将位图标记居中显示（Google Maps Android API v2）

Question

当我从自定义位图添加标记时，标记并没有居中显示在我指定的位置。

我是这样添加的：

    // ID tramo
    final int tramoId = tr.getId();
    // Nodos
    final Nodo[] nodos = tr.getNodos();

    final PolylineOptions p = new PolylineOptions();
    MarkerOptions m = new MarkerOptions();
    // Seteamos posicion de linea y marker
    m.position(semisuma(nodos));
    for (final Nodo n : nodos) {
        p.add(n.getLatLng());
    }
    // Color de linea y marker
    BitmapDescriptor icon = null;
    if (tr.getCapacidad() == 0) {
        p.color(0xFF000000);
        m = null;
    } else if (tr.getCapacidad() - tr.getPlazasOcupadas() == 0) {
        p.color(0xEEFF0000);
        final TextDrawable drawable = new TextDrawable(0, 0xEEFF0000,
                0xFFFFFFFF);
        icon = BitmapDescriptorFactory.fromBitmap(fromDrawable(drawable));
    } else {
        p.color(0xEE00FFFF);
        final TextDrawable drawable = new TextDrawable(0, 0xEE00FFFF,
                0xFFFFFFFF);
        icon = BitmapDescriptorFactory.fromBitmap(fromDrawable(drawable));
    }
    if (m != null) {
        m.title(String.valueOf(tramoId));
        m.icon(icon);
    }
    if (polylinesTramo.get(idTramo) != null) {
        polylinesTramo.get(idTramo).remove();
    }
    if (markersTramo.get(idTramo) != null) {
        markersTramo.get(idTramo).remove();
    }
    polylinesTramo.put(idTramo, map.getMap().addPolyline(p));
    if (marker != null) {
        markersTramo.put(idTramo, map.getMap().addMarker(m));
    }

这是TextDrawable的代码：

package com.cidaut.blueparking.ui;

import android.graphics.Canvas;
import android.graphics.ColorFilter;
import android.graphics.Paint;
import android.graphics.PixelFormat;
import android.graphics.drawable.Drawable;

public class TextDrawable extends Drawable {

    private final String text;
    private final Paint paint;
    private final int centroX = 13;
    private final int centroY = 16;
    private final float textSize;
    private final float whereToDrawX;
    private final int bgColor;

    public TextDrawable(final int text, final int bgColor, final int textColor) {
        this(String.valueOf(text), bgColor, textColor);
    }

    public TextDrawable(final String text, final int bgColor, final int textColor) {
        this.text = text;
        this.bgColor = bgColor;
        this.paint = new Paint();
        paint.setColor(textColor);
        paint.setTextSize(14f);
        paint.setAntiAlias(true);
        paint.setFakeBoldText(true);
        paint.setStyle(Paint.Style.FILL);
        paint.setTextAlign(Paint.Align.LEFT);
        textSize = paint.measureText(text);
        whereToDrawX = centroX - (textSize / 2);
    }

    @Override
    public void draw(final Canvas canvas) {
        canvas.drawColor(bgColor);
        canvas.drawText(text, whereToDrawX, centroY, paint);
    }

    @Override
    public void setAlpha(final int alpha) {
        paint.setAlpha(alpha);
    }

    @Override
    public void setColorFilter(final ColorFilter cf) {
        paint.setColorFilter(cf);
    }

    @Override
    public int getOpacity() {
        return PixelFormat.TRANSLUCENT;
    }
}

这里是fromDrawable方法。

protected Bitmap fromDrawable(final Drawable drawable) {
    final Bitmap bitmap = Bitmap.createBitmap(25, 25, Config.ARGB_8888);
    final Canvas canvas = new Canvas(bitmap);
    drawable.setBounds(0, 0, canvas.getWidth(), canvas.getHeight());
    drawable.draw(canvas);
    return bitmap;
}

我应该添加什么代码才能使标记居中显示?

- Charlie-Blake

Answer 1

只需将标记的锚点设置为0.5和0.5（图标中心即可）。

...
MarkerOptions m = new MarkerOptions();
m.anchor(0.5f, 0.5f);
...

默认的锚点值为(0.5f, 1.0f)。 您可以在此处阅读有关标记的信息。

- stevo.mit

Answer 2

如果您使用标记，则需要重新指定锚点以使图像居中。正如文档所说：“锚点：图像上将放置在标记的LatLng位置的点。这默认为图像左侧的50％和图像底部。”。

如果您希望默认情况下图像居中，可以考虑使用GroundOverlay而不是Marker。请参见GroundOverlay，“默认情况下，锚点距离图像顶部和图像左侧均为50％。”

- Fr4nz