private static final void releasePointerList(Pointer pointer) {
if (pointer != null) {
synchronized (sPool) {
int count = sRecycledPointerCount;
if (count >= POINTER_POOL_CAPACITY) {
return;
}
Pointer tail = pointer;
for (; ; ) {
count += 1;
if (count >= POINTER_POOL_CAPACITY) {
break;
}
Pointer next = tail.next;
if (next == null) {
break;
}
tail = next;
}
tail.next = sRecycledPointerListHead;
sRecycledPointerCount = count;
sRecycledPointerListHead = pointer;
}
}
}
private static final void releasePointer(Pointer pointer) {
synchronized (sPool) {
if (sRecycledPointerCount < POINTER_POOL_CAPACITY) {
pointer.next = sRecycledPointerListHead;
sRecycledPointerCount += 1;
sRecycledPointerListHead = pointer;
}
}
}
private static final Pointer obtainPointer() {
synchronized (sPool) {
if (sRecycledPointerCount != 0) {
Pointer element = sRecycledPointerListHead;
sRecycledPointerCount -= 1;
sRecycledPointerListHead = element.next;
element.next = null;
return element;
}
}
return new Pointer();
}
/**
* Add a user's movement to the tracker. You should call this for the initial {@link
* MotionEvent#ACTION_DOWN}, the following {@link MotionEvent#ACTION_MOVE} events that you
* receive, and the final {@link MotionEvent#ACTION_UP}. You can, however, call this for whichever
* events you desire.
*
* @param ev The MotionEvent you received and would like to track.
*/
public void addMovement(MotionEvent ev) {
final int historySize = ev.getHistorySize();
final int pointerCount = ev.getPointerCount();
final int lastTouchIndex = mLastTouchIndex;
final int nextTouchIndex = (lastTouchIndex + 1) % NUM_PAST;
final int finalTouchIndex = (nextTouchIndex + historySize) % NUM_PAST;
final int generation = mGeneration++;
mLastTouchIndex = finalTouchIndex;
// Update pointer data.
Pointer previousPointer = null;
for (int i = 0; i < pointerCount; i++) {
final int pointerId = ev.getPointerId(i);
// Find the pointer data for this pointer id.
// This loop is optimized for the common case where pointer ids in the event
// are in sorted order. However, we check for this case explicitly and
// perform a full linear scan from the start if needed.
Pointer nextPointer;
if (previousPointer == null || pointerId < previousPointer.id) {
previousPointer = null;
nextPointer = mPointerListHead;
} else {
nextPointer = previousPointer.next;
}
final Pointer pointer;
for (; ; ) {
if (nextPointer != null) {
final int nextPointerId = nextPointer.id;
if (nextPointerId == pointerId) {
pointer = nextPointer;
break;
}
if (nextPointerId < pointerId) {
nextPointer = nextPointer.next;
continue;
}
}
// Pointer went down. Add it to the list.
// Write a sentinel at the end of the pastTime trace so we will be able to
// tell when the trace started.
pointer = obtainPointer();
pointer.id = pointerId;
pointer.pastTime[lastTouchIndex] = Long.MIN_VALUE;
pointer.next = nextPointer;
if (previousPointer == null) {
mPointerListHead = pointer;
} else {
previousPointer.next = pointer;
}
break;
}
pointer.generation = generation;
previousPointer = pointer;
final float[] pastX = pointer.pastX;
final float[] pastY = pointer.pastY;
final long[] pastTime = pointer.pastTime;
for (int j = 0; j < historySize; j++) {
final int touchIndex = (nextTouchIndex + j) % NUM_PAST;
pastX[touchIndex] = ev.getHistoricalX(i, j);
pastY[touchIndex] = ev.getHistoricalY(i, j);
pastTime[touchIndex] = ev.getHistoricalEventTime(j);
}
pastX[finalTouchIndex] = ev.getX(i);
pastY[finalTouchIndex] = ev.getY(i);
pastTime[finalTouchIndex] = ev.getEventTime();
}
// Find removed pointers.
previousPointer = null;
for (Pointer pointer = mPointerListHead; pointer != null; ) {
final Pointer nextPointer = pointer.next;
if (pointer.generation != generation) {
// Pointer went up. Remove it from the list.
if (previousPointer == null) {
mPointerListHead = nextPointer;
} else {
previousPointer.next = nextPointer;
}
releasePointer(pointer);
} else {
previousPointer = pointer;
}
pointer = nextPointer;
}
}