Development of Application Event Logging

When to Use

The event logging function helps applications log various information generated during running.

Available APIs

JS application event logging APIs are provided by the hiAppEvent module.

APIs for Event Logging

API Return Value Description
write(string eventName, EventType type, object keyValues, AsyncCallback<void> callback): void void Logs application events in asynchronous mode. This method uses an asynchronous callback to return the result.
write(string eventName, EventType type, object keyValues): Promise<void> Promise<void> Logs application events in asynchronous mode. This method uses a promise to return the result.

When an asynchronous callback is used, the return value can be processed directly in the callback. When a promise is used, the return value can also be processed in the promise in a similar way. For details about the result codes, see Event Verification Result Codes.

APIs for Event Logging Configuration

API Return Value Description
configure(ConfigOption config) boolean Sets the configuration options for application event logging.
The value true indicates that the operation is successful, and value false indicates the opposite.

Event Verification Result Codes

Result Code Cause Check Rule Processing Method
0 None Event verification is successful. Event logging is normal. No action is required.
-1 Invalid event name The event name is not empty and contains a maximum of 48 characters.
The event name consists of only the following characters: digits (0 to 9), letters (a to z), and underscore (_).
The event name does not start with a digit or underscore (_).		 Ignore this event and do not perform logging.
-2 Invalid event parameter type The event name must be a string.
The event type must be a number.
The key value must be an object.		 Ignore this event and do not perform logging.
-99 Application event logging disabled The application event logging function is disabled. Ignore this event and do not perform logging.
-100 Unknown error None Ignore this event and do not perform logging.
1 Invalid key name The key name is not empty and contains a maximum of 16 characters.
The key name consists of only the following characters: digits (0 to 9), letters (a to z), and underscore (_).
The key name does not start with a digit or underscore (_).
The key name does not end with an underscore (_).		 Ignore the key-value pair and continue to perform logging.
2 Invalid key type The key must be a string. Ignore the key-value pair and continue to perform logging.
3 Invalid value type The supported value types vary depending on the programming language:
boolean, number, string, or Array [basic element]		 Ignore the key-value pair and continue to perform logging.
4 Value too long The value can contain a maximum of 8*1024 characters. Ignore the key-value pair and continue to perform logging.
5 Excess key-value pairs The number of key-value pairs must be less than or equal to 32. Ignore the excess key-value pairs and continue to perform logging.
6 Excess elements in a list value The number of elements in a list value must be less than or equal to 100. Truncate the list with only the first 100 elements retained, and continue to perform logging.
7 Invalid list value A list value can only be a basic element.
The elements in a list value must be of the same type.		 Ignore the key-value pair and continue to perform logging.

How to Develop

In this example, an application event is logged after the application startup execution page is loaded.

  1. Create a JS application project. In the displayed Project window, choose entry > src > main > js > default > pages > index, and double-click index.js. Add the code to log the initial application event after page loading. The sample code is as follows:

    import hiAppEvent from '@ohos.hiAppEvent'

export default {
    data: {
        title: ""
    },
    onInit() {
        this.title = this.$t('strings.world');

        // 1. Callback mode
        hiAppEvent.write("start_event", hiAppEvent.EventType.BEHAVIOR, {"int_data":100, "str_data":"strValue"}, (err, value) => {
            if (err) {
                console.error(`failed to write event because ${err.code}`);
                return;
            }
            console.log(`success to write event: ${value}`);
        });

        // 2. Promise mode
        hiAppEvent.write("start_event", hiAppEvent.EventType.BEHAVIOR, {"int_data":100, "str_data":"strValue"})
            .then((value) => {
                console.log(`success to write event: ${value}`);
            }).catch((err) => {
                console.error(`failed to write event because ${err.code}`);
            });
 
        // 3. Set the application event logging switch.
        hiAppEvent.configure({
            disable: true
        });

        // 4. Set the maximum size of the event file storage directory. The default value is 10M.
        hiAppEvent.configure({
            maxStorage: '100M'
        });
    }
}

  2. Tap the run button on the application UI to run the project.