fix bug

Author: “

android/app/build.gradle

@@ -30,7 +30,7 @@ def keystoreProperties = new Properties()
 keystoreProperties.load(new FileInputStream(keystorePropertiesFile))
 
 android {
-    compileSdkVersion 27
+    compileSdkVersion 28
 
     lintOptions {
         disable 'InvalidPackage'
@@ -40,10 +40,11 @@ android {
         // TODO: Specify your own unique Application ID (https://developer.android.com/studio/build/application-id.html).
         applicationId "com.ngu.wanandroidngu"
         minSdkVersion 16
-        targetSdkVersion 27
+        targetSdkVersion 28
         versionCode flutterVersionCode.toInteger()
         versionName flutterVersionName
-        testInstrumentationRunner "android.support.test.runner.AndroidJUnitRunner"
+        testInstrumentationRunner "androidx.test.runner.AndroidJUnitRunner"
+        multiDexEnabled true
     }
 
     signingConfigs {
@@ -68,6 +69,6 @@ flutter {
 
 dependencies {
     testImplementation 'junit:junit:4.12'
-    androidTestImplementation 'com.android.support.test:runner:1.0.2'
-    androidTestImplementation 'com.android.support.test.espresso:espresso-core:3.0.2'
+    androidTestImplementation 'androidx.test:runner:1.1.0'
+    androidTestImplementation 'androidx.test.espresso:espresso-core:3.1.0'
 }

android/gradle.properties

@@ -1 +1,3 @@
+android.enableJetifier=true
+android.useAndroidX=true
 org.gradle.jvmargs=-Xmx1536M