天行健 君子當自強而不息

 

本篇是 使用DirectInput進行交互（1）的續篇。

設置數據格式

每種設備都有一種用于讀取數據的特定數據格式，需要考慮的東西也很多，包括鍵、鼠標按鍵、軸等。因此要使程序從設備讀取數據，首先必須告訴 DirectInput讀取這種數據所采用的格式。通過 IDirectInputDevice8::SetDataFormat函數即可滿足上述要求。

Sets the data format for the DirectInput device.

HRESULT SetDataFormat(
  LPCDIDATAFORMAT lpdf
);

Parameters

lpdf

Address of a structure that describes the format of the data that the DirectInputDevice should return. An application can define its own DIDATAFORMAT structure or use one of the following predefined global variables:

• c_dfDIKeyboard
• c_dfDIMouse
• c_dfDIMouse2
• c_dfDIJoystick
• c_dfDIJoystick2

Return Values

If the method succeeds, the return value is DI_OK. If the method fails, the return value can be one of the following error values: DIERR_ACQUIRED, DIERR_INVALIDPARAM, DIERR_NOTINITIALIZED.

Remarks

The data format must be set before the device can be acquired by using the IDirectInputDevice8 Interface method. It is necessary to set the data format only once. The data format cannot be changed while the device is acquired.

If the application is using action mapping, the data format is set instead by the call to IDirectInputDevice8::SetActionMap.

SetDataFormat函數只有一個參數，這個參數是一個指向DIDATAFORMAT結構體的指針，此結構體的定義如下：

Describes a device's data format. This structure is used with the IDirectInputDevice8::SetDataFormat method.

typedef struct DIDATAFORMAT {
    DWORD dwSize;
    DWORD dwObjSize;
    DWORD dwFlags;
    DWORD dwDataSize;
    DWORD dwNumObjs;
    LPDIOBJECTDATAFORMAT rgodf;
} DIDATAFORMAT, *LPDIDATAFORMAT;

Members

dwSize

Size of this structure, in bytes.

dwObjSize

Size of the DIOBJECTDATAFORMAT structure, in bytes.

dwFlags

Flags describing other attributes of the data format. This value can be one of the following:

DIDF_ABSAXIS

The axes are in absolute mode. Setting this flag in the data format is equivalent to manually setting the axis mode property, using the IDirectInputDevice8::SetProperty method. This cannot be combined with DIDF_RELAXIS flag.

DIDF_RELAXIS

The axes are in relative mode. Setting this flag in the data format is equivalent to manually setting the axis mode property using the IDirectInputDevice8::SetProperty method. This cannot be combined with the DIDF_ABSAXIS flag.

dwDataSize

Size of a data packet returned by the device, in bytes. This value must be a multiple of 4 and must exceed the largest offset value for an object's data within the data packet.

dwNumObjs

Number of objects in the rgodf array.

rgodf

Address to an array of DIOBJECTDATAFORMAT structures. Each structure describes how one object's data should be reported in the device data. Typical errors include placing two pieces of information in the same location and placing one piece of information in more than one location.

Remarks

Applications do not typically need to create a DIDATAFORMAT structure. An application can use one of the predefined global data format variables, c_dfDIMouse, c_dfDIMouse2, c_dfDIKeyboard, c_dfDIJoystick, or c_dfDIJoystick2.

Applications that need to create a DIDATAFORMAT structure must first call IDirectInputDevice8::EnumObjects to determine the available objects for the current device. This is because the IDirectInputDevice8::SetDataFormat method will return DIERR_INVALIDPARAM if an an object is described in the DIDATAFORMAT structure but does not exist on the current device.

The following code example sets a data format for a device that has an X-axis and a Y-axis:

 

結構體中的rgodf是一個指向DIOBJECTDATAFORMAT結構體的指針，其定義如下：

Describes a device object's data format for use with the IDirectInputDevice8::SetDataFormat method.

typedef struct DIOBJECTDATAFORMAT {
    CONST GUID * pguid;
    DWORD dwOfs;
    DWORD dwType;
    DWORD dwFlags;
} DIOBJECTDATAFORMAT, *LPDIOBJECTDATAFORMAT;

Members

pguid

Unique identifier for the axis, button, or other input source. When requesting a data format, making this member NULL indicates that any type of object is permissible.

dwOfs

Offset within the data packet where the data for the input source is stored. This value must be a multiple of 4 for DWORD size data, such as axes. It can be byte-aligned for buttons.

dwType

Device type that describes the object. It is a combination of the following flags describing the object type (axis, button, and so forth) and containing the object-instance number in the middle 16 bits. When requesting a data format, the instance portion must be set to DIDFT_ANYINSTANCE to indicate that any instance is permissible, or to DIDFT_MAKEINSTANCE(n) to restrict the request to instance n. See the examples under Remarks.

DIDFT_ABSAXIS

The object selected by the IDirectInputDevice8::SetDataFormat method must be an absolute axis.

DIDFT_AXIS

The object selected by the IDirectInputDevice8::SetDataFormat method must be an absolute or relative axis.

DIDFT_BUTTON

The object selected by the IDirectInputDevice8::SetDataFormat method must be a push button or a toggle button.

DIDFT_FFACTUATOR

The object selected by the IDirectInputDevice8::SetDataFormat method must contain a force-feedback actuator; in other words, it must be possible to apply forces to the object.

DIDFT_FFEFFECTTRIGGER

The object selected by the IDirectInputDevice8::SetDataFormat method must be a valid force-feedback effect trigger.

DIDFT_POV

The object selected by the IDirectInputDevice8::SetDataFormat method must be a point-of-view controller.

DIDFT_PSHBUTTON

The object selected by the IDirectInputDevice8::SetDataFormat method must be a push button.

DIDFT_RELAXIS

The object selected by IDirectInputDevice8::SetDataFormat must be a relative axis.

DIDFT_TGLBUTTON

The object selected by IDirectInputDevice8::SetDataFormat must be a toggle button.

DIDFT_VENDORDEFINED

The object selected by IDirectInputDevice8::SetDataFormat must be of a type defined by the manufacturer.

dwFlags

Zero or more of the following values:

DIDOI_ASPECTACCEL

The object selected by IDirectInputDevice8::SetDataFormat must report acceleration information.

DIDOI_ASPECTFORCE

The object selected by IDirectInputDevice8::SetDataFormat must report force information.

DIDOI_ASPECTPOSITION

The object selected by IDirectInputDevice8::SetDataFormat must report position information.

DIDOI_ASPECTVELOCITY

The object selected by IDirectInputDevice8::SetDataFormat must report velocity information.

Remarks

A data format is made up of several DIOBJECTDATAFORMAT structures, one for each object (axis, button, and so on). An array of these structures is contained in the DIDATAFORMAT structure that is passed to IDirectInputDevice8::SetDataFormat. An application typically does not need to create an array of DIOBJECTDATAFORMAT structures; rather, it can use one of the predefined data formats, c_dfDIMouse, c_dfDIMouse2, c_dfDIKeyboard, c_dfDIJoystick, or c_dfDIJoystick2, which have predefined settings for DIOBJECTDATAFORMAT.

The following object data format specifies that DirectInput should choose the first available axis and report its value in the DWORD at offset 4 in the device data.

 

The following object data format specifies that the x-axis of the device should be stored in the DWORD at offset 12 in the device data. If the device has more than one x-axis, the first available one should be selected.

 

The following object data format specifies that DirectInput should choose the first available button and report its value in the high bit of the byte at offset 16 in the device data.

 

The following object data format specifies that button 0 of the device should be reported as the high bit of the byte stored at offset 18 in the device data.

If the device does not have a button 0, the attempt to set this data format fails.

 

來看看宏DIOBJECTDATAFORMAT的定義：

The DIDFT_MAKEINSTANCE macro creates an instance identifier of a device object for packing in the dwType member of the DIOBJECTDATAFORMAT structure.

#define DIDFT_MAKEINSTANCE(n) ((WORD)(n) << 8)

Parameters

n

Type is WORD. Instance of the object; for example, 1 for button 1 of a mouse.

設置協作級別

首先必須面對一個事實，那就是每個程序都會使用許多輸入設備。幾乎每個程序都會使用鍵盤和鼠標，同時某些程序還會使用游戲桿。在處理的時候，必須同其他可能仍在運行的應用程序共享對這些設備的訪問，或者應用程序獨占對設備的所有訪問，這樣除非該應用程序結束了對設備的訪問，否則就不允許其他應用程序控制這些設備。

設置協作級別的函數是IDirectInputDevice8::SetCooperativeLevel。

Establishes the cooperative level for this instance of the device. The cooperative level determines how this instance of the device interacts with other instances of the device and the rest of the system.

HRESULT SetCooperativeLevel(
  HWND hwnd,
  DWORD dwFlags
);

Parameters

hwnd

Window handle to be associated with the device. This parameter must be a valid top-level window handle that belongs to the process. The window associated with the device must not be destroyed while it is still active in a DirectInput device.

dwFlags

Flags that describe the cooperative level associated with the device. The following flags are defined:

DISCL_BACKGROUND

The application requires background access. If background access is granted, the device can be acquired at any time, even when the associated window is not the active window.

DISCL_EXCLUSIVE

The application requires exclusive access. If exclusive access is granted, no other instance of the device can obtain exclusive access to the device while it is acquired. However, nonexclusive access to the device is always permitted, even if another application has obtained exclusive access. An application that acquires the mouse or keyboard device in exclusive mode should always unacquire the devices when it receives WM_ENTERSIZEMOVE and WM_ENTERMENULOOP messages. Otherwise, the user cannot manipulate the menu or move and resize the window.

DISCL_FOREGROUND

The application requires foreground access. If foreground access is granted, the device is automatically unacquired when the associated window moves to the background.

DISCL_NONEXCLUSIVE

The application requires nonexclusive access. Access to the device does not interfere with other applications that are accessing the same device.

DISCL_NOWINKEY

Disable the Windows logo key. Setting this flag ensures that the user cannot inadvertently break out of the application. Note, however, that DISCL_NOWINKEY has no effect when the default action mapping user interface (UI) is displayed, and the Windows logo key will operate normally as long as that UI is present.

Return Values

If the method succeeds, the return value is DI_OK. If the method fails, the return value can be one of the following error values: DIERR_INVALIDPARAM, DIERR_NOTINITIALIZED, E_HANDLE.

Remarks

Applications must specify either DISCL_FOREGROUND or DISCL_BACKGROUND; it is an error to specify both or neither. Similarly, applications must specify either DISCL_EXCLUSIVE or DISCL_NONEXCLUSIVE.

If the system mouse is acquired in exclusive mode, the pointer is removed from the screen until the device is unacquired. This applies only to a mouse created by passing GUID_SysMouse to IDirectInput8::CreateDevice.

Applications that select the background exclusive mode cooperative level are not guaranteed to retain access to the device if another application requests exclusive access. When a background exclusive mode application loses access, calls to DirectInput device methods will fail and return DIERR_NOTACQUIRED. The application can regain access to the device by manually unacquiring the device and reaquiring it.

Applications must call this method before acquiring the device by using the IDirectInputDevice8 Interface method.

設置特殊屬性

設置設備的特殊屬性，包括軸模式（axis mode），緩沖區（buffering）以及最大最小范圍。

對于軸模式，有兩個選擇：相對和絕對。絕對模式基于一個中心坐標來報告坐標。位于這個點左邊或上面的值都報告成負值，同時位于這個點右邊或下面的值都報告成正值。相對坐標就是當前位置同上一個位置之間的距離差。

至于緩沖區，可以設置緩沖到數據緩沖區中的數據量。這樣就可以隨意讀取設備的數據而無需擔心會遺漏數據。當情況比較簡單的時候，使用緩沖區的數據對游戲開發而言就沒有多大必要了。

最后一個特殊性屬性是設備的最小和最大范圍設置。舉例來說，將游戲桿推動到最左邊就會產生最小值，而推動到最右邊就會產生最大值。這兩邊產生何種值取決于具體的設置，只有游戲桿才會涉及到最小和最大范圍設置。

用于設置特殊屬性的函數是 IDirectInputDevice8::SetProperty。

Sets properties that define the device behavior. These properties include input buffer size and axis mode.

HRESULT SetProperty(
  REFGUID rguidProp,
  LPCDIPROPHEADER pdiph
);

Parameters

rguidProp

Reference to (C++) or address of (C) the globally unique identifier (GUID) identifying the property to be set. This can be one of the predefined values, or a pointer to a GUID that identifies the property. The following property values are predefined for an input device:

DIPROP_APPDATA

Sets the application-defined value associated with an in-game action, as a DIPROPPOINTER.

DIPROP_AUTOCENTER

Specifies whether device objects are self centering. This setting applies to the entire device, rather than to any particular object, so the dwHow member of the associated DIPROPDWORD structure must be DIPH_DEVICE.

The dwData member can be one of the following values.

DIPROPAUTOCENTER_OFF: The device should not automatically center when the user releases the device. An application that uses force feedback should disable autocentering before playing effects.

DIPROPAUTOCENTER_ON: The device should automatically center when the user releases the device.

Not all devices support the autocenter property.

DIPROP_AXISMODE

Sets the axis mode. The value being set (DIPROPAXISMODE_ABS or DIPROPAXISMODE_REL) must be specified in the dwData member of the associated DIPROPDWORD structure. See the description of the pdiph parameter for more information. This setting applies to the entire device, so the dwHow member of the associated DIPROPDWORD structure must be set to DIPH_DEVICE.

DIPROP_BUFFERSIZE

Sets the input buffer size. The value being set must be specified in the dwData member of the associated DIPROPDWORD structure. See Remarks. This setting applies to the entire device, so the dwHow member of the associated DIPROPDWORD structure must be set to DIPH_DEVICE.

DIPROP_CALIBRATION

Predefined property that allows the application to access the information that DirectInput uses to manipulate axes that require calibration. This property exists primarily for applications of the control panel type. Normal applications should not need to deal with calibration information.

You can access the calibration mode property for an axis by setting the dwHow member of the DIPROPHEADER structure to DIPH_BYID or to DIPH_BYOFFSET and setting the dwObj member to the object ID or offset, respectively.

Control panel applications that set new calibration data must also invoke the IDirectInputJoyConfig::SendNotify method to notify other applications of the change in calibration. For more information about IDirectInputJoyConfig::SendNotify, see the DirectX Driver Development Kit (DDK).

DIPROP_CALIBRATIONMODE

Enables the application to specify whether DirectInput should retrieve calibrated or uncalibrated data from an axis. By default, DirectInput retrieves calibrated data.

Setting the calibration mode for the entire device is equivalent to setting it for each axis individually.

The dwData member of the DIPROPDWORD structure can be one of the following values:

DIPROPCALIBRATIONMODE_COOKED: DirectInput should return data after applying calibration information. This is the default mode.

DIPROPCALIBRATIONMODE_RAW: DirectInput should return raw, uncalibrated data. This mode is typically used only by applications of the control panel type. Note that raw data might include negative values.

Setting a device into raw mode causes the dead zone, saturation, and range settings to be ignored.

DIPROP_CPOINTS

This property is unsupported. Sets calibration points used for the adjustment of incoming raw data. The values being set must be specified as CPOINT types in the cp array of the associated DIPROPCPOINTS structure. This setting applies to individual device objects, so the dwHow member of the associated DIPROPHEADER structure must be set to either DIPH_BYID or DIPH_BYOFFSET.

DIPROP_DEADZONE

Sets the value for the dead zone of a joystick, in the range from 0 through 10,000, where 0 indicates that there is no dead zone, 5,000 indicates that the dead zone extends over 50 percent of the physical range of the axis on both sides of center, and 10,000 indicates that the entire physical range of the axis is dead. When the axis is within the dead zone, it is reported as being at the center of its range. This setting can be applied to either the entire device or to a specific axis.

DIPROP_FFGAIN

Sets the gain for the device. This setting applies to the entire device, rather than to any particular object, so the dwHow member of the associated DIPROPDWORD structure must be DIPH_DEVICE.

The dwData member contains a gain value that is applied to all effects created on the device. The value is an integer in the range from 0 through 10,000, specifying the amount by which effect magnitudes should be scaled for the device. For example, a value of 10,000 indicates that all effect magnitudes are to be taken at face value. A value of 9,000 indicates that all effect magnitudes are to be reduced to 90 percent of their nominal magnitudes.

DirectInput always checks the gain value before setting the gain property. If the gain is outside of the range (less than zero or greater than 10,000), IDirectInputDevice8::SetProperty will return DIERR_INVALIDPARAM. Otherwise, if successful, it will return DI_OK, even if the device does not support force feedback.

Setting a gain value is useful when an application wants to scale down the strength of all force-feedback effects uniformly, based on user preferences.

Unlike other properties, the gain can be set when the device is in an acquired state.

DIPROP_INSTANCENAME

This property exists for advanced applications that want to change the friendly instance name of a device (as returned in the tszInstanceName member of the DIDEVICEINSTANCE structure) to distinguish it from similar devices that are plugged in simultaneously. Most applications should have no need to change the friendly name.

This setting applies to the entire device, so the dwHow member of the associated DIPROPDWORD structure must be set to DIPH_DEVICE.

The pdiph parameter must be a pointer to the diph member of a DIPROPSTRING structure.

DIPROP_PRODUCTNAME

This property exists for advanced applications that want to change the friendly product name of a device (as returned in the tszProductName member of the DIDEVICEINSTANCE structure) to distinguish it from similar devices which are plugged in simultaneously. Most applications should have no need to change the friendly name.

This setting applies to the entire device, so the dwHow member of the associated DIPROPDWORD structure must be set to DIPH_DEVICE.

The pdiph parameter must be a pointer to the diph member of a DIPROPSTRING structure.

Setting the product name is only useful for changing the user-defined name of an analog joystick on Microsoft Windows 98, Windows 2000, and Windows Millennium Edition (Windows Me) computers. In other cases, attempting to set this property will still return DI_OK. However, the name is not stored in a location used by IDirectInputDevice8::GetProperty.

DIPROP_RANGE

Sets the range of values an object can possibly report. The minimum and maximum values are taken from the lmin and lmax members of the associated DIPROPRANGE structure.

For some devices, this is a read-only property.

You cannot set a reverse range; lmax must be greater than lmin.

DIPROP_SATURATION

Sets the value for the saturation zones of a joystick, in the range from 0 through 10,000. The saturation level is the point at which the axis is considered to be at its most extreme position. For example, if the saturation level is set to 9,500, the axis reaches the extreme of its range when it has moved 95 percent of the physical distance from its center position (or from the dead zone). This setting can be applied to either the entire device or a specific axis.

pdiph

Address of the DIPROPHEADER structure contained within the type-specific property structure.

Return Values

If the method succeeds, the return value is DI_OK or DI_PROPNOEFFECT. If the method fails, the return value can be one of the following error values: DIERR_INVALIDPARAM DIERR_NOTINITIALIZED, DIERR_OBJECTNOTFOUND, DIERR_UNSUPPORTED.

Remarks

The buffer size determines the amount of data that the buffer can hold between calls to the IDirectInputDevice8::GetDeviceData method before data is lost. This value may be set to 0 to indicate that the application does not read buffered data from the device. If the buffer size in the dwData member of the DIPROPDWORD structure is too large for the device to support it, then the largest possible buffer size is set.

在調用SetProperty函數時始終要使用的DIPROPHEADER結構體定義如下：

Serves as a header for all property structures.

typedef struct DIPROPHEADER {
    DWORD dwSize;
    DWORD dwHeaderSize;
    DWORD dwObj;
    DWORD dwHow;
} DIPROPHEADER, *LPDIPROPHEADER;

Members

dwSize

Size of the enclosing structure. This member must be initialized before the structure is used.

dwHeaderSize

Size of the DIPROPHEADER structure.

dwObj

Object for which the property is to be accessed. The value set for this member depends on the value specified in the dwHow member.

dwHow

Value that specifies how the dwObj member should be interpreted. This value can be one of the following:

DIPH_DEVICE

The dwObj member must be 0.

DIPH_BYOFFSET

The dwObj member is the offset into the current data format of the object whose property is being accessed.

DIPH_BYUSAGE

The dwObj member is the human interface device usage page and usage values in packed form.

DIPH_BYID

The dwObj member is the object type/instance identifier. This identifier is returned in the dwType member of the DIDEVICEOBJECTINSTANCE structure returned from a previous call to the IDirectInputDevice8::EnumObjects member.

獲得設備

在使用任何設備之前，首先必須獲得設備。只有獲得了設備才能確保程序能夠訪問設備，以及同其他程序共享訪問還是完全控制設備。要注意的是其他程序可能會爭奪并搶走對設備的控制權，要補救這種情況就必須重新獲得設備。何時必須獲得設備？第一種情況就是在創建接口的時候，原因在于使用設備之前必須首先獲得它。另一種情況就是當另一個程序搶走了對設備的控制，同時 DirectInput通知了程序時。

調用IDirectInputDevice8::Acquire函數即可獲得設備。

Obtains access to the input device.

HRESULT Acquire();

Parameters

None.

Return Values

If the method succeeds, the return value is DI_OK, or S_FALSE if the device was already acquired. If the method fails, the return value can be one of the following error values: DIERR_INVALIDPARAM, DIERR_NOTINITIALIZED, DIERR_OTHERAPPHASPRIO.

Remarks

Before a device can be acquired, a data format must be set by using the IDirectInputDevice8::SetDataFormat method or IDirectInputDevice8::SetActionMap method. If the data format has not been set, IDirectInputDevice8 Interface returns DIERR_INVALIDPARAM.

Devices must be acquired before calling the IDirectInputDevice8::GetDeviceState or IDirectInputDevice8::GetDeviceData methods for that device.

Device acquisition does not use a reference count. Therefore, if an application calls the IDirectInputDevice8 Interface method twice, then calls the IDirectInputDevice8 Interface method once, the device is unacquired.

If IDirectInputDevice8::BuildActionMap succeeds but no actions have been mapped, a subsequent call to IDirectInputDevice8::SetActionMap will return DI_OK but a call to IDirectInputDevice8 Interface will fail with DIERR_INVALIDPARAM.

輪詢設備

輪詢可以準備設備并在合適的情況下讀取設備數據，因為數據可能具有臨界時間。游戲桿就是這樣的設備，要從設備讀取數據，計算機需要發送一個電子脈沖給它。雖然輪詢對于游戲桿輸入而言是必須的，但是對鍵盤或鼠標來說卻并不需要輪詢。

輪詢設備需要使用IDirectInputDevice8::Poll函數。

Retrieves data from polled objects on a DirectInput device. If the device does not require polling, calling this method has no effect. If a device that requires polling is not polled periodically, no new data is received from the device. Calling this method causes DirectInput to update the device state, generate input events (if buffered data is enabled), and set notification events (if notification is enabled).

HRESULT Poll();

Parameters

None.

Return Values

If the method succeeds, the return value is DI_OK, or DI_NOEFFECT if the device does not require polling. If the method fails, the return value can be one of the following error values: DIERR_INPUTLOST, DIERR_NOTACQUIRED, DIERR_NOTINITIALIZED.

Remarks

Before a device data can be polled, the data format must be set by using the IDirectInputDevice8::SetDataFormat or IDirectInputDevice8::SetActionMap method, and the device must be acquired by using the IDirectInputDevice8 Interface method.

讀取數據

經過以上的步驟，就剩下最后一步了，那就是使用 IDirectInputDevice8::GetDeviceState函數讀取設備數據。為了存儲設備的信息，必須傳遞一個數據緩沖區給此函數，這樣程序才能使用設備的信息，每種設備的數據各不相同。

Retrieves immediate data from the device.

HRESULT GetDeviceState(
  DWORD cbData,
  LPVOID lpvData
);

Parameters

cbData

Size of the buffer in the lpvData parameter, in bytes.

lpvData

Address of a structure that receives the current state of the device. The format of the data is established by a prior call to the IDirectInputDevice8::SetDataFormat method.

Return Values

If the method succeeds, the return value is DI_OK. If the method fails, the return value can be one of the following error values: DIERR_INPUTLOST, DIERR_INVALIDPARAM, DIERR_NOTACQUIRED, DIERR_NOTINITIALIZED, E_PENDING.

Remarks

Before device data can be obtained, set the cooperative level by using the IDirectInputDevice8::SetCooperativeLevel method, then set the data format by using IDirectInputDevice8::SetDataFormat, and acquire the device by using the IDirectInputDevice8 Interface method.

The five predefined data formats require corresponding device state structures according to the following table:

Data format	State structure
c_dfDIMouse	DIMOUSESTATE
c_dfDIMouse2	DIMOUSESTATE2
c_dfDIKeyboard	array of 256 bytes
c_dfDIJoystick	DIJOYSTATE
c_dfDIJoystick2	DIJOYSTATE2

For example, if you passed the c_dfDIMouse format to the IDirectInputDevice8::SetDataFormat method, you must pass a DIMOUSESTATE structure to the IDirectInputDevice8::GetDeviceState method.

無論是哪種設備，下面的代碼都能讀取其數據。它們考慮了丟失設備并在適當的時刻重新獲得設備的情況，必須傳遞一個指向緩沖區的指針給下面這個函數，緩沖區的大小要能夠保存設備信息以及讀取的數據量。

使用DirectInput處理鍵盤

如果調用成功，下面的初始化函數則返回一個指向新創建的IDirectInputDevice8對象的指針；反之當函數調用失敗時，返回NULL。只需給此函數傳遞父窗口的句柄和與定義的DirectInput對象即可。
 
要存儲鍵盤數據，必須使用一個大小為256字節的數組，每個字節存儲一個鍵的狀態，這樣就給出了保存256個鍵的空間。每個字節存儲鍵當前的狀態信息，即鍵是否被按下。要得到鍵的狀態，就要檢查高位（字節），如果置位，鍵就被按下；如果清零，鍵就未被按下。在DirectInput 中，每個鍵都有一個屬于自己的宏，這些宏都以DIK_為前綴。A鍵定義為DIK_A，ESC為DIK_ESCAPE等。查閱DX SDK或DInput.h可以得到其他鍵的宏。

點擊下載源碼和工程

完整源碼如下：
 
運行效果：



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