Buttons in mapsforge

[Medyn]

hi ,i'm trying to put button over the mapsforge maps 

But it displays an error 

AndroidGraphicFactory.createInstance(this.getApplication());
this.mapView = new MapView(this);
setContentView(this.mapView);
this.mapView.setClickable(true);
this.mapView.getMapScaleBar().setVisible(true);
this.mapView.setBuiltInZoomControls(true);
this.mapView.setZoomLevelMin((byte) 10);
this.mapView.setZoomLevelMax((byte) 20);
tileCache = AndroidUtil.createTileCache(this, "mapcache",
        mapView.getModel().displayModel.getTileSize(), 1f,
        this.mapView.getModel().frameBufferModel.getOverdrawFactor());
this.mapView.setCenter(new LatLong(14.499502, 44.423186));
this.mapView.setZoomLevel((byte) 12);

MapDataStore mapDataStore = new MapFile(new File(Environment.getExternalStorageDirectory(), MAP_FILE));
tileRendererLayer = new TileRendererLayer(tileCache, mapDataStore,
        this.mapView.getModel().mapViewPosition, AndroidGraphicFactory.INSTANCE);
tileRendererLayer.setXmlRenderTheme(InternalRenderTheme.OSMARENDER);
this.mapView.getLayerManager().getLayers().add(tileRendererLayer);
btnShowLocation = (Button) findViewById(R.id.location);

btnShowLocation.setOnClickListener(new View.OnClickListener() {
    @Override
    public void onClick(View arg0) {
        // create class object
        gps = new GPSlocation(MainActivity.this);

        // check if GPS enabled
        if(gps.canGetLocation()){

            double latitude = gps.getLatitude();
            double longitude = gps.getLongitude();

            // \n is for new line
            Toast.makeText(getApplicationContext(), "Your Location is - \nLat: " + latitude + "\nLong: " + longitude, Toast.LENGTH_LONG).show();
        }else{
            // can't get location
            // GPS or Network is not enabled
            // Ask user to enable GPS/network in settings
            gps.showSettingsAlert();
        }

    }
});

                                                            FATAL EXCEPTION: main
                                                                                  Process: com.example.lifemakers.mapsforge, PID: 29270
                                                                                  java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.lifemakers.mapsforge/com.example.lifemakers.mapsforge.MainActivity}: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.widget.RelativeLayout.addView(android.view.View, int)' on a null object reference
                                                                                      at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2434)
                                                                                      at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2494)
                                                                                      at android.app.ActivityThread.access$900(ActivityThread.java:157)
                                                                                      at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1356)
                                                                                      at android.os.Handler.dispatchMessage(Handler.java:102)
                                                                                      at android.os.Looper.loop(Looper.java:148)
                                                                                      at android.app.ActivityThread.main(ActivityThread.java:5527)
                                                                                      at java.lang.reflect.Method.invoke(Native Method)
                                                                                      at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:730)
                                                                                      at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:620)
                                                                                   Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.widget.RelativeLayout.addView(android.view.View, int)' on a null object reference
                                                                                      at com.example.lifemakers.mapsforge.MainActivity.start_map(MainActivity.java:57)
                                                                                      at com.example.lifemakers.mapsforge.MainActivity.per(MainActivity.java:156)
                                                                                      at com.example.lifemakers.mapsforge.MainActivity.onCreate(MainActivity.java:47)
                                                                                      at android.app.Activity.performCreate(Activity.java:6272)
                                                                                      at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1108)
                                                                                      at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2387)
                                                                                      at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2494) 
                                                                                      at android.app.ActivityThread.access$900(ActivityThread.java:157) 
                                                                                      at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1356) 
                                                                                      at android.os.Handler.dispatchMessage(Handler.java:102) 
                                                                                      at android.os.Looper.loop(Looper.java:148) 
                                                                                      at android.app.ActivityThread.main(ActivityThread.java:5527) 
                                                                                      at java.lang.reflect.Method.invoke(Native Method) 
                                                                                      at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:730) 
                                                                                      at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:620) 

[Emux]

That code does not help us to see the layout and what is on exception line.

Nevertheless if you want to have the map view and above custom buttons, you can setContentView a RelativeLayout, and add in it the map view and then the buttons.

See map rotation example in Samples how it works.

--
Emux

[yogesh10446]

Rather than programmatically  adding your buttons to the map view, its better that you use the xml files to add other views to the mapview. Its much easier and you can perceive the look of your map in the preview.

activity_map.xml

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

    <com.example.mapsforge.views.RotateView
        android:id="@+id/rotateView"
        android:layout_width="fill_parent"
        android:layout_height="fill_parent" >

        <org.mapsforge.map.android.view.MapView
            android:id="@+id/mapView"
            android:layout_width="fill_parent"
            android:layout_height="fill_parent" />

    </com.example.mapsforge.views.RotateView>

    <LinearLayout
        android:id="@+id/zoom_controls"
        android:orientation="vertical"
        android:layout_alignParentRight="true"
        android:padding="10dp"
        android:layout_centerVertical="true"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content">

        <ImageButton
            android:id="@+id/map_zoom_in"
            android:src="@drawable/ic_icon_add_holo_light"
            android:layout_gravity="end"
            android:padding="3dp"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content" />

        <ImageButton
            android:id="@+id/map_zoom_out"
            android:src="@drawable/ic_icon_minus_holo_light"
            android:layout_gravity="end"
            android:layout_marginTop="5dp"
            android:padding="3dp"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content" />

    </LinearLayout>


    <TextView
        android:id="@+id/attribution"
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:layout_alignParentBottom="true"
        android:layout_marginBottom="1dp"
        android:gravity="center"
        android:singleLine="true"
        android:visibility="gone"
        android:text="Map data © OpenStreetMap contributors"
        android:textColor="#000"
        android:textSize="4pt" />

    <com.example.mapsforge.views.MapScaleBarView
        android:id="@+id/mapScaleBarView"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignParentBottom="true"
        android:layout_alignParentLeft="true"
        android:layout_alignParentStart="true"
        android:layout_margin="5dp" />

</RelativeLayout>

And then in the activity, as always

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    //create tht graphic factory required by the mapsforge library at the start of the activity
    AndroidGraphicFactory.createInstance(getApplication());
    setContentView(R.layout.activity_map_with_drawer);
    //get necessary views
    this.mapview = (MapView) findViewById(R.id.mapView);
    //Other lines of code
    ImageButton zoomIn = (ImageButton)findViewById(R.id.map_zoom_in);
    ...
    ...
    ...

}