harmony 鸿蒙System Applications

2022-08-09
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System Applications

Symptom

When the LiteOS-A kernel (Hi3516 or Hi3518) directly calls the API provided by the KV store, the compiled executable program fails to run.

Possible Causes

The compiled executable program is run directly without being converted to an application using AbilityKit APIs. In this case, the Bundle Manager Service (BMS) cannot correctly set the path for storing application data during application installation. As a result, the KV store fails to run.

Solution

Call the UtilsSetEnv function of the KV store to set the data storage path.

UtilsSetEnv("/storage/com.example.kv");

There is no such a global variable.

You can obtain DOM elements via the ref attribute. You can use methods of the obtained elements but cannot change their attributes. The sample code is as follows:



   
   


/* index.js */
export default {
    data: {
        images:[
            {src:"common/frame1.png"},
            {src:"common/frame2.png"},
            {src:"common/frame3.png"}
        ]
    },
    handleClick(){
        // Obtain the component through the $refs attribute. (The ref attribute of the component has been set to animator in the HML file.)
        const animator = this.$refs.animator;
        const state = animator.getState();
        if(state == "paused"){
            animator.resume();
        }else if(state == "stopped"){
            animator.start();
        }else{
            animator.pause();
        }
    }
}

You can pass values through params of the router.replace method. The sample code is as follows:

Set params to the values to be passed on a page. The sample code is as follows:

router.replace({
    uri:'pages/detail/detail',  // URI of the page to be redirected to.
    params:{transferData:this.data}  // Data to be transferred. You need to define the data amount and name.
});

Receive the passed values on another page.

onInit(){
    const data = this.transferData;  // Use the onInit function to receive the passed data.
}

Call the scrollTo method of the list. The input parameter of this method is the index of the target item. You can specify an item index, or obtain the index through the scrollend event.

Yes. The component supports multiple lines. You can use the Enter key to start a new line. If you do not set the height attribute of the text, the component automatically starts a new line based on the content.

Symptom

The component added to the .hml file cannot be displayed.

Possible Causes

The width and height of the component may not be set.
The style setting may be incorrect.

Solution

Check whether the width and height values are set explicitly.
Check whether the style of the component is set correctly.

There are three ways to implement page scrolling: scroll, , or . For a root component with scroll set, the scrolling effect is automatically implemented when the component size exceeds the screen size. For details, see the development specifications.

The left and top attributes must work with the component, except those of the root component.

The object or its attributes are not defined before dynamic binding.

You can use the and (with top and left attributes) components to implement relative positioning and absolute positioning.

You can use display, show, or if to display or hide a component. When an if clause evaluates to false, the corresponding component will be removed from the VDOM. When show is set to false, the component will be invisible during rendering, but will not be removed from the VDOM.

The margin attribute cannot be set for child components of the component.

Only one page exists when the application is running. Therefore, the router.replace function destroys the previous page and then creates a new one. For pages involving event subscription, an event should be subscribed every time a page is created, and unsubscribed before page switching.

Do not use too many dynamic bindings because they consume too much memory.

If the total length of child components, except for the first and last ones, is greater than the length of , the loop attribute takes effect.

Do not include too many elements in an array. Avoid frequent operations on a large array.

Symptom

After the hdc_std list targets command is executed, [Empty] is displayed.

Solution
1. The device cannot be identified.
Check whether HDC Device exists under the Universal Serial Bus controllers in the Device Manager. If HDC Device does not exist, the device cannot be connected. In this case, disconnect and then reconnect the USB connection between the test PC and the OpenHarmony device, or burn the latest image.
1. hdc_std works improperly. Run the hdc kill command to terminate the hdc_std process or run the hdc start -r command to restart the hdc service. Then, run the hdc list targets command to check whether device information can be obtained.
2. hdc_std does not match the device. If the latest image is burnt on the device, the latest hdc_std version must be used.

Symptom

After you click hdc_std.exe, the file fails to execute.

Solution

hdc_std.exe requires no installation. You can use it after placing it to a local directory or adding the tool path to environment variables. Run the cmd command and then run the hdc_std command to start the tool.

harmony 鸿蒙FAQs

harmony 鸿蒙Compilation and Building

harmony 鸿蒙Burning

harmony 鸿蒙Environment Setup

harmony 鸿蒙Kernel

harmony 鸿蒙FAQs Overview

harmony 鸿蒙Porting

harmony 鸿蒙Startup

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