package cn.sinata.xldutils.view.gesture;
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import android.view.MotionEvent;
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/**
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* Component that detects translation, scale and rotation based on touch events.
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* <p>
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* This class notifies its listeners whenever a gesture begins, updates or ends.
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* The instance of this detector is passed to the listeners, so it can be queried
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* for pivot, translation, scale or rotation.
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*/
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public class TransformGestureDetector implements MultiPointerGestureDetector.Listener {
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/** The listener for receiving notifications when gestures occur. */
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public interface Listener {
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/** Responds to the beginning of a gesture. */
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public void onGestureBegin(TransformGestureDetector detector);
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/** Responds to the update of a gesture in progress. */
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public void onGestureUpdate(TransformGestureDetector detector);
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/** Responds to the end of a gesture. */
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public void onGestureEnd(TransformGestureDetector detector);
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}
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private final MultiPointerGestureDetector mDetector;
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private Listener mListener = null;
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public TransformGestureDetector(MultiPointerGestureDetector multiPointerGestureDetector) {
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mDetector = multiPointerGestureDetector;
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mDetector.setListener(this);
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}
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/** Factory method that creates a new instance of TransformGestureDetector */
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public static TransformGestureDetector newInstance() {
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return new TransformGestureDetector(MultiPointerGestureDetector.newInstance());
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}
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/**
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* Sets the listener.
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* @param listener listener to set
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*/
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public void setListener(Listener listener) {
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mListener = listener;
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}
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/**
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* Resets the component to the initial state.
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*/
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public void reset() {
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mDetector.reset();
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}
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/**
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* Handles the given motion event.
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* @param event event to handle
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* @return whether or not the event was handled
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*/
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public boolean onTouchEvent(final MotionEvent event) {
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return mDetector.onTouchEvent(event);
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}
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@Override
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public void onGestureBegin(MultiPointerGestureDetector detector) {
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if (mListener != null) {
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mListener.onGestureBegin(this);
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}
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}
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@Override
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public void onGestureUpdate(MultiPointerGestureDetector detector) {
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if (mListener != null) {
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mListener.onGestureUpdate(this);
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}
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}
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@Override
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public void onGestureEnd(MultiPointerGestureDetector detector) {
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if (mListener != null) {
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mListener.onGestureEnd(this);
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}
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}
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private float calcAverage(float[] arr, int len) {
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float sum = 0;
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for (int i = 0; i < len; i++) {
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sum += arr[i];
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}
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return (len > 0) ? sum / len : 0;
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}
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/** Restarts the current gesture */
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public void restartGesture() {
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mDetector.restartGesture();
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}
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/** Gets whether gesture is in progress or not */
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public boolean isGestureInProgress() {
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return mDetector.isGestureInProgress();
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}
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/** Gets the X coordinate of the pivot point */
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public float getPivotX() {
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return calcAverage(mDetector.getStartX(), mDetector.getCount());
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}
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/** Gets the Y coordinate of the pivot point */
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public float getPivotY() {
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return calcAverage(mDetector.getStartY(), mDetector.getCount());
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}
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/** Gets the X component of the translation */
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public float getTranslationX() {
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return calcAverage(mDetector.getCurrentX(), mDetector.getCount()) -
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calcAverage(mDetector.getStartX(), mDetector.getCount());
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}
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/** Gets the Y component of the translation */
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public float getTranslationY() {
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return calcAverage(mDetector.getCurrentY(), mDetector.getCount()) -
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calcAverage(mDetector.getStartY(), mDetector.getCount());
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}
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/** Gets the scale */
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public float getScale() {
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if (mDetector.getCount() < 2) {
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return 1;
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} else {
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float startDeltaX = mDetector.getStartX()[1] - mDetector.getStartX()[0];
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float startDeltaY = mDetector.getStartY()[1] - mDetector.getStartY()[0];
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float currentDeltaX = mDetector.getCurrentX()[1] - mDetector.getCurrentX()[0];
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float currentDeltaY = mDetector.getCurrentY()[1] - mDetector.getCurrentY()[0];
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float startDist = (float) Math.hypot(startDeltaX, startDeltaY);
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float currentDist = (float) Math.hypot(currentDeltaX, currentDeltaY);
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return currentDist / startDist;
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}
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}
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/** Gets the rotation in radians */
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public float getRotation() {
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if (mDetector.getCount() < 2) {
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return 0;
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} else {
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float startDeltaX = mDetector.getStartX()[1] - mDetector.getStartX()[0];
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float startDeltaY = mDetector.getStartY()[1] - mDetector.getStartY()[0];
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float currentDeltaX = mDetector.getCurrentX()[1] - mDetector.getCurrentX()[0];
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float currentDeltaY = mDetector.getCurrentY()[1] - mDetector.getCurrentY()[0];
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float startAngle = (float) Math.atan2(startDeltaY, startDeltaX);
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float currentAngle = (float) Math.atan2(currentDeltaY, currentDeltaX);
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return currentAngle - startAngle;
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}
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}
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}
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