Question

我正在开发一个显示地图视图的应用，并覆盖我从互联网上下载的图片。

应用等待用户按下按钮，然后将地图置于用户当前位置的中心位置。

一切都很好。但是当我将测试手机（Galaxy SIII）更新为Jelly Bean时，我觉得事情搞砸了。

当我按下按钮获取当前GPS位置，使地图居中并覆盖图像时，应用程序崩溃。

以下是LogCat的输出。我不确定它是什么意思，所以如果你能帮助我理解它，我会非常感激！

从我的代码中摘录我认为是问题：

Button监听器：

mUpdateButton.setOnClickListener(new View.OnClickListener() 
    {
        public void onClick(View arg0) 
        {
            // Start listening for location
            myLocationManager.requestLocationUpdates(LocationManager.GPS_PROVIDER,0,0,myLocationListener);

            // Get Lat and Long coordinates, and format them
            MyLat = (int)(myLocationManager.getLastKnownLocation(LocationManager.GPS_PROVIDER).getLatitude()*1000000);
            MyLong = (int)(myLocationManager.getLastKnownLocation(LocationManager.GPS_PROVIDER).getLongitude()*1000000);

            // Save the Lat and Long into a GeoPoint
            GeoPoint initGeoPoint = new GeoPoint(MyLat,MyLong);

            // Center location on current pos
            CenterLocatio(initGeoPoint, 10);

            // Stop listening for location
            myLocationManager.removeUpdates(myLocationListener);
        }
    });

CenterLocatio功能：

private void CenterLocatio(GeoPoint centerGeoPoint, int zoomLevel)
{
    myMapController.animateTo(centerGeoPoint);
    myMapController.setZoom(zoomLevel);

    myLongitude.setText("Longitude: "+
            String.valueOf((float)centerGeoPoint.getLongitudeE6()/1000000)
            );
    myLatitude.setText("Latitude: "+
            String.valueOf((float)centerGeoPoint.getLatitudeE6()/1000000)
            );



    // Get location of the storage location
    File extStore = Environment.getExternalStorageDirectory();
    String PATH = extStore + "/data/tntechpie/";
    // Add new overlay to Map
    List<Overlay> mapOverlays = myMapView.getOverlays();
    // Set drawable to the downloaded image from the storage location
    //Drawable drawable = this.getResources().getDrawable(R.drawable.androidmarker);

    @SuppressWarnings("deprecation")
    Drawable drawable = new BitmapDrawable(PATH + "testMap.gif");
    myItemizedOverlay itemizedoverlay = new myItemizedOverlay(drawable, this);

    OverlayItem overlayitem = new OverlayItem(centerGeoPoint, "", "");
    itemizedoverlay.addOverlay(overlayitem);
    mapOverlays.add(itemizedoverlay);
};

LogCat输出：

01-22 12:34:31.062: I/MapActivity(6919): Handling network change notification:CONNECTED
01-22 12:34:31.062: E/MapActivity(6919): Couldn't get connection factory client
01-22 12:34:33.465: D/AndroidRuntime(6919): Shutting down VM
01-22 12:34:33.465: W/dalvikvm(6919): threadid=1: thread exiting with uncaught exception (group=0x41f44438)
01-22 12:34:33.475: E/AndroidRuntime(6919): FATAL EXCEPTION: main
01-22 12:34:33.475: E/AndroidRuntime(6919): java.lang.NullPointerException
01-22 12:34:33.475: E/AndroidRuntime(6919):     at com.androidlocation.MainActivity$1.onClick(MainActivity.java:120)
01-22 12:34:33.475: E/AndroidRuntime(6919):     at android.view.View.performClick(View.java:4198)
01-22 12:34:33.475: E/AndroidRuntime(6919):     at android.view.View$PerformClick.run(View.java:17158)
01-22 12:34:33.475: E/AndroidRuntime(6919):     at android.os.Handler.handleCallback(Handler.java:615)
01-22 12:34:33.475: E/AndroidRuntime(6919):     at android.os.Handler.dispatchMessage(Handler.java:92)
01-22 12:34:33.475: E/AndroidRuntime(6919):     at android.os.Looper.loop(Looper.java:137)
01-22 12:34:33.475: E/AndroidRuntime(6919):     at android.app.ActivityThread.main(ActivityThread.java:4918)
01-22 12:34:33.475: E/AndroidRuntime(6919):     at java.lang.reflect.Method.invokeNative(Native Method)
01-22 12:34:33.475: E/AndroidRuntime(6919):     at java.lang.reflect.Method.invoke(Method.java:511)
01-22 12:34:33.475: E/AndroidRuntime(6919):     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1004)
01-22 12:34:33.475: E/AndroidRuntime(6919):     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:771)
01-22 12:34:33.475: E/AndroidRuntime(6919):     at dalvik.system.NativeStart.main(Native Method)
01-22 12:34:41.924: I/Process(6919): Sending signal. PID: 6919 SIG: 9

Answer 1

java.lang.NullPointerException 
    at com.androidlocation.MainActivity$1.onClick(MainActivity.java:120)

这个错误意味着在第120行，你要求一个等于什么的变量（即null）来做某事。问题可能发生在onClick()方法中：

MyLat = (int)(myLocationManager.getLastKnownLocation(LocationManager.GPS_PROVIDER).getLatitude()*1000000);
MyLong = (int)(myLocationManager.getLastKnownLocation(LocationManager.GPS_PROVIDER).getLongitude()*1000000);

但如果最近没有可用修补程序，则getLastKnownLocation()可能会返回null。在尝试从中读取之前，您应该检查它是否返回可用值。

Location lastknown = myLocationManager.getLastKnownLocation(LocationManager.GPS_PROVIDER);
if(lastKnown != null) {
    // Read the lat / long data
}

Answer 2

我猜你没有初始化 myLocationManager ，但由于你没有标记哪一行是120，我无法确定。

试试这样。（或者更好地移动此行而不是onCreate方法 - 每次单击按钮时都不需要初始化它。）

myLocationManager = (LocationManager)getSystemService(Context.LOCATION_SERVICE); // add this line
myLocationManager.requestLocationUpdates(LocationManager.GPS_PROVIDER,0,0,myLocationListener);

另一种可能性是这段代码：

(myLocationManager.getLastKnownLocation(LocationManager.GPS_PROVIDER)

返回null - 比Sam建议的那样（检查它是否为空）。

我的Android应用程序崩溃了，不了解Eclipse中的Logcat

2 个答案: