osmdroid API解读（十一）

osmdroid-android org.osmdroid.views.overlay包

表示覆盖物的基类，可以在MapView的顶层显示。为了添加一个overlay，需要创建一个此类的子类实体，并添加到MapView.getOverlays()的列表中。

此类实现了类似于android.view.GestureDetector.SimpleOnGestureListener和GestureDetector.OnGestureListener的手势监听器。不同之处在于为方法添加了新的参数。

1. Overlay

public abstract class Overlay implements OverlayConstants {    //静态常量    private static AtomicInteger sOrdinal = new AtomicInteger();    protected static final float SHADOW_X_SKEW = -0.8999999761581421f;    protected static final float SHADOW_Y_SCALE = 0.5f;    private static final Rect mRect = new Rect();    //可用性    private boolean mEnabled = true;    //过期    @Deprecated    public Overlay(final Context ctx) {    }    public Overlay() {    }    /**     * Sets whether the Overlay is marked to be enabled. This setting does nothing by default, but     * should be checked before calling draw().     */    //该图层是否被标记为可用。默认为可用，在使用draw()方法前应调用    public void setEnabled(final boolean pEnabled) {        this.mEnabled = pEnabled;    }    public boolean isEnabled() {        return this.mEnabled;    }    /**     * Since the menu-chain will pass through several independent Overlays, menu IDs cannot be fixed     * at compile time. Overlays should use this method to obtain and store a menu id for each menu     * item at construction time. This will ensure that two overlays don't use the same id.     *     * @return an integer suitable to be used as a menu identifier     */    //由于 menu-chain 传递通过多个独立的覆盖物，menu IDs并不能在编译时固定。此方法用于为构造menu item时获取并存储一个menu id。此方法可以确保两个图层不使用相同的id。    protected final static int getSafeMenuId() {        return sOrdinal.getAndIncrement();    }    protected final static int getSafeMenuIdSequence(final int count) {        return sOrdinal.getAndAdd(count);    }    //在map上绘制overlay。此方法在所有活动图层设置为shadow=true以画下阴影层调用，然后再设置shadow=false再次调用。调用者应该在调用此方法之前检查isEnabled()。默认情况下不画任何东西。    public abstract void draw(final Canvas c, final MapView osmv, final boolean shadow);    // ===========================================================    // Methods    // ===========================================================    /**     * Override to perform clean up of resources before shutdown. By default does nothing.     *      */    //应该被复写在关闭之前执行清理资源工作    public void onDetach(final MapView mapView) {    }    //默认情况下不做任何时，返回false。如果你处理了则返回true。若返回true，其他图层将对此事件不做任何处理。    public boolean onKeyDown(final int keyCode, final KeyEvent event, final MapView mapView) {        return false;    }    public boolean onKeyUp(final int keyCode, final KeyEvent event, final MapView mapView) {        return false;    }    public boolean onTrackballEvent(final MotionEvent event, final MapView mapView) {        return false;    }    //利用此可阻止触摸相关的的事件。    public boolean onTouchEvent(final MotionEvent event, final MapView mapView) {        return false;    }    /** GestureDetector.OnDoubleTapListener **/    public boolean onDoubleTap(final MotionEvent e, final MapView mapView) {        return false;    }    public boolean onDoubleTapEvent(final MotionEvent e, final MapView mapView) {        return false;    }    public boolean onSingleTapConfirmed(final MotionEvent e, final MapView mapView) {        return false;    }    /** OnGestureListener **/    public boolean onDown(final MotionEvent e, final MapView mapView) {        return false;    }    public boolean onFling(final MotionEvent pEvent1, final MotionEvent pEvent2,            final float pVelocityX, final float pVelocityY, final MapView pMapView) {        return false;    }    public boolean onLongPress(final MotionEvent e, final MapView mapView) {        return false;    }    public boolean onScroll(final MotionEvent pEvent1, final MotionEvent pEvent2,            final float pDistanceX, final float pDistanceY, final MapView pMapView) {        return false;    }    public void onShowPress(final MotionEvent pEvent, final MapView pMapView) {        return;    }    public boolean onSingleTapUp(final MotionEvent e, final MapView mapView) {        return false;    }    //方便平移画Drawable的方法，x、y时像素坐标。你可以通过MapView.getProjection()方法将经纬度坐标转换为像素坐标。    protected synchronized static void drawAt(final Canvas canvas, final Drawable drawable,                                              final int x, final int y, final boolean shadow,                                              final float aMapOrientation) {        canvas.save();        canvas.rotate(-aMapOrientation, x, y);        drawable.copyBounds(mRect);        drawable.setBounds(mRect.left + x, mRect.top + y, mRect.right + x, mRect.bottom + y);        drawable.draw(canvas);        drawable.setBounds(mRect);        canvas.restore();    }    /**     * Interface definition for overlays that contain items that can be snapped to (for example,     * when the user invokes a zoom, this could be called allowing the user to snap the zoom to an     * interesting point.)     */    //用于对overlays的包含项进行改变。比如当使用者调用缩放，允许使用者将缩放水平调整到相应的值。    public interface Snappable {        //检查给定的x、y是否接近于某个项，从而将当前动作调整到此项上        boolean onSnapToItem(int x, int y, Point snapPoint, IMapView mapView);    }}

1.1 IconOverlay

图标型Overlay，可以在Overlay中放入一个icon

public class IconOverlay extends Overlay {    //通常icon在像素坐标系中的位置    public static final float ANCHOR_CENTER=0.5f, ANCHOR_LEFT=0.0f, ANCHOR_TOP=0.0f, ANCHOR_RIGHT=1.0f, ANCHOR_BOTTOM=1.0f;    protected Drawable mIcon        = null;//图标    protected IGeoPoint mPosition   = null;//位置    protected float mBearing = 0.0f;    protected float mAnchorU = ANCHOR_CENTER , mAnchorV=ANCHOR_CENTER;    protected float mAlpha = 1.0f; //opaque    protected boolean mFlat = false; //billboard;    protected Point mPositionPixels = new Point();    public IconOverlay() {    }    public IconOverlay(IGeoPoint position, Drawable icon) {        set(position, icon);    }    //画图标到图上    @Override    public void draw(Canvas canvas, MapView mapView, boolean shadow) {        if (shadow)            return;        if (mIcon == null)            return;        if (mPosition == null)            return;        final Projection pj = mapView.getProjection();        pj.toPixels(mPosition, mPositionPixels);        int width = mIcon.getIntrinsicWidth();        int height = mIcon.getIntrinsicHeight();        Rect rect = new Rect(0, 0, width, height);        rect.offset(-(int)(mAnchorU*width), -(int)(mAnchorV*height));        mIcon.setBounds(rect);        mIcon.setAlpha((int) (mAlpha * 255));        float rotationOnScreen = (mFlat ? -mBearing : mapView.getMapOrientation()-mBearing);        drawAt(canvas, mIcon, mPositionPixels.x, mPositionPixels.y, false, rotationOnScreen);    }    public IGeoPoint getPosition() {        return mPosition;    }    public IconOverlay set(IGeoPoint position, Drawable icon) {        this.mPosition = position;        this.mIcon = icon;        return this;    }    public IconOverlay moveTo(final MotionEvent event, final MapView mapView){        final Projection pj = mapView.getProjection();        moveTo(pj.fromPixels((int) event.getX(), (int) event.getY()), mapView);        return this;    }    public IconOverlay moveTo(final IGeoPoint position, final MapView mapView){        mPosition = position;        mapView.invalidate();        return this;    }}

1.1.1 ClickableIconOverlay

可点击图标的Overlay，在IconOverlay基础上添加了点击处理机制

public abstract class ClickableIconOverlay<DataType> extends IconOverlay {    protected int mId = 0;    private DataType mData = null;    //非UI线程创建    protected ClickableIconOverlay(DataType data) {        mData = data;    }    //标记被点击回调方法    abstract protected boolean onMarkerClicked(MapView mapView, int markerId, IGeoPoint makerPosition, DataType markerData);    //回收利用本类    public ClickableIconOverlay set(int id, IGeoPoint position, Drawable icon, DataType data) {        set(position, icon);        mId = id;        mData = data;        return this;    }    //确定该点是否是该图标的事件    protected boolean hitTest(final MotionEvent event, final MapView mapView){        final Projection pj = mapView.getProjection();        // sometime at higher zoomlevels pj is null        if ((mPosition == null) || (mPositionPixels == null) || (pj == null)) return false;        pj.toPixels(mPosition, mPositionPixels);        final Rect screenRect = pj.getIntrinsicScreenRect();        int x = -mPositionPixels.x + screenRect.left + (int) event.getX();        int y = -mPositionPixels.y + screenRect.top + (int) event.getY();        boolean hit = mIcon.getBounds().contains(x, y);        return hit;    }    //处理单次tap事件    @Override public boolean onSingleTapConfirmed(final MotionEvent event, final MapView mapView) {        boolean touched = hitTest(event, mapView);        if (touched) {            return onMarkerClicked(mapView, mId, mPosition, mData);        } else {            return super.onSingleTapConfirmed(event, mapView);        }    }    //处理长按事件，本类中并未处理    public boolean onLongPress(final MotionEvent event, final MapView mapView) {        boolean touched = hitTest(event, mapView);        if (touched) {            return onMarkerLongPress(mapView, mId, mPosition, mData);        } else {            return super.onLongPress(event, mapView);        }    }    protected boolean onMarkerLongPress(MapView mapView, int markerId, IGeoPoint geoPosition, Object data) {        return false;    }    public static ClickableIconOverlay find(List<ClickableIconOverlay> list, int id) {        for (ClickableIconOverlay item : list) {            if ((item != null) && (item.mId == id)) return item;        }        return null;    }    public int getID() {        return mId;    }    public DataType getData() {        return mData;    }}

1.2 关于ItemOverlay

1.2.0 OverlayItem

可以被显示在ItemizedOverlay或ItemizedIconOverlay的选项。描述了一个有标题和描述的坐标

public class OverlayItem {    public static final int ITEM_STATE_FOCUSED_MASK = 4;    public static final int ITEM_STATE_PRESSED_MASK = 1;    public static final int ITEM_STATE_SELECTED_MASK = 2;    protected static final Point DEFAULT_MARKER_SIZE = new Point(26, 94);    public enum HotspotPlace {        NONE, CENTER, BOTTOM_CENTER, TOP_CENTER, RIGHT_CENTER, LEFT_CENTER, UPPER_RIGHT_CORNER, LOWER_RIGHT_CORNER, UPPER_LEFT_CORNER, LOWER_LEFT_CORNER    }    protected final String mUid;    protected final String mTitle;    protected final String mSnippet;    protected final IGeoPoint mGeoPoint;    protected Drawable mMarker;    protected HotspotPlace mHotspotPlace;    public OverlayItem(final String aTitle, final String aSnippet, final IGeoPoint aGeoPoint) {        this(null, aTitle, aSnippet, aGeoPoint);    }    public OverlayItem(final String aUid, final String aTitle, final String aDescription,            final IGeoPoint aGeoPoint) {        this.mTitle = aTitle;        this.mSnippet = aDescription;        this.mGeoPoint = aGeoPoint;        this.mUid = aUid;    }    //Get & Set 要标记的的图标    public Drawable getMarker(final int stateBitset) {        // marker not specified        if (mMarker == null) {            return null;        }        // set marker state appropriately        setState(mMarker, stateBitset);        return mMarker;    }    public void setMarker(final Drawable marker) {        this.mMarker = marker;    }    //设置相应状态的图片以匹配相应状态的bitset    public static void setState(final Drawable drawable, final int stateBitset) {        final int[] states = new int[3];        int index = 0;        if ((stateBitset & ITEM_STATE_PRESSED_MASK) > 0)            states[index++] = android.R.attr.state_pressed;        if ((stateBitset & ITEM_STATE_SELECTED_MASK) > 0)            states[index++] = android.R.attr.state_selected;        if ((stateBitset & ITEM_STATE_FOCUSED_MASK) > 0)            states[index++] = android.R.attr.state_focused;        drawable.setState(states);    }    public Drawable getDrawable() {        return this.mMarker;    }    public int getWidth() {        return this.mMarker.getIntrinsicWidth();    }    public int getHeight() {        return this.mMarker.getIntrinsicHeight();    }    ...}

1.2.1 ItemizedOverlay

画一系列的标志点到图上。具有低索引的item最后被画，因此作为顶端标记。它也首先检查ontap。这个类是通用类，因此你可以自定义ItemizedOverlay子类，并用ontap()回传。

public abstract class ItemizedOverlay<Item extends OverlayItem> extends Overlay implements        Overlay.Snappable {    protected final Drawable mDefaultMarker;//默认的图标    private final ArrayList<Item> mInternalItemList;//内部点    private boolean[] mInternalItemDisplayedList;//确定是否显示    private final Rect mRect = new Rect();    private final Point mCurScreenCoords = new Point();    protected boolean mDrawFocusedItem = true;    private Item mFocusedItem;    private boolean mPendingFocusChangedEvent = false;    private OnFocusChangeListener mOnFocusChangeListener;    private final float[] mMatrixValues = new float[9];    private final Matrix mMatrix = new Matrix();    protected float scaleX=1f;    protected float scaleY=1f;    protected abstract Item createItem(int i);    @Deprecated    public ItemizedOverlay(Context ctx, final Drawable pDefaultMarker) {        this(pDefaultMarker);    }    public ItemizedOverlay(final Drawable pDefaultMarker) {        super();        if (pDefaultMarker == null) {            throw new IllegalArgumentException("You must pass a default marker to ItemizedOverlay.");        }        this.mDefaultMarker = pDefaultMarker;        mInternalItemList = new ArrayList<Item>();    }    @Override    public void onDetach(MapView mapView){        if (mDefaultMarker!=null){            //release the bitmap        }    }    @Override    public void draw(Canvas canvas, MapView mapView, boolean shadow) {        if (shadow) {            return;        }        if (mPendingFocusChangedEvent && mOnFocusChangeListener != null)            mOnFocusChangeListener.onFocusChanged(this, mFocusedItem);        mPendingFocusChangedEvent = false;        final Projection pj = mapView.getProjection();        final int size = this.mInternalItemList.size();        if (mInternalItemDisplayedList == null || mInternalItemDisplayedList.length != size) {            mInternalItemDisplayedList = new boolean[size];        }          canvas.getMatrix(mMatrix);//获取画布的矩阵          mMatrix.getValues(mMatrixValues);//將值clone到mMatrixValues中            //确定缩放比例          scaleX = (float) Math.sqrt(mMatrixValues[Matrix.MSCALE_X]               * mMatrixValues[Matrix.MSCALE_X] + mMatrixValues[Matrix.MSKEW_Y]               * mMatrixValues[Matrix.MSKEW_Y]);          scaleY = (float) Math.sqrt(mMatrixValues[Matrix.MSCALE_Y]               * mMatrixValues[Matrix.MSCALE_Y] + mMatrixValues[Matrix.MSKEW_X]               * mMatrixValues[Matrix.MSKEW_X]);        /* Draw in backward cycle, so the items with the least index are on the front. */        for (int i = size - 1; i >= 0; i--) {            final Item item = getItem(i);            if (item == null) {                continue;            }            pj.toPixels(item.getPoint(), mCurScreenCoords);            mInternalItemDisplayedList[i] = onDrawItem(canvas,item, mCurScreenCoords, mapView.getMapOrientation());        }    }     //子类利用createItem(int)后，在使用其它方法前，应立即使用该方法    protected final void populate() {        final int size = size();        mInternalItemList.clear();        mInternalItemList.ensureCapacity(size);        for (int a = 0; a < size; a++) {            mInternalItemList.add(createItem(a));        }        mInternalItemDisplayedList = null;    }    获取某位置的选项    public final Item getItem(final int position) {        try {            return mInternalItemList.get(position);        }catch(final IndexOutOfBoundsException e) {            return null;        }    }    //将一个item画到画布上    protected boolean onDrawItem(final Canvas canvas, final Item item, final Point curScreenCoords,            final float aMapOrientation) {        final int state = (mDrawFocusedItem && (mFocusedItem == item) ? OverlayItem.ITEM_STATE_FOCUSED_MASK                : 0);        final Drawable marker = (item.getMarker(state) == null) ? getDefaultMarker(state) : item                .getMarker(state);        final HotspotPlace hotspot = item.getMarkerHotspot();        boundToHotspot(marker, hotspot);        int x = mCurScreenCoords.x;        int y = mCurScreenCoords.y;        canvas.save();        canvas.rotate(-aMapOrientation, x, y);        marker.copyBounds(mRect);        marker.setBounds(mRect.left + x, mRect.top + y, mRect.right + x, mRect.bottom + y);        canvas.scale(1 / scaleX, 1 / scaleY, x, y);        final boolean displayed = Rect.intersects(marker.getBounds(), canvas.getClipBounds());        if (displayed) {            marker.draw(canvas);        }        marker.setBounds(mRect);        canvas.restore();        return displayed;        /*        final int state = (mDrawFocusedItem && (mFocusedItem == item) ? OverlayItem.ITEM_STATE_FOCUSED_MASK                : 0);        final Drawable marker = (item.getMarker(state) == null) ? getDefaultMarker(state) : item                .getMarker(state);        final HotspotPlace hotspot = item.getMarkerHotspot();        boundToHotspot(marker, hotspot);        // draw it        Overlay.drawAt(canvas, marker, curScreenCoords.x, curScreenCoords.y, false, aMapOrientation);*/    }    //获取显示的选项列表    public List<Item> getDisplayedItems() {        final List<Item> result = new ArrayList<>();        if (mInternalItemDisplayedList == null) {            return result;        }        for (int i = 0 ; i < mInternalItemDisplayedList.length ; i ++) {            if (mInternalItemDisplayedList[i]) {                result.add(getItem(i));            }        }        return result;    }    //获取默认的图片    protected Drawable getDefaultMarker(final int state) {        OverlayItem.setState(mDefaultMarker, state);        return mDefaultMarker;    }    protected boolean hitTest(final Item item, final android.graphics.drawable.Drawable marker, final int hitX,            final int hitY) {        return marker.getBounds().contains(hitX, hitY);    }    @Override    public boolean onSingleTapConfirmed(MotionEvent e, MapView mapView) {        final Projection pj = mapView.getProjection();        final Rect screenRect = pj.getIntrinsicScreenRect();        final int size = this.size();        for (int i = 0; i < size; i++) {            final Item item = getItem(i);            if (item == null) {                continue;            }            pj.toPixels(item.getPoint(), mCurScreenCoords);            final int state = (mDrawFocusedItem && (mFocusedItem == item) ?                    OverlayItem.ITEM_STATE_FOCUSED_MASK : 0);            final Drawable marker = (item.getMarker(state) == null) ?                    getDefaultMarker(state) : item.getMarker(state);            boundToHotspot(marker, item.getMarkerHotspot());            if (hitTest(item, marker, -mCurScreenCoords.x + screenRect.left + (int) e.getX(),                    -mCurScreenCoords.y + screenRect.top + (int) e.getY())) {                // We have a hit, do we get a response from onTap?                if (onTap(i)) {                    // We got a response so consume the event                    return true;                }            }        }        return super.onSingleTapConfirmed(e, mapView);    }    protected boolean onTap(int index) {        return false;    }    public void setDrawFocusedItem(final boolean drawFocusedItem) {        mDrawFocusedItem = drawFocusedItem;    }    public void setFocus(final Item item) {        mPendingFocusChangedEvent = item != mFocusedItem;        mFocusedItem = item;    }    public Item getFocus() {        return mFocusedItem;    }    protected synchronized Drawable boundToHotspot(final Drawable marker, HotspotPlace hotspot) {        final int markerWidth = marker.getIntrinsicWidth();        final int markerHeight = marker.getIntrinsicHeight();        mRect.set(0, 0, 0 + markerWidth, 0 + markerHeight);        if (hotspot == null) {            hotspot = HotspotPlace.BOTTOM_CENTER;        }        switch (hotspot) {        default:        case NONE:            break;        case CENTER:            mRect.offset(-markerWidth / 2, -markerHeight / 2);            break;        case BOTTOM_CENTER:            mRect.offset(-markerWidth / 2, -markerHeight);            break;        case TOP_CENTER:            mRect.offset(-markerWidth / 2, 0);            break;        case RIGHT_CENTER:            mRect.offset(-markerWidth, -markerHeight / 2);            break;        case LEFT_CENTER:            mRect.offset(0, -markerHeight / 2);            break;        case UPPER_RIGHT_CORNER:            mRect.offset(-markerWidth, 0);            break;        case LOWER_RIGHT_CORNER:            mRect.offset(-markerWidth, -markerHeight);            break;        case UPPER_LEFT_CORNER:            mRect.offset(0, 0);            break;        case LOWER_LEFT_CORNER:            mRect.offset(0, -markerHeight);            break;        }        marker.setBounds(mRect);        return marker;    }    public void setOnFocusChangeListener(OnFocusChangeListener l) {        mOnFocusChangeListener = l;    }    public static interface OnFocusChangeListener {        void onFocusChanged(ItemizedOverlay<?> overlay, OverlayItem newFocus);    }}

1.2.1.1 ItemizedIconOverlay

带有icon item的Overlay。

public class ItemizedIconOverlay<Item extends OverlayItem> extends ItemizedOverlay<Item> {    ...}

1.2.1.2 ItemizedOverlayWithFocus

有焦点的、带有icon item的Overlay。

public class ItemizedOverlayWithFocus<Item extends OverlayItem> extends ItemizedIconOverlay<Item> {    ...}

1.2.2 ItemizedOverlayControlView

用于ItemizedOverlay中item的的控制。

public class ItemizedOverlayControlView extends LinearLayout {    protected ImageButton mPreviousButton;    protected ImageButton mNextButton;    protected ImageButton mCenterToButton;    protected ImageButton mNavToButton;    protected ItemizedOverlayControlViewListener mLis;    ...    public interface ItemizedOverlayControlViewListener {        public void onPrevious();        public void onNext();        public void onCenter();        public void onNavTo();    }}

1.3 MapEventsOverlay

用于检查地图事件的空覆盖物，并把事件传递给MapEventsReceiver

public class MapEventsOverlay extends Overlay {    private MapEventsReceiver mReceiver;    @Deprecated    public MapEventsOverlay(Context ctx, MapEventsReceiver receiver) {        this(receiver);    }    //传递一个地图事件接收者    public MapEventsOverlay(MapEventsReceiver receiver) {        super();        mReceiver = receiver;    }    @Override public void draw(Canvas c, MapView osmv, boolean shadow) {        //Nothing to draw    }    @Override public boolean onSingleTapConfirmed(MotionEvent e, MapView mapView){        Projection proj = mapView.getProjection();        GeoPoint p = (GeoPoint)proj.fromPixels((int)e.getX(), (int)e.getY());        return mReceiver.singleTapConfirmedHelper(p);    }    @Override public boolean onLongPress(MotionEvent e, MapView mapView) {        Projection proj = mapView.getProjection();        GeoPoint p = (GeoPoint)proj.fromPixels((int)e.getX(), (int)e.getY());        //throw event to the receiver:        return mReceiver.longPressHelper(p);    }}

1.4 NonAcceleratedOverlay

将不兼容硬件加速的Overlay用于硬件加速的MapView。它会为Overlay创建一个屏幕尺寸的位图，然后再画Bitmap到硬件加速的canvas上。由于有多余的工作，所以不会画shadow图层

public abstract class NonAcceleratedOverlay extends Overlay {    ...}

1.5 OverlayWithIW

一个包含title、snippet、description的Overlay，这些信息可以在一个弹出的InfoWindow窗口中显示，处理tap事件并在相应的位置显示InfoWindow。

public abstract class OverlayWithIW extends Overlay {    //InfoWindow handling    protected String mTitle, mSnippet, mSubDescription;    protected InfoWindow mInfoWindow;    protected Object mRelatedObject;    ...}

1.5.1 Marker

marker是一个放在特殊点的icon，可以弹出InfoWindow

• icon可以是任何Android标准的Drawable
• icon可以随时改变
• InfoWindow持有标准的Android View，它可以像处理Android组件如按钮等
• 支持sub-description，显示在snippet下以小的字体显示在InfoWindow中。
• 支持在InfoWindow中显示图片。
• 支持触摸marker后将地图居中在marker位置
• 如果使用的是同一个InfoWindow打开一个InfoWindow自动关闭其他的InfoWindow显示

• 事件监听应该设置给每一个marker

  public class Marker extends OverlayWithIW {

  ...

  }

1.5.2 Polyline

Polyline是一个点列表，线段连接点与点。

public class Polyline extends OverlayWithIW {    ...}

1.5.3 polygon

polygon是地球表面的多边形，可以有一个弹出的InfoWindow。

public class Polygon extends OverlayWithIW {

...

}

1.5.3.1 LinearRing

多边形区域的轮廓线，或多边形区域的一个洞。

class LinearRing implements SegmentClipper.SegmentClippable{    ...}

1.6 ScaleBarOverlay

比例尺Overlay

public class ScaleBarOverlay extends Overlay implements GeoConstants {    ...}

1.7 ZoomButtonsOverlay

替换标准的ZoomButtonsController

public class ZoomButtonsOverlay extends Overlay {    ...}

1.8 CopyrightOverlay

所有权Overlay

public class CopyrightOverlay extends Overlay {    ...}

2 多个Overlay的管理与使用

2.1 OverlayManager

Overlay管理者，用于管理多个

public interface OverlayManager extends List<Overlay> {    ...}   

2.1.1 DefaultOverlayManager

默认的瓦片管理者需要添加一个地图式瓦片Overlay以及多个Overlay。

public class DefaultOverlayManager extends AbstractList<Overlay> implements OverlayManager {private TilesOverlay mTilesOverlay;private final CopyOnWriteArrayList<Overlay> mOverlayList;    ...}   

2.2 FolderOverlay

一个管理多个Overlay的Overlay，内部含有一个OverlayManager属性，用于真正管理多个Overlay。

public class FolderOverlay extends Overlay {    protected OverlayManager mOverlayManager;    protected String mName, mDescription;    ...}