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presentLoadingText() {

  let start=2000;
  let count=0;
  let scanTime;
  let deadTimer;

////////////////////////////////////////
  let startLoad=()=>{
    loadBar();
    return this.load.present();
}

let loadBar=()=>{
    if(this.load&&this.load.instance){
      stopLoader();
    }
    this.load=this.loading.create({
         content: 'Loading Please Wait...'
       });
}

let stopLoader=()=>{
  this.load.dismissAll();
  this.load=null;
}
/////////////////////////////////////


  //this.Loading.present();  
  let start_Scan=()=>{    
   startLoad();
   scanTime=setInterval(scan,start)
  }    
  let scan=()=>{//判斷式應該是寫在這
    console.log(this.irislist.length)

    if(this.irislist.length==0){
        ++count;
        if(count==5){
          startDeadTimer();
          count=0;
        }else{
          endDeadTimer();
          
        }
    }else{
        console.log("IRIS DETECTED")
        endScan();
    }

  }
 
  let endScan=()=>{
    console.log("scan cancelled")
    clearInterval(scanTime)
    stopLoader();
  }
 
  let startDeadTimer=()=> {
      deadTimer = setTimeout(() => {
      //endScan();
      clearInterval(scanTime)
      deadTimer = null;
      console.log('[Hint] hide loading bar and show confirm here');

      let alert = this.alertctrl.create({
        title: 'Confirm Waiting...',
        message: 'No IRIS detected... <br> keep waiting?',
        buttons: [
          { 
            text: 'Cancel',
            role: 'cancel',
            handler: () => {
              console.log('Cancel clicked');
              endScan();
            }
          },
          {
            text: 'Yes',
            handler: () => {
              start_Scan();
            } 
          }
        ]
      });  
      alert.present();
     //confirm('keep waiting?') ? start_Scan() : endScan();
    }, 500);
  }

  let endDeadTimer=()=> {
    clearTimeout(deadTimer);
    deadTimer = null; 
  }

  start_Scan(); 
}