# Subscribing to Freeze Events (ArkTS) ## Available APIs For details about how to use the APIs (such as parameter usage constraints and value ranges), see [Application Event Logging](../reference/apis-performance-analysis-kit/js-apis-hiviewdfx-hiappevent.md). **API for Setting Custom Event Parameters** | API | Description | | --------------------------------------------------- | -------------------------------------------- | | setEventParam(params: Record<string, ParamType>, domain: string, name?: string): Promise<void> | Sets custom event parameters.| **Subscription APIs** | API | Description | | --------------------------------------------------- | -------------------------------------------- | | addWatcher(watcher: Watcher): AppEventPackageHolder | Adds a watcher to listen for application events.| | removeWatcher(watcher: Watcher): void | Removes a watcher to unsubscribe from application events.| ## How to Develop The following describes how to subscribe to the freeze event triggered by a button click. 1. Create an ArkTS application project. In the **entry/src/main/ets/entryability/EntryAbility.ets** file, import the dependent modules. ```ts import { BusinessError } from '@kit.BasicServicesKit'; import { hiAppEvent, hilog } from '@kit.PerformanceAnalysisKit'; ``` 2. In the **entry/src/main/ets/entryability/EntryAbility.ets** file, set the custom parameters in **onCreate()**. The sample code is as follows: ```ts // Assign a value to params, which is a key-value pair. let params: Record = { "test_data": 100, }; // Set custom parameters for the freeze event. hiAppEvent.setEventParam(params, hiAppEvent.domain.OS, hiAppEvent.event.APP_FREEZE).then(() => { hilog.info(0x0000, 'testTag', `HiAppEvent success to set svent param`); }).catch((err: BusinessError) => { hilog.error(0x0000, 'testTag', `HiAppEvent code: ${err.code}, message: ${err.message}`); }); ``` 3. In the **entry/src/main/ets/entryability/EntryAbility.ets** file, add a watcher in **onCreate()** to subscribe to system events. The sample code is as follows: ```ts hiAppEvent.addWatcher({ // Set the watcher name. The system identifies different watchers based on their names. name: "watcher", // Add the system events to watch, for example, freeze events. appEventFilters: [ { domain: hiAppEvent.domain.OS, names: [hiAppEvent.event.APP_FREEZE] } ], // Implement a callback for the registered system event so that you can apply custom processing to the event data obtained. onReceive: (domain: string, appEventGroups: Array) => { hilog.info(0x0000, 'testTag', `HiAppEvent onReceive: domain=${domain}`); for (const eventGroup of appEventGroups) { // The event name uniquely identifies a system event. hilog.info(0x0000, 'testTag', `HiAppEvent eventName=${eventGroup.name}`); for (const eventInfo of eventGroup.appEventInfos) { // Apply custom processing to the event data obtained, for example, print the event data in the log. hilog.info(0x0000, 'testTag', `HiAppEvent eventInfo.domain=${eventInfo.domain}`); hilog.info(0x0000, 'testTag', `HiAppEvent eventInfo.name=${eventInfo.name}`); hilog.info(0x0000, 'testTag', `HiAppEvent eventInfo.eventType=${eventInfo.eventType}`); // Obtain the timestamp of the freeze event. hilog.info(0x0000, 'testTag', `HiAppEvent eventInfo.params.time=${eventInfo.params['time']}`); // Obtain the foreground and background status of the application when the freeze event occurs. hilog.info(0x0000, 'testTag', `HiAppEvent eventInfo.params.foreground=${eventInfo.params['foreground']}`); // Obtain the version information of the application. hilog.info(0x0000, 'testTag', `HiAppEvent eventInfo.params.bundle_version=${eventInfo.params['bundle_version']}`); // Obtain the bundle name of the application. hilog.info(0x0000, 'testTag', `HiAppEvent eventInfo.params.bundle_name=${eventInfo.params['bundle_name']}`); // Obtain the process name of the application. hilog.info(0x0000, 'testTag', `HiAppEvent eventInfo.params.process_name=${eventInfo.params['process_name']}`); // Obtain the process ID of the application. hilog.info(0x0000, 'testTag', `HiAppEvent eventInfo.params.pid=${eventInfo.params['pid']}`); hilog.info(0x0000, 'testTag', `HiAppEvent eventInfo.params.uid=${eventInfo.params['uid']}`); hilog.info(0x0000, 'testTag', `HiAppEvent eventInfo.params.uuid=${eventInfo.params['uuid']}`); // Obtain the exception type and cause of the freeze event. hilog.info(0x0000, 'testTag', `HiAppEvent eventInfo.params.exception=${JSON.stringify(eventInfo.params['exception'])}`); // Obtain the log information when the freeze event occurs. hilog.info(0x0000, 'testTag', `HiAppEvent eventInfo.params.hilog.size=${eventInfo.params['hilog'].length}`); // Obtain the messages that are not yet processed by the main thread when the freeze event occurs. hilog.info(0x0000, 'testTag', `HiAppEvent eventInfo.params.event_handler.size=${eventInfo.params['event_handler'].length}`); hilog.info(0x0000, 'testTag', `HiAppEvent eventInfo.params.event_handler_size_3s=${eventInfo.params['event_handler_size_3s']}`); hilog.info(0x0000, 'testTag', `HiAppEvent eventInfo.params.event_handler_size_6s=${eventInfo.params['event_handler_size_6s']}`); // Obtain the synchronous binder call information when the freeze event occurs. hilog.info(0x0000, 'testTag', `HiAppEvent eventInfo.params.peer_binder.size=${eventInfo.params['peer_binder'].length}`); // Obtain the full thread call stack when the freeze event occurs. hilog.info(0x0000, 'testTag', `HiAppEvent eventInfo.params.threads.size=${eventInfo.params['threads'].length}`); // Obtain the memory information when the freeze event occurs. hilog.info(0x0000, 'testTag', `HiAppEvent eventInfo.params.memory=${JSON.stringify(eventInfo.params['memory'])}`); // Obtain the error log file when the freeze event occurs. hilog.info(0x0000, 'testTag', `HiAppEvent eventInfo.params.external_log=${JSON.stringify(eventInfo.params['external_log'])}`); hilog.info(0x0000, 'testTag', `HiAppEvent eventInfo.params.log_over_limit=${eventInfo.params['log_over_limit']}`); // Obtain the custom test_data of the freeze event. hilog.info(0x0000, 'testTag', `HiAppEvent eventInfo.params.test_data=${eventInfo.params['test_data']}`); } } } }); ``` 4. In the **entry/src/main/ets/pages/index.ets** file, add the **appFreeze** button and construct a scenario for triggering a freeze event in **onClick()**. The sample code is as follows: ```ts Button("appFreeze").onClick(()=>{ // Construct a scenario in onClick() for triggering a freeze event. setTimeout(() => { while (true) {} }, 1000) }) ``` 5. In DevEco Studio, click the **Run** button to run the project. Then, click the **appfreeze** button to trigger a freeze event. 6. The application crashes. After restarting the application, you can view the following event information in the **Log** window. ```text HiAppEvent onReceive: domain=OS HiAppEvent eventName=APP_FREEZE HiAppEvent eventInfo.domain=OS HiAppEvent eventInfo.name=APP_FREEZE HiAppEvent eventInfo.eventType=1 HiAppEvent eventInfo.params.time=1711440881768 HiAppEvent eventInfo.params.foreground=true HiAppEvent eventInfo.params.bundle_version=1.0.0 HiAppEvent eventInfo.params.bundle_name=com.example.myapplication HiAppEvent eventInfo.params.process_name=com.example.myapplication HiAppEvent eventInfo.params.pid=3197 HiAppEvent eventInfo.params.uid=20010043 HiAppEvent eventInfo.params.uuid=27fac7098da46efe1cae9904946ec06c5acc91689c365efeefb7a23a0c37df77 HiAppEvent eventInfo.params.exception={"message":"App main thread is not response!","name":"THREAD_BLOCK_6S"} HiAppEvent eventInfo.params.hilog.size=77 HiAppEvent eventInfo.params.event_handler.size=6 HiAppEvent eventInfo.params.event_handler_size_3s=5 HiAppEvent eventInfo.params.event_handler_size_6s=6 HiAppEvent eventInfo.params.peer_binder.size=0 HiAppEvent eventInfo.params.threads.size=28 HiAppEvent eventInfo.params.memory={"pss":0,"rss":0,"sys_avail_mem":1361464,"sys_free_mem":796232,"sys_total_mem":1992340,"vss":0} HiAppEvent eventInfo.params.external_log=["/data/storage/el2/log/hiappevent/APP_FREEZE_1711440899240_3197.log"] HiAppEvent eventInfo.params.log_over_limit=false HiAppEvent eventInfo.params.test_data=100 ```