HarmonyOS SaveButton 申请临时权限失败

SaveButton({ text: SaveDescription.SAVE_IMAGE, buttonType: ButtonType.Normal })  
  .height($r('app.float.size_50'))  
  .width('100%')  
  .fontColor($r('app.color.main_text_color'))  
  .fontSize($r('app.float.size_text_16'))  
  .backgroundColor(Color.White)  
  .onClick(async (event, result) => {  
    if (result == SaveButtonOnClickResult.SUCCESS) {  
      this.downloadImage()  
    }  
  })