Uniform Data Structs (C/C++)
When to Use
Uniform data structs are provided to define data of common uniform data types. For example, the data struct for the system-defined home screen icon (whose uniform data type is OH_UdsAppItem) is provided to help you easily define the data.
Applications can directly use the uniform data structs in certain scenarios. For example, in the drag-and-drop operation across applications, you can write the data (encapsulated in a uniform struct) to be dragged to DragEvent. The target application (application requesting the data) reads the data from DragEvent and parses the data in the uniform data struct. Using uniform data structs for data interaction between applications effectively reduces the development workload in your application experience.
Basic Concepts
- UDS
A uniform data struct (UDS) defines the data of a certain type (specified by a UTD). Uniform data structs allow unified parsing standards to be used in data interaction, which minimizes the adaptation workload. Uniform data structs are used for data interaction across applications and devices, such as, the drag-and-drop operations.
Available APIs
For details about the APIs, see uds.h.
| API | Description |
|---|---|
| OH_UdmfData* OH_UdmfData_Create() | Creates an OH_UdmfData instance and a pointer to it. |
| OH_UdmfRecord* OH_UdmfRecord_Create() | Creates an OH_UdmfRecord instance and a pointer to it. |
| OH_UdsPlainText* OH_UdsPlainText_Create() | Creates an OH_UdsPlainText instance and a pointer to it. |
| int OH_UdmfRecord_GetPlainText(OH_UdmfRecord* pThis, OH_UdsPlainText* plainText) | Obtains OH_UdsPlainText data from an OH_UdmfRecord instance. |
| int OH_UdsPlainText_SetContent(OH_UdsPlainText* pThis, const char* content) | Sets the plaintext content for an OH_UdsPlainText instance. |
| int OH_UdmfRecord_AddPlainText(OH_UdmfRecord* pThis, OH_UdsPlainText* plainText) | Adds OH_UdsPlainText data to an OH_UdmfRecord instance. |
| int OH_UdmfData_AddRecord(OH_UdmfData* pThis, OH_UdmfRecord* record) | Adds OH_UdmfRecord data to an OH_UdmfData instance. |
| OH_UdsFileUri* OH_UdsFileUri_Create() | Creates an OH_UdsFileUri instance and a pointer to it. |
| int OH_UdsFileUri_SetFileUri(OH_UdsFileUri* pThis, const char* fileUri) | Sets the URI information for an OH_UdsFileUri instance. |
| int OH_UdsFileUri_SetFileType(OH_UdsFileUri* pThis, const char* fileType) | Sets the file type for an OH_UdsFileUri instance. |
| int OH_UdmfRecord_AddFileUri(OH_UdmfRecord* pThis, OH_UdsFileUri* fileUri) | Adds OH_UdsFileUri data to an OH_UdmfData instance. |
| int OH_Udmf_SetUnifiedData(Udmf_Intention intention, OH_UdmfData* unifiedData,char* key, unsigned int keyLen) | Sets an OH_UdmfData instance in the UDMF database. |
| void OH_UdsPlainText_Destroy(OH_UdsPlainText* pThis) | Destroys an OH_UdsPlainText instance. |
| void OH_UdmfData_Destroy(OH_UdmfData* pThis) | Destroys an OH_UdmfData instance. |
| void OH_UdsFileUri_Destroy(OH_UdsFileUri* pThis) | Destroys an OH_UdsFileUri instance. |
Adding Dynamic Link Libraries
Add the following libraries to CMakeLists.txt.
libudmf.so, libhilog_ndk.z.so
Including Header Files
#include <database/udmf/uds.h>
#include <database/udmf/udmf.h>
#include <database/udmf/udmf_meta.h>
#include <hilog/log.h>
#undef LOG_TAG
#define LOG_TAG "MY_LOG"
Using the PlainText Data Struct
- Create a pointer to an PlainText object.
- Set content for the PlainText object.
- Obtain data.
- Destroy all the pointers created.
// 1. Create a pointer to an PlainText object.
OH_UdmfRecord *plainTextRecord = OH_UdmfRecord_Create();
OH_UdsPlainText *plainText = OH_UdsPlainText_Create();
char content[] = "hello world";
// 2. Set content for the PlainText object.
OH_UdsPlainText_SetContent(plainText, content);
OH_UdmfRecord_AddPlainText(plainTextRecord, plainText);
// 3. Obtain PlainText data.
OH_UdsPlainText *plainText2 = OH_UdsPlainText_Create();
OH_UdmfRecord_GetPlainText(plainTextRecord, plainText2);
const char *content2 = OH_UdsPlainText_GetContent(plainText2);
OH_LOG_INFO(LOG_APP, "content = %{public}s.", content2);
// 4. Destroy all the pointers created.
OH_UdsPlainText_Destroy(plainText);
OH_UdmfRecord_Destroy(plainTextRecord);
OH_UdsPlainText_Destroy(plainText2);
Using the fileUri Data Struct
- Create a struct for the fileUri data.
- Set the URL and description for the fileUri.
- Create an OH_UdmfRecord object and set fileUri data to it.
- Obtain the fileUri data.
- Destroy all the pointers created.
// 1. Create a struct for the fileUri data.
const char *uri = "https://xxx/xx/xx.jpg";
OH_UdsFileUri *fileUri = OH_UdsFileUri_Create();
// 2. Set the URL and description for the fileUri.
OH_UdsFileUri_SetFileUri(fileUri, uri);
OH_UdsFileUri_SetFileType(fileUri, UDMF_META_IMAGE);
// 3. Create an OH_UdmfRecord object and set fileUri data to it.
OH_UdmfRecord *record = OH_UdmfRecord_Create();
OH_UdmfRecord_AddFileUri(record, fileUri);
// 4. Obtain the fileUri data.
OH_UdsFileUri *fileUri1 = OH_UdsFileUri_Create();
OH_UdmfRecord_GetFileUri(record, fileUri1);
const char *fileUriStr = OH_UdsFileUri_GetFileUri(fileUri1);
OH_LOG_INFO(LOG_APP, "fileUri1 = %{public}s.", fileUriStr);
// 5. Destroy all the pointers created.
OH_UdsFileUri_Destroy(fileUri);
OH_UdmfRecord_Destroy(record);
OH_UdsFileUri_Destroy(fileUri1);