| /* |
| * 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.view; |
| |
| import android.content.Context; |
| |
| /** |
| * Detects transformation gestures involving more than one pointer ("multitouch") |
| * using the supplied {@link MotionEvent}s. The {@link OnScaleGestureListener} |
| * callback will notify users when a particular gesture event has occurred. |
| * This class should only be used with {@link MotionEvent}s reported via touch. |
| * |
| * To use this class: |
| * <ul> |
| * <li>Create an instance of the {@code ScaleGestureDetector} for your |
| * {@link View} |
| * <li>In the {@link View#onTouchEvent(MotionEvent)} method ensure you call |
| * {@link #onTouchEvent(MotionEvent)}. The methods defined in your |
| * callback will be executed when the events occur. |
| * </ul> |
| * @hide Pending API approval |
| */ |
| public class ScaleGestureDetector { |
| /** |
| * The listener for receiving notifications when gestures occur. |
| * If you want to listen for all the different gestures then implement |
| * this interface. If you only want to listen for a subset it might |
| * be easier to extend {@link SimpleOnScaleGestureListener}. |
| * |
| * An application will receive events in the following order: |
| * <ul> |
| * <li>One {@link OnScaleGestureListener#onScaleBegin()} |
| * <li>Zero or more {@link OnScaleGestureListener#onScale()} |
| * <li>One {@link OnScaleGestureListener#onTransformEnd()} |
| * </ul> |
| */ |
| public interface OnScaleGestureListener { |
| /** |
| * Responds to scaling events for a gesture in progress. |
| * Reported by pointer motion. |
| * |
| * @param detector The detector reporting the event - use this to |
| * retrieve extended info about event state. |
| * @return Whether or not the detector should consider this event |
| * as handled. If an event was not handled, the detector |
| * will continue to accumulate movement until an event is |
| * handled. This can be useful if an application, for example, |
| * only wants to update scaling factors if the change is |
| * greater than 0.01. |
| */ |
| public boolean onScale(ScaleGestureDetector detector); |
| |
| /** |
| * Responds to the beginning of a scaling gesture. Reported by |
| * new pointers going down. |
| * |
| * @param detector The detector reporting the event - use this to |
| * retrieve extended info about event state. |
| * @return Whether or not the detector should continue recognizing |
| * this gesture. For example, if a gesture is beginning |
| * with a focal point outside of a region where it makes |
| * sense, onScaleBegin() may return false to ignore the |
| * rest of the gesture. |
| */ |
| public boolean onScaleBegin(ScaleGestureDetector detector); |
| |
| /** |
| * Responds to the end of a scale gesture. Reported by existing |
| * pointers going up. If the end of a gesture would result in a fling, |
| * {@link onTransformFling()} is called instead. |
| * |
| * Once a scale has ended, {@link ScaleGestureDetector#getFocusX()} |
| * and {@link ScaleGestureDetector#getFocusY()} will return the location |
| * of the pointer remaining on the screen. |
| * |
| * @param detector The detector reporting the event - use this to |
| * retrieve extended info about event state. |
| */ |
| public void onScaleEnd(ScaleGestureDetector detector); |
| } |
| |
| /** |
| * A convenience class to extend when you only want to listen for a subset |
| * of scaling-related events. This implements all methods in |
| * {@link OnScaleGestureListener} but does nothing. |
| * {@link OnScaleGestureListener#onScale(ScaleGestureDetector)} and |
| * {@link OnScaleGestureListener#onScaleBegin(ScaleGestureDetector)} return |
| * {@code true}. |
| */ |
| public class SimpleOnScaleGestureListener implements OnScaleGestureListener { |
| |
| public boolean onScale(ScaleGestureDetector detector) { |
| return true; |
| } |
| |
| public boolean onScaleBegin(ScaleGestureDetector detector) { |
| return true; |
| } |
| |
| public void onScaleEnd(ScaleGestureDetector detector) { |
| // Intentionally empty |
| } |
| } |
| |
| private static final float PRESSURE_THRESHOLD = 0.67f; |
| |
| private Context mContext; |
| private OnScaleGestureListener mListener; |
| private boolean mGestureInProgress; |
| |
| private MotionEvent mPrevEvent; |
| private MotionEvent mCurrEvent; |
| |
| private float mFocusX; |
| private float mFocusY; |
| private float mPrevFingerDiffX; |
| private float mPrevFingerDiffY; |
| private float mCurrFingerDiffX; |
| private float mCurrFingerDiffY; |
| private float mCurrLen; |
| private float mPrevLen; |
| private float mScaleFactor; |
| private float mCurrPressure; |
| private float mPrevPressure; |
| private long mTimeDelta; |
| |
| public ScaleGestureDetector(Context context, OnScaleGestureListener listener) { |
| mContext = context; |
| mListener = listener; |
| } |
| |
| public boolean onTouchEvent(MotionEvent event) { |
| final int action = event.getAction(); |
| boolean handled = true; |
| |
| if (!mGestureInProgress) { |
| if ((action == MotionEvent.ACTION_POINTER_1_DOWN || |
| action == MotionEvent.ACTION_POINTER_2_DOWN) && |
| event.getPointerCount() >= 2) { |
| // We have a new multi-finger gesture |
| |
| // Be paranoid in case we missed an event |
| reset(); |
| |
| mPrevEvent = MotionEvent.obtain(event); |
| mTimeDelta = 0; |
| |
| setContext(event); |
| mGestureInProgress = mListener.onScaleBegin(this); |
| } |
| } else { |
| // Transform gesture in progress - attempt to handle it |
| switch (action) { |
| case MotionEvent.ACTION_POINTER_1_UP: |
| case MotionEvent.ACTION_POINTER_2_UP: |
| // Gesture ended |
| setContext(event); |
| |
| // Set focus point to the remaining finger |
| int id = (((action & MotionEvent.ACTION_POINTER_ID_MASK) |
| >> MotionEvent.ACTION_POINTER_ID_SHIFT) == 0) ? 1 : 0; |
| mFocusX = event.getX(id); |
| mFocusY = event.getY(id); |
| |
| mListener.onScaleEnd(this); |
| mGestureInProgress = false; |
| |
| reset(); |
| break; |
| |
| case MotionEvent.ACTION_CANCEL: |
| mListener.onScaleEnd(this); |
| mGestureInProgress = false; |
| |
| reset(); |
| break; |
| |
| case MotionEvent.ACTION_MOVE: |
| setContext(event); |
| |
| // Only accept the event if our relative pressure is within |
| // a certain limit - this can help filter shaky data as a |
| // finger is lifted. |
| if (mCurrPressure / mPrevPressure > PRESSURE_THRESHOLD) { |
| final boolean updatePrevious = mListener.onScale(this); |
| |
| if (updatePrevious) { |
| mPrevEvent.recycle(); |
| mPrevEvent = MotionEvent.obtain(event); |
| } |
| } |
| break; |
| } |
| } |
| return handled; |
| } |
| |
| private void setContext(MotionEvent curr) { |
| if (mCurrEvent != null) { |
| mCurrEvent.recycle(); |
| } |
| mCurrEvent = MotionEvent.obtain(curr); |
| |
| mCurrLen = -1; |
| mPrevLen = -1; |
| mScaleFactor = -1; |
| |
| final MotionEvent prev = mPrevEvent; |
| |
| final float px0 = prev.getX(0); |
| final float py0 = prev.getY(0); |
| final float px1 = prev.getX(1); |
| final float py1 = prev.getY(1); |
| final float cx0 = curr.getX(0); |
| final float cy0 = curr.getY(0); |
| final float cx1 = curr.getX(1); |
| final float cy1 = curr.getY(1); |
| |
| final float pvx = px1 - px0; |
| final float pvy = py1 - py0; |
| final float cvx = cx1 - cx0; |
| final float cvy = cy1 - cy0; |
| mPrevFingerDiffX = pvx; |
| mPrevFingerDiffY = pvy; |
| mCurrFingerDiffX = cvx; |
| mCurrFingerDiffY = cvy; |
| |
| mFocusX = cx0 + cvx * 0.5f; |
| mFocusY = cy0 + cvy * 0.5f; |
| mTimeDelta = curr.getEventTime() - prev.getEventTime(); |
| mCurrPressure = curr.getPressure(0) + curr.getPressure(1); |
| mPrevPressure = prev.getPressure(0) + prev.getPressure(1); |
| } |
| |
| private void reset() { |
| if (mPrevEvent != null) { |
| mPrevEvent.recycle(); |
| mPrevEvent = null; |
| } |
| if (mCurrEvent != null) { |
| mCurrEvent.recycle(); |
| mCurrEvent = null; |
| } |
| } |
| |
| /** |
| * Returns {@code true} if a two-finger scale gesture is in progress. |
| * @return {@code true} if a scale gesture is in progress, {@code false} otherwise. |
| */ |
| public boolean isInProgress() { |
| return mGestureInProgress; |
| } |
| |
| /** |
| * Get the X coordinate of the current gesture's focal point. |
| * If a gesture is in progress, the focal point is directly between |
| * the two pointers forming the gesture. |
| * If a gesture is ending, the focal point is the location of the |
| * remaining pointer on the screen. |
| * If {@link isInProgress()} would return false, the result of this |
| * function is undefined. |
| * |
| * @return X coordinate of the focal point in pixels. |
| */ |
| public float getFocusX() { |
| return mFocusX; |
| } |
| |
| /** |
| * Get the Y coordinate of the current gesture's focal point. |
| * If a gesture is in progress, the focal point is directly between |
| * the two pointers forming the gesture. |
| * If a gesture is ending, the focal point is the location of the |
| * remaining pointer on the screen. |
| * If {@link isInProgress()} would return false, the result of this |
| * function is undefined. |
| * |
| * @return Y coordinate of the focal point in pixels. |
| */ |
| public float getFocusY() { |
| return mFocusY; |
| } |
| |
| /** |
| * Return the current distance between the two pointers forming the |
| * gesture in progress. |
| * |
| * @return Distance between pointers in pixels. |
| */ |
| public float getCurrentSpan() { |
| if (mCurrLen == -1) { |
| final float cvx = mCurrFingerDiffX; |
| final float cvy = mCurrFingerDiffY; |
| mCurrLen = (float)Math.sqrt(cvx*cvx + cvy*cvy); |
| } |
| return mCurrLen; |
| } |
| |
| /** |
| * Return the previous distance between the two pointers forming the |
| * gesture in progress. |
| * |
| * @return Previous distance between pointers in pixels. |
| */ |
| public float getPreviousSpan() { |
| if (mPrevLen == -1) { |
| final float pvx = mPrevFingerDiffX; |
| final float pvy = mPrevFingerDiffY; |
| mPrevLen = (float)Math.sqrt(pvx*pvx + pvy*pvy); |
| } |
| return mPrevLen; |
| } |
| |
| /** |
| * Return the scaling factor from the previous scale event to the current |
| * event. This value is defined as |
| * ({@link getCurrentSpan()} / {@link getPreviousSpan()}). |
| * |
| * @return The current scaling factor. |
| */ |
| public float getScaleFactor() { |
| if (mScaleFactor == -1) { |
| mScaleFactor = getCurrentSpan() / getPreviousSpan(); |
| } |
| return mScaleFactor; |
| } |
| |
| /** |
| * Return the time difference in milliseconds between the previous |
| * accepted scaling event and the current scaling event. |
| * |
| * @return Time difference since the last scaling event in milliseconds. |
| */ |
| public long getTimeDelta() { |
| return mTimeDelta; |
| } |
| |
| /** |
| * Return the event time of the current event being processed. |
| * |
| * @return Current event time in milliseconds. |
| */ |
| public long getEventTime() { |
| return mCurrEvent.getEventTime(); |
| } |
| } |