在地图上标记当前位置，Android

我按照一些教程创建了一个应用程序，用一个标记显示用户在地图上的当前位置。但由于某些原因，我无法完成标记部分？其他部分工作正常，但每当我添加标记代码时，应用程序就会崩溃。
代码如下：

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;
    }
}

公共类LocationActivity扩展了MapActivity{
私有地图视图；
私人位置经理lm；
私人场所；
专用地图控制器；
地质点p=零；
Drawable defaultMarker=null；
@凌驾
创建时的公共void（Bundle savedInstanceState）{
super.onCreate（savedInstanceState）；
setContentView（R.layout.main）；
mapView=（mapView）findViewById（R.id.mapView）；
//显示放大/缩小按钮
mapView.SetBuilTinZoomControl（真）；
//地图的标准视图（地图/卫星）
mapView.setSatellite（假）；
//获取用于放大/缩小的地图控制器
mc=mapView.getController（）；
//缩放级别
mc.setZoom（18）；
MyLocationOverlay MyLocationOverlay=新建MyLocationOverlay（）；
List=mapView.getOverlays（）；
列表。添加（myLocationOverlay）；
lm=（LocationManager）getSystemService（Context.LOCATION\u服务）；
ll=新的MyLocationListener（）；
lm.RequestLocationUpdate（LocationManager.GPS_提供程序，0，0，ll）；
//获取启动中的当前位置
地质点初始地质点=新的地质点（（int）（lm.getLastKnownLocation）(
LocationManager.GPS_PROVIDER）.getLatitude（）*1000000），
（int）（lm.getLastKnownLocation（LocationManager.GPS\U提供商）
.getLongitude（）*1000000））；
动画师（初始点）；
}
受保护类MyLocationOverlay扩展了com.google.android.maps.Overlay{
@凌驾
公共布尔绘制（画布、地图视图、地图视图、布尔阴影、，
很久以前）{
油漆=新油漆（）；
super.draw（画布、地图视图、阴影）；
//将lat/lng点转换为屏幕上的坐标。
点myScreenCoords=新点（）；
getProjection（）.toPixels（p，myScreenCoords）；
油漆。设置行程宽度（1）；
setARGB（255、255、255、255）；
绘制.设置样式（绘制.样式.笔划）；
位图bmp=BitmapFactory.decodeResource（getResources（），
R.可拉拔、推压）；
drawBitmap（bmp，myScreenCoods.x，myScreenCoods.y，paint）；
canvas.drawText（“我在这里…”）、myscreencoods.x、myscreencoods.y、，
油漆）；
返回true；
}
}
私有类MyLocationListener实现LocationListener{
已更改位置上的公共void（位置argLocation）{
地质点myGeoPoint=新地质点(
（int）（argLocation.getLatitude（）*1000000），
（int）（argLocation.getLongitude（）*1000000））；
/*
*它将显示位置更改消息
*Toast.makeText（getBaseContext（），“新位置纬度[”
*+argLocation.getLatitude（）+“]经度[”+
*argLocation.getLongitude（）+“]”，Toast.LENGTH_SHORT.show（）；
*/
动画师（myGeoPoint）；
}
公共无效onProviderDisabled（字符串提供程序）{}
公共无效onProviderEnabled（字符串提供程序）{}
public void onStatusChanged（字符串提供程序、int状态、Bundle extra）{}
}
受保护的布尔值isRouteDisplayed（）{
返回false；
}
}

以下是日志：

    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

---

01-19 05:31:43.011:DEBUG/AndroidRuntime（759）：>>>>>>>>>>>>>>>>>>AndroidRuntime START这可能有助于您解决byg问题：

MyLocationOverlay中的地质点“p”为空。当您用“p”重播“GeoPoint initGeoPoint”时，您可以解决这个问题。
在日志中查看这行
01-19 05:31:46.541:ERROR/AndroidRuntime（770）：在pro.googlemapp.LocationActivity$MyLocationOverlay.draw（LocationActivity.java:101）

这是指地质点p。开始时，您将p的值设置为null（如“asdf”所述），并且从不将其值更改为地质点，这就是为什么您会得到
java.lang.NullPointerException

例如，可以如下设置p的值：
p=new GeoPoint（19240000，-99120000）mapView.getProjection（）.toPixels（p，myScreenCoords）之前你的代码

祝你好运
你构建MyLocationOverlay的方式可能有一些问题

MyLocationOverlay MyLocationOverlay=新建MyLocationOverlay（此为地图视图）

根据需要，您需要传递一个上下文和一个mapview参数

然后把这些代码放在后面

mylocationOverlay.enableMyLocation();
mapView.getOverlays().add(locationOverlay);

也放

mylocationOverlay.enableMyLocation（）

希望这能对您有所帮助。
这是因为MyLocationListener类中的Geopoint p值为null。因此，当您调用mapView.getProjection（）.toPixels（p，myScreenCoords）时；因为p为null，所以它无法转换toPixels并引发异常。您只需在LocationActivity中将您的地质点p声明为静态，就可以克服此问题。
请发布崩溃日志好吗？如果我们能看到堆栈跟踪，这样我们就能知道哪一行崩溃了，这会很有帮助。