android输入设备配置文件加载过程分析

最新推荐文章于 2024-04-02 17:42:01 发布

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最新推荐文章于 2024-04-02 17:42:01 发布 · 2k 阅读

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本文深入探讨了Android系统中输入设备配置文件的加载过程，从frameworks/base/libs/ui/Keyboard.cpp到frameworks/base/services/input/InputReader.cpp，详细解析了相关源码和流程。

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frameworks/base/libs/ui/Keyboard.cpp:

String8 KeyMap::getPath(const InputDeviceIdentifier& deviceIdentifier,
        const String8& name, InputDeviceConfigurationFileType type) {
    return name.isEmpty()
            ? getInputDeviceConfigurationFilePathByDeviceIdentifier(deviceIdentifier, type)//根据设备配置信息到配置文件目录查找文件
            : getInputDeviceConfigurationFilePathByName(name, type);//直接根据设备名称搜索文件
}

status_t KeyMap::loadKeyLayout(const InputDeviceIdentifier& deviceIdentifier,
        const String8& name) {
    String8 path(getPath(deviceIdentifier, name,//此处有调用
            INPUT_DEVICE_CONFIGURATION_FILE_TYPE_KEY_LAYOUT));
    if (path.isEmpty()) {
        return NAME_NOT_FOUND;
    }

    KeyLayoutMap* map;
    status_t status = KeyLayoutMap::load(path, &map);
    if (status) {
        return status;
    }

    keyLayoutFile.setTo(path);
    keyLayoutMap = map;
    return OK;
}

status_t KeyMap::loadKeyCharacterMap(const InputDeviceIdentifier& deviceIdentifier,
        const String8& name) {
    String8 path(getPath(deviceIdentifier, name,//此处也有调用
            INPUT_DEVICE_CONFIGURATION_FILE_TYPE_KEY_CHARACTER_MAP));
    if (path.isEmpty()) {
        return NAME_NOT_FOUND;
    }

    KeyCharacterMap* map;
    status_t status = KeyCharacterMap::load(path, &map);
    if (status) {
        return status;
    }

    keyCharacterMapFile.setTo(path);
    keyCharacterMap = map;
    return OK;
}

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"),//查看键盘是否有指定布局文件
                keyLayoutName)) {
            status_t status = loadKeyLayout(deviceIdenfifier, keyLayoutName);
            if (status == NAME_NOT_FOUND) {
                LOGE("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"),//查看是否指定键盘字符映射文件
                keyCharacterMapName)) {
            status_t status = loadKeyCharacterMap(deviceIdenfifier, keyCharacterMapName);
            if (status == NAME_NOT_FOUND) {
                LOGE("Configuration for keyboard device '%s' requested keyboard character "
                        "map '%s' but it was not found.",
                        deviceIdenfifier.name.string(), keyLayoutName.string());
            }
        }

        if (isComplete()) {//如果指定的文件
            return OK;
        }
    }

    // Try searching by device identifier.
    if (probeKeyMap(deviceIdenfifier, String8::empty())) {//按默认规则查找配置文件
        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"))) {//直接名称搜索Gerneric
        return OK;
    }

    // Try the Virtual key map as a last resort.
    if (