MainActivity.java

package com.reststopperpro.android.activity;

import android.Manifest;
import android.content.pm.PackageManager;
import android.os.Bundle;
import android.support.annotation.NonNull;
import android.support.annotation.Nullable;
import android.support.v4.app.ActivityCompat;
import android.support.v7.app.AppCompatActivity;
import android.view.View;

import com.google.android.gms.common.ConnectionResult;
import com.google.android.gms.common.api.GoogleApiClient;
import com.google.android.gms.location.LocationServices;
import com.reststopperpro.android.R;

public class MainActivity extends AppCompatActivity implements
        ActivityCompat.OnRequestPermissionsResultCallback,
        GoogleApiClient.ConnectionCallbacks,
        GoogleApiClient.OnConnectionFailedListener {

    private static final int LOCATION_PERMISSION_REQUEST = 100;
    private GoogleApiClient googleApiClient;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);

        setContentView(R.layout.main);

        setUpGoogleApiClient();
    }

    private void setUpGoogleApiClient() {
        googleApiClient = new GoogleApiClient.Builder(this)
                .enableAutoManage(this, this)
                .addConnectionCallbacks(this)
                .addApi(LocationServices.API)
                .build();
    }

    // the view has one button, this is its "onClick"
    public void onNearbyClicked(View view) {
        if (locationPermissionGranted()) {
            showNearbyActivity();
        } else {
            requestLocationPermissionForNearbyList();
        }
    }

    private void showNearbyActivity() {
        // TODO: only show the next activity if we have a google api client
        // if we don't do we wait and keep checking?
        if (!googleApiClient.isConnected()) {
            // TODO: what should we do? sleep and try again?
        } else {
            // go ahead and show the nearby list
        }
    }

    private void requestLocationPermissionForNearbyList() {
        ActivityCompat.requestPermissions(this,
                new String[] { Manifest.permission.ACCESS_FINE_LOCATION },
                LOCATION_PERMISSION_REQUEST);
    }

    private boolean locationPermissionGranted() {
        return ActivityCompat.checkSelfPermission(this,
                Manifest.permission.ACCESS_FINE_LOCATION) == PackageManager.PERMISSION_GRANTED;
    }

    @Override
    public void onRequestPermissionsResult(int requestCode, String permissions[],
                                          int[] grantResults) {
        switch (requestCode) {
            case LOCATION_PERMISSION_REQUEST:
                if (permissionGranted(grantResults)) {
                    showNearbyActivity();
                }
                return;
        }

    }

    private boolean permissionGranted(int[] grantResults) {
        return grantResults.length > 0 &&
                grantResults[0] == PackageManager.PERMISSION_GRANTED;
    }

    @Override
    public void onConnected(@Nullable Bundle bundle) {
       // TODO: figure out what to do here
    }

    @Override
    public void onConnectionSuspended(int i) {
        // TODO: figure out what to do here
    }

    @Override
    public void onConnectionFailed(@NonNull ConnectionResult connectionResult) {
        // TODO: figure out what to do here
    }
}