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How to enable back button in webview?

I am creating an application with webview (an application in which a website is displayed).
Currently, if I click the back button, the app closes the application
What I am looking for is not that a button with an arrow appears in the action bar and it takes me back, because I have eliminated that bar, what I want is to be able to use the buttons on the cell phone.
I hope you can help me, here the code of the MainActivity.java and the AndroidManifiest.xml
MainActivity.java
public class MainActivity extends AppCompatActivity {
private View decorView;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
WebView webView = findViewById(R.id.mywebview);
webView.getSettings().setJavaScriptEnabled(true);
webView.setWebViewClient(new WebViewClient());
webView.setWebChromeClient(new myChrome());
webView.loadUrl("https://mywebview.com/");
decorView = getWindow().getDecorView();
decorView.setOnSystemUiVisibilityChangeListener(new View.OnSystemUiVisibilityChangeListener() {
#Override
public void onSystemUiVisibilityChange(int visibility) {
if (visibility == 0)
decorView.setSystemUiVisibility(hideSystemBars());
}
});
}
#Override
public void onWindowFocusChanged(boolean hasFocus) {
super.onWindowFocusChanged(hasFocus);
if (hasFocus) {
decorView.setSystemUiVisibility(hideSystemBars());
}
}
AndroidManifiest.xml
<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="com.Dessert.decov">
<uses-permission android:name="android.permission.INTERNET" />
<uses-permission android:name="android.permission.ACCESS_WIFI_STATE" />
<uses-permission android:name="android.permission.ACCESS_NETWORK_STATE" />
<uses-permission android:name="android.permission.FOREGROUND_SERVICE" />
<uses-permission android:name="android.permission.RECEIVE_BOOT_COMPLETED" />
<uses-permission android:name="android.permission.WAKE_LOCK" />
<application
android:allowBackup="true"
android:icon="#mipmap/ic_launcher"
android:label="#string/app_name"
android:roundIcon="#mipmap/ic_launcher_round"
android:supportsRtl="true"
android:theme="#style/Theme.DESSERT">
<activity
android:name=".MainActivity"
android:exported="true"
android:configChanges="screenSize|orientation">
<intent-filter>
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.LAUNCHER" />
</intent-filter>
</activity>
</application>
</manifest>

Not able to fetch current latitude and longitude in android

I am new in android and i am trying to get my current location latitude and longitude and for this i am using 'com.google.android.gms:play-services:8.4.0' and i am getting this error
java.lang.IllegalArgumentException: GoogleApiClient parameter is required.
and i referred to previous stckoverflow answers but it didnot helped me.Please help me, thanks in advance
and here is the code of Mapsactivity.java
public class MapsActivity extends FragmentActivity{
private GoogleMap mMap;
AppLocationService appLocationService;
GoogleApiClient mGoogleApiClient;
private Location mLastLocation;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_maps);
setUpMapIfNeeded();
}
private void setUpMapIfNeeded() {
if (mMap == null) {
mMap = ((SupportMapFragment)
getSupportFragmentManager().findFragmentById(R.id.map))
.getMap();
if (mMap != null) {
displayLocation();
}
}
}
private void displayLocation() {
mLastLocation = LocationServices.FusedLocationApi
.getLastLocation(mGoogleApiClient);
if (mLastLocation != null) {
double latitude = mLastLocation.getLatitude();
double longitude = mLastLocation.getLongitude();
Log.d("result", latitude + ", " + longitude);
} else {
Log.d("result2","(Couldn't get the location. Make sure location is
enabled on the device)");
}
}
}
And here is the code of my manifest file
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="com.example.malli.myapplication" >
<uses-permission android:name="android.permission.INTERNET" />
<uses-permission android:name="android.permission.ACCESS_NETWORK_STATE" />
<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />
<uses-permission
android:name="com.google.android.providers.gsf.permission.READ_GSERVICES"
/>
<uses-permission android:name="android.permission.ACCESS_FINE_LOCATION" />
<uses-permission android:name="android.permission.ACCESS_COARSE_LOCATION" />
<application
android:allowBackup="true"
android:icon="#mipmap/ic_launcher"
android:label="#string/app_name"
android:theme="#style/AppTheme" >
<meta-data
android:name="com.google.android.gms.version"
android:value="#integer/google_play_services_version" />
<meta-data
android:name="com.google.android.maps.v2.API_KEY"
android:value="#string/google_maps_key" />
<activity
android:name=".MapsActivity"
android:label="#string/title_activity_maps" >
<meta-data
android:name="com.google.android.gms.version"
android:value="#integer/google_play_services_version"/>
<intent-filter>
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.LAUNCHER" />
</intent-filter>
</activity>
</application>

you have not initialized your mGoogleApiClient variable. please intialize it first.
mGoogleApiClient = new GoogleApiClient.Builder(this)
.addConnectionCallbacks(this)
.addOnConnectionFailedListener(this)
.addApi(LocationServices.API).build();
mLastLocation = LocationServices.FusedLocationApi
.getLastLocation(mGoogleApiClient);
Note : this is just a sample to initialize GoogleApiClient

Android Studio setmylocationenabled(true) throws SecurityException

I've encountered a problem. My program throes SecurityException, even if I declraed all the Permissions.
Here is MapsActivity class:
public class MapsActivity extends FragmentActivity implements OnMapReadyCallback {
private GoogleMap mMap;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_maps);
// Obtain the SupportMapFragment and get notified when the map is ready to be used.
SupportMapFragment mapFragment = (SupportMapFragment) getSupportFragmentManager()
.findFragmentById(R.id.map);
mapFragment.getMapAsync(this);}
public void onMapReady(GoogleMap googleMap) {
try{
mMap = googleMap;
// Add a marker in Sydney and move the camera
LatLng sydney = new LatLng(-34, 151);
mMap.addMarker(new MarkerOptions().position(sydney).title("Marker in Sydney"));
mMap.moveCamera(CameraUpdateFactory.newLatLng(sydney));
mMap.setMyLocationEnabled(true);
mMap.getUiSettings().setMyLocationButtonEnabled(true);
// set map type
}
Here is the Manifest:
<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="mazebug.danuleoshaleosha">
<uses-permission android:name="android.permission.INTERNET" />
<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />
<uses-permission android:name="android.permission.ACCESS_NETWORK_STATE" />
<uses-permission android:name="com.google.android.providers.gsf.permission.READ_GSERVICES" />
<uses-permission android:name="android.permission.ACCESS_COARSE_LOCATION" />
<uses-permission android:name="android.permission.ACCESS_FINE_LOCATION" />
<application
android:allowBackup="true"
android:icon="#mipmap/ic_launcher"
android:label="#string/app_name"
android:supportsRtl="true"
android:theme="#style/AppTheme">
<activity android:name=".MainActivity">
<intent-filter>
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.LAUNCHER" />
</intent-filter>
</activity>
<activity android:name=".Interface" />
<activity android:name=".Main2Activity" />
<activity android:name=".Main22Activity" />
<activity android:name=".SFR_Table" />
<activity android:name=".sfrtable2" />
<activity android:name=".sfrtable3" />
<activity android:name=".sfrtable4" />
<activity android:name=".sfrtable5" />
<activity android:name=".sfrtable6" />
<activity android:name=".sfrtable7" />
<activity android:name=".mySfrs" />
<activity android:name=".Search_bySiteName" />
<activity android:name=".Search_byDate" />
<activity android:name=".Search_byLocation" />
<activity android:name=".Found_1" />
<activity android:name=".Found_2" />
<activity android:name=".Found_3" />
<activity android:name=".Edit_first" />
<activity android:name=".Edit_1_2" />
<activity android:name=".Edit_1_3" />
<activity android:name=".Edit_1_4" />
<activity android:name=".Edit_1_5" />
<activity android:name=".Edit_1_6" />
<activity android:name=".Edit_1_7" />
<activity android:name=".testing" />
<meta-data
android:name="com.google.android.gms.version"
android:value="#integer/google_play_services_version" />
<activity android:name=".Main23Activity" />
<!--
The API key for Google Maps-based APIs is defined as a string resource.
(See the file "res/values/google_maps_api.xml").
Note that the API key is linked to the encryption key used to sign the APK.
You need a different API key for each encryption key, including the release key that is used to
sign the APK for publishing.
You can define the keys for the debug and release targets in src/debug/ and src/release/.
-->
<meta-data
android:name="com.google.android.geo.API_KEY"
android:value="AIzaSyA-z6nM3WoXwP7dBzIdz1_dssl8X81xttg" />
<activity
android:name=".MapsActivity"
android:label="#string/title_activity_maps"></activity>
</application>
Here is the thrown Exception
FATAL EXCEPTION: main Process: mazebug.danuleoshaleosha, PID: 13162
java.lang.SecurityException: my location requires permission ACCESS_FINE_LOCATION or ACCESS_COARSE_LOCATION
at com.google.maps.api.android.lib6.e.ev.c(Unknown Source)
at com.google.android.gms.maps.internal.j.onTransact(SourceFile:274)
at android.os.Binder.transact(Binder.java:387)
at com.google.android.gms.maps.internal.IGoogleMapDelegate$zza$zza.setMyLocationEnabled(Unknown Source)
at com.google.android.gms.maps.GoogleMap.setMyLocationEnabled(Unknown Source)
at mazebug.danuleoshaleosha.MapsActivity.onMapReady(MapsActivity.java:51)
at com.google.android.gms.maps.SupportMapFragment$zza$1.zza(Unknown Source)
at com.google.android.gms.maps.internal.zzo$zza.onTransact(Unknown Source)
at android.os.Binder.transact(Binder.java:387)
at com.google.android.gms.maps.internal.be.a(SourceFile:82)
at com.google.maps.api.android.lib6.e.fb.run(Unknown Source)
at android.os.Handler.handleCallback(Handler.java:739)
at android.os.Handler.dispatchMessage(Handler.java:95)
at android.os.Looper.loop(Looper.java:148)
at android.app.ActivityThread.main(ActivityThread.java:5417)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:726)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:616)
I'm pretty confused, 'cause it seems like I granted the required permissions.
Please give me a piece of advice. Thanks!

Try change the code.
// Add a marker in Sydney and move the camera
LatLng sydney = new LatLng(-34, 151);
mMap.addMarker(new MarkerOptions().position(sydney).title("Marker in Sydney"));
mMap.moveCamera(CameraUpdateFactory.newLatLng(sydney));
if (ActivityCompat.checkSelfPermission(this, android.Manifest.permission.ACCESS_FINE_LOCATION) != PackageManager.PERMISSION_GRANTED && ActivityCompat.checkSelfPermission(this, android.Manifest.permission.ACCESS_COARSE_LOCATION) != PackageManager.PERMISSION_GRANTED) return;
mMap.setMyLocationEnabled(true);
mMap.getUiSettings().setMyLocationButtonEnabled(true);

Google Map is getting loaded but marker is not getting shown on the map in android native app

I just wrote a simple program to an add maker on the Google map. When I run the app on the mobile, the marker is not visible but the Google map is getting loaded. Please help me out. I wrote the program based on Google documentation. (https://developers.google.com/maps/documentation/android/marker#add_a_marker). Here is the code.
MainActivity
public class MainActivity extends Activity {
GoogleMap mMap;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
if(mMap== null){
mMap= ((MapFragment)getFragmentManager().findFragmentById(R.id.map)).getMap();
}
mMap.addMarker(new MarkerOptions()
.position(new LatLng(0, 0))
.title("Hello world"));
}
#Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.main, menu);
return true;
}
}
Activity_main.xml
<fragment xmlns:android="http://schemas.android.com/apk/res/android"
android:id="#+id/map"
android:layout_width="match_parent"
android:layout_height="match_parent"
class="com.google.android.gms.maps.MapFragment"
xmlns:map="http://schemas.android.com/apk/res-auto"
map:cameraBearing="112.5"
map:cameraTargetLat="-33.796923"
map:cameraTargetLng="150.922433"
map:cameraTilt="30"
map:cameraZoom="6"
map:mapType="normal"
map:uiCompass="false"
map:uiRotateGestures="true"
map:uiScrollGestures="false"
map:uiTiltGestures="true"
map:uiZoomControls="false"
map:uiZoomGestures="true"/>
Manifest.xml
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="com.example.dummymaptest"
android:versionCode="1"
android:versionName="1.0" >
<permission
android:name="com.example.dummymaptest.permission.MAPS_RECEIVE"
android:protectionLevel="signature"/>
<uses-permission android:name="com.example.dummymaptest.permission.MAPS_RECEIVE"/>
<uses-sdk
android:minSdkVersion="12"
android:targetSdkVersion="18" />
<uses-permission android:name="android.permission.INTERNET" />
<uses-permission android:name="android.permission.ACCESS_NETWORK_STATE" />
<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />
<uses-permission android:name="com.google.android.providers.gsf.permission.READ_GSERVICES" />
<uses-permission android:name="android.permission.ACCESS_COARSE_LOCATION" />
<uses-permission android:name="android.permission.ACCESS_FINE_LOCATION" />
<uses-feature
android:glEsVersion="0x00020000"
android:required="true"/>
<application
android:allowBackup="true"
android:icon="#drawable/ic_launcher"
android:label="#string/app_name"
android:theme="#style/AppTheme" >
<meta-data
android:name="com.google.android.maps.v2.API_KEY"
android:value="key" />
<meta-data android:name="com.google.android.gms.version"
android:value="#integer/google_play_services_version" />
<activity
android:name="com.example.dummymaptest.MainActivity"
android:label="#string/app_name" >
<intent-filter>
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.LAUNCHER" />
</intent-filter>
</activity>
</application>
</manifest>

You have not created marker object. Do it like this:
Marker marker = mMap.addMarker(new MarkerOptions()
.position(new LatLng(0, 0))
.title("Hello world"));
Marker will be shown somewhere around africa.

You are adding marker with lat-long 0,0, so the marker would somewhere in the sea near africa. Give some real lat-long, then the marker will surely get displayed.

Gmaps not getting displayed on emulator.

while developing android app with gmaps i got error like this and my code as follows
the app wont run unless you update google play services shows in emulator
<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="fill_parent"
android:layout_height="fill_parent" >
<fragment
android:id="#+id/map"
android:name="com.google.android.gms.maps.MapFragment"
android:layout_width="match_parent"
android:layout_height="match_parent"/>
</RelativeLayout>
mainfest
<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="com.ant"
android:versionCode="1"
android:versionName="1.0" >
<uses-sdk
android:minSdkVersion="12"
android:targetSdkVersion="17" />
<uses-permission android:name="android.permission.INTERNET"/>
<uses-permission android:name="android.permission.ACCESS_NETWORK_STATE"/>
<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE"/>
<uses-permission android:name="com.google.android.providers.gsf.permission.READ_GSERVICES"/>
<uses-feature
android:glEsVersion="0x00020000"
android:required="true"/>
<meta-data
android:name="com.google.android.maps.v2.API_KEY"
android:value="AIzaSyAGcKOhosFI0OO_QbvaNSzDdRqj3S2tEvE"/>
<application
android:allowBackup="true"
android:icon="#drawable/ic_launcher"
android:label="#string/app_name"
android:theme="#style/AppTheme" >
<activity
android:name="com.ant.MainActivity"
android:label="#string/app_name" >
<intent-filter>
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.LAUNCHER" />
</intent-filter>
</activity>
<meta-data android:name="com.google.android.gms.version" android:value="#integer/google_play_services_version" />
</application>
</manifest>
and my main activity is like this
mainactivity.java
package com.ant;
import com.google.android.gms.maps.GoogleMap;
import com.google.android.gms.maps.MapFragment;
import android.os.Bundle;
import android.app.Activity;
import android.view.Menu;
import android.widget.Toast;
import android.app.Activity;
import android.os.Bundle;
public class MainActivity extends Activity {
// Google Map
private GoogleMap googleMap;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
try {
// Loading map
initilizeMap();
} catch (Exception e) {
e.printStackTrace();
}
}
/**
* function to load map. If map is not created it will create it for you
* */
private void initilizeMap() {
if (googleMap == null) {
googleMap = ((MapFragment) getFragmentManager().findFragmentById(
R.id.map)).getMap();
// check if map is created successfully or not
if (googleMap == null) {
Toast.makeText(getApplicationContext(),
"Sorry! unable to create maps", Toast.LENGTH_SHORT)
.show();
}
}
}
#Override
protected void onResume() {
super.onResume();
initilizeMap();
}
}

Please remove app from your device and reinstall.