1# @ohos.app.ability.DriverExtensionAbility (Driver Extension Ability) 2 3The **DriverExtensionAbility** module provides the ExtensionAbility related to drivers. It provides lifecycle callbacks to be invoked when a driver is created, destroyed, connected, or disconnected. 4 5> **NOTE** 6> 7> The initial APIs of this module are supported since API version 10. Newly added APIs will be marked with a superscript to indicate their earliest API version. 8> The APIs of this module can be used only in the stage model. 9 10## Modules to Import 11 12```ts 13import { DriverExtensionAbility } from '@kit.DriverDevelopmentKit'; 14``` 15 16## Attributes 17 18**System capability**: SystemCapability.Driver.ExternalDevice 19 20 21| Name| Type| Readable| Writable| Description| 22| -------- | -------- | -------- | -------- | -------- | 23| context | [DriverExtensionContext](js-apis-inner-application-driverExtensionContext.md) | Yes| No| Context of the **DriverExtension**. This context is inherited from **ExtensionContext**.| 24 25 26## DriverExtensionAbility.onInit 27 28onInit(want: Want): void; 29 30Called when a DriverExtensionAbility is created to initialize the service logic. 31 32**System capability**: SystemCapability.Driver.ExternalDevice 33 34**Parameters** 35 36| Name| Type| Mandatory| Description| 37| -------- | -------- | -------- | -------- | 38| want | [Want](../apis-ability-kit/js-apis-app-ability-want.md) | Yes| Want information related to this DriverExtensionAbility, including the ability name and bundle name.| 39 40**Example** 41 42 ```ts 43 import { DriverExtensionAbility } from '@kit.DriverDevelopmentKit'; 44 import { Want } from '@kit.AbilityKit'; 45 class DriverExt extends DriverExtensionAbility { 46 onInit(want : Want) { 47 console.log('onInit, want: ${want.abilityName}'); 48 } 49 } 50 ``` 51 52 53## DriverExtensionAbility.onRelease 54 55onRelease(): void; 56 57Called when this DriverExtensionAbility is destroyed to clear resources. 58 59**System capability**: SystemCapability.Driver.ExternalDevice 60 61**Example** 62 63 ```ts 64 class DriverExt extends DriverExtensionAbility { 65 onRelease() { 66 console.log('onRelease'); 67 } 68 } 69 ``` 70 71 72## DriverExtensionAbility.onConnect 73 74onConnect(want: Want): rpc.RemoteObject | Promise<rpc.RemoteObject>; 75 76Called following **onCreate()** when a DriverExtensionAbility is started by calling **connectAbility()**. A **RemoteObject** object is returned for communication between the server and client. 77 78**System capability**: SystemCapability.Driver.ExternalDevice 79 80**Parameters** 81 82| Name| Type| Mandatory| Description| 83| -------- | -------- | -------- | -------- | 84| want | [Want](../apis-ability-kit/js-apis-app-ability-want.md)| Yes| Want information related to this DriverExtensionAbility, including the ability name and bundle name.| 85 86**Return value** 87 88| Type| Description| 89| -------- | -------- | 90| rpc.RemoteObject | A **RemoteObject** object used for communication between the server and client.| 91 92**Example** 93 94 ```ts 95 import { DriverExtensionAbility } from '@kit.DriverDevelopmentKit'; 96 import { rpc } from '@kit.IPCKit'; 97 import { Want } from '@kit.AbilityKit'; 98 class StubTest extends rpc.RemoteObject{ 99 constructor(des : string) { 100 super(des); 101 } 102 onRemoteMessageRequest(code : number, data : rpc.MessageSequence, reply : rpc.MessageSequence, option : rpc.MessageOption) { 103 // This interface must be overridden. 104 return true; 105 } 106 } 107 class DriverExt extends DriverExtensionAbility { 108 onConnect(want : Want) { 109 console.log('onConnect , want: ${want.abilityName}'); 110 return new StubTest('test'); 111 } 112 } 113 ``` 114 115If the returned **RemoteObject** object depends on an asynchronous API, you can use the asynchronous lifecycle. 116 117 ```ts 118 import { DriverExtensionAbility } from '@kit.DriverDevelopmentKit'; 119 import { rpc } from '@kit.IPCKit'; 120 import { Want } from '@kit.AbilityKit'; 121 class StubTest extends rpc.RemoteObject{ 122 constructor(des : string) { 123 super(des); 124 } 125 onRemoteMessageRequest(code : number, data : rpc.MessageSequence, reply : rpc.MessageSequence, option : rpc.MessageOption) { 126 // This interface must be overridden. 127 return true; 128 } 129 } 130 async function getDescriptor() { 131 // Call the asynchronous function. 132 return "asyncTest" 133 } 134 class DriverExt extends DriverExtensionAbility { 135 async onConnect(want : Want) { 136 console.log(`onConnect , want: ${want.abilityName}`); 137 let descriptor = await getDescriptor(); 138 return new StubTest(descriptor); 139 } 140 } 141 ``` 142 143## DriverExtensionAbility.onDisconnect 144 145onDisconnect(want: Want): void | Promise\<void>; 146 147Called when a client is disconnected from this DriverExtensionAbility. 148 149**System capability**: SystemCapability.Driver.ExternalDevice 150 151**Parameters** 152 153| Name| Type| Mandatory| Description| 154| -------- | -------- | -------- | -------- | 155| want |[Want](../apis-ability-kit/js-apis-app-ability-want.md)| Yes| Want information related to this DriverExtensionAbility, including the ability name and bundle name.| 156 157**Example** 158 159 ```ts 160 import { DriverExtensionAbility } from '@kit.DriverDevelopmentKit'; 161 import { Want } from '@kit.AbilityKit'; 162 class DriverExt extends DriverExtensionAbility { 163 onDisconnect(want : Want) { 164 console.log('onDisconnect, want: ${want.abilityName}'); 165 } 166 } 167 ``` 168 169After the **onDisconnect** lifecycle callback is executed, the application may exit. As a result, the asynchronous function in **onDisconnect** may fail to be executed correctly, for example, asynchronously writing data to the database. The asynchronous lifecycle can be used to ensure that the subsequent lifecycle continues after the asynchronous **onDisconnect** is complete. 170 171 ```ts 172 import { DriverExtensionAbility } from '@kit.DriverDevelopmentKit'; 173 import { Want } from '@kit.AbilityKit'; 174 class DriverExt extends DriverExtensionAbility { 175 async onDisconnect(want : Want) { 176 console.log('onDisconnect, want: ${want.abilityName}'); 177 // Call the asynchronous function. 178 } 179 } 180 ``` 181 182 183## DriverExtensionAbility.onDump 184 185onDump(params: Array\<string>): Array\<string>; 186 187Dumps client information. 188 189**System capability**: SystemCapability.Driver.ExternalDevice 190 191**Parameters** 192 193| Name| Type| Mandatory| Description| 194| -------- | -------- | -------- | -------- | 195| params | Array\<string> | Yes| Parameters in the form of a command.| 196 197**Example** 198 199 ```ts 200 class DriverExt extends DriverExtensionAbility { 201 onDump(params : Array<string>) { 202 console.log(`dump, params: ${JSON.stringify(params)}`); 203 return ['params']; 204 } 205 } 206 ``` 207 208## DriverExtensionContext 209 210type DriverExtensionContext = _DriverExtensionContext; 211 212**DriverExtensionAbility** context. 213 214**System capability**: SystemCapability.Driver.ExternalDevice 215 216 217| Type| Description| 218| -------- | -------- | 219| _DriverExtensionContext | **DriverExtensionAbility** context, which is inherited from **ExtensionContext**. For details about how to use the context, see [DriverExtensionContext](js-apis-inner-application-driverExtensionContext.md).| 220