好吧，我明白了！Luis的回答对我和OpenStreetMap都有帮助。这是我想出的：
<your.own.package.path>;import android.content.Context;import android.graphics.Canvas;import android.graphics.Color;import android.graphics.Matrix;import android.graphics.Paint;import android.graphics.Paint.Style;import android.graphics.Picture;import android.graphics.Rect;import android.location.Location;import android.util.Log;import com.google.android.maps.GeoPoint;import com.google.android.maps.MapView;import com.google.android.maps.Overlay;import com.google.android.maps.Projection;import com.iqqn.uppgift5.GameMapActivity;public class ScaleBarOverlay extends Overlay{ // =========================================================== // Fields // =========================================================== // Defaults boolean enabled = true; float xOffset = 10; float yOffset = 10; float lineWidth = 2; int textSize = 12; boolean imperial = false; boolean nautical = false; boolean latitudeBar = true; boolean longitudeBar = false; // Internal protected final MapView mapView; protected final GameMapActivity master; private Context context; protected final Picture scaleBarPicture = new Picture(); private final Matrix scaleBarMatrix = new Matrix(); private int lastZoomLevel = -1; float xdpi; float ydpi; int screenWidth; int screenHeight; // =========================================================== // Constructors // =========================================================== public ScaleBarOverlay(Context _context, GameMapActivity master, MapView mapView) { super(); this.master = master; this.context = _context; this.mapView = mapView; xdpi = this.context.getResources().getDisplayMetrics().xdpi; ydpi = this.context.getResources().getDisplayMetrics().ydpi; screenWidth = this.context.getResources().getDisplayMetrics().widthPixels; screenHeight = this.context.getResources().getDisplayMetrics().heightPixels; } // =========================================================== // Getter & Setter // =========================================================== public boolean isEnabled() { return enabled; } public void setEnabled(boolean enabled) { this.enabled = enabled; } public float getLineWidth() { return lineWidth; } public void setLineWidth(float lineWidth) { this.lineWidth = lineWidth; } public boolean isImperial() { return imperial; } public void setImperial() { this.imperial = true; this.nautical = false; createScaleBarPicture(); } public boolean isNautical() { return nautical; } public void setNautical() { this.nautical = true; this.imperial = false; createScaleBarPicture(); } public void setMetric() { this.nautical = false; this.imperial = false; createScaleBarPicture(); } public void drawLatitudeScale(boolean latitude) { this.latitudeBar = latitude; } public void drawLongitudeScale(boolean longitude) { this.longitudeBar = longitude; } @Override public void draw(Canvas canvas, MapView localMapView, boolean shadow) { if (this.enabled) { // Draw the overlay if (shadow == false) { final int zoomLevel = localMapView.getZoomLevel(); if (zoomLevel != lastZoomLevel) { lastZoomLevel = zoomLevel; createScaleBarPicture(); } this.scaleBarMatrix.setTranslate(-1 * (scaleBarPicture.getWidth() / 2 - 0.5f), -1 * (scaleBarPicture.getHeight() / 2 - 0.5f)); this.scaleBarMatrix.postTranslate(xdpi/2, ydpi/2 + canvas.getHeight()-50); canvas.save(); canvas.setMatrix(scaleBarMatrix); canvas.drawPicture(scaleBarPicture); canvas.restore(); } } } // =========================================================== // Methods // =========================================================== public void disableScaleBar() { this.enabled = false; } public boolean enableScaleBar() { return this.enabled = true; } private void createScaleBarPicture() { // We want the scale bar to be as long as the closest round-number miles/kilometers // to 1-inch at the latitude at the current center of the screen. Projection projection = mapView.getProjection(); if (projection == null) { return; } Location locationP1 = new Location("ScaleBar location p1"); Location locationP2 = new Location("ScaleBar location p2"); // Two points, 1-inch apart in x/latitude, centered on screen GeoPoint p1 = projection.fromPixels((int) ((screenWidth / 2) - (xdpi / 2)), screenHeight/2); GeoPoint p2 = projection.fromPixels((int) ((screenWidth / 2) + (xdpi / 2)), screenHeight/2); locationP1.setLatitude(p1.getLatitudeE6()/1E6); locationP2.setLatitude(p2.getLatitudeE6()/1E6); locationP1.setLongitude(p1.getLongitudeE6()/1E6); locationP2.setLongitude(p2.getLongitudeE6()/1E6); float xMetersPerInch = locationP1.distanceTo(locationP2); p1 = projection.fromPixels(screenWidth/2, (int) ((screenHeight / 2) - (ydpi / 2))); p2 = projection.fromPixels(screenWidth/2, (int) ((screenHeight / 2) + (ydpi / 2))); locationP1.setLatitude(p1.getLatitudeE6()/1E6); locationP2.setLatitude(p2.getLatitudeE6()/1E6); locationP1.setLongitude(p1.getLongitudeE6()/1E6); locationP2.setLongitude(p2.getLongitudeE6()/1E6); float yMetersPerInch = locationP1.distanceTo(locationP2); final Paint barPaint = new Paint(); barPaint.setColor(Color.BLACK); barPaint.setAntiAlias(true); barPaint.setStyle(Style.FILL); barPaint.setAlpha(255); final Paint textPaint = new Paint(); textPaint.setColor(Color.BLACK); textPaint.setAntiAlias(true); textPaint.setStyle(Style.FILL); textPaint.setAlpha(255); textPaint.setTextSize(textSize); final Canvas canvas = scaleBarPicture.beginRecording((int)xdpi, (int)ydpi); if (latitudeBar) { String xMsg = scaleBarLengthText(xMetersPerInch, imperial, nautical); Rect xTextRect = new Rect(); textPaint.getTextBounds(xMsg, 0, xMsg.length(), xTextRect); int textSpacing = (int)(xTextRect.height() / 5.0); canvas.drawRect(xOffset, yOffset, xOffset + xdpi, yOffset + lineWidth, barPaint); canvas.drawRect(xOffset + xdpi, yOffset, xOffset + xdpi + lineWidth, yOffset + xTextRect.height() + lineWidth + textSpacing, barPaint); if (!longitudeBar) { canvas.drawRect(xOffset, yOffset, xOffset + lineWidth, yOffset + xTextRect.height() + lineWidth + textSpacing, barPaint); } canvas.drawText(xMsg, (xOffset + xdpi/2 - xTextRect.width()/2), (yOffset + xTextRect.height() + lineWidth + textSpacing), textPaint); } if (longitudeBar) { String yMsg = scaleBarLengthText(yMetersPerInch, imperial, nautical); Rect yTextRect = new Rect(); textPaint.getTextBounds(yMsg, 0, yMsg.length(), yTextRect); int textSpacing = (int)(yTextRect.height() / 5.0); canvas.drawRect(xOffset, yOffset, xOffset + lineWidth, yOffset + ydpi, barPaint); canvas.drawRect(xOffset, yOffset + ydpi, xOffset + yTextRect.height() + lineWidth + textSpacing, yOffset + ydpi + lineWidth, barPaint); if (! latitudeBar) { canvas.drawRect(xOffset, yOffset, xOffset + yTextRect.height() + lineWidth + textSpacing, yOffset + lineWidth, barPaint); } float x = xOffset + yTextRect.height() + lineWidth + textSpacing; float y = yOffset + ydpi/2 + yTextRect.width()/2; canvas.rotate(-90, x, y); canvas.drawText(yMsg, x, y + textSpacing, textPaint); } scaleBarPicture.endRecording(); } private String scaleBarLengthText(float meters, boolean imperial, boolean nautical) { if (this.imperial) { if (meters >= 1609.344) { return (meters / 1609.344) + "mi"; } else if (meters >= 1609.344/10) { return ((meters / 160.9344) / 10.0) + "mi"; } else { return (meters * 3.2808399) + "ft"; } } else if (this.nautical) { if (meters >= 1852) { return ((meters / 1852)) + "nm"; } else if (meters >= 1852/10) { return (((meters / 185.2)) / 10.0) + "nm"; } else { return ((meters * 3.2808399)) + "ft"; } } else { if (meters >= 1000) { return ((meters / 1000)) + "km"; } else if (meters > 100) { return ((meters / 100.0) / 10.0) + "km"; } else { return meters + "m"; } } } @Override public boolean onTap(GeoPoint point, MapView mapView) { // Do not react to screen taps. return false; }}在onCreate（）中以以下方式使用它：
...scaleBarOverlay = new ScaleBarOverlay(this.getbaseContext(), this, myMapView);List<Overlay> overlays = myMapView.getOverlays();// Add scale bar overlayscaleBarOverlay.setMetric();overlays.add(scaleBarOverlay);...
希望这对任何人都有帮助=）这将在API级别7+上起作用。我尚未在API级别14+上对其进行测试，并且我知道一些硬件加速的东西“不”在那里工作，例如使用画布绘制图片。但我认为它将与录音一起使用。
再次感谢路易斯！
//亚历山大
