1# UIAbility Usage
2
3
4When using the [UIAbility](../reference/apis-ability-kit/js-apis-app-ability-uiAbility.md) component, you must specify a startup page and obtain the context, [UIAbilityContext](../reference/apis-ability-kit/js-apis-inner-application-uiAbilityContext.md).
5
6
7## Specifying the Startup Page of UIAbility
8
9If no startup page is specified, a white screen occurs after the application is started. You can use [loadContent()](../reference/apis-arkui/js-apis-window.md#loadcontent9) of [WindowStage](../reference/apis-arkui/js-apis-window.md#windowstage9) to set the startup page in the [onWindowStageCreate()](../reference/apis-ability-kit/js-apis-app-ability-uiAbility.md#uiabilityonwindowstagecreate) callback of the [UIAbility](../reference/apis-ability-kit/js-apis-app-ability-uiAbility.md) instance.
10
11
12```ts
13import { UIAbility } from '@kit.AbilityKit';
14import { window } from '@kit.ArkUI';
15
16export default class EntryAbility extends UIAbility {
17  onWindowStageCreate(windowStage: window.WindowStage): void {
18    // Main window is created. Set a main page for this ability.
19    windowStage.loadContent('pages/Index', (err, data) => {
20      // ...
21    });
22  }
23  // ...
24}
25```
26
27> **NOTE**
28>
29> When you create UIAbility in DevEco Studio, the UIAbility instance loads the **Index** page as its startup page. Therefore, you only need to replace the **Index** page path with the required startup page path.
30
31
32## Obtaining the Context of UIAbility
33
34The [UIAbility](../reference/apis-ability-kit/js-apis-app-ability-uiAbility.md) class has its own context, which is an instance of the [UIAbilityContext](../reference/apis-ability-kit/js-apis-inner-application-uiAbilityContext.md) class. The [UIAbilityContext](../reference/apis-ability-kit/js-apis-inner-application-uiAbilityContext.md) class has attributes such as **abilityInfo** and **currentHapModuleInfo**. UIAbilityContext can be used to obtain the UIAbility configuration information, such as the code path, bundle name, ability name, and environment status required by the application. It can also be used to obtain methods to operate the UIAbility instance, such as [startAbility()](../reference/apis-ability-kit/js-apis-inner-application-uiAbilityContext.md#uiabilitycontextstartability), [connectServiceExtensionAbility()](../reference/apis-ability-kit/js-apis-inner-application-uiAbilityContext.md#uiabilitycontextconnectserviceextensionability), and [terminateSelf()](../reference/apis-ability-kit/js-apis-inner-application-uiAbilityContext.md#uiabilitycontextterminateself).
35
36The [getContext](../reference/apis-arkui/js-apis-getContext.md#getcontext) API enables you to obtain the context of the ability (either UIAbilityContext or [ExtensionContext](../reference/apis-ability-kit/js-apis-inner-application-extensionContext.md)) on the current page.
37
38- You can use **this.context** to obtain the context of a UIAbility instance.
39
40  ```ts
41  import { UIAbility, AbilityConstant, Want } from '@kit.AbilityKit';
42
43  export default class EntryAbility extends UIAbility {
44    onCreate(want: Want, launchParam: AbilityConstant.LaunchParam): void {
45      // Obtain the context of the UIAbility instance.
46      let context = this.context;
47      // ...
48    }
49  }
50  ```
51
52- Import the context module and define the **context** variable in the component.
53
54  ```ts
55  import { common, Want } from '@kit.AbilityKit';
56
57  @Entry
58  @Component
59  struct Page_EventHub {
60    private context = getContext(this) as common.UIAbilityContext;
61
62    startAbilityTest(): void {
63      let want: Want = {
64        // Want parameter information.
65      };
66      this.context.startAbility(want);
67    }
68
69    // Page display.
70    build() {
71      // ...
72    }
73  }
74  ```
75
76  You can also define variables after importing the context module but before using [UIAbilityContext](../reference/apis-ability-kit/js-apis-inner-application-uiAbilityContext.md).
77
78
79  ```ts
80  import { common, Want } from '@kit.AbilityKit';
81
82  @Entry
83  @Component
84  struct Page_UIAbilityComponentsBasicUsage {
85    startAbilityTest(): void {
86      let context = getContext(this) as common.UIAbilityContext;
87      let want: Want = {
88        // Want parameter information.
89      };
90      context.startAbility(want);
91    }
92
93    // Page display.
94    build() {
95      // ...
96    }
97  }
98  ```
99
100- To stop the [UIAbility](../reference/apis-ability-kit/js-apis-app-ability-uiAbility.md) instance after the service is not needed, call [terminateSelf()](../reference/apis-ability-kit/js-apis-inner-application-uiAbilityContext.md#uiabilitycontextterminateself).
101
102  ```ts
103  import { common } from '@kit.AbilityKit';
104  import { BusinessError } from '@kit.BasicServicesKit';
105
106  @Entry
107  @Component
108  struct Page_UIAbilityComponentsBasicUsage {
109    // Page display.
110    build() {
111      Column() {
112        //...
113        Button('FuncAbilityB')
114          .onClick(() => {
115            let context = getContext(this) as common.UIAbilityContext;
116            try {
117              context.terminateSelf((err: BusinessError) => {
118                if (err.code) {
119                  // Process service logic errors.
120                  console.error(`terminateSelf failed, code is ${err.code}, message is ${err.message}`);
121                  return;
122                }
123                // Carry out normal service processing.
124                console.info('terminateSelf succeed');
125              });
126            } catch (err) {
127              // Capture the synchronization parameter error.
128              let code = (err as BusinessError).code;
129              let message = (err as BusinessError).message;
130              console.error(`terminateSelf failed, code is ${code}, message is ${message}`);
131            }
132          })
133      }
134    }
135  }
136  ```
137