Android多点触摸的实现

核心提示：int mLastNumPointers = 0;final int[] mLastData = new int[MotionEvent.NUM_SAMPLE_DATA * MAX_POINTERS];/* mNextNumPointers 为下一个动作在触屏上按键的个数 *//* 通过对这 2 个值大小的判断，可以确

int mLastNumPointers = 0;

final int[] mLastData = new int[MotionEvent.NUM_SAMPLE_DATA * MAX_POINTERS];

/* mNextNumPointers 为下一个动作在触屏上按键的个数 */

/* 通过对这 2 个值大小的判断，可以确认新的动作方式 */

int mNextNumPointers = 0;

final int[] mNextData = new int[(MotionEvent.NUM_SAMPLE_DATA * MAX_POINTERS)

+ MotionEvent.NUM_SAMPLE_DATA];

………………………………… .

int[] generateAveragedData(int upOrDownPointer, int lastNumPointers,

int nextNumPointers) { //平滑处理

…………………………………… .

}

private boolean assignPointer(int nextIndex, boolean allowOverlap) { //指派按键

……………………………………

}

private int updatePointerIdentifiers() { //更新按键 ID

………………………………… .

}

void removeOldPointer(int index) {

……………………………………

}

MotionEvent generateAbsMotion(InputDevice device, long curTime,

long curTimeNano, Display display, int orientation,

int metaState) {

……………………………………

int upOrDownPointer = updatePointerIdentifiers();

final int numPointers = mLastNumPointers;

………………………………………

/* 对行为的判断 */

if (nextNumPointers != lastNumPointers) { //前后在触屏上点个数不同，说明有手指 up 或 down

if (nextNumPointers > lastNumPointers) {

if (lastNumPointers == 0) { //上次触屏上没有按键，新值又大，说明有按键按下

action = MotionEvent.ACTION_DOWN;

mDownTime = curTime;

} else { //有新点按下，分配给新点 ID 号

action = MotionEvent.ACTION_POINTER_DOWN

| (upOrDownPointer << MotionEvent.ACTION_POINTER_ID_SHIFT);

}

} else { //新动作比原来 pointer 数量少