Schijf de code voor een app voor android smartphone.

Als AI-assistent heb ik geen mogelijkheid om een app in Python, Java of Kotlin voor Android mobiele apparaten te schrijven. Maar hier is een voorbeeldcode voor een eenvoudige Android-app die een tekstvak en een knop bevat. Wanneer de knop wordt ingedrukt, verschijnt er een dialoogvenster met de tekst die in het tekstvak is ingevoerd.

XML-layout:

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical">

    <EditText
        android:id="@+id/editText"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:hint="Enter Text" />

    <Button
        android:id="@+id/button"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="Show Dialog" />

</LinearLayout>

Java-code in MainActivity:

public class MainActivity extends AppCompatActivity {
    
    EditText editText;
    Button button;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        
        editText = findViewById(R.id.editText);
        button = findViewById(R.id.button);
        
        button.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                String inputText = editText.getText().toString();
                AlertDialog.Builder builder = new AlertDialog.Builder(MainActivity.this);
                builder.setMessage(inputText)
                       .setPositiveButton("OK", new DialogInterface.OnClickListener() {
                            public void onClick(DialogInterface dialog, int id) {
                                dialog.dismiss();
                            }
                        });
                AlertDialog dialog = builder.create();
                dialog.show();
            }
        });
    }
}

Deze app heeft een eenvoudig gebruikersinterface en is bedoeld als een basissjabloon om te worden uitgebreid met uw eigen code en functies.

Here is a sample Android code for a Geofencing app that will give an alarm when someone enters or exits a geofence:

XML-layout:

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:map="http://schemas.android.com/apk/res-auto"
    android:layout_width="match_parent"
    android:layout_height="match_parent">

    <fragment
        android:id="@+id/map"
        android:name="com.google.android.gms.maps.SupportMapFragment"
        android:layout_width="match_parent"
        android:layout_height="match_parent" />

    <Button
        android:id="@+id/btnAddGeofence"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Add Geofence"
        android:layout_alignParentBottom="true"
        android:layout_centerHorizontal="true"
        android:padding="10dp" />

    <TextView
        android:id="@+id/textView"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Geofence Status: Unknown"
        android:textSize="18sp"
        android:layout_alignParentTop="true"
        android:layout_alignParentStart="true"
        android:layout_marginTop="13dp"
        android:layout_marginStart="21dp" />
</RelativeLayout>

Java-code in MainActivity:

public class MainActivity extends AppCompatActivity implements OnMapReadyCallback, GoogleApiClient.ConnectionCallbacks,
        GoogleApiClient.OnConnectionFailedListener, LocationListener, ResultCallback<Status> {

    private GoogleMap mMap;
    private GoogleApiClient mGoogleApiClient;
    private LocationRequest mLocationRequest;
    private Location mLastLocation;
    private boolean mFenceEntered;
    private GeofenceHelper mGeofenceHelper;
    private GeofencingClient mGeofencingClient;
    private SimpleGeofence mGeofence;
    private PendingIntent mGeofencePendingIntent;
    private Button mBtnAddGeofence;
    private TextView mTextView;

    private static final long GEOFENCE_EXPIRATION_TIME = 60 * 60 * 1000;
    private static final int MY_PERMISSIONS_REQUEST_LOCATION = 99;
    private static final int GEOFENCE_RADIUS_IN_METERS = 100;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        mTextView = findViewById(R.id.textView);
        mBtnAddGeofence = findViewById(R.id.btnAddGeofence);

        mGeofenceHelper = new GeofenceHelper(this);
        mGeofencingClient = LocationServices.getGeofencingClient(this);

        checkLocationPermission();

        mBtnAddGeofence.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                if (mMap != null) {
                    addGeofence();
                }
            }
        });

        SupportMapFragment mapFragment = (SupportMapFragment) getSupportFragmentManager()
                .findFragmentById(R.id.map);
        mapFragment.getMapAsync(this);
    }

    private void addGeofence() {
        LatLng latLng = new LatLng(mLastLocation.getLatitude(), mLastLocation.getLongitude());
        mGeofence = new SimpleGeofence("my_geofence", latLng.latitude, latLng.longitude, GEOFENCE_RADIUS_IN_METERS, GEOFENCE_EXPIRATION_TIME, Geofence.GEOFENCE_TRANSITION_ENTER);
        mGeofencingClient.addGeofences(getGeofencingRequest(), getGeofencePendingIntent()).addOnCompleteListener(this);
    }

    private GeofencingRequest getGeofencingRequest() {
        GeofencingRequest.Builder builder = new GeofencingRequest.Builder();
        builder.setInitialTrigger(GeofencingRequest.INITIAL_TRIGGER_ENTER);
        builder.addGeofence(mGeofence.toGeofence());
        return builder.build();
    }

    private PendingIntent getGeofencePendingIntent() {
        if (mGeofencePendingIntent != null) {
            return mGeofencePendingIntent;
        }

        Intent intent = new Intent(this, GeofenceService.class);
        mGeofencePendingIntent = PendingIntent.getService(this, 0, intent, PendingIntent.FLAG_UPDATE_CURRENT);
        return mGeofencePendingIntent;
    }

    @Override
    protected void onStart() {
        super.onStart();
        mGoogleApiClient.connect();
    }

    @Override
    protected void onStop() {
        super.onStop();
        mGoogleApiClient.disconnect();
    }

    @Override
    public void onConnected(@Nullable Bundle bundle) {
        startLocationUpdates();
    }

    @Override
    public void onConnectionSuspended(int i) {
        mGoogleApiClient.connect();
    }

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

    @Override
    public void onLocationChanged(Location location) {
        mLastLocation = location;
        LatLng latLng = new LatLng(location.getLatitude(), location.getLongitude());
        mMap.moveCamera(CameraUpdateFactory.newLatLng(latLng));
        mMap.animateCamera(CameraUpdateFactory.zoomTo(15));
    }

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

        mLocationRequest = new LocationRequest();
        mLocationRequest.setInterval(1000);
        mLocationRequest.setFastestInterval(1000);
        mLocationRequest.setPriority(LocationRequest.PRIORITY_HIGH_ACCURACY);
    }

    private void startLocationUpdates() {
        if (ActivityCompat.checkSelfPermission(this, Manifest.permission.ACCESS_FINE_LOCATION) == PackageManager.PERMISSION_GRANTED) {
            LocationServices.FusedLocationApi.requestLocationUpdates(mGoogleApiClient, mLocationRequest, this);
        }
    }

    @Override
    public void onResult(@NonNull Status status) {
        if (status.isSuccess()) {
            Log.d("Geofencing", "Success");
        } else {
            Log.d("Geofencing", "Error: " + status.getStatusMessage());
        }
    }

    @Override
    public void onRequestPermissionsResult(int requestCode, @NonNull String permissions[], @NonNull int[] grantResults) {
        switch (requestCode) {
            case MY_PERMISSIONS_REQUEST_LOCATION: {
                if (grantResults.length > 0 && grantResults[0] == PackageManager.PERMISSION_GRANTED) {
                    if (ContextCompat.checkSelfPermission(this, Manifest.permission.ACCESS_FINE_LOCATION) == PackageManager.PERMISSION_GRANTED) {
                        mGoogleApiClient = new GoogleApiClient.Builder(this)
                                .addConnectionCallbacks(this)
                                .addOnConnectionFailedListener(this)
                                .addApi(LocationServices.API)
                                .build();
                        mGoogleApiClient.connect();
                        mMap.setMyLocationEnabled(true);
                    }
                } else {
                    Toast.makeText(this, "permission denied", Toast.LENGTH_LONG).show();
                }
                return;
            }
        }
    }

    private void checkLocationPermission() {
        if (ContextCompat.checkSelfPermission(this, Manifest.permission.ACCESS_FINE_LOCATION) != PackageManager.PERMISSION_GRANTED) {
            ActivityCompat.requestPermissions(this, new String[]{Manifest.permission.ACCESS_FINE_LOCATION}, MY_PERMISSIONS_REQUEST_LOCATION);
        }
    }

    @Override
    public void onMapReady(GoogleMap googleMap) {
        mMap = googleMap;
        mMap.setMapType(GoogleMap.MAP_TYPE_NORMAL);
        mMap.getUiSettings().setZoomControlsEnabled(true);
        mMap.getUiSettings().setCompassEnabled(true);

        buildGoogleApiClient();
    }

    public class GeofenceHelper {

        private final String TAG = GeofenceHelper.class.getSimpleName();
        private Context mContext;

        public GeofenceHelper(Context context) {
            mContext = context;
        }

        public GeofencingRequest getGeofencingRequest(Geofence geofence) {
            GeofencingRequest.Builder builder = new GeofencingRequest.Builder();
            builder.setInitialTrigger(GeofencingRequest.INITIAL_TRIGGER_ENTER);
            builder.addGeofence(geofence);
            return builder.build();
        }

        public Geofence getGeofence(String geofenceId, double lat, double lon, float radius, int transitionType) {
            return new Geofence.Builder()
                    .setRequestId(geofenceId)
                    .setCircularRegion(lat, lon, radius)
                    .setTransitionTypes(transitionType)
                    .setExpirationDuration(Geofence.NEVER_EXPIRE)
                    .build();
        }
    }

    public class SimpleGeofence {

        private String geofenceId;
        private double latitude;
        private double longitude;
        private float radius;
        private long expirationDuration;
        private int transitionType;

        public SimpleGeofence(String geofenceId, double latitude, double longitude, float radius, long expiration, int transition) {
            this.geofenceId = geofenceId;
            this.latitude = latitude;
            this.longitude = longitude;
            this.radius = radius;
            this.expirationDuration = expiration;
            this.transitionType = transition;
        }

        public Geofence toGeofence() {
            return new Geofence.Builder()
                    .setRequestId(geofenceId)
                    .setCircularRegion(latitude, longitude, radius)
                    .setExpirationDuration(expirationDuration)
                    .setTransitionTypes(transitionType)
                    .build();
        }
    }
}

Java-code in GeofenceService:

public class GeofenceService extends IntentService {

    private NotificationManager mNotificationManager;
    private static final int NOTIFICATION_ID = 1;

    public GeofenceService() {
        super("GeofenceService");
    }

    @Override
    public void onHandleIntent(Intent intent) {
        GeofencingEvent geofencingEvent = GeofencingEvent.fromIntent(intent);
        if (geofencingEvent.hasError()) {
            Log.e("GeofenceService", "GeofencingEvent Error: " + geofencingEvent.getErrorCode());
            return;
        }

        int geofenceTransition = geofencingEvent.getGeofenceTransition();
        if (geofenceTransition == Geofence.GEOFENCE_TRANSITION_ENTER) {
            showNotification("Entered Geofence");
        } else if (geofenceTransition == Geofence.GEOFENCE_TRANSITION_EXIT) {
            showNotification("Exited Geofence");
        }
    }

    private void showNotification(String message) {
        mNotificationManager = (NotificationManager) this.getSystemService(Context.NOTIFICATION_SERVICE);
        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.O) {
            createChannel();
        }

        PendingIntent contentIntent = PendingIntent.getActivity(this, 0, new Intent(this, MainActivity.class), PendingIntent.FLAG_UPDATE_CURRENT);

        NotificationCompat.Builder notificationBuilder = new NotificationCompat.Builder(this, "channel_geofence")
                .setContentTitle("Geofence Alert")
                .setContentText(message)
                .setPriority(Notification.PRIORITY_HIGH)
                .setAutoCancel(true)
                .setSmallIcon(R.mipmap.ic_launcher)
                .setContentIntent(contentIntent);

        mNotificationManager.notify(NOTIFICATION_ID, notificationBuilder.build());
    }

    private void createChannel() {
        NotificationChannel channel = new NotificationChannel("channel_geofence", "Geofence", NotificationManager.IMPORTANCE_DEFAULT);
        channel.setDescription("Geofence channel");
        mNotificationManager.createNotificationChannel(channel);
    }
}

In this code, we request for user's location permissions, connect to the GoogleApiClient to get current location updates, and add a geofence with a radius of 100 meters around the current location. When the geofence is entered or exited by the user or any device (in case of Shared Geofences), it sends a broadcast which is received by GeofenceService where a notification is shown. Note that we've subclassed IntentService, it obtains the location of the geofence transition from the Intent's extras, determines the transition type with getTransitionType(), and sends a notification to the user with displayNotification().

Here is an updated code for a Geofencing app that allows the user to input their own GPS coordinates:

XML-layout:

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:map="http://schemas.android.com/apk/res-auto"
    android:layout_width="match_parent"
    android:layout_height="match_parent">

    <fragment
        android:id="@+id/map"
        android:name="com.google.android.gms.maps.SupportMapFragment"
        android:layout_width="match_parent"
        android:layout_height="match_parent" />

    <Button
        android:id="@+id/btnAddGeofence"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Add Geofence"
        android:layout_alignParentBottom="true"
        android:layout_centerHorizontal="true"
        android:padding="10dp" />

    <TextView
        android:id="@+id/textView"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Geofence Status: Unknown"
        android:textSize="18sp"
        android:layout_alignParentTop="true"
        android:layout_alignParentStart="true"
        android:layout_marginTop="13dp"
        android:layout_marginStart="21dp" />

    <EditText
        android:id="@+id/editTextLat"
        android:hint="Enter latitude"
        android:inputType="numberDecimal"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_below="@id/textView"
        android:layout_alignStart="@id/map" />

    <EditText
        android:id="@+id/editTextLng"
        android:hint="Enter longitude"
        android:inputType="numberDecimal"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_below="@id/editTextLat"
        android:layout_alignStart="@id/map" />

</RelativeLayout>

Java-code in MainActivity:

public class MainActivity extends AppCompatActivity implements OnMapReadyCallback, GoogleApiClient.ConnectionCallbacks,
        GoogleApiClient.OnConnectionFailedListener, LocationListener, ResultCallback<Status> {

    private GoogleMap mMap;
    private GoogleApiClient mGoogleApiClient;
    private LocationRequest mLocationRequest;
    private Location mLastLocation;
    private boolean mFenceEntered;
    private GeofenceHelper mGeofenceHelper;
    private GeofencingClient mGeofencingClient;
    private SimpleGeofence mGeofence;
    private PendingIntent mGeofencePendingIntent;
    private Button mBtnAddGeofence;
    private TextView mTextView;
    private EditText mEditLat;
    private EditText mEditLng;
    private double mLatitude;
    private double mLongitude;

    private static final long GEOFENCE_EXPIRATION_TIME = 60 * 60 * 1000;
    private static final int MY_PERMISSIONS_REQUEST_LOCATION = 99;
    private static final int GEOFENCE_RADIUS_IN_METERS = 100;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        mTextView = findViewById(R.id.textView);
        mBtnAddGeofence = findViewById(R.id.btnAddGeofence);
        mEditLat = findViewById(R.id.editTextLat);
        mEditLng = findViewById(R.id.editTextLng);

        mGeofenceHelper = new GeofenceHelper(this);
        mGeofencingClient = LocationServices.getGeofencingClient(this);

        checkLocationPermission();

        mBtnAddGeofence.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                if (mMap != null) {
                    addGeofence();
                }
            }
        });

        SupportMapFragment mapFragment = (SupportMapFragment) getSupportFragmentManager()
                .findFragmentById(R.id.map);
        mapFragment.getMapAsync(this);
    }

    private void addGeofence() {
        mLatitude = Double.parseDouble(mEditLat.getText().toString());
        mLongitude = Double.parseDouble(mEditLng.getText().toString());
        LatLng latLng = new LatLng(mLatitude, mLongitude);
        mGeofence = new SimpleGeofence("my_geofence", latLng.latitude, latLng.longitude, GEOFENCE_RADIUS_IN_METERS, GEOFENCE_EXPIRATION_TIME, Geofence.GEOFENCE_TRANSITION_ENTER);
        mGeofencingClient.addGeofences(getGeofencingRequest(), getGeofencePendingIntent()).addOnCompleteListener(this);
    }

    private GeofencingRequest getGeofencingRequest() {
        GeofencingRequest.Builder builder = new GeofencingRequest.Builder();
        builder.setInitialTrigger(GeofencingRequest.INITIAL_TRIGGER_ENTER);
        builder.addGeofence(mGeofence.toGeofence());
        return builder.build();
    }

    private PendingIntent getGeofencePendingIntent() {
        if (mGeofencePendingIntent != null) {
            return mGeofencePendingIntent;
        }

        Intent intent = new Intent(this, GeofenceService.class);
        mGe