16e7c69efSopenharmony_ci# Observer 26e7c69efSopenharmony_ci 36e7c69efSopenharmony_ci### Overview 46e7c69efSopenharmony_ci 56e7c69efSopenharmony_ciThis sample demonstrates how to use observer APIs to subscribe to events of network status, signal status, call status, cellular data, and SIM card status changes. 66e7c69efSopenharmony_ci 76e7c69efSopenharmony_ci 86e7c69efSopenharmony_ci 96e7c69efSopenharmony_ci 106e7c69efSopenharmony_ci### Concepts 116e7c69efSopenharmony_ci 126e7c69efSopenharmony_ci`@ohos.telephony.observer` 136e7c69efSopenharmony_ci 146e7c69efSopenharmony_ci A module that allows you to register observers to subscribe to events of mobile network, signal, call, and SIM card status changes. 156e7c69efSopenharmony_ci 166e7c69efSopenharmony_ci### Required Permissions 176e7c69efSopenharmony_ci 186e7c69efSopenharmony_ciThe following permission must be declared in the `module.json5` file: 196e7c69efSopenharmony_ci 206e7c69efSopenharmony_ci**ohos.permission.GET_NETWORK_INFO**: Obtains the network status. 216e7c69efSopenharmony_ci 226e7c69efSopenharmony_ci**ohos.permission.READ_CALL_LOG**: Obtains the call status. 236e7c69efSopenharmony_ci 246e7c69efSopenharmony_ci### How to Use 256e7c69efSopenharmony_ci 266e7c69efSopenharmony_ci1. Open the application and enable all event subscription switches. 276e7c69efSopenharmony_ci 286e7c69efSopenharmony_ci2. Enable or disable the mobile network once to trigger a network status change. 296e7c69efSopenharmony_ci 306e7c69efSopenharmony_ci3. Make a call to trigger a call status change. 316e7c69efSopenharmony_ci 326e7c69efSopenharmony_ci4. Remove and insert the SIM card to trigger a SIM card status and signal status change. 336e7c69efSopenharmony_ci 346e7c69efSopenharmony_ci5. Touch the **Details** button. A page is displayed, showing the related status change events. 356e7c69efSopenharmony_ci 366e7c69efSopenharmony_ci### Constraints 376e7c69efSopenharmony_ci 386e7c69efSopenharmony_ci1. This sample can only be run on standard-system devices. 396e7c69efSopenharmony_ci 406e7c69efSopenharmony_ci2. This sample demonstrates the stage model, which supports only API version 9. 416e7c69efSopenharmony_ci 426e7c69efSopenharmony_ci3. This sample requires DevEco Studio 3.1 Canary1 (Build Version: 3.1.0.100) to compile and run. 43
