Android多点触摸的实现——1.6patch 一 .doc

Android多点触摸的实现1.6patch（一）第一章摘要在Linux内核支持的基础上，Android在其2.0源码中加入多点触摸功能。由此触摸屏在Android的frameworks被完全分为2种实现途径：单点触摸屏的单点方式，多点触摸屏的单点和多点方式。第二章软件位在Linux的input.h中，多点触摸功能依赖于以下几个主要的软件位：.#define SYN_REPORT 0#define SYN_CONFIG 1#define SYN_MT_REPORT 2.#define ABS_MT_TOUCH_MAJOR0x30/* Major axis of touching ellipse */#define ABS_MT_TOUCH_MINOR0x31/* Minor axis (omit if circular) */#define ABS_MT_WIDTH_MAJOR0x32/* Major axis of approaching ellipse */#define ABS_MT_WIDTH_MINOR0x33/* Minor axis (omit if circular) */#define ABS_MT_ORIENTATION0x34/* Ellipse orientation */#define ABS_MT_POSITION_X0x35/* Center X ellipse position */#define ABS_MT_POSITION_Y0x36/* Center Y ellipse position */#define ABS_MT_TOOL_TYPE0x37/* Type of touching device */#define ABS_MT_BLOB_ID 0x38/* Group a set of packets as a blob */在Android中对应的软件位定义在RawInputEvent.java中:.public class RawInputEvent . public static final int CLASS_TOUCHSCREEN_MT = 0x00000010;. public static final int ABS_MT_TOUCH_MAJOR = 0x30; public static final int ABS_MT_TOUCH_MINOR = 0x31; public static final int ABS_MT_WIDTH_MAJOR = 0x32; public static final int ABS_MT_WIDTH_MINOR = 0x33; public static final int ABS_MT_ORIENTATION = 0x34; public static final int ABS_MT_POSITION_X = 0x35; public static final int ABS_MT_POSITION_Y = 0x36; public static final int ABS_MT_TOOL_TYPE = 0x37; public static final int ABS_MT_BLOB_ID = 0x38;.public static final int SYN_REPORT = 0; public static final int SYN_CONFIG = 1;public static final int SYN_MT_REPORT = 2;.在Android中，多点触摸的实现方法在具体的代码实现中和单点是完全区分开的。在Android代码的EventHub.cpp中，单点屏和多点屏由如下代码段来判定：int EventHub:open_device(const char *deviceName)if (test_bit(ABS_MT_TOUCH_MAJOR, abs_bitmask)& test_bit(ABS_MT_POSITION_X, abs_bitmask)& test_bit(ABS_MT_POSITION_Y, abs_bitmask) device-classes |= CLASS_TOUCHSCREEN | CLASS_TOUCHSCREEN_MT;/ LOGI(It is a multi-touch screen!); /single-touch?else if (test_bit(BTN_TOUCH, key_bitmask)& test_bit(ABS_X, abs_bitmask) & test_bit(ABS_Y, abs_bitmask) device-classes |= CLASS_TOUCHSCREEN;/ LOGI(It is a single-touch screen!);.我们知道，在触摸屏驱动中，通常在probe函数中会调用input_set_abs_params给设备的input_dev结构体初始化，这些input_dev的参数会在Android的EventHub.cpp中被读取。如上可知，如果我们的触摸屏想被当成多点屏被处理，只需要在驱动中给input_dev额外增加以下几个参数即可：input_set_abs_params(mcs_data.input, ABS_MT_POSITION_X, pdata-abs_x_min, pdata-abs_x_max, 0, 0);input_set_abs_params(mcs_data.input, ABS_MT_POSITION_Y, pdata-abs_y_min, pdata-abs_y_max, 0, 0);input_set_abs_params(mcs_data.input, ABS_MT_TOUCH_MAJOR, 0, 15, 0, 0); /相当于单点屏的ABX_PRESSUREinput_set_abs_params(mcs_data.input, ABS_MT_WIDTH_MAJOR, 0, 15, 0, 0); /相当于单点屏的ABS_TOOL_WIDTH注：为了让我们的驱动代码支持所有的Android版本，无论是多点屏还是单点屏，一般都会保留单点屏的事件，如ABS_TOUCH, ABS_PRESSURE, ABS_X, ABS_Y等。另外，由于在Android2.0前支持多点的frameworks大多是用HAT0X,HAT0Y来实现的，所以一般也会上报这2个事件。第三章同步方式由于多点触摸技术需要采集到多个点，然后再一起处理这些点，所以在软件实现中需要保证每一波点的准确性和完整性。因此，Linux内核提供了input_mt_sync(struct input_dev * input)函数。在每波的每个点上报后需要紧跟一句input_mt_sync(), 当这波所有点上报后再使用input_sync()进行同步。例如一波要上报3个点：/* 上报点1*/.input_mt_sync(input);/* 上报点2*/.input_mt_sync(input);/* 上报点3*/.input_mt_sync(input);input_sync(input);注：即使是仅上报一个点的单点事件，也需要一次input_my_sync。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, doesnt 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_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.mNextDatadi.mAbs.mAddingPointerOffset + MotionEvent.SAMPLE_PRESSURE = ev.value; else if (ev.scancode = RawInputEvent.ABS_MT_POSITION_X) di.mAbs.changed = true; di.mAbs.mNextDatadi.mAbs.mAddingPointerOffset + MotionEvent.SAMPLE_X = ev.value; else if (ev.scancode = RawInputEvent.ABS_MT_POSITION_Y) di.mAbs.changed = true; di.mAbs.mNextDatadi.mAbs.mAddingPointerOffset + MotionEvent.SAMPLE_Y = ev.value; else if (ev.scancode = RawInputEvent.ABS_MT_WIDTH_MAJOR) di.mAbs.changed = true; di.mAbs.mNextDatadi.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.curTouchValsMotionEvent.SAMPLE_X = ev.value; else if (ev.scancode = RawInputEvent.ABS_Y) di.mAbs.changed = true; di.curTouchValsMotionEvent.SAMPLE_Y = ev.value; else if (ev.scancode = RawInputEvent.ABS_PRESSURE) di.mAbs.changed = true; di.curTouchValsMotionEvent.SAMPLE_PRESSURE = ev.value; di.curTouchValsMotionEvent.NUM_SAMPLE_DATA + MotionEvent.SAMPLE_PRESSURE = ev.value; else if (ev.scancode = RawInputEvent.ABS_TOOL_WIDTH) di.mAbs.changed = true; di.curTouchValsMotionEvent.SAMPLE_SIZE = ev.value; di.curTouchValsMotionEvent.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 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 if (numPointers = 1) /原来只有1个点按下，所以现在的动作是全部按键up action = MotionEvent.ACTION_UP; else /原来有多点按下，现在是ACTION_POINTER_UP动作， action = MotionEvent.ACTION_POINTER_UP | (upOrDownPointer MotionEvent.ACTION_POINTER_ID_SHIFT); currentMove = null; else /前后触屏pointer个数