我不确定这里发生了什么。我正在添加声明，以便在长按时使手机振动。我把声明置于错误的位置，电话不断振动。所以我拔掉了电话并将其关闭。然后我删除了导致我的手机执行此操作的代码。然后尝试在添加代码之前重新启动应用程序，我现在就知道了。我不确定发生了什么，因为代码与它工作时完全一样。缓存的文件会导致这个吗？
这是我的logcat：
10-28 17:34:51.381: W/dalvikvm(718): threadid=1: thread exiting with uncaught exception (group=0x40a13300)
10-28 17:34:51.389: E/AndroidRuntime(718): FATAL EXCEPTION: main
10-28 17:34:51.389: E/AndroidRuntime(718): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.almyz125.stamp/com.almyz125.stamp.Map}: java.lang.NullPointerException
10-28 17:34:51.389: E/AndroidRuntime(718): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2059)
10-28 17:34:51.389: E/AndroidRuntime(718): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2084)
10-28 17:34:51.389: E/AndroidRuntime(718): at android.app.ActivityThread.access$600(ActivityThread.java:130)
10-28 17:34:51.389: E/AndroidRuntime(718): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1195)
10-28 17:34:51.389: E/AndroidRuntime(718): at android.os.Handler.dispatchMessage(Handler.java:99)
10-28 17:34:51.389: E/AndroidRuntime(718): at android.os.Looper.loop(Looper.java:137)
10-28 17:34:51.389: E/AndroidRuntime(718): at android.app.ActivityThread.main(ActivityThread.java:4745)
10-28 17:34:51.389: E/AndroidRuntime(718): at java.lang.reflect.Method.invokeNative(Native Method)
10-28 17:34:51.389: E/AndroidRuntime(718): at java.lang.reflect.Method.invoke(Method.java:511)
10-28 17:34:51.389: E/AndroidRuntime(718): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:786)
10-28 17:34:51.389: E/AndroidRuntime(718): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:553)
10-28 17:34:51.389: E/AndroidRuntime(718): at dalvik.system.NativeStart.main(Native Method)
10-28 17:34:51.389: E/AndroidRuntime(718): Caused by: java.lang.NullPointerException
10-28 17:34:51.389: E/AndroidRuntime(718): at com.almyz125.stamp.Map.onCreate(Map.java:88)
10-28 17:34:51.389: E/AndroidRuntime(718): at android.app.Activity.performCreate(Activity.java:5008)
10-28 17:34:51.389: E/AndroidRuntime(718): at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1079)
10-28 17:34:51.389: E/AndroidRuntime(718): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2023)
10-28 17:34:51.389: E/AndroidRuntime(718): ... 11 more
这是我的代码：
public class Map extends MapActivity implements LocationListener {
// variable for determining long press and then automatically adding a pin
// to the map
private int minMillisecondThresholdForLongClick = 800;
private long startTimeForLongClick = 0;
private float xScreenCoordinateForLongClick;
private float yScreenCoordinateForLongClick;
private float xtolerance = 10;// x pixels that your finger can be off but
// still constitute a long press
private float ytolerance = 10;// y pixels that your finger can be off but
// still constitute a long press
private float xlow; // actual screen coordinate when you subtract the
// tolerance
private float xhigh; // actual screen coordinate when you add the tolerance
private float ylow; // actual screen coordinate when you subtract the
// tolerance
private float yhigh; // actual screen coordinate when you add the tolerance
// Variables
MapView mapView;
MapController mc;
long start;
long stop;
int x, y, longTemp, latTemp;
GeoPoint touchPoint;
LocationManager lm;
Drawable d;
Location lastKnownLoc;
List<Overlay> mapoverlays;
GeoPoint gp;
private MyLocationOverlay myLocOverlay, compass;
// Auto Generated Methods
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
// sets view to map
setContentView(R.layout.main);
mapView = (MapView) findViewById(R.id.mvMain);
mc = mapView.getController();
compass = new MyLocationOverlay(Map.this, mapView);
d = getResources().getDrawable(R.drawable.icon);
mapoverlays = mapView.getOverlays();
myLocOverlay = new MyLocationOverlay(this, mapView);
mapoverlays = mapView.getOverlays();
lm = (LocationManager) getSystemService(Context.LOCATION_SERVICE);
lastKnownLoc = lm.getLastKnownLocation(LocationManager.GPS_PROVIDER);
longTemp = (int) (lastKnownLoc.getLongitude() * 1e6);
latTemp = (int) (lastKnownLoc.getLatitude() * 1e6);
gp = new GeoPoint(latTemp, longTemp);
// enables on screen zoom buttons
mapView.setBuiltInZoomControls(true);
// create overlay that shows our location
// add this overlay to the map and refresh it
mapView.getOverlays().add(myLocOverlay);
mapView.invalidate();
mapoverlays.add(compass);
compass.enableMyLocation();
compass.enableCompass();
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
// TODO Auto-generated method stub
// return super.onCreateOptionsMenu(menu);
MenuInflater inflater = getMenuInflater();
inflater.inflate(R.menu.options, menu);
return true;
}
@Override
public boolean onMenuItemSelected(int featureId, MenuItem item) {
// handle on menu item selected here
super.onMenuItemSelected(featureId, item);
// if item is selected satellite view is toggled
if (item.getItemId() == R.id.opt_tog_view) {
toggleSat();
}
return true;
}
// method to toggles satellite view called in option menu
public void toggleSat() {
if (mapView.isSatellite()) {
mapView.setSatellite(false);
} else {
mapView.setSatellite(true);
}
}
// Volume keys zoom in and out.
public boolean onKeyDown(int keyCode, KeyEvent event) {
mc = mapView.getController();
switch (keyCode) {
case KeyEvent.KEYCODE_VOLUME_UP:
mc.zoomIn();
break;
case KeyEvent.KEYCODE_VOLUME_DOWN:
mc.zoomOut();
break;
}
return super.onKeyDown(keyCode, event);
}
@Override
protected boolean isRouteDisplayed() {
// TODO Auto-generated method stub
return false;
}
@Override
protected void onPause() {
// TODO Auto-generated method stub
super.onPause();
compass.disableMyLocation();
compass.disableCompass();
myLocOverlay.disableMyLocation();
}
@Override
protected void onResume() {
// TODO Auto-generated method stub
super.onResume();
gp = new GeoPoint(latTemp, longTemp);
myLocOverlay.enableMyLocation();
compass.enableMyLocation();
compass.enableCompass();
mapoverlays.add(compass);
}
@Override
public void onLocationChanged(Location location) {
// TODO Auto-generated method stub
}
@Override
public void onProviderDisabled(String arg0) {
// TODO Auto-generated method stub
}
@Override
public void onProviderEnabled(String arg0) {
// TODO Auto-generated method stub
}
@Override
public void onStatusChanged(String arg0, int arg1, Bundle arg2) {
// TODO Auto-generated method stub
}
@Override
public boolean dispatchTouchEvent(MotionEvent ev) {
/*
* We want to capture the place the user long pressed on the map and add
* a marker (pin) on the map at that lat/long. This solution: 1. Allows
* you to set the time threshold for what constitutes a long press 2.
* Doesn't get fooled by scrolling, multi-touch, or non-multi-touch
* events
*
* Thank you Roger Kind Kristiansen for the main idea
*/
// get the action from the MotionEvent: down, move, or up
int actionType = ev.getAction();
if (actionType == MotionEvent.ACTION_DOWN) {
// user pressed the button down so let's initialize the main
// variables that we care about:
// later on when the "Action Up" event fires, the "DownTime" should
// match the "startTimeForLongClick" that we set here
// the coordinate on the screen should not change much during the
// long press
startTimeForLongClick = ev.getEventTime();
xScreenCoordinateForLongClick = ev.getX();
yScreenCoordinateForLongClick = ev.getY();
} else if (actionType == MotionEvent.ACTION_MOVE) {
// For non-long press actions, the move action can happen a lot
// between ACTION_DOWN and ACTION_UP
if (ev.getPointerCount() > 1) {
// easiest way to detect a multi-touch even is if the pointer
// count is greater than 1
// next thing to look at is if the x and y coordinates of the
// person's finger change.
startTimeForLongClick = 0; // instead of a timer, just reset
// this class variable and in our
// ACTION_UP event, the DownTime
// value will not match and so we
// can reset.
} else {
// I know that I am getting to the same action as above,
// startTimeForLongClick=0, but I want the processor
// to quickly skip over this step if it detects the pointer
// count > 1 above
float xmove = ev.getX(); // where is their finger now?
float ymove = ev.getY();
// these next four values allow you set a tiny box around their
// finger in case
// they don't perfectly keep their finger still on a long click.
xlow = xScreenCoordinateForLongClick - xtolerance;
xhigh = xScreenCoordinateForLongClick + xtolerance;
ylow = yScreenCoordinateForLongClick - ytolerance;
yhigh = yScreenCoordinateForLongClick + ytolerance;
if ((xmove < xlow || xmove > xhigh)
|| (ymove < ylow || ymove > yhigh)) {
// out of the range of an acceptable long press, reset the
// whole process
startTimeForLongClick = 0;
}
}
} else if (actionType == MotionEvent.ACTION_UP) {
// determine if this was a long click:
long eventTime = ev.getEventTime();
long downTime = ev.getDownTime(); // this value will match the
// startTimeForLongClick
// variable as long as we didn't
// reset the
// startTimeForLongClick
// variable because we detected
// nonsense that invalidated a
// long press in the ACTION_MOVE
// block
// make sure the start time for the original "down event" is the
// same as this event's "downTime"
if (startTimeForLongClick == downTime) {
// see if the event time minus the start time is within the
// threshold
if ((eventTime - startTimeForLongClick) > minMillisecondThresholdForLongClick) {
// make sure we are at the same spot where we started the
// long click
float xup = ev.getX();
float yup = ev.getY();
// I don't want the overhead of a function call:
xlow = xScreenCoordinateForLongClick - xtolerance;
xhigh = xScreenCoordinateForLongClick + xtolerance;
ylow = yScreenCoordinateForLongClick - ytolerance;
yhigh = yScreenCoordinateForLongClick + ytolerance;
if ((xup > xlow && xup < xhigh)
&& (yup > ylow && yup < yhigh)) {
// **** safe to process your code for an actual long
// press ****
// comment out these next rows after you confirm in
// logcat that the long press works
long totaltime = eventTime - startTimeForLongClick;
String strtotaltime = Long.toString(totaltime);
Log.d("long press detected: ", strtotaltime);
// Below is code from my touchy class
x = (int) ev.getX();
y = (int) ev.getY();
touchPoint = mapView.getProjection().fromPixels(x, y);
Builder alert = new AlertDialog.Builder(Map.this);
alert.setTitle("Pick an option.");
alert.setNeutralButton("Place a marker",
new DialogInterface.OnClickListener() {
public void onClick(DialogInterface dialog,
int which) {
OverlayItem overlayItem = new OverlayItem(
touchPoint, "What's up",
"2nd String");
Mark custom = new Mark(d, Map.this);
custom.dropMarker(overlayItem);
mapoverlays.add(custom);
}
});
alert.setPositiveButton("Get Address",
new DialogInterface.OnClickListener() {
public void onClick(DialogInterface dialog,
int which) {
Geocoder geocoder = new Geocoder(
getBaseContext(), Locale
.getDefault());
try {
List<Address> address = geocoder.getFromLocation(
touchPoint.getLatitudeE6() / 1E6,
touchPoint.getLongitudeE6() / 1E6,
1);
if (address.size() > 0) {
String display = "";
for (int i = 0; i < address
.get(0)
.getMaxAddressLineIndex(); i++) {
display += address.get(0)
.getAddressLine(i)
+ "\n";
}
Toast t = Toast.makeText(
getBaseContext(),
display,
Toast.LENGTH_LONG);
t.show();
}
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} finally {
}
}
});
alert.show();
}
}
}
}
return super.dispatchTouchEvent(ev) && true;
}
}
这是我的清单：
<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="com.almyz125.stamp" >
<uses-permission android:name="android.permission.INTERNET" />
<uses-sdk
android:minSdkVersion="8"
android:targetSdkVersion="16" />
<uses-permission android:name="android.permission.ACCESS_FINE_LOCATION" />
<uses-permission android:name="android.permission.ACCESS_COARSE_LOCATION" />
<application
android:icon="@drawable/icon"
android:label="@string/activity_main_map" >
<uses-library android:name="com.google.android.maps" />
<activity
android:name="com.almyz125.stamp.Map"
android:label="STAMP" >
<intent-filter>
<category android:name="android.intent.category.LAUNCHER" >
</category>
<action android:name="android.intent.action.MAIN" >
</action>
</intent-filter>
</activity>
</application>
</manifest>
答案 0 :(得分：2)
在创建包含MyLocationOverlay的活动时，您无法确定getLastKnownLocation是否为null，因此您必须像下面的代码段一样对其进行说明：
if(lastKnownLoc != null){
longTemp = (int) (lastKnownLoc.getLongitude() * 1e6);
latTemp = (int) (lastKnownLoc.getLatitude() * 1e6);
gp = new GeoPoint(latTemp, longTemp);
}
在您重新启动手机之前它的工作原理仅仅是因为Android之前修复了您的位置，但情况可能并非总是如此。
您可能还想尝试使用runOnFirstFix方法作为解决问题的更好方法。
compass.runOnFirstFix(new Runnable() {
@Override
public void run() {
Location location = compass.getLastFix();
//do your location code here
}
});