How to draw a small marker image and keep refreshing its position on my CUSTOM map image? - Android

Question

I am currently developing a tracking system to plot out the user's movement trajectory inside a room or whaterever.

Now i have managed to import my map into the app and the map is free to be zoomed and moved. The next step is to place a marker to indicate the user location on the map and move the mark around OVER the map. (like floating on the map)

I read it somewhere and think this may be done with MyLocationOverlay, but most of the examples online are all to apply it onto the google map. However, in my case, my map is not google map, it is my OWN map. (The map can be the map of my room or even a map that I draw myself!)

I have done the tracking algorithm, i.e. I know where to place my marker image.

So the only question remains is how to present the marker image on top of the map image.

In details, I have a self-defined view, MapView, as follows:

package com.example.drsystem;

import android.content.Context;
import android.graphics.Canvas;
import android.graphics.drawable.Drawable;
import android.util.AttributeSet;
import android.util.Log;
import android.view.MotionEvent;
import android.view.ScaleGestureDetector;
import android.view.View;

public class MapView extends View {

    private static final int INVALID_POINTER_ID = -1;

    private Drawable mImage;
    private float mPosX;
    private float mPosY;

    private float mLastTouchX;
    private float mLastTouchY;
    private int mActivePointerId = INVALID_POINTER_ID;

    private ScaleGestureDetector mScaleDetector;
    private float mScaleFactor = 1.f;

    public MapView(Context context) {
        this(context, null, 0);

        mImage = getResources().getDrawable(R.drawable.lv12n);
        mImage.setBounds(0, 0, mImage.getIntrinsicWidth(), mImage.getIntrinsicHeight());
    }

    // called when XML tries to inflate this View
    public MapView(Context context, AttributeSet attrs) {
        this(context, attrs, 0);

        mImage = getResources().getDrawable(R.drawable.lv12n);
        mImage.setBounds(0, 0, mImage.getIntrinsicWidth(), mImage.getIntrinsicHeight());
    }

    public MapView(Context context, AttributeSet attrs, int defStyle) {
        super(context, attrs, defStyle);
        mScaleDetector = new ScaleGestureDetector(context, new ScaleListener());
    }

    @Override
    public boolean onTouchEvent(MotionEvent ev) {
        // Let the ScaleGestureDetector inspect all events.
        mScaleDetector.onTouchEvent(ev);

        final int action = ev.getAction();
        switch (action & MotionEvent.ACTION_MASK) {
        case MotionEvent.ACTION_DOWN: {
            final float x = ev.getX();
            final float y = ev.getY();

            mLastTouchX = x;
            mLastTouchY = y;
            mActivePointerId = ev.getPointerId(0);
            break;
        }

        case MotionEvent.ACTION_MOVE: {
            final int pointerIndex = ev.findPointerIndex(mActivePointerId);
            final float x = ev.getX(pointerIndex);
            final float y = ev.getY(pointerIndex);

            // Only move if the ScaleGestureDetector isn't processing a gesture.
            if (!mScaleDetector.isInProgress()) {
                final float dx = x - mLastTouchX;
                final float dy = y - mLastTouchY;

                mPosX += dx;
                mPosY += dy;

                invalidate();
            }

            mLastTouchX = x;
            mLastTouchY = y;

            break;
        }

        case MotionEvent.ACTION_UP: {
            mActivePointerId = INVALID_POINTER_ID;
            break;
        }

        case MotionEvent.ACTION_CANCEL: {
            mActivePointerId = INVALID_POINTER_ID;
            break;
        }

        case MotionEvent.ACTION_POINTER_UP: {
            final int pointerIndex = (ev.getAction() & MotionEvent.ACTION_POINTER_INDEX_MASK) >> MotionEvent.ACTION_POINTER_INDEX_SHIFT;
            final int pointerId = ev.getPointerId(pointerIndex);
            if (pointerId == mActivePointerId) {
                // This was our active pointer going up. Choose a new
                // active pointer and adjust accordingly.
                final int newPointerIndex = pointerIndex == 0 ? 1 : 0;
                mLastTouchX = ev.getX(newPointerIndex);
                mLastTouchY = ev.getY(newPointerIndex);
                mActivePointerId = ev.getPointerId(newPointerIndex);
            }
            break;
        }
        }

        return true;
    }

    @Override
    public void onDraw(Canvas canvas) {
        super.onDraw(canvas);

        canvas.save();
        Log.d("MapView", "X: " + mPosX + " Y: " + mPosY);
        canvas.translate(mPosX, mPosY);
        canvas.scale(mScaleFactor, mScaleFactor);
        mImage.draw(canvas);
        canvas.restore();
    }

    private class ScaleListener extends ScaleGestureDetector.SimpleOnScaleGestureListener {
        @Override
        public boolean onScale(ScaleGestureDetector detector) {
            mScaleFactor *= detector.getScaleFactor();

            // Don't let the object get too small or too large.
            mScaleFactor = Math.max(0.1f, Math.min(mScaleFactor, 10.0f));

            invalidate();
            return true;
        }
    }

}

Up to here, the map is successfully input into the app, and it is both movable and zoomable.

And then, I insert this custom view into the layout XML file as follows:

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:paddingBottom="@dimen/activity_vertical_margin"
    android:paddingLeft="@dimen/activity_horizontal_margin"
    android:paddingRight="@dimen/activity_horizontal_margin"
    android:paddingTop="@dimen/activity_vertical_margin"
    tools:context=".MapView" >

    <com.example.drsystem.MapView
        android:id="@+id/mapView1"
        android:layout_width="fill_parent"
        android:layout_height="400dp"
        android:layout_above="@+id/button2"
        android:layout_alignParentLeft="true"
        android:layout_alignParentRight="true"
        android:layout_alignParentTop="true" />

 ...

</RelativeLayout>

Based on all this info, how may I draw a dot and constantly update its position on my map?

Update:

The question is simply about putting another small image on top of a custom view and moving it around.

I also attach the screenshot here for your reference:

The area above the buttons and textviews is my MapView

Answer 1

To start with, use LocationClient API's (instead of LocationManager) since they work really well with mixed gps providers wifi and network. They also use sensors to recognize a movement so that they can save on battery.

I use the following LocationOverlay cod placing my icons on the map. Customize it for your need. Its a bit rough but works.

private class LocationMarker extends ItemizedOverlay<OverlayItem> {
    private Activity appContext;
    private List<OverlayItem> items = new ArrayList<OverlayItem>();
    private Drawable marker = null;
    private OverlayItem inDrag = null;
    private ImageView dragImage = null;
    private int xDragImageOffset = 0;
    private int yDragImageOffset = 0;
    private int xDragTouchOffset = 0;
    private int yDragTouchOffset = 0;
    private MapView location;
    private boolean pickupOrDrop;

    public LocationMarker(Activity newAppContext, MapView newLocation, Drawable newMarker,
            ImageView newPoint, boolean newWhichPoint) {
        super(newMarker);
        this.appContext = newAppContext;
        this.location = newLocation;
        this.marker = newMarker;
        this.dragImage = newPoint;
        this.pickupOrDrop = newWhichPoint;

        xDragImageOffset = dragImage.getDrawable().getIntrinsicWidth() / 2;
        yDragImageOffset = dragImage.getDrawable().getIntrinsicHeight();
        populate();
    }

    public void placeMarker(GeoPoint myPoint) {
        OverlayItem toDrop = new OverlayItem(myPoint, "", "");
        items.add(toDrop);
        populate();
    }

    @Override
    protected OverlayItem createItem(int i) {
        return (items.get(i));
    }

    @Override
    public void draw(Canvas canvas, MapView mapView, boolean shadow) {
        super.draw(canvas, mapView, shadow);
        boundCenterBottom(marker);
    }

    @Override
    public int size() {
        return (items.size());
    }

    @Override
    public boolean onTouchEvent(MotionEvent event, MapView mapView) {
        if (pickupOrDrop != whichPoint)
            return false;
        final int action = event.getAction();
        final int x = (int) event.getX();
        final int y = (int) event.getY();
        boolean result = false;

        // Draw temp image
        if (action == MotionEvent.ACTION_DOWN) {
            Log.d("iTaxeeta:Overlay", "Action Down" + marker.toString());
            GeoPoint myPoint = null;
            if (items.isEmpty()) {
                if (whichPoint == PICKUP) {
                    myPoint = source = location.getProjection().fromPixels(
                            x - xDragTouchOffset, y - yDragTouchOffset);
                } else if (whichPoint == DROP) {
                    myPoint = destination = location.getProjection().fromPixels(
                            x - xDragTouchOffset, y - yDragTouchOffset);
                }
                OverlayItem toDrop = new OverlayItem(myPoint, "", "");
                items.add(toDrop);
                populate();
            }
            for (OverlayItem item : items) {
                Point p = new Point(0, 0);
                Log.d("iTaxeeta:Overlay", item.getTitle());
                location.getProjection().toPixels(item.getPoint(), p);
                if (hitTest(item, marker, x - p.x, y - p.y)) {
                    result = true;
                    inDrag = item;
                    items.remove(inDrag);
                    populate();

                    xDragTouchOffset = 0;
                    yDragTouchOffset = 0;
                    setDragImagePosition(p.x, p.y);

                    dragImage.setVisibility(View.VISIBLE);
                    xDragTouchOffset = x - p.x;
                    yDragTouchOffset = y - p.y;

                    break;
                } 
                else {
                    items.clear();
                    populate();
                    if (whichPoint == PICKUP)
                        myPoint = source = location.getProjection().fromPixels(
                                x - xDragTouchOffset, y - yDragTouchOffset);
                    else if (whichPoint == DROP)
                        myPoint = destination = location.getProjection().fromPixels(
                                x - xDragTouchOffset, y - yDragTouchOffset);
                    new GetGeoAddress((IActionBar) appContext, myPoint).execute();
                    OverlayItem toDrop = new OverlayItem(myPoint, "", "");
                    items.add(toDrop);
                    populate();
                    if (source != null && destination != null) {
                        searchCabs.setEnabled(true);
                        // tip.startAnimation(rollUpAnimation);
                        searchCabs.setTextColor(Color.parseColor("#eeeee4"));
                        if (whichPoint == PICKUP)
                            searchCabs.setBackgroundColor(Color.parseColor("#fe000a"));
                        else if (whichPoint == DROP)
                            searchCabs.setBackgroundColor(Color.parseColor("#17ee27"));
                    }
                    break;
                }
            }
        }
        // Draw temp image while moving finger across the screen
        else if (action == MotionEvent.ACTION_MOVE && inDrag != null) {
            Log.d("iTaxeeta:Overlay", "Action Move" + marker.toString());
            setDragImagePosition(x, y);
            result = true;
        }
        // Position the selected point now
        else if (action == MotionEvent.ACTION_UP && inDrag != null) {
            GeoPoint myPoint = null;
            Log.d("iTaxeeta:Overlay", "Action Up" + marker.toString());
            dragImage.setVisibility(View.VISIBLE);
            if (whichPoint == PICKUP)
                myPoint = source = location.getProjection().fromPixels(x - xDragTouchOffset,
                        y - yDragTouchOffset);
            else if (whichPoint == DROP)
                myPoint = destination = location.getProjection().fromPixels(
                        x - xDragTouchOffset, y - yDragTouchOffset);
            OverlayItem toDrop = new OverlayItem(myPoint, inDrag.getTitle(),
                    inDrag.getSnippet());
            items.add(toDrop);
            populate();
            inDrag = null;
            new GetGeoAddress((IActionBar) appContext, myPoint).execute();
            if (source != null && destination != null) {
                searchCabs.setEnabled(true);
                // tip.startAnimation(rollUpAnimation);
                searchCabs.setTextColor(Color.parseColor("#eeeee4"));
                if (whichPoint == PICKUP)
                    searchCabs.setBackgroundColor(Color.parseColor("#fe000a"));
                else if (whichPoint == DROP)
                    searchCabs.setBackgroundColor(Color.parseColor("#17ee27"));
            }
            result = true;

        }

        return (result || super.onTouchEvent(event, mapView));
    }