Android多点触摸的实现（2）

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在Android的KeyInputQueue.java中，系统创建了一个线程，然后把所有的Input事件放入一个队列：

public abstract class KeyInputQueue {

……………………

Thread mThread = new Thread("InputDeviceReader") {

public void run() {

android.os.Process.setThreadPriority(

android.os.Process.THREAD_PRIORITY_URGENT_DISPLAY);

try {

RawInputEvent ev = new RawInputEvent();

while (true) {

InputDevice di;

// block, doesn't release the monitor

readEvent(ev);

if (ev.type == RawInputEvent.EV_DEVICE_ADDED) {

synchronized (mFirst) {

di = newInputDevice(ev.deviceId);

mDevices.put(ev.deviceId, di);

configChanged = true;

}

} else if (ev.type == RawInputEvent.EV_DEVICE_REMOVED) {

synchronized (mFirst) {

Log.i(TAG, "Device removed: id=0x"

+ Integer.toHexString(ev.deviceId));

di = mDevices.get(ev.deviceId);

if (di != null) {

mDevices.delete(ev.deviceId);

configChanged = true;

} else {

Log.w(TAG, "Bad device id: " + ev.deviceId);

}

} else {

di = getInputDevice(ev.deviceId);

// first crack at it

send = preprocessEvent(di, ev);

if (ev.type == RawInputEvent.EV_KEY) {

di.mMetaKeysState = makeMetaState(ev.keycode,

ev.value != 0, di.mMetaKeysState);

mHaveGlobalMetaState = false;

}

if (di == null) {

continue;

}

if (configChanged) {

synchronized (mFirst) {

addLocked(di, SystemClock.uptimeMillis(), 0,

RawInputEvent.CLASS_CONFIGURATION_CHANGED,

null);

}

if (!send) {

continue;

}

synchronized (mFirst) {

……………………….

if (type == RawInputEvent.EV_KEY &&

(classes&RawInputEvent.CLASS_KEYBOARD) != 0 &&

(scancode < RawInputEvent.BTN_FIRST ||

scancode > RawInputEvent.BTN_LAST)) {

/* 键盘按键事件 */

…………………….

} else if (ev.type == RawInputEvent.EV_KEY) {

/* 下面是EV_KEY事件分支，只支持单点的触摸屏有按键事件，

* 而支持多点的触摸屏没有按键事件，只有绝对坐标事件

if (ev.scancode == RawInputEvent.BTN_TOUCH &&

(classes&(RawInputEvent.CLASS_TOUCHSCREEN

|RawInputEvent.CLASS_TOUCHSCREEN_MT))

== RawInputEvent.CLASS_TOUCHSCREEN) {

/* 只支持单点的触摸屏的按键事件 */

…………………………………

} else if (ev.scancode == RawInputEvent.BTN_MOUSE &&

(classes&RawInputEvent.CLASS_TRACKBALL) != 0) {

/* 鼠标和轨迹球 */

……………………….

} else if (ev.type == RawInputEvent.EV_ABS &&

(classes&RawInputEvent.CLASS_TOUCHSCREEN_MT) != 0) {

/* 下面才是多点触摸屏上报的事件 */

if (ev.scancode == RawInputEvent.ABS_MT_TOUCH_MAJOR) {

di.mAbs.changed = true;

di.mAbs.mNextData[di.mAbs.mAddingPointerOffset

+ MotionEvent.SAMPLE_PRESSURE] = ev.value;

} else if (ev.scancode == RawInputEvent.ABS_MT_POSITION_X) {

di.mAbs.changed = true;

di.mAbs.mNextData[di.mAbs.mAddingPointerOffset

+ MotionEvent.SAMPLE_X] = ev.value;

} else if (ev.scancode == RawInputEvent.ABS_MT_POSITION_Y) {

di.mAbs.changed = true;

di.mAbs.mNextData[di.mAbs.mAddingPointerOffset

+ MotionEvent.SAMPLE_Y] = ev.value;

} else if (ev.scancode == RawInputEvent.ABS_MT_WIDTH_MAJOR) {

di.mAbs.changed = true;

di.mAbs.mNextData[di.mAbs.mAddingPointerOffset

+ MotionEvent.SAMPLE_SIZE] = ev.value;

}

/* 上面这段就是多点触摸屏要用到的事件上报部分;

* 使用一个数组mNextData来保存，其中di.mAbs.mAddingPointerOffset

* 是当前点的偏移量，在每个点中还在MotionEvent中定义了X,Y,PRESSURE

* SIZE等偏移量，多点触摸屏的压力值由绝对坐标事件ABS_MT_TOUCH_MAJOR确定。

} else if (ev.type == RawInputEvent.EV_ABS &&

(classes&RawInputEvent.CLASS_TOUCHSCREEN) != 0) {

/* 这里是对单点触摸屏上报坐标事件的新的处理方法，同样使用了数组来保存 */

if (ev.scancode == RawInputEvent.ABS_X) {

di.mAbs.changed = true;

di.curTouchVals[MotionEvent.SAMPLE_X] = ev.value;

} else if (ev.scancode == RawInputEvent.ABS_Y) {

di.mAbs.changed = true;

di.curTouchVals[MotionEvent.SAMPLE_Y] = ev.value;

} else if (ev.scancode == RawInputEvent.ABS_PRESSURE) {

di.mAbs.changed = true;

di.curTouchVals[MotionEvent.SAMPLE_PRESSURE] = ev.value;

di.curTouchVals[MotionEvent.NUM_SAMPLE_DATA

+ MotionEvent.SAMPLE_PRESSURE] = ev.value;

} else if (ev.scancode == RawInputEvent.ABS_TOOL_WIDTH) {

di.mAbs.changed = true;

di.curTouchVals[MotionEvent.SAMPLE_SIZE] = ev.value;

di.curTouchVals[MotionEvent.NUM_SAMPLE_DATA

+ MotionEvent.SAMPLE_SIZE] = ev.value;

}

…………………………………………….}

/* 下面是关键的同步处理方法 */

if (ev.type == RawInputEvent.EV_SYN

&& ev.scancode == RawInputEvent.SYN_MT_REPORT

&& di.mAbs != null) {

/* 在这里实现了对SYN_MT_REPORT事件的处理，

* 改变了di.mAbs.mAddingPointerOffset的值，从而将

* 新增的点的参数保存到下一组偏移量的位置。

…………………….

final int newOffset = (num <= InputDevice.MAX_POINTERS)

? (num * MotionEvent.NUM_SAMPLE_DATA)

: (InputDevice.MAX_POINTERS *

MotionEvent.NUM_SAMPLE_DATA);

di.mAbs.mAddingPointerOffset = newOffset;

di.mAbs.mNextData[newOffset

+ MotionEvent.SAMPLE_PRESSURE] = 0;

}

……………….

} else if (send || (ev.type == RawInputEvent.EV_SYN

&& ev.scancode == RawInputEvent.SYN_REPORT)) {

/* 这里实现了对SYN_REPORT事件的处理

* 如果是单点触摸屏，即使用di.curTouchVals数组保存的点

* 转化为多点触摸屏的mNextData数组保存

* 最后是调用InputDevice中的generateAbsMotion处理这个数组。这个函数

* 的具体实现方法将在后面补充

…………………………..

ms.finish(); //重置所有点和偏移量

……………………..

}

由于上层的代码仍然使用ABS_X, ABS_Y这些事件，为了使多点触摸屏代码有良好的兼容性，在KeyInputQueue.java的最后，我们将多点事件类型转化为单点事件类型，返回一个新的InputDevice:

private InputDevice newInputDevice(int deviceId) {

int classes = getDeviceClasses(deviceId);

String name = getDeviceName(deviceId);

InputDevice.AbsoluteInfo absX;

InputDevice.AbsoluteInfo absY;

InputDevice.AbsoluteInfo absPressure;

InputDevice.AbsoluteInfo absSize;

if ((classes&RawInputEvent.CLASS_TOUCHSCREEN_MT) != 0) {

absX = loadAbsoluteInfo(deviceId,

RawInputEvent.ABS_MT_POSITION_X, "X");

absY = loadAbsoluteInfo(deviceId,

RawInputEvent.ABS_MT_POSITION_Y, "Y");

absPressure = loadAbsoluteInfo(deviceId,

RawInputEvent.ABS_MT_TOUCH_MAJOR, "Pressure");

absSize = loadAbsoluteInfo(deviceId,

RawInputEvent.ABS_MT_WIDTH_MAJOR, "Size");

} else if ((classes&RawInputEvent.CLASS_TOUCHSCREEN) != 0) {

absX = loadAbsoluteInfo(deviceId,

RawInputEvent.ABS_X, "X");

absY = loadAbsoluteInfo(deviceId,

RawInputEvent.ABS_Y, "Y");

absPressure = loadAbsoluteInfo(deviceId,

RawInputEvent.ABS_PRESSURE, "Pressure");

absSize = loadAbsoluteInfo(deviceId,

RawInputEvent.ABS_TOOL_WIDTH, "Size");

} else {

absX = null;

absY = null;

absPressure = null;

absSize = null;

}

return new InputDevice(deviceId, classes, name, absX, absY, absPressure, absSize);

}