related to the gesture. */ + public long getEventTime() { + return mLastEventTime; + } + + /** Returns true if the scale gesture is in progress and false otherwise. */ + public boolean isInProgress() { + return getPointersDown() == 2; + } + + /* Sends the requested scale gesture notification to the listener. */ + private void sendScaleGesture(EventType eventType) { + switch (eventType) { + case BEGIN: + mScaleResult = mListener.onScaleBegin(this); + break; + case CONTINUE: + if (mScaleResult) { + mListener.onScale(this); + } + break; + case END: + if (mScaleResult) { + mListener.onScaleEnd(this); + } + break; + } + } + + /* + * Returns the pointer info corresponding to the given pointer index, or null if the pointer + * isn't one that's being tracked. + */ + private PointerInfo pointerInfoForEventIndex(MotionEvent event, int index) { + int id = event.getPointerId(index); + for (PointerInfo pointerInfo : mPointerInfo) { + if (pointerInfo.getId() == id) { + return pointerInfo; + } + } + return null; + } + + private enum EventType { + BEGIN, + CONTINUE, + END, + } + + /* Encapsulates information about one of the two fingers involved in the gesture. */ + private static class PointerInfo { + /* A free list that recycles pointer info objects, to reduce GC pauses. */ + private static Stack<PointerInfo> sPointerInfoFreeList; + + private int mId; + private PointF mCurrent, mPrevious; + + private PointerInfo() { + // External users should use create() instead. + } + + /* Creates or recycles a new PointerInfo instance from an event and a pointer index. */ + public static PointerInfo create(MotionEvent event, int index) { + if (sPointerInfoFreeList == null) { + sPointerInfoFreeList = new Stack<PointerInfo>(); + } + + PointerInfo pointerInfo; + if (sPointerInfoFreeList.empty()) { + pointerInfo = new PointerInfo(); + } else { + pointerInfo = sPointerInfoFreeList.pop(); + } + + pointerInfo.populate(event, index); + return pointerInfo; + } + + /* + * Fills in the fields of this instance from the given motion event and pointer index + * within that event. + */ + public void populate(MotionEvent event, int index) { + mId = event.getPointerId(index); + mPrevious = mCurrent; + mCurrent = new PointF(event.getX(index), event.getY(index)); + } + + public void recycle() { + mId = -1; + mPrevious = mCurrent = null; + sPointerInfoFreeList.push(this); + } + + public int getId() { return mId; } + public PointF getCurrent() { return mCurrent; } + public PointF getPrevious() { return mPrevious; } + + @Override + public String toString() { + if (mId == -1) { + return "(up)"; + } + + try { + String prevString; + if (mPrevious == null) { + prevString = "n/a"; + } else { + prevString = PointUtils.toJSON(mPrevious).toString(); + } + + // The current position should always be non-null. + String currentString = PointUtils.toJSON(mCurrent).toString(); + return "id=" + mId + " cur=" + currentString + " prev=" + prevString; + } catch (JSONException e) { + throw new RuntimeException(e); + } + } + } + + public static interface SimpleScaleGestureListener { + public boolean onScale(SimpleScaleGestureDetector detector); + public boolean onScaleBegin(SimpleScaleGestureDetector detector); + public void onScaleEnd(SimpleScaleGestureDetector detector); + } +} + |