我正在努力添加根据当前缩放级别在屏幕上显示当前长度的地图比例。我有一种感觉，它可能存在一些预定义的类来使用，但我不知道......？我已经搜索了很多，但找不到任何东西。
我非常感谢任何帮助=）
// 亚历克斯
问问题
7258 次
2 回答
6
好的，我现在明白了！路易斯的回答对我帮助很大，对 OpenStreetMap 也有很大帮助。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
// ===========================================================
/**
* @return the enabled
*/
public boolean isEnabled() {
return enabled;
}
/**
* @param enabled the enabled to set
*/
public void setEnabled(boolean enabled) {
this.enabled = enabled;
}
/**
* @return the lineWidth
*/
public float getLineWidth() {
return lineWidth;
}
/**
* @param lineWidth the lineWidth to set
*/
public void setLineWidth(float lineWidth) {
this.lineWidth = lineWidth;
}
/**
* @return the imperial
*/
public boolean isImperial() {
return imperial;
}
/**
* @param imperial the imperial to set
*/
public void setImperial() {
this.imperial = true;
this.nautical = false;
createScaleBarPicture();
}
/**
* @return the nautical
*/
public boolean isNautical() {
return nautical;
}
/**
* @param nautical the nautical to set
*/
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() 中使用以下方式：
...
scaleBarOverlay = new ScaleBarOverlay(this.getBaseContext(), this, myMapView);
List<Overlay> overlays = myMapView.getOverlays();
// Add scale bar overlay
scaleBarOverlay.setMetric();
overlays.add(scaleBarOverlay);
...
希望这对任何人都有帮助 =) 这将从 API 级别 7+ 开始工作。不过，我还没有在 API 级别 14+ 上对其进行测试，而且我知道一些硬件加速的东西“不”在那里工作，比如用画布绘制图片。但我认为它会与录音一起工作。
再次感谢路易斯！
// 亚历山大
于 2012-10-19T12:43:07.543 回答
3
据我所知，没有预先定义的课程可以做到这一点。
一种可能性是创建一个覆盖来检查当前的经度跨度，因为它会随着纬度而变化，然后以正确的大小绘制比例。
您可以在下面找到有关如何执行此操作的示例：
比例尺叠加
public class CopyOfScaleBarOverlay extends Overlay {
private static final String STR_M = "m";
private static final String STR_KM = "km";
//Constants
private static float scaleBarProportion = 0.25f;
private float cMarginLeft=4;
private float cLineTopSize=8;
private float cMarginTop=6;
private float cMarginBottom=2;
private float cTextSize=12;
private float distanceFromBottom=100;
//instantiation
private Context context;
private Paint paintLine, paintText, paintRectangle;
private Location l0;
private Location l1;
private float ds;
private int width, height, pi;
private float marginLeft, marginTop, marginBottom, lineTopSize;
private String unit;
public CopyOfScaleBarOverlay(Context context){
super();
this.context=context;
paintText= new TextPaint();
paintText.setARGB(180, 0, 0, 0);
paintText.setAntiAlias(true);
paintText.setTextAlign(Align.CENTER);
paintRectangle = new Paint();
paintRectangle.setARGB(80,255,255,255);
paintRectangle.setAntiAlias(true);
paintLine = new Paint();
paintLine.setARGB(180, 0, 0, 0);
paintLine.setAntiAlias(true);
l0 = new Location("none");
l1 = new Location("none");
ds=this.context.getApplicationContext().getResources().getDisplayMetrics().density;
width=this.context.getApplicationContext().getResources().getDisplayMetrics().widthPixels;
height=this.context.getApplicationContext().getResources().getDisplayMetrics().heightPixels;
pi = (int) (height - distanceFromBottom *ds);
marginLeft=cMarginLeft*ds;
lineTopSize=cLineTopSize*ds;
marginTop=cMarginTop*ds;
marginBottom=cMarginBottom*ds;
}
@Override
public void draw(Canvas canvas, MapView mapview, boolean shadow) {
super.draw(canvas, mapview, shadow);
if(mapview.getZoomLevel() > 1){
//Calculate scale bar size and units
GeoPoint g0 = mapview.getProjection().fromPixels(0, height/2);
GeoPoint g1 = mapview.getProjection().fromPixels(width, height/2);
l0.setLatitude(g0.getLatitudeE6()/1E6);
l0.setLongitude(g0.getLongitudeE6()/1E6);
l1.setLatitude(g1.getLatitudeE6()/1E6);
l1.setLongitude(g1.getLongitudeE6()/1E6);
float d01=l0.distanceTo(l1);
float d02=d01*scaleBarProportion;
// multiply d02 by a unit conversion factor if needed
float cd02;
if(d02 > 1000){
unit = STR_KM;
cd02 = d02 / 1000;
} else{
unit = STR_M;
cd02 = d02;
}
int i=1;
do{
i *=10;
}while (i <= cd02);
i/=10;
float dcd02=(int)(cd02/i)*i;
float bs=dcd02*width/d01*d02/cd02;
String text=String.format("%.0f %s", dcd02, unit);
paintText.setTextSize(cTextSize * ds);
float text_x_size=paintText.measureText(text);
float x_size = bs + text_x_size/2 + 2*marginLeft;
//Draw rectangle
canvas.drawRect(0,pi,x_size,pi+marginTop+paintText.getFontSpacing()+marginBottom, paintRectangle);
//Draw line
canvas.drawLine(marginLeft, pi+marginTop, marginLeft + bs, pi+marginTop, paintLine);
//Draw line tops
canvas.drawLine(marginLeft, pi+marginTop - lineTopSize/2, marginLeft, pi+marginTop + lineTopSize/2, paintLine);
canvas.drawLine(marginLeft +bs, pi+marginTop - lineTopSize/2, marginLeft+bs, pi+marginTop + lineTopSize/2, paintLine);
//Draw line midle
canvas.drawLine(marginLeft + bs/2, pi+marginTop - lineTopSize/3, marginLeft + bs/2, pi+marginTop + lineTopSize/3, paintLine);
//Draw line quarters
canvas.drawLine(marginLeft + bs/4, pi+marginTop - lineTopSize/4, marginLeft + bs/4, pi+marginTop + lineTopSize/4, paintLine);
canvas.drawLine(marginLeft + 3*bs/4, pi+marginTop - lineTopSize/4, marginLeft + 3*bs/4, pi+marginTop + lineTopSize/4, paintLine);
//Draw text
canvas.drawText(text, marginLeft +bs, pi+marginTop+paintText.getFontSpacing(), paintText);
}
}
}
使用
在扩展的活动中MapActivity，添加以下内容：
mapView.getOverlays().add(new CopyOfScaleBarOverlay(this));
笔记
该示例使用公制单位。要使用不同的单位系统，d02请在上面的代码中乘以单位转换因子并使用单位名称调整字符串。
好好享受。
于 2012-10-19T00:16:21.247 回答