在地图上标记当前位置，Android
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StackOverFlow
Marking Current Location on Map, Android
提问by deewangan
I followed some tutorials to create an application that shows the current position of the user on the map with a marking. But for some reasons I can't get to work the marking part? The other parts work well, but whenever I add the marking code the application crashes.
Here is the code:
我按照一些教程创建了一个应用程序，该应用程序通过标记显示用户在地图上的当前位置。但是由于某些原因我无法开始标记部分？其他部分运行良好，但每当我添加标记代码时，应用程序就会崩溃。
这是代码：
public class LocationActivity extends MapActivity {
private MapView mapView;
private LocationManager lm;
private LocationListener ll;
private MapController mc;
GeoPoint p = null;
Drawable defaultMarker = null;
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
mapView = (MapView) findViewById(R.id.mapView);
// show zoom in/out buttons
mapView.setBuiltInZoomControls(true);
// Standard view of the map(map/sat)
mapView.setSatellite(false);
// get controller of the map for zooming in/out
mc = mapView.getController();
// Zoom Level
mc.setZoom(18);
MyLocationOverlay myLocationOverlay = new MyLocationOverlay();
List<Overlay> list = mapView.getOverlays();
list.add(myLocationOverlay);
lm = (LocationManager) getSystemService(Context.LOCATION_SERVICE);
ll = new MyLocationListener();
lm.requestLocationUpdates(LocationManager.GPS_PROVIDER, 0, 0, ll);
// Get the current location in start-up
GeoPoint initGeoPoint = new GeoPoint((int) (lm.getLastKnownLocation(
LocationManager.GPS_PROVIDER).getLatitude() * 1000000),
(int) (lm.getLastKnownLocation(LocationManager.GPS_PROVIDER)
.getLongitude() * 1000000));
mc.animateTo(initGeoPoint);
}
protected class MyLocationOverlay extends com.google.android.maps.Overlay {
@Override
public boolean draw(Canvas canvas, MapView mapView, boolean shadow,
long when) {
Paint paint = new Paint();
super.draw(canvas, mapView, shadow);
// Converts lat/lng-Point to OUR coordinates on the screen.
Point myScreenCoords = new Point();
mapView.getProjection().toPixels(p, myScreenCoords);
paint.setStrokeWidth(1);
paint.setARGB(255, 255, 255, 255);
paint.setStyle(Paint.Style.STROKE);
Bitmap bmp = BitmapFactory.decodeResource(getResources(),
R.drawable.push);
canvas.drawBitmap(bmp, myScreenCoords.x, myScreenCoords.y, paint);
canvas.drawText("I am here...", myScreenCoords.x, myScreenCoords.y,
paint);
return true;
}
}
private class MyLocationListener implements LocationListener {
public void onLocationChanged(Location argLocation) {
GeoPoint myGeoPoint = new GeoPoint(
(int) (argLocation.getLatitude() * 1000000),
(int) (argLocation.getLongitude() * 1000000));
/*
* it will show a message on location change
* Toast.makeText(getBaseContext(), "New location latitude ["
* +argLocation.getLatitude() + "] longitude [" +
* argLocation.getLongitude()+"]", Toast.LENGTH_SHORT).show();
*/
mc.animateTo(myGeoPoint);
}
public void onProviderDisabled(String provider) {}
public void onProviderEnabled(String provider) {}
public void onStatusChanged(String provider, int status, Bundle extras) {}
}
protected boolean isRouteDisplayed() {
return false;
}
}
here is the logcat:
这是logcat：
01-19 05:31:43.011: DEBUG/AndroidRuntime(759): >>>>>>>>>>>>>> AndroidRuntime START <<<<<<<<<<<<<<
01-19 05:31:43.011: DEBUG/AndroidRuntime(759): CheckJNI is ON
01-19 05:31:43.411: DEBUG/AndroidRuntime(759): --- registering native functions ---
01-19 05:31:43.431: INFO/jdwp(759): received file descriptor 19 from ADB
01-19 05:31:43.431: INFO/jdwp(759): Ignoring second debugger -- accepting and dropping
01-19 05:31:44.531: INFO/ActivityManager(583): Starting activity: Intent { flg=0x10000000 cmp=pro.googlemapp/.LocationActivity }
01-19 05:31:44.641: DEBUG/AndroidRuntime(759): Shutting down VM
01-19 05:31:44.641: DEBUG/dalvikvm(759): DestroyJavaVM waiting for non-daemon threads to exit
01-19 05:31:44.641: DEBUG/dalvikvm(759): DestroyJavaVM shutting VM down
01-19 05:31:44.641: DEBUG/dalvikvm(759): HeapWorker thread shutting down
01-19 05:31:44.651: DEBUG/dalvikvm(759): HeapWorker thread has shut down
01-19 05:31:44.651: DEBUG/jdwp(759): JDWP shutting down net...
01-19 05:31:44.651: DEBUG/jdwp(759): +++ peer disconnected
01-19 05:31:44.651: INFO/dalvikvm(759): Debugger has detached; object registry had 1 entries
01-19 05:31:44.661: DEBUG/dalvikvm(759): VM cleaning up
01-19 05:31:44.681: INFO/ActivityManager(583): Start proc pro.googlemapp for activity pro.googlemapp/.LocationActivity: pid=770 uid=10025 gids={3003}
01-19 05:31:44.761: DEBUG/dalvikvm(759): LinearAlloc 0x0 used 676436 of 4194304 (16%)
01-19 05:31:44.801: INFO/jdwp(770): received file descriptor 20 from ADB
01-19 05:31:44.822: INFO/dalvikvm(770): ignoring registerObject request in thread=3
01-19 05:31:44.851: INFO/jdwp(770): Ignoring second debugger -- accepting and dropping
01-19 05:31:44.851: ERROR/jdwp(770): Failed writing handshake bytes: Broken pipe (-1 of 14)
01-19 05:31:44.851: INFO/dalvikvm(770): Debugger has detached; object registry had 0 entries
01-19 05:31:45.320: ERROR/ActivityThread(770): Failed to find provider info for com.google.settings
01-19 05:31:45.320: ERROR/ActivityThread(770): Failed to find provider info for com.google.settings
01-19 05:31:45.340: ERROR/ActivityThread(770): Failed to find provider info for com.google.settings
01-19 05:31:45.781: DEBUG/LocationManager(770): Constructor: service = android.location.ILocationManager$Stub$Proxy@4379d9f0
01-19 05:31:45.791: WARN/GpsLocationProvider(583): Duplicate add listener for uid 10025
01-19 05:31:45.791: DEBUG/GpsLocationProvider(583): setMinTime 0
01-19 05:31:45.791: DEBUG/GpsLocationProvider(583): startNavigating
01-19 05:31:45.831: INFO/jdwp(770): received file descriptor 27 from ADB
01-19 05:31:46.001: INFO/MapActivity(770): Handling network change notification:CONNECTED
01-19 05:31:46.001: ERROR/MapActivity(770): Couldn't get connection factory client
01-19 05:31:46.451: DEBUG/dalvikvm(770): GC freed 4539 objects / 298952 bytes in 118ms
01-19 05:31:46.470: DEBUG/AndroidRuntime(770): Shutting down VM
01-19 05:31:46.470: WARN/dalvikvm(770): threadid=3: thread exiting with uncaught exception (group=0x4001aa28)
01-19 05:31:46.481: ERROR/AndroidRuntime(770): Uncaught handler: thread main exiting due to uncaught exception
01-19 05:31:46.541: ERROR/AndroidRuntime(770): java.lang.NullPointerException
01-19 05:31:46.541: ERROR/AndroidRuntime(770): at com.google.android.maps.PixelConverter.toPixels(PixelConverter.java:58)
01-19 05:31:46.541: ERROR/AndroidRuntime(770): at com.google.android.maps.PixelConverter.toPixels(PixelConverter.java:48)
01-19 05:31:46.541: ERROR/AndroidRuntime(770): at pro.googlemapp.LocationActivity$MyLocationOverlay.draw(LocationActivity.java:101)
01-19 05:31:46.541: ERROR/AndroidRuntime(770): at com.google.android.maps.OverlayBundle.draw(OverlayBundle.java:42)
01-19 05:31:46.541: ERROR/AndroidRuntime(770): at com.google.android.maps.MapView.onDraw(MapView.java:476)
01-19 05:31:46.541: ERROR/AndroidRuntime(770): at android.view.View.draw(View.java:6274)
01-19 05:31:46.541: ERROR/AndroidRuntime(770): at android.view.ViewGroup.drawChild(ViewGroup.java:1526)
01-19 05:31:46.541: ERROR/AndroidRuntime(770): at android.view.ViewGroup.dispatchDraw(ViewGroup.java:1256)
01-19 05:31:46.541: ERROR/AndroidRuntime(770): at android.view.ViewGroup.drawChild(ViewGroup.java:1524)
01-19 05:31:46.541: ERROR/AndroidRuntime(770): at android.view.ViewGroup.dispatchDraw(ViewGroup.java:1256)
01-19 05:31:46.541: ERROR/AndroidRuntime(770): at android.view.View.draw(View.java:6277)
01-19 05:31:46.541: ERROR/AndroidRuntime(770): at android.widget.FrameLayout.draw(FrameLayout.java:352)
01-19 05:31:46.541: ERROR/AndroidRuntime(770): at android.view.ViewGroup.drawChild(ViewGroup.java:1526)
01-19 05:31:46.541: ERROR/AndroidRuntime(770): at android.view.ViewGroup.dispatchDraw(ViewGroup.java:1256)
01-19 05:31:46.541: ERROR/AndroidRuntime(770): at android.view.ViewGroup.drawChild(ViewGroup.java:1524)
01-19 05:31:46.541: ERROR/AndroidRuntime(770): at android.view.ViewGroup.dispatchDraw(ViewGroup.java:1256)
01-19 05:31:46.541: ERROR/AndroidRuntime(770): at android.view.View.draw(View.java:6277)
01-19 05:31:46.541: ERROR/AndroidRuntime(770): at android.widget.FrameLayout.draw(FrameLayout.java:352)
01-19 05:31:46.541: ERROR/AndroidRuntime(770): at com.android.internal.policy.impl.PhoneWindow$DecorView.draw(PhoneWindow.java:1883)
01-19 05:31:46.541: ERROR/AndroidRuntime(770): at android.view.ViewRoot.draw(ViewRoot.java:1332)
01-19 05:31:46.541: ERROR/AndroidRuntime(770): at android.view.ViewRoot.performTraversals(ViewRoot.java:1097)
01-19 05:31:46.541: ERROR/AndroidRuntime(770): at android.view.ViewRoot.handleMessage(ViewRoot.java:1613)
01-19 05:31:46.541: ERROR/AndroidRuntime(770): at android.os.Handler.dispatchMessage(Handler.java:99)
01-19 05:31:46.541: ERROR/AndroidRuntime(770): at android.os.Looper.loop(Looper.java:123)
01-19 05:31:46.541: ERROR/AndroidRuntime(770): at android.app.ActivityThread.main(ActivityThread.java:4203)
01-19 05:31:46.541: ERROR/AndroidRuntime(770): at java.lang.reflect.Method.invokeNative(Native Method)
01-19 05:31:46.541: ERROR/AndroidRuntime(770): at java.lang.reflect.Method.invoke(Method.java:521)
01-19 05:31:46.541: ERROR/AndroidRuntime(770): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:791)
01-19 05:31:46.541: ERROR/AndroidRuntime(770): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:549)
01-19 05:31:46.541: ERROR/AndroidRuntime(770): at dalvik.system.NativeStart.main(Native Method)
01-19 05:31:46.551: INFO/Process(583): Sending signal. PID: 770 SIG: 3
01-19 05:31:46.581: INFO/dalvikvm(770): threadid=7: reacting to signal 3
01-19 05:31:46.661: INFO/dalvikvm(770): Wrote stack trace to '/data/anr/traces.txt'
01-19 05:31:46.871: INFO/ARMAssembler(583): generated scanline__00000077:03515104_00000000_00000000 [ 27 ipp] (41 ins) at [0x2c69c8:0x2c6a6c] in 973448 ns
01-19 05:31:46.911: INFO/ARMAssembler(583): generated scanline__00000077:03515104_00001001_00000000 [ 64 ipp] (84 ins) at [0x2c6a70:0x2c6bc0] in 1985378 ns
01-19 05:31:49.881: INFO/Process(770): Sending signal. PID: 770 SIG: 9
01-19 05:31:49.931: INFO/ActivityManager(583): Process pro.googlemapp (pid 770) has died.
01-19 05:31:49.941: WARN/GpsLocationProvider(583): Unneeded remove listener for uid 1000
01-19 05:31:49.941: DEBUG/GpsLocationProvider(583): stopNavigating
01-19 05:31:49.951: INFO/WindowManager(583): WIN DEATH: Window{438891c0 pro.googlemapp/pro.googlemapp.LocationActivity paused=false}
01-19 05:31:50.111: WARN/UsageStats(583): Unexpected resume of com.android.launcher while already resumed in pro.googlemapp
01-19 05:31:50.200: WARN/InputManagerService(583): Got RemoteException sending setActive(false) notification to pid 770 uid 10025
回答by alvan
the way you construct the MyLocationOverlay might have some problem.
您构造 MyLocationOverlay 的方式可能存在一些问题。
MyLocationOverlay mylocationOverlay = new MyLocationOverlay(this, mapView);
MyLocationOverlay mylocationOverlay = new MyLocationOverlay(this, mapView);
according to the google code apiyou need to pass a context and a mapview param.
根据谷歌代码api，您需要传递上下文和地图视图参数。
and then put these code after that
然后把这些代码放在后面
mylocationOverlay.enableMyLocation();
mapView.getOverlays().add(locationOverlay);
also put
还放
mylocationOverlay.enableMyLocation();in the onResume() method
mylocationOverlay.enableMyLocation();在 onResume() 方法中
Hope this could help you.
希望这可以帮助你。
回答by asdf
The GeoPoint "p" in the MyLocationOverlay is null. When you replay "GeoPoint initGeoPoint" with "p" you can solve this problem.
MyLocationOverlay 中的 GeoPoint "p" 为空。当你用“p”重放“GeoPoint initGeoPoint”时，你可以解决这个问题。
回答by mnish
In your logs look at this line 01-19 05:31:46.541: ERROR/AndroidRuntime(770): at pro.googlemapp.LocationActivity$MyLocationOverlay.draw(LocationActivity.java:101)
在您的日志中查看这一行 01-19 05:31:46.541: ERROR/AndroidRuntime(770): at pro.googlemapp.LocationActivity$MyLocationOverlay.draw(LocationActivity.java:101)
This refers to the GeoPoint p. At the beginning you set the value of pto null(as "asdf" says) and never change its value to a GeoPoint and that is why you get java.lang.NullPointerException.
这是指 GeoPoint p。一开始，您将p的值设置为null（如“asdf”所说）并且永远不会将其值更改为 GeoPoint，这就是您得到java.lang.NullPointerException.
For example you can set the value of plike this: p = new GeoPoint(19240000,-99120000);and of course this must happen before this line mapView.getProjection().toPixels(p, myScreenCoords);of your code.
例如，您可以像这样设置p的值：p = new GeoPoint(19240000,-99120000);当然这必须发生在mapView.getProjection().toPixels(p, myScreenCoords);您的代码的这一行之前。
Good luck
祝你好运
回答by mPrinC
This is something which might help you in sloving your byg:
这可能会帮助你爱你的 byg：
回答by Krishnakant Dalal
This is because Geopoint p value is null in class MyLocationListener. So when you called mapView.getProjection().toPixels(p, myScreenCoords); because p is null it is unable to convert toPixels and throws Exception. You can overcome on this by just declare your GeoPoint p as static in your LocationActivity.
这是因为 Geopoint p 值在 MyLocationListener 类中为空。所以当你调用 mapView.getProjection().toPixels(p, myScreenCoords); 因为 p 为空，所以无法转换为像素并抛出异常。您可以通过在 LocationActivity 中将 GeoPoint p 声明为静态来克服这一点。
