Image is not saving in android gallery. whereas It is work properly on emultor

i'm making qr code maker/scanner app where, i am using image_gallery_saver package. when i make qr and download qr, in emulator it is working properly but when i make apk file and install in android phone it is not downloading. anyone has any idea. below is my manifest.xml

   <manifest xmlns:android="http://schemas.android.com/apk/res/android"
   package="com.gamelien.qr_app">
   <uses-permission android:name="android.permission.READ_EXTERNAL_STORAGE"/>
   <uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE"/>
   <uses-permission android:name="android.permission.INTERNET"/>
   
  <application
       android:requestLegacyExternalStorage="true"
       android:label="qr_app"
       android:icon="@mipmap/ic_launcher">
       <activity
           android:name=".MainActivity"
           android:launchMode="singleTop"
           android:theme="@style/LaunchTheme"
           android:configChanges="orientation|keyboardHidden|keyboard|screenSize|smallestScreenSize|locale|layoutDirection|fontScale|screenLayout|density|uiMode"
           android:hardwareAccelerated="true"
           android:windowSoftInputMode="adjustResize">
           <!-- Specifies an Android theme to apply to this Activity as soon as
                the Android process has started. This theme is visible to the user
                while the Flutter UI initializes. After that, this theme continues
                to determine the Window background behind the Flutter UI. -->
           <meta-data
             android:name="io.flutter.embedding.android.NormalTheme"
             android:resource="@style/NormalTheme"
             />
           <!-- Displays an Android View that continues showing the launch screen
                Drawable until Flutter paints its first frame, then this splash
                screen fades out. A splash screen is useful to avoid any visual
                gap between the end of Android's launch screen and the painting of
                Flutter's first frame. -->
           <meta-data
             android:name="io.flutter.embedding.android.SplashScreenDrawable"
             android:resource="@drawable/launch_background"
             />
           <intent-filter>
               <action android:name="android.intent.action.MAIN"/>
               <category android:name="android.intent.category.LAUNCHER"/>
           </intent-filter>
       </activity>
       <!-- Don't delete the meta-data below.
            This is used by the Flutter tool to generate GeneratedPluginRegistrant.java -->
       <meta-data
           android:name="flutterEmbedding"
           android:value="2" />
   </application>
</manifest> 

and below is my image_gallery_saver method which is called on button press

void qrSaveToGallery() async {
    final result =
        await ImageGallerySaver.saveImage(_imageFile); // Save image to gallery
  }