Question

我正在使用此代码覆盖我在谷歌地图上的位置使用GPS这个代码在我有Android 3.1时工作但是当操作系统升级到3.2时它停止工作并且强制关闭错误在最后出现。

此档案是位置叠加

import android.graphics.Canvas;
import android.graphics.Paint;
import android.graphics.Point;
import android.graphics.RectF;
import android.location.Location;
import com.google.android.maps.GeoPoint;
import com.google.android.maps.MapView;
import com.google.android.maps.Overlay;
import com.google.android.maps.Projection;

public class MyPositionOverlay extends Overlay {

  private final int mRadius = 5;

  Location location;

  public Location getLocation() {
    return location;
  }
  public void setLocation(Location location) {
    this.location = location;
  }

  @Override
  public boolean onTap(GeoPoint point, MapView mapView) {
    return false;
  }

  @Override
  public void draw(Canvas canvas, MapView mapView, boolean shadow) {
    Projection projection = mapView.getProjection();

    if (shadow == false) {
      // Get the current location    
      Double latitude = location.getLatitude()*1E6;
      Double longitude = location.getLongitude()*1E6;
      GeoPoint geoPoint; 
      geoPoint = new 
        GeoPoint(latitude.intValue(),longitude.intValue());

      // Convert the location to screen pixels     
      Point point = new Point();
      projection.toPixels(geoPoint, point);

      RectF oval = new RectF(point.x - mRadius, point.y - mRadius, 
                             point.x + mRadius, point.y + mRadius);

      // Setup the paint
      Paint paint = new Paint();
      paint.setARGB(250, 255, 255, 255);
      paint.setAntiAlias(true);
      paint.setFakeBoldText(true);

      Paint backPaint = new Paint();
      backPaint.setARGB(175, 50, 50, 50);
      backPaint.setAntiAlias(true);

      RectF backRect = new RectF(point.x + 2 + mRadius, 
                                 point.y - 3*mRadius,
                                 point.x + 65, point.y + mRadius);

      // Draw the marker    
      canvas.drawOval(oval, paint);
      canvas.drawRoundRect(backRect, 5, 5, backPaint);
      canvas.drawText("Here I Am", 
                      point.x + 2*mRadius, point.y, 
                      paint);
    }
    super.draw(canvas, mapView, shadow);
  }
}

这是主文件

import java.io.IOException;
import java.util.List;
import java.util.Locale;

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

import android.content.Context;
import android.location.Address;
import android.location.Criteria;
import android.location.Geocoder;
import android.location.Location;
import android.location.LocationListener;
import android.location.LocationManager;
import android.os.Bundle;
import android.widget.TextView;

public class WhereAmI extends MapActivity {
  @Override
  protected boolean isRouteDisplayed() {
    return false;
  }

  MapController mapController;
  MyPositionOverlay positionOverlay;

  @Override
  public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.main);

    MapView myMapView = (MapView)findViewById(R.id.myMapView);
    mapController = myMapView.getController();

    myMapView.setSatellite(true);
    myMapView.setStreetView(true);
    myMapView.displayZoomControls(false);

    mapController.setZoom(17);

    // Add the MyPositionOverlay
    positionOverlay = new MyPositionOverlay();
    List<Overlay> overlays = myMapView.getOverlays();
    overlays.add(positionOverlay);

    LocationManager locationManager;
    String context = Context.LOCATION_SERVICE;
    locationManager = (LocationManager)getSystemService(context);

    Criteria criteria = new Criteria();
    criteria.setAccuracy(Criteria.ACCURACY_FINE);
    criteria.setAltitudeRequired(false);
    criteria.setBearingRequired(false);
    criteria.setCostAllowed(true);
    criteria.setPowerRequirement(Criteria.POWER_LOW);
    String provider = locationManager.getBestProvider(criteria, true);

    Location location = locationManager.getLastKnownLocation(provider);

    updateWithNewLocation(location);

    locationManager.requestLocationUpdates(provider, 2000, 10,   
                                           locationListener);
  }

  private final LocationListener locationListener = new LocationListener() {
    public void onLocationChanged(Location location) {
      updateWithNewLocation(location);
    }

    public void onProviderDisabled(String provider){
      updateWithNewLocation(null);
    }

    public void onProviderEnabled(String provider){ }
    public void onStatusChanged(String provider, int status, 
                                Bundle extras){ }
  };

  private void updateWithNewLocation(Location location) {
    String latLongString;
    TextView myLocationText;
    myLocationText = (TextView)findViewById(R.id.myLocationText);
    String addressString = "No address found";

    if (location != null) {
         // Update my location marker
        positionOverlay.setLocation(location);

      // Update the map location.
      Double geoLat = location.getLatitude()*1E6;
      Double geoLng = location.getLongitude()*1E6;
      GeoPoint point = new GeoPoint(geoLat.intValue(), 
                                    geoLng.intValue());

      mapController.animateTo(point);

      double lat = location.getLatitude();
      double lng = location.getLongitude();
      latLongString = "Lat:" + lat + "\nLong:" + lng;

      double latitude = location.getLatitude();
      double longitude = location.getLongitude();

      Geocoder gc = new Geocoder(this, Locale.getDefault());
      try {
        List<Address> addresses = gc.getFromLocation(latitude, 
                                                     longitude, 1);
        StringBuilder sb = new StringBuilder();
        if (addresses.size() > 0) {
          Address address = addresses.get(0);

          for (int i = 0; i < address.getMaxAddressLineIndex(); i++)
            sb.append(address.getAddressLine(i)).append("\n");

            sb.append(address.getLocality()).append("\n");
            sb.append(address.getPostalCode()).append("\n");
            sb.append(address.getCountryName());
        }
        addressString = sb.toString();
      } catch (IOException e) {}
    } else {
      latLongString = "No location found";
    }
    myLocationText.setText("Your Current Position is:\n" + 
                            latLongString + "\n" + addressString);
  }
}

for xml

<LinearLayout 
  xmlns:android="http://schemas.android.com/apk/res/android"
  android:orientation="vertical"
  android:layout_width="fill_parent"
  android:layout_height="fill_parent">
  <TextView
    android:id="@+id/myLocationText"
    android:layout_width="fill_parent"
    android:layout_height="wrap_content"
    android:text="@string/hello"
  />
  <com.google.android.maps.MapView
    android:id="@+id/myMapView"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent"
    android:enabled="true"
    android:clickable="true"
    android:apiKey="0LSm5iUqsTW3O-7e74GQTt4pQKnxW7YVu-3Cftg"
  />
</LinearLayout>

logcat输出错误

09-07 13:33:43.180: ERROR/AndroidRuntime(1811): FATAL EXCEPTION: main
09-07 13:33:43.180: ERROR/AndroidRuntime(1811): java.lang.NullPointerException
09-07 13:33:43.180: ERROR/AndroidRuntime(1811):     at com.paad.whereami.MyPositionOverlay.draw(MyPositionOverlay.java:37)
09-07 13:33:43.180: ERROR/AndroidRuntime(1811):     at com.google.android.maps.Overlay.draw(Overlay.java:179)
09-07 13:33:43.180: ERROR/AndroidRuntime(1811):     at com.google.android.maps.OverlayBundle.draw(OverlayBundle.java:45)
09-07 13:33:43.180: ERROR/AndroidRuntime(1811):     at com.google.android.maps.MapView.onDraw(MapView.java:530)
09-07 13:33:43.180: ERROR/AndroidRuntime(1811):     at android.view.View.draw(View.java:9279)
09-07 13:33:43.180: ERROR/AndroidRuntime(1811):     at android.view.ViewGroup.drawChild(ViewGroup.java:2584)
09-07 13:33:43.180: ERROR/AndroidRuntime(1811):     at android.view.ViewGroup.dispatchDraw(ViewGroup.java:2189)
09-07 13:33:43.180: ERROR/AndroidRuntime(1811):     at android.view.ViewGroup.drawChild(ViewGroup.java:2582)
09-07 13:33:43.180: ERROR/AndroidRuntime(1811):     at android.view.ViewGroup.dispatchDraw(ViewGroup.java:2189)
09-07 13:33:43.180: ERROR/AndroidRuntime(1811):     at android.view.ViewGroup.drawChild(ViewGroup.java:2582)
09-07 13:33:43.180: ERROR/AndroidRuntime(1811):     at android.view.ViewGroup.dispatchDraw(ViewGroup.java:2189)
09-07 13:33:43.180: ERROR/AndroidRuntime(1811):     at android.view.ViewGroup.drawChild(ViewGroup.java:2582)
09-07 13:33:43.180: ERROR/AndroidRuntime(1811):     at android.view.ViewGroup.dispatchDraw(ViewGroup.java:2189)
09-07 13:33:43.180: ERROR/AndroidRuntime(1811):     at android.view.View.draw(View.java:9282)
09-07 13:33:43.180: ERROR/AndroidRuntime(1811):     at android.widget.FrameLayout.draw(FrameLayout.java:419)
09-07 13:33:43.180: ERROR/AndroidRuntime(1811):     at com.android.internal.policy.impl.PhoneWindow$DecorView.draw(PhoneWindow.java:1923)
09-07 13:33:43.180: ERROR/AndroidRuntime(1811):     at android.view.ViewRoot.draw(ViewRoot.java:1695)
09-07 13:33:43.180: ERROR/AndroidRuntime(1811):     at android.view.ViewRoot.performTraversals(ViewRoot.java:1410)
09-07 13:33:43.180: ERROR/AndroidRuntime(1811):     at android.view.ViewRoot.handleMessage(ViewRoot.java:2040)
09-07 13:33:43.180: ERROR/AndroidRuntime(1811):     at android.os.Handler.dispatchMessage(Handler.java:99)
09-07 13:33:43.180: ERROR/AndroidRuntime(1811):     at android.os.Looper.loop(Looper.java:132)
09-07 13:33:43.180: ERROR/AndroidRuntime(1811):     at android.app.ActivityThread.main(ActivityThread.java:4123)
09-07 13:33:43.180: ERROR/AndroidRuntime(1811):     at java.lang.reflect.Method.invokeNative(Native Method)
09-07 13:33:43.180: ERROR/AndroidRuntime(1811):     at java.lang.reflect.Method.invoke(Method.java:491)
09-07 13:33:43.180: ERROR/AndroidRuntime(1811):     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:841)
09-07 13:33:43.180: ERROR/AndroidRuntime(1811):     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:599)
09-07 13:33:43.180: ERROR/AndroidRuntime(1811):     at dalvik.system.NativeStart.main(Native Method)

Answer 1

我怀疑这是导致空指针的操作系统版本。更可能是因为当调用draw时，overlay类中的'location'为null。

在draw方法中替换

if (shadow == false) {

带

if ((shadow == false) && (location != null)) {

谷歌地图叠加

1 个答案: