無法在android mapview中的兩個地點之間繪製路徑？

Question

我遵循開發者指南Hello Views示例來開發MapView並繪製這兩個地點之間的路徑。我得到了兩個地點，但我無法在它們之間畫出路徑。

爲了解決這個問題我通過修改一點點跟着計算器問題

http://stackoverflow.com/questions/2176397 

36 upvoted答案。但仍然無法解決問題。

我的代碼如下

package com.softtrends.mapview; 

import java.util.List; 

import com.google.android.maps.GeoPoint; 
import com.google.android.maps.MapActivity; 
import com.google.android.maps.MapView; 
import com.google.android.maps.Overlay; 
import com.google.android.maps.OverlayItem; 

import android.graphics.drawable.Drawable; 
import android.os.Bundle; 

public class MapViewEx extends MapActivity { 
/** Called when the activity is first created. */ 
@Override 
public void onCreate(Bundle savedInstanceState) { 
    super.onCreate(savedInstanceState); 
    setContentView(R.layout.main); 
    MapView mapView = (MapView)findViewById(R.id.mapview); 
    mapView.setBuiltInZoomControls(true); 
    //mapView.setStreetView(true); 

    List<Overlay> mapOverlays = mapView.getOverlays(); 
    Drawable drawable = this.getResources().getDrawable(R.drawable.icon); 
    MapViewEx2 itemizedOverlay = new MapViewEx2(drawable); 

    GeoPoint point1 = new GeoPoint(19240000,-99120000); 
    OverlayItem overlayitem1 = new OverlayItem(point1, "Hola, Mundo!", "I'm in Mexico City!"); 

    GeoPoint point2 = new GeoPoint((int)(1.352566007*1E6),(int)(103.78921587*1E6)); 
    OverlayItem overlayitem2 = new OverlayItem(point2, null, null); 

    itemizedOverlay.addOverlay(overlayitem1); 
    itemizedOverlay.addOverlay(overlayitem2); 
    mapOverlays.add(itemizedOverlay); 
} 

@Override 
protected boolean isRouteDisplayed() { 
    return false; 
} 
} 

上面一個是我的活動類。我有另一個覆蓋類如下給出

package com.softtrends.mapview; 

import java.util.ArrayList; 

import com.google.android.maps.ItemizedOverlay; 
import com.google.android.maps.MapView; 
import com.google.android.maps.OverlayItem; 
import com.google.android.maps.Projection; 

import android.app.AlertDialog; 
import android.content.Context; 
import android.graphics.Canvas; 
import android.graphics.Color; 
import android.graphics.Paint; 
import android.graphics.Path; 
import android.graphics.Point; 
import android.graphics.drawable.Drawable; 

public class MapViewEx2 extends ItemizedOverlay<OverlayItem> { 
private ArrayList<OverlayItem> mOverlays = new ArrayList<OverlayItem>(); 
Context mContext; 
public MapViewEx2(Drawable defaultMarker) { 
    super(boundCenterBottom(defaultMarker)); 
} 

public MapViewEx2(Drawable defaultMarker, Context context){ 
    super(defaultMarker); 
    mContext = context; 
} 

public void addOverlay(OverlayItem overlay) { 
    mOverlays.add(overlay); 
    populate(); 
} 

@Override 
protected OverlayItem createItem(int i) { 
    return mOverlays.get(i); 
} 

@Override 
public int size() { 
    return mOverlays.size(); 
} 

@Override 
protected boolean onTap(int index) { 
    OverlayItem item = mOverlays.get(index); 
    AlertDialog.Builder dialog = new AlertDialog.Builder(mContext); 
    dialog.setTitle(item.getTitle()); 
    dialog.setMessage(item.getSnippet()); 
    dialog.show(); 
    return true; 
} 

public void draw(Canvas canvas, MapView map, boolean shadow){ 

    super.draw(canvas, map, shadow); 
    Paint mPaint = new Paint(); 
    mPaint.setDither(true); 
    mPaint.setColor(Color.RED); 
    mPaint.setStyle(Paint.Style.FILL_AND_STROKE); 
    mPaint.setStrokeJoin(Paint.Join.ROUND); 
    mPaint.setStrokeCap(Paint.Cap.ROUND); 
    mPaint.setStrokeWidth(2); 

    Point p1 = new Point(); 
    Point p2 = new Point(); 
    Path path = new Path(); 
    Projection projection = map.getProjection(); 
    projection.toPixels(mOverlays.get(0).getPoint(), p1); 
    projection.toPixels(mOverlays.get(1).getPoint(), p2); 
    path.moveTo(p2.x, p2.y); 
    path.moveTo(p1.x, p1.y); 
    canvas.drawPath(path, mPaint); 
} 
} 

有人請說我在哪裏犯了錯誤。如果可能，請解釋何時調用第二個類的draw（）方法？

Answer 1

請按照本教程，它會幫助你。

http://eagle.phys.utk.edu/guidry/android/mapOverlayDemo.html

這也是一種方式。

public void draw(Canvas canvas, MapView mapv, boolean shadow) 
     { 
      super.draw(canvas, mapv, shadow); 

      Paint mPaint = new Paint(); 
      mPaint.setDither(true); 
      mPaint.setColor(Color.RED); 
      mPaint.setStyle(Paint.Style.FILL_AND_STROKE); 
      mPaint.setStrokeJoin(Paint.Join.ROUND); 
      mPaint.setStrokeCap(Paint.Cap.ROUND); 
      mPaint.setStrokeWidth(2); 


     GeoPoint gP1 = new GeoPoint(19240000,-99120000); 
      GeoPoint gP2 = new GeoPoint(37423157, -122085008); 


      Point p1 = new Point(); 
      Point p2 = new Point(); 

      Path path = new Path(); 

      Projection projection = mapv.getProjection(); 
      projection.toPixels(gP1, p1); 
      projection.toPixels(gP2, p2); 

      path.moveTo(p2.x, p2.y); 
      path.lineTo(p1.x,p1.y); 

      canvas.drawPath(path, mPaint); 
     } 

    }