我正在努力添加一个地图比例，根据当前的缩放级别在屏幕上显示当前长度。我有一种感觉，它可能存在一些预定义的类使用，但我不知道......？我经常搜索但找不到任何东西。
我非常感谢任何帮助=）
// Alex
答案 0 :(得分：6)
好吧，我现在明白了！路易斯的回答给了我很多帮助，也帮助了OpenStreetMap。这就是我想出的：
<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);
...
希望这可以帮助任何人=）这将从API级别7+开始。我没有在API级别14+上测试它，我知道一些硬件加速的东西“不”在那里工作就像用画布绘制图片。但我认为它适用于录音。
再次感谢路易斯！
//亚历山大
答案 1 :(得分：3)
据我所知，没有一个预先设定的课程。
一种可能性是创建一个覆盖，检查当前经度范围，因为它会相应地改变纬度，然后以正确的大小绘制比例。
Bellow你可以找到一个如何做到这一点的例子：
ScaleBar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
在您展开MapActivity的活动中，添加以下内容：
mapView.getOverlays().add(new CopyOfScaleBarOverlay(this));
注意
该示例使用公制单位。要使用其他单位系统，请将上面代码中的d02乘以单位转换因子，然后使用单位名称调整字符串。
享受它。