How to programmatically hide Imageview

I have a linearlayout with three icons as below

I have a linearlayout with three icons as below

 <ImageView
            android:id="@+id/cities"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content          
            android:src="@drawable/city" />
    &lt;ImageView
        android:id="@+id/red"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"           
        android:src="@drawable/red"
        android:visibility="gone" 
        /&gt;
    &lt;ImageView
        android:id="@+id/deal"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"       
        android:src="@drawable/deal" /&gt;

initially the middle icon is hidden (android:visibility="gone") I have a login screen..when the login i success I want the icon to be visible ..tried as below..but itz not working

public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);

setContentView(R.layout.fyelogin);                    
etPassword = (EditText)findViewById(R.id.password);
btnLogin = (Button)findViewById(R.id.login_button);
btnCancel = (Button)findViewById(R.id.cancel_button);
lblResult = (TextView)findViewById(R.id.result);

final ImageView details = (ImageView)findViewById(R.id.red); 

btnLogin.setOnClickListener(new OnClickListener() {
    public void onClick(View v) {

        String password = etPassword.getText().toString();

        if(password.equals("guest")){
            lblResult.setText("password successful.");

giving error @ this line  -----&gt;  details.setVisibility(View.VISIBLE);

        } else {
            lblResult.setText("password doesn't match.");
        }

        finish();
    }
});


My Android app not supporting Android version 9

I have made an android app which uses webView. Everything was fine until I tried my app on Android P. On Android "P" the app is directly showing the error page that the app can't use Internet connection even though it is ON.

I have made an android app which uses webView. Everything was fine until I tried my app on Android P. On Android "P" the app is directly showing the error page that the app can't use Internet connection even though it is ON.

Android Manifest File:

    <?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="com.xxx.xxxxx.xxxxx">
&lt;!-- android:roundIcon="@mipmap/ic_launcher_round" --&gt;

&lt;uses-permission android:name="android.permission.INTERNET" /&gt;
&lt;uses-permission android:name="android.permission.ACCESS_NOTIFICATION_POLICY"/&gt;
&lt;uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" /&gt;
&lt;uses-permission android:name="android.permission.CAMERA" /&gt;

&lt;application
    android:allowBackup="true"
    android:icon="@drawable/icon"
    android:label="@string/app_name"
    android:hardwareAccelerated="true"
    android:supportsRtl="true"
    android:theme="@style/AppTheme"&gt;
    &lt;activity android:name="com.xxxxx.xxxxx.xxxxxx.MainActivity"&gt;
        &lt;intent-filter&gt;
            &lt;action android:name="android.intent.action.MAIN" /&gt;

            &lt;category android:name="android.intent.category.LAUNCHER" /&gt;
        &lt;/intent-filter&gt;
    &lt;/activity&gt;
&lt;/application&gt;

</manifest>

Gradle File:

    apply plugin: 'com.android.application'

android {
compileSdkVersion 28
defaultConfig {
applicationId "com.xxx.xxx.xxx"
minSdkVersion 19
targetSdkVersion 28
versionCode 3
versionName "3.0"
testInstrumentationRunner "android.support.test.runner.AndroidJUnitRunner"
}
buildTypes {
release {
minifyEnabled false
proguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.pro'
}
}
}

dependencies {
implementation fileTree(dir: 'libs', include: ['*.jar'])
implementation 'com.android.support:appcompat-v7:28.0.0'
implementation 'com.android.support.constraint:constraint-layout:1.1.3'
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'
implementation 'com.android.support:design:28.0.0'
}

On Getting error in Android P, directly this section is being accessed:

public void onReceivedError(WebView view, int errorCode,
String description, String failingUrl) {
// You can redirect to your own page instead getting the default error page

            super.onReceivedError(view, errorCode, description, failingUrl);
            String path = Uri.parse("file:///android_asset/error.html").toString();
            webView.loadUrl("about:blank");
            view.loadUrl(path);
        }


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Running a project in Android Studio - Could not find com.android.tools.build:aapt2:3.3.0-5013011

This is the error message I receive. I downloaded an older project and found solutions to the other error messages. Yet, how can I fix this problem/error message?

Could not find com.android.tools.build:aapt2:3.3.0-5013011.

Searched in the following locations:
  - file:/C:/Users/dimi1/AppData/Local/Android/Sdk/extras/m2repository/com/android/tools/build/aapt2/3.3.0-5013011/aapt2-3.3.0-5013011.pom
  - file:/C:/Users/dimi1/AppData/Local/Android/Sdk/extras/m2repository/com/android/tools/build/aapt2/3.3.0-5013011/aapt2-3.3.0-5013011-windows.jar
  - file:/C:/Users/dimi1/AppData/Local/Android/Sdk/extras/google/m2repository/com/android/tools/build/aapt2/3.3.0-5013011/aapt2-3.3.0-5013011.pom
  - file:/C:/Users/dimi1/AppData/Local/Android/Sdk/extras/google/m2repository/com/android/tools/build/aapt2/3.3.0-5013011/aapt2-3.3.0-5013011-windows.jar
  - file:/C:/Users/dimi1/AppData/Local/Android/Sdk/extras/android/m2repository/com/android/tools/build/aapt2/3.3.0-5013011/aapt2-3.3.0-5013011.pom
  - file:/C:/Users/dimi1/AppData/Local/Android/Sdk/extras/android/m2repository/com/android/tools/build/aapt2/3.3.0-5013011/aapt2-3.3.0-5013011-windows.jar
  - https://jcenter.bintray.com/com/android/tools/build/aapt2/3.3.0-5013011/aapt2-3.3.0-5013011.pom
  - https://jcenter.bintray.com/com/android/tools/build/aapt2/3.3.0-5013011/aapt2-3.3.0-5013011-windows.jar
Required by:
    project :app

This is the error message I receive. I downloaded an older project and found solutions to the other error messages. Yet, how can I fix this problem/error message?