Android Input 输入系统学习

原文在

Android输入设备的映射
使用指令dumpsys input 可以看到以下信息
130|shell@cv6a638_base:/ # dumpsys input                                       
INPUT MANAGER (dumpsys input)
 
Event Hub State:
  BuiltInKeyboardId: -2
  Devices:
    -1: Virtual
      Classes: 0x40000023
      Path: <virtual>
      Descriptor: a718a782d34bc767f46c232dd527998ea7fd
      Location: 
      ControllerNumber: 0
      UniqueId: <virtual>
      Identifier: bus=0x0000, vendor=0x0000, product=0x0000, version=0x0000
      KeyLayoutFile: /system/usr/keylayout/Generic.kl
      KeyCharacterMapFile: /system/usr/keychars/Virtual.kcm
      ConfigurationFile: 
      HaveKeyboardLayoutOverlay: false
    1: MStar Smart TV Keypad
      Classes: 0x00000001
      Path: /dev/input/event2
      Descriptor: 8f43d929a9472e8dcd48a6c41e2435e8eaff35
      Location: 
      ControllerNumber: 0
      UniqueId: 
      Identifier: bus=0x0006, vendor=0x3697, product=0x0002, version=0x0000
      KeyLayoutFile: /system/usr/keylayout/Vendor_3697_Product_0002.kl
      KeyCharacterMapFile: /system/usr/keychars/Generic.kcm
      ConfigurationFile: 
      HaveKeyboardLayoutOverlay: false
    2: MCE IR Keyboard/Mouse (ir)
      Classes: 0x0000000b
      Path: /dev/input/event1
      Descriptor: 2b7a30c0f74e1362d8ef86c5e4f12150af666f
      Location: /input0
      ControllerNumber: 0
      UniqueId: 
      Identifier: bus=0x0000, vendor=0x0000, product=0x0000, version=0x0000
      KeyLayoutFile: /system/usr/keylayout/Generic.kl
      KeyCharacterMapFile: /system/usr/keychars/Generic.kcm
      ConfigurationFile: 
      HaveKeyboardLayoutOverlay: false
    3: MStar Smart TV IR Receiver
      Classes: 0x00000001
      Path: /dev/input/event0
      Descriptor: 0e50bdc18d3ae0b6f247100cbd99062d93c208eb
      Location: /dev/ir
      ControllerNumber: 0
      UniqueId: 
      Identifier: bus=0x0018, vendor=0x3697, product=0x0001, version=0x0001
      KeyLayoutFile: /system/usr/keylayout/Vendor_3697_Product_0001.kl
      KeyCharacterMapFile: /system/usr/keychars/Generic.kcm
      ConfigurationFile: 
      HaveKeyboardLayoutOverlay: false
    4: AVRCP
      Classes: 0x80000001
      Path: /dev/input/event3
      Descriptor: 065b1db3afd7f700b4049a883d405d76233a40
      Location: 
      ControllerNumber: 0
      UniqueId: 
      Identifier: bus=0x0005, vendor=0x0000, product=0x0000, version=0x0000
      KeyLayoutFile: /system/usr/keylayout/AVRCP.kl
      KeyCharacterMapFile: /system/usr/keychars/Generic.kcm
      ConfigurationFile: 
      HaveKeyboardLayoutOverlay: false
 
Input Reader State:
  Device -1: Virtual
    Generation: 2
    IsExternal: false
    Sources: 0x00000301
    KeyboardType: 2
    Keyboard Input Mapper:
      Parameters:
        HasAssociatedDisplay: false
        OrientationAware: false
      KeyboardType: 2
      Orientation: 0
      KeyDowns: 0 keys currently down
      MetaState: 0x0
      DownTime: 0
  Device 1: MStar Smart TV Keypad
    Generation: 9
    IsExternal: false
    Sources: 0x00000101
    KeyboardType: 1
    Keyboard Input Mapper:
      Parameters:
        HasAssociatedDisplay: false
        OrientationAware: false
      KeyboardType: 1
      Orientation: 0
      KeyDowns: 0 keys currently down
      MetaState: 0x0
      DownTime: 0
  Device 2: MCE IR Keyboard/Mouse (ir)
    Generation: 11
    IsExternal: false
    Sources: 0x00002103
    KeyboardType: 2
    Motion Ranges:
      X: source=0x00002002, min=0.000, max=1919.000, flat=0.000, fuzz=0.000, resolution=0.000
      Y: source=0x00002002, min=0.000, max=1079.000, flat=0.000, fuzz=0.000, resolution=0.000
      PRESSURE: source=0x00002002, min=0.000, max=1.000, flat=0.000, fuzz=0.000, resolution=0.000
    Keyboard Input Mapper:
      Parameters:
        HasAssociatedDisplay: false
        OrientationAware: false
      KeyboardType: 2
      Orientation: 0
      KeyDowns: 0 keys currently down
      MetaState: 0x0
      DownTime: 0
    Cursor Input Mapper:
      Parameters:
        HasAssociatedDisplay: true
        Mode: pointer
        OrientationAware: false
      XScale: 1.000
      YScale: 1.000
      XPrecision: 1.000
      YPrecision: 1.000
      HaveVWheel: false
      HaveHWheel: false
      VWheelScale: 1.000
      HWheelScale: 1.000
      Orientation: 0
      ButtonState: 0x00000000
      Down: false
      DownTime: 0
  Device 3: MStar Smart TV IR Receiver
    Generation: 4
    IsExternal: false
    Sources: 0x00000101
    KeyboardType: 1
    Keyboard Input Mapper:
      Parameters:
        HasAssociatedDisplay: false
        OrientationAware: false
      KeyboardType: 1
      Orientation: 0
      KeyDowns: 0 keys currently down
      MetaState: 0x0
      DownTime: 0
  Device 4: AVRCP
    Generation: 12
    IsExternal: true
    Sources: 0x00000101
    KeyboardType: 1
    Keyboard Input Mapper:
      Parameters:
        HasAssociatedDisplay: false
        OrientationAware: false
      KeyboardType: 1
      Orientation: 0
      KeyDowns: 0 keys currently down
      MetaState: 0x0
      DownTime: 0
  Configuration:
    ExcludedDeviceNames: []
    VirtualKeyQuietTime: 0.0ms
    PointerVelocityControlParameters: scale=1.000, lowThreshold=500.000, highThreshold=3000.000, acceleration=3.000
    WheelVelocityControlParameters: scale=1.000, lowThreshold=15.000, highThreshold=50.000, acceleration=4.000
    PointerGesture:
      Enabled: true
      QuietInterval: 100.0ms
      DragMinSwitchSpeed: 50.0px/s
      TapInterval: 150.0ms
      TapDragInterval: 300.0ms
      TapSlop: 20.0px
      MultitouchSettleInterval: 100.0ms
      MultitouchMinDistance: 15.0px
      SwipeTransitionAngleCosine: 0.3
      SwipeMaxWidthRatio: 0.2
      MovementSpeedRatio: 0.8
      ZoomSpeedRatio: 0.3
 
Input Dispatcher State:
  DispatchEnabled: 1
  DispatchFrozen: 0
  FocusedApplication: name='AppWindowToken{42534628 token=Token{42532cb8 ActivityRecord{4255e728 u0 com.assem.launcher/.MainActivity t1}}}', dispatchingTimeout=5000.000ms
  FocusedWindow: name='Window{425a9768 u0 com.assem.launcher/com.assem.launcher.MainActivity}'
  TouchDown: false
  TouchSplit: false
  TouchDeviceId: -1
  TouchSource: 0x00000000
  TouchDisplayId: -1
  TouchedWindows: <none>
  Windows:
    0: name='Window{424d0270 u0 NotificationPanel}', displayId=0, paused=false, hasFocus=false, hasWallpaper=false, visible=false, canReceiveKeys=false, flags=0x01820300, type=0x000007e8, layer=211000, frame=[1152,-75][1920,1080], scale=1.000000, touchableRegion=[1152,-75][1920,1080], inputFeatures=0x00000000, ownerPid=2137, ownerUid=10003, dispatchingTimeout=5000.000ms
    1: name='Window{42514f48 u0 KeyguardScrim}', displayId=0, paused=false, hasFocus=false, hasWallpaper=false, visible=false, canReceiveKeys=false, flags=0x00110900, type=0x000007ed, layer=121000, frame=[0,0][1920,1080], scale=1.000000, touchableRegion=[0,0][1920,1080], inputFeatures=0x00000000, ownerPid=2067, ownerUid=1000, dispatchingTimeout=5000.000ms
    2: name='Window{425a9768 u0 com.assem.launcher/com.assem.launcher.MainActivity}', displayId=0, paused=false, hasFocus=true, hasWallpaper=false, visible=true, canReceiveKeys=true, flags=0x01810520, type=0x00000001, layer=21005, frame=[0,0][1920,1080], scale=1.000000, touchableRegion=[0,0][1920,1080], inputFeatures=0x00000000, ownerPid=2301, ownerUid=1000, dispatchingTimeout=5000.000ms
    3: name='Window{424c7c38 u0 com.android.systemui.ImageWallpaper}', displayId=0, paused=false, hasFocus=false, hasWallpaper=false, visible=true, canReceiveKeys=false, flags=0x00000318, type=0x000007dd, layer=21000, frame=[0,0][1920,1280], scale=1.000000, touchableRegion=[0,0][1920,1280], inputFeatures=0x00000000, ownerPid=2137, ownerUid=10003, dispatchingTimeout=5000.000ms
  MonitoringChannels:
    0: 'WindowManager (server)'
  RecentQueue: length=5
    DeviceResetEvent(deviceId=-1), policyFlags=0x00000000, age=20457.2ms
    DeviceResetEvent(deviceId=3), policyFlags=0x00000000, age=20457.2ms
    DeviceResetEvent(deviceId=2), policyFlags=0x00000000, age=20457.2ms
    DeviceResetEvent(deviceId=1), policyFlags=0x00000000, age=20457.2ms
    DeviceResetEvent(deviceId=4), policyFlags=0x00000000, age=2033442.2ms
  PendingEvent: <none>
  InboundQueue: <empty>
  Connections:
    0: channelName='425a9768 com.assem.launcher/com.assem.launcher.MainActivity (server)', windowName='Window{425a9768 u0 com.assem.launcher/com.assem.launcher.MainActivity}', status=NORMAL, monitor=false, inputPublisherBlocked=false
      OutboundQueue: <empty>
      WaitQueue: <empty>
    1: channelName='WindowManager (server)', windowName='monitor', status=NORMAL, monitor=true, inputPublisherBlocked=false
      OutboundQueue: <empty>
      WaitQueue: <empty>
    2: channelName='42514f48 KeyguardScrim (server)', windowName='Window{42514f48 u0 KeyguardScrim}', status=NORMAL, monitor=false, inputPublisherBlocked=false
      OutboundQueue: <empty>
      WaitQueue: <empty>
    3: channelName='424d0270 NotificationPanel (server)', windowName='Window{424d0270 u0 NotificationPanel}', status=NORMAL, monitor=false, inputPublisherBlocked=false
      OutboundQueue: <empty>
      WaitQueue: <empty>
    4: channelName='424c7c38 com.android.systemui.ImageWallpaper (server)', windowName='Window{424c7c38 u0 com.android.systemui.ImageWallpaper}', status=NORMAL, monitor=false, inputPublisherBlocked=false
      OutboundQueue: <empty>
      WaitQueue: <empty>
  AppSwitch: not pending
  Configuration:
    KeyRepeatDelay: 50.0ms
    KeyRepeatTimeout: 500.0ms
 
 
shell@cv6a638_base:/ # 
我们可以看到在KeyLayoutFile条目中看到加载的按键映射文件，都是根据厂商ID和产品ID匹配对应文件的，例如
vendor为0x3697，product 为0x0001，那么对应的配置文件为/system/usr/keylayout/Vendor_3697_Product_0001.kl
另外该命令还很多信息可挖，例如KeyRepeatDelay: 50.0ms，KeyRepeatTimeout: 500.0ms在按键性能优化时，就可以起到作用。

使用ioctl(fd, EVIOCGID, &inputId)读取出设备标识信息赋给identifier，并创建Device，接着loadConfigurationLocked接在配置，最后使用addDeviceLocked添加设备信息。

按键布局文件(kl)加载
由上面分析指导，每个Device都对应一个设备，底层配置文件中的映射关系都需要load到android系统中才能被使用，我们可以先看EventHub的子类Device
struct Device {
        Device* next;
 
        int fd; // may be -1 if device is virtual
        const int32_t id;
        const String8 path;
        const InputDeviceIdentifier identifier;
 
        uint32_t classes;
 
        uint8_t keyBitmask[(KEY_MAX + 1) / 8];
        uint8_t absBitmask[(ABS_MAX + 1) / 8];
        uint8_t relBitmask[(REL_MAX + 1) / 8];
        uint8_t swBitmask[(SW_MAX + 1) / 8];
        uint8_t ledBitmask[(LED_MAX + 1) / 8];
        uint8_t ffBitmask[(FF_MAX + 1) / 8];
        uint8_t propBitmask[(INPUT_PROP_MAX + 1) / 8];
 
        String8 configurationFile;
        PropertyMap* configuration;
        VirtualKeyMap* virtualKeyMap;
        KeyMap keyMap;
 
        sp<KeyCharacterMap> overlayKeyMap;
        sp<KeyCharacterMap> combinedKeyMap;
 
        bool ffEffectPlaying;
        int16_t ffEffectId; // initially -1
 
        int32_t controllerNumber;
 
        int32_t timestampOverrideSec;
        int32_t timestampOverrideUsec;
 
        Device(int fd, int32_t id, const String8& path, const InputDeviceIdentifier& identifier);
        ~Device();
 
        void close();
 
        inline bool isVirtual() const { return fd < 0; }
 
        const sp<KeyCharacterMap>& getKeyCharacterMap() const {
            if (combinedKeyMap != NULL) {
                return combinedKeyMap;
            }
            return keyMap.keyCharacterMap;
        }
    }

子类Device中函数KeyMap keyMap，该对象就是一个按键映射对象，接着分析如何加载
// Load the keymap for the device.
status_t EventHub::loadKeyMapLocked(Device* device) {
    return device->keyMap.load(device->identifier, device->configuration);
}
其实进入loadKeyMapLocked有两各入口，createVirtualKeyboardLocked和openDeviceLocked，后者则是我们上面分析的一条路径。
device->keyMap.load(device->identifier, device->configuration)也即进入Device：：load
status_t KeyMap::load(const InputDeviceIdentifier& deviceIdenfifier,
        const PropertyMap* deviceConfiguration) {
    // Use the configured key layout if available.
    if (deviceConfiguration) {
        String8 keyLayoutName;
        if (deviceConfiguration->tryGetProperty(String8("keyboard.layout"),
                keyLayoutName)) {
            status_t status = loadKeyLayout(deviceIdenfifier, keyLayoutName);
            if (status == NAME_NOT_FOUND) {
                ALOGE("Configuration for keyboard device '%s' requested keyboard layout '%s' but "
                        "it was not found.",
                        deviceIdenfifier.name.string(), keyLayoutName.string());
            }
        }
 
        String8 keyCharacterMapName;
        if (deviceConfiguration->tryGetProperty(String8("keyboard.characterMap"),
                keyCharacterMapName)) {
            status_t status = loadKeyCharacterMap(deviceIdenfifier, keyCharacterMapName);
            if (status == NAME_NOT_FOUND) {
                ALOGE("Configuration for keyboard device '%s' requested keyboard character "
                        "map '%s' but it was not found.",
                        deviceIdenfifier.name.string(), keyLayoutName.string());
            }
        }
 
        if (isComplete()) {
            return OK;
        }
    }
 
    // Try searching by device identifier.
    if (probeKeyMap(deviceIdenfifier, String8::empty())) {
        return OK;
    }
 
    // Fall back on the Generic key map.
    // TODO Apply some additional heuristics here to figure out what kind of
    //      generic key map to use (US English, etc.) for typical external keyboards.
    if (probeKeyMap(deviceIdenfifier, String8("Generic"))) {
        return OK;
    }
 
    // Try the Virtual key map as a last resort.
    if (probeKeyMap(deviceIdenfifier, String8("Virtual"))) {
        return OK;
    }
 
    // Give up!
    ALOGE("Could not determine key map for device '%s' and no default key maps were found!",
            deviceIdenfifier.name.string());
    return NAME_NOT_FOUND;
}
接着进入loadKeyLayout
status_t KeyMap::loadKeyLayout(const InputDeviceIdentifier& deviceIdentifier,
        const String8& name) {
    String8 path(getPath(deviceIdentifier, name,
            INPUT_DEVICE_CONFIGURATION_FILE_TYPE_KEY_LAYOUT));
    if (path.isEmpty()) {
        return NAME_NOT_FOUND;
    }
 
    status_t status = KeyLayoutMap::load(path, &keyLayoutMap);
    if (status) {
        return status;
    }
 
    keyLayoutFile.setTo(path);
    return OK;
}

/* Types of input device configuration files. */
enum InputDeviceConfigurationFileType {
    INPUT_DEVICE_CONFIGURATION_FILE_TYPE_CONFIGURATION = 0,     /* .idc file */
    INPUT_DEVICE_CONFIGURATION_FILE_TYPE_KEY_LAYOUT = 1,        /* .kl file */
    INPUT_DEVICE_CONFIGURATION_FILE_TYPE_KEY_CHARACTER_MAP = 2, /* .kcm file */
};
INPUT_DEVICE_CONFIGURATION_FILE_TYPE_KEY_LAYOUT就代表着.kl 类型文件，紧接着进入KeyLayoutMap::load(path, &keyLayoutMap)
status_t KeyLayoutMap::load(const String8& filename, sp<KeyLayoutMap>* outMap) {
    outMap->clear();
 
    Tokenizer* tokenizer;
    status_t status = Tokenizer::open(filename, &tokenizer);
    if (status) {
        ALOGE("Error %d opening key layout map file %s.", status, filename.string());
    } else {
        sp<KeyLayoutMap> map = new KeyLayoutMap();
        if (!map.get()) {
            ALOGE("Error allocating key layout map.");
            status = NO_MEMORY;
        } else {
#if DEBUG_PARSER_PERFORMANCE
            nsecs_t startTime = systemTime(SYSTEM_TIME_MONOTONIC);
#endif
            Parser parser(map.get(), tokenizer);
            status = parser.parse();
#if DEBUG_PARSER_PERFORMANCE
            nsecs_t elapsedTime = systemTime(SYSTEM_TIME_MONOTONIC) - startTime;
            ALOGD("Parsed key layout map file '%s' %d lines in %0.3fms.",
                    tokenizer->getFilename().string(), tokenizer->getLineNumber(),
                    elapsedTime / 1000000.0);
#endif
            if (!status) {
                *outMap = map;
            }
        }
        delete tokenizer;
    }
    return status;
}

KeyLayoutMap::Parser完成.kl 文件内容的解析
status_t KeyLayoutMap::Parser::parse() {
    while (!mTokenizer->isEof()) {
#if DEBUG_PARSER
        ALOGD("Parsing %s: '%s'.", mTokenizer->getLocation().string(),
                mTokenizer->peekRemainderOfLine().string());
#endif
 
        mTokenizer->skipDelimiters(WHITESPACE);
 
        if (!mTokenizer->isEol() && mTokenizer->peekChar() != '#') {
            String8 keywordToken = mTokenizer->nextToken(WHITESPACE);
            if (keywordToken == "key") {
                mTokenizer->skipDelimiters(WHITESPACE);
                status_t status = parseKey();
                if (status) return status;
            } else if (keywordToken == "axis") {
                mTokenizer->skipDelimiters(WHITESPACE);
                status_t status = parseAxis();
                if (status) return status;
            } else {
                ALOGE("%s: Expected keyword, got '%s'.", mTokenizer->getLocation().string(),
                        keywordToken.string());
                return BAD_VALUE;
            }
 
            mTokenizer->skipDelimiters(WHITESPACE);
            if (!mTokenizer->isEol() && mTokenizer->peekChar() != '#') {
                ALOGE("%s: Expected end of line or trailing comment, got '%s'.",
                        mTokenizer->getLocation().string(),
                        mTokenizer->peekRemainderOfLine().string());
                return BAD_VALUE;
            }
        }
 
        mTokenizer->nextLine();
    }
    return NO_ERROR;
}