Enabling .bin File Sharing on HarmonyOS with Custom UTDs and Skills (Fix ‘No Available App to Open’)

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Enabling .bin File Sharing on HarmonyOS with Custom UTDs and Skills (Fix ‘No Available App to Open’)

Requirement Description

On phones, long-pressing a .bin file in File Manager and tapping Share shows “No available way to open”. Images/videos invoke apps correctly. We need to enable sharing/receiving of .bin by defining and declaring a custom UTD and updating the target app’s skills so it appears on the share/open sheet.

Background Knowledge

HarmonyOS uses Uniform Data Type Descriptors (UTDs) to identify file/data types. Apps can declare custom UTDs and express support via skills. If no prebuilt UTD exists for a given extension, HarmonyOS may generate a dynamic UTD (prefix flex.). Declaring your own UTD and mapping skills allows your app to appear as a handler for that file type. See Uniform Data Type Descriptors (overview). (Huawei Developer)

Tip: getParamByName() in ArkUI Navigation returns an array because it aggregates params for all same-named destinations in the stack—useful when diagnosing route parameter handling while testing share flows. (Huawei Developer)

Implementation Steps

Declare a skill for opening the file

In your ability’s module.json5, add a skills item indicating you can view files with your custom UTD:

{
  "skills": [
    {
      "actions": [
        "ohos.want.action.viewData"
      ],
      "uris": [
        {
          "scheme": "file",
          "linkFeature": "FileOpen",
          "type": "com.example.myapplication.bin"
        }
      ]
    }
  ]
}

• type equals your custom TypeId from the UTD declaration file.

Provide the custom UTD declaration

Create resources/rawfile/utd.json5 and declare your type:

{
  "UniformDataTypeDeclarations": [
    {
      "TypeId": "com.example.myapplication.bin",
      "BelongingToTypes": [ "general.object" ],
      "FilenameExtensions": [ ".bin" ],
      "MIMETypes": [ "application/octet-stream" ],
      "Description": "My document.",
      "ReferenceURL": "https://www.mycompany.com/my-document"
    }
  ]
}

• - TypeId must be unique (e.g., ${bundleName}.${type}), using only digits, letters, - and ..

(Alternative) Support a dynamic UTD (“flex.*”)

If the sender yields a dynamic UTD for .bin (for example, flex.zh45depjomjuw4), the receiver can also declare a sendData skill for that UTD to appear in the share panel:

{
  "skills": [
    {
      "actions": [ "ohos.want.action.sendData" ],
      "uris": [
        {
          "scheme": "file",
          "utd": "flex.zh45depjomjuw4",
          "maxFileSupported": 1
        }
      ]
    }
  ]
}

• - Dynamic UTDs typically start with flex..

Build, install, and test

• - Rebuild the app and install.
  • In Files: create or pick a .bin, long-press → Share (or Open with) → your app should appear.
  • If your app is the sender, ensure you set the Want with the matching action/URI/UTD so the platform can resolve the target. See Want references. (Huawei Developer)

Code Snippet

• module.json5 (skills): see Step 1/3 above.
• resources/rawfile/utd.json5: see Step 2 above.

// Index.ets — Wearable demo for UTD lookup (.bin) — HarmonyOS 6 / API 19+

import uniformTypeDescriptor from '@ohos.data.uniformTypeDescriptor'

@Entry
@Component
struct Index {
  @State private extInput: string = '.bin'
  @State private detectedUtd: string = ''
  @State private note: string = 'Enter extension (e.g., .bin) and tap Detect.'

  private detect(): void {
    try {
      const utd: string = uniformTypeDescriptor.getUniformDataTypeByFilenameExtension(this.extInput)
      this.detectedUtd = utd
      this.note = utd.startsWith('flex.')
        ? 'Dynamic UTD detected (flex.*). Consider declaring custom TypeId and/or accept this flex.* in skills.'
        : 'Predefined/custom UTD detected. Make sure your skills use this TypeId.'
    } catch (e) {
      this.detectedUtd = ''
      this.note = `Lookup failed: ${JSON.stringify(e)}`
    }
  }

  build() {
    Column({ space: 8 }) {
      Text('UTD Share Demo (Wearable)').fontSize(16).fontWeight(FontWeight.Medium)
        .fontColor(Color.Black)

      Text('Check the UTD the system resolves for an extension.').fontSize(12).opacity(0.8)
        .fontColor(Color.Black)


      Row({ space: 6 }) {
        TextInput({ placeholder: '.bin', text: this.extInput })
          .onChange((v: string) => this.extInput = v)
          .width('60%')
          .fontColor(Color.Black)
          .backgroundColor(Color.White)

        Button('Detect').onClick(() => this.detect())
      }

      Column({ space: 4 }) {
        Text(`UTD: ${this.detectedUtd || '-'}`).fontSize(14)
          .fontColor(Color.Black)

        Text(this.note).fontSize(12).maxLines(3)
          .fontColor(Color.Black)
      }
      .width('100%')
      .padding(8)
      .backgroundColor(0xFFFFFF)
      .borderRadius(12)
    }
    .width('100%')
    .height('100%')
    .padding(12)
    .backgroundColor(0xF0F6FF)
  }
}

Test Results

• Verified on API 19 Release with HarmonyOS 5.1.1/6 SDK using DevEco Studio 5.1.1+: the app appears on the share/open sheet for .bin.

Limitations or Considerations

• Choose a stable TypeId; changing it requires coordinated sender/receiver updates.
• Some sources may still emit dynamic UTDs; handle both custom TypeId and flex.* cases.
• Keep MIME (application/octet-stream) and extension mapping accurate.
• For multi-file share, adjust maxFileSupported.

Related Documents or Links

• Uniform Data Type Descriptors (overview)
• Navigation (reference note for getParamByName array)
• Want (JS reference)

Written by Bunyamin Eymen Alagoz