Activities lifecycle after pushed android button "recents" create new activity but dont destroy old activity

Question

When i push android button "recents" and select my app again to go back to de app, the lifecycle of MapsActivity execute onCreate again and create a new instance of MapsActivity.

That´s ok, but the old MapsActivity still running in background and that´s a problem because both MapsActivity have counters and still running and counting with different values in the same variables, like independent new variables.

The counter is in onLocationChanged() and called as "clock". onLocationChanged() update automaticaly ever 5 seconds.

example: counter is running : 1, 2, 3, 4, 5, ... at this point i push android button "recent" (the system execute onCreate) counter still running like that : 6, 1, 7, 2, 8, 3, ... at this point a push again android button "recent" (execute onCreate) counter still running like that : 9, 4, 1, 10, 5, 2, 11, 6, 3, ...

I suppose the lifecycle of MapsActivity not destroy old activities.

I need only one sequencial counter running, and i guess the old MapsActivity must die :)

any idea to solve my problem ? Thanks a lot!

below the manifest.xml

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="com.example.sasse.myapplication">

    <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">

        <meta-data
            android:name="com.google.android.geo.API_KEY"
            android:value="@string/google_maps_key" />

        <activity
            android:name=".MapsActivity"
            android:label="@string/title_activity_maps">
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />

                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>
    </application>

</manifest>

layout activity_maps.xml

<fragment xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:map="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:id="@+id/map"
    android:name="com.google.android.gms.maps.SupportMapFragment"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context="com.example.sasse.myapplication.MapsActivity" />

Maps_activity

package com.example.sasse.myapplication;

import android.*;
import android.Manifest;
import android.content.pm.PackageManager;
import android.location.Location;
import android.os.Build;
import android.support.annotation.NonNull;
import android.support.v4.app.ActivityCompat;
import android.support.v4.app.FragmentActivity;
import android.os.Bundle;
import android.support.v4.content.ContextCompat;
import android.util.Log;
import android.widget.Toast;

import com.google.android.gms.common.ConnectionResult;
import com.google.android.gms.common.api.GoogleApiClient;
import com.google.android.gms.common.api.GoogleApiClient.ConnectionCallbacks;
import com.google.android.gms.common.api.GoogleApiClient.OnConnectionFailedListener;
import com.google.android.gms.location.LocationListener;
import com.google.android.gms.location.LocationRequest;
import com.google.android.gms.location.LocationServices;
import com.google.android.gms.maps.CameraUpdateFactory;
import com.google.android.gms.maps.GoogleMap;
import com.google.android.gms.maps.OnMapReadyCallback;
import com.google.android.gms.maps.SupportMapFragment;
import com.google.android.gms.maps.model.LatLng;
import com.google.android.gms.maps.model.MarkerOptions;

public class MapsActivity extends FragmentActivity implements LocationListener, ConnectionCallbacks, OnConnectionFailedListener, OnMapReadyCallback {

    private static final String TAG = "MapsActivity";
    private GoogleMap mMap;
    protected GoogleApiClient mGoogleApiClient;
    protected LocationRequest mLocationRequest;
    public int clock = 0;

    @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);
        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.M) {
            checkLocationPermission();
        }
    }

    @Override
    public void onMapReady(GoogleMap googleMap) {
        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));
        //Initialize Google Play Services
        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.M) {
            if (ContextCompat.checkSelfPermission(this,
                    android.Manifest.permission.ACCESS_FINE_LOCATION)
                    == PackageManager.PERMISSION_GRANTED) {
                buildGoogleApiClient();
                mMap.setMyLocationEnabled(true);
            }
        } else {
            buildGoogleApiClient();
            mMap.setMyLocationEnabled(true);
        }

    }

    public void onLocationChanged(Location location) {

        clock++;
        if (clock>=10) {

            Toast.makeText(this, "clock : "+clock, Toast.LENGTH_SHORT).show();
            clock=0;
        }
        Log.i(TAG, "= = = = = >>> clock : "+clock);
    }

    // ---------------------------------------------------------------------------------------------
    // ---------------- VERIFICAÇÃO DA CONEXÃO COM O SERVIDOR DO GOOGLE MAPS-----------------------
    // ---------------------------------------------------------------------------------------------
    public static final int MY_PERMISSIONS_REQUEST_LOCATION = 99;

    public boolean checkLocationPermission() {
        if (ContextCompat.checkSelfPermission(this,
                android.Manifest.permission.ACCESS_FINE_LOCATION)
                != PackageManager.PERMISSION_GRANTED) {

            // Asking user if explanation is needed
            if (ActivityCompat.shouldShowRequestPermissionRationale(this,
                    android.Manifest.permission.ACCESS_FINE_LOCATION)) {

                // Show an explanation to the user *asynchronously* -- don't block
                // this thread waiting for the user's response! After the user
                // sees the explanation, try again to request the permission.

                //Prompt the user once explanation has been shown
                ActivityCompat.requestPermissions(this,
                        new String[]{android.Manifest.permission.ACCESS_FINE_LOCATION},
                        MY_PERMISSIONS_REQUEST_LOCATION);
            } else {
                // No explanation needed, we can request the permission.
                ActivityCompat.requestPermissions(this,
                        new String[]{android.Manifest.permission.ACCESS_FINE_LOCATION},
                        MY_PERMISSIONS_REQUEST_LOCATION);
            }
            return false;
        } else {
            return true;
        }
    }

    public void onRequestPermissionsResult(int requestCode, @NonNull String permissions[], @NonNull int[] grantResults) {
        switch (requestCode) {
            case MY_PERMISSIONS_REQUEST_LOCATION: {
                // If request is cancelled, the result arrays are empty.
                if (grantResults.length > 0 && grantResults[0] == PackageManager.PERMISSION_GRANTED) {
                    // permission was granted. Do the
                    // contacts-related task you need to do.
                    if (ContextCompat.checkSelfPermission(this,
                            android.Manifest.permission.ACCESS_FINE_LOCATION)
                            == PackageManager.PERMISSION_GRANTED) {
                        if (mGoogleApiClient == null) {
                            buildGoogleApiClient();
                        }
                        mMap.setMyLocationEnabled(true);
                    }
                } else {
                    // Permission denied, Disable the functionality that depends on this permission.
                    Toast.makeText(this, "permission denied", Toast.LENGTH_LONG).show();
                }
            }
            // other 'case' lines to check for other permissions this app might request.
            // You can add here other case statements according to your requirement.
        }
    }

    protected synchronized void buildGoogleApiClient() {
        mGoogleApiClient = new GoogleApiClient.Builder(this)
                .addConnectionCallbacks(this)
                .addOnConnectionFailedListener(this)
                .addApi(LocationServices.API)
                .build();
        mGoogleApiClient.connect();
    }

    public void onConnected(Bundle bundle) {
        mLocationRequest = new LocationRequest();
        mLocationRequest.setInterval(5000);
        mLocationRequest.setFastestInterval(5000);
        mLocationRequest.setPriority(LocationRequest.PRIORITY_BALANCED_POWER_ACCURACY);
        if (ContextCompat.checkSelfPermission(this,
                Manifest.permission.ACCESS_FINE_LOCATION)
                == PackageManager.PERMISSION_GRANTED) {
            LocationServices.FusedLocationApi.requestLocationUpdates(mGoogleApiClient, mLocationRequest, this);
        }
    }

    public void onConnectionSuspended(int i) {
    }

    public void onConnectionFailed(@NonNull ConnectionResult connectionResult) {
    }
}

Answer 1

Try using launchMode="singleTop" for activity