更新到 API 19 真的很烦人。我真的很难弄清楚如何处理 google play 服务。但是，当我运行它时，这个错误会显示给我。
11-11 04:25:27.214: E/AndroidRuntime(1340): java.lang.RuntimeException: Unable to start activity
ComponentInfo{com.synergy88studios.quezoncityguide/com.synergy88studios.quezoncityguide.QuezonCityMap}: java.lang.NullPointerException
logcat 指向我课堂上的这一行：
map.getUiSettings().setCompassEnabled(true);
我不知道这里可能有什么问题。
这是我的课：
public class QuezonCityMap extends FragmentActivity {
final Context context = this;
Button routes;
double latitude = 14.635576;
double longitude = 121.033115;
LatLng latlng = new LatLng(14.6353475, 121.0327501);
LatLngBounds QC = new LatLngBounds(
new LatLng(14.656669, 120.998598), new LatLng(14.666965, 121.098934));
MarkerOptions marker = new MarkerOptions().position(new LatLng(latitude, longitude)).title("Shell").snippet("Sa tabi ng Estuar Building");
Marker mark;
GoogleMap map;
ArrayList<LatLng> markerPoints;
TextView tvDistanceDuration;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_quezon_city_map);
tvDistanceDuration = (TextView) findViewById(R.id.tv_distance_time);
// Initializing
markerPoints = new ArrayList<LatLng>();
// Getting reference to SupportMapFragment of the activity_main
SupportMapFragment fm = (SupportMapFragment)getSupportFragmentManager().findFragmentById(R.id.map);
// Getting Map for the SupportMapFragment
map = fm.getMap();
// Set Compass Enabled
map.getUiSettings().setCompassEnabled(true);
map.getUiSettings().setRotateGesturesEnabled(true);
// create marker
// Changing marker icon
marker.icon(BitmapDescriptorFactory.fromResource(R.drawable.share));
map.moveCamera(CameraUpdateFactory.newLatLngZoom(QC.getCenter(), 12));
// Enable MyLocation Button in the Map
map.setMyLocationEnabled(true);
mark = map.addMarker(marker);
//button
map.setOnCameraChangeListener(new OnCameraChangeListener() {
@Override
public void onCameraChange(CameraPosition arg0) {
// adding marker
if(arg0.zoom <16){
mark.setVisible(false);}
else
mark.setVisible(true);
if(arg0.zoom > 17){
mark.setIcon(BitmapDescriptorFactory.fromResource(R.drawable.share));
}
}
});
// Setting onclick event listener for the map
map.setOnMapClickListener(new OnMapClickListener() {
@Override
public void onMapClick(LatLng point) {
// Already two locations
if(markerPoints.size()>1){
markerPoints.clear();
map.clear();
MarkerOptions marker = new MarkerOptions().position(new LatLng(latitude, longitude)).title("Shell").snippet("Sa tabi ng Estuar Building");
// Changing marker icon
marker.icon(BitmapDescriptorFactory.fromResource(R.drawable.share));
// adding marker
map.addMarker(marker);
}
// Adding new item to the ArrayList
markerPoints.add(point);
// Creating MarkerOptions
MarkerOptions options = new MarkerOptions();
// Setting the position of the marker
options.position(point);
/**
* For the start location, the color of marker is GREEN and
* for the end location, the color of marker is RED.
*/
if(markerPoints.size()==1){
options.icon(BitmapDescriptorFactory.defaultMarker(BitmapDescriptorFactory.HUE_GREEN));
}else if(markerPoints.size()==2){
options.icon(BitmapDescriptorFactory.defaultMarker(BitmapDescriptorFactory.HUE_RED));
}
// Add new marker to the Google Map Android API V2
map.addMarker(options);
// Checks, whether start and end locations are captured
if(markerPoints.size() >= 2){
LatLng origin = markerPoints.get(0);
LatLng dest = markerPoints.get(1);
// Getting URL to the Google Directions API
String url = getDirectionsUrl(origin, dest);
DownloadTask downloadTask = new DownloadTask();
// Start downloading json data from Google Directions API
downloadTask.execute(url);
}
}
});
}
private String getDirectionsUrl(LatLng origin,LatLng dest){
// Origin of route
String str_origin = "origin="+origin.latitude+","+origin.longitude;
// Destination of route
String str_dest = "destination="+dest.latitude+","+dest.longitude;
// Sensor enabled
String sensor = "sensor=false";
// Building the parameters to the web service
String parameters = str_origin+"&"+str_dest+"&"+sensor;
// Output format
String output = "json";
// Building the url to the web service
String url = "https://maps.googleapis.com/maps/api/directions/"+output+"?"+parameters;
return url;
}
/** A method to download json data from url */
private String downloadUrl(String strUrl) throws IOException{
String data = "";
InputStream iStream = null;
HttpURLConnection urlConnection = null;
try{
URL url = new URL(strUrl);
// Creating an http connection to communicate with url
urlConnection = (HttpURLConnection) url.openConnection();
// Connecting to url
urlConnection.connect();
// Reading data from url
iStream = urlConnection.getInputStream();
BufferedReader br = new BufferedReader(new InputStreamReader(iStream));
StringBuffer sb = new StringBuffer();
String line = "";
while( ( line = br.readLine()) != null){
sb.append(line);
}
data = sb.toString();
br.close();
}catch(Exception e){
Log.d("Exception while downloading url", e.toString());
}finally{
iStream.close();
urlConnection.disconnect();
}
return data;
}
// Fetches data from url passed
private class DownloadTask extends AsyncTask<String, Void, String>{
// Downloading data in non-ui thread
@Override
protected String doInBackground(String... url) {
// For storing data from web service
String data = "";
try{
// Fetching the data from web service
data = downloadUrl(url[0]);
}catch(Exception e){
Log.d("Background Task",e.toString());
}
return data;
}
// Executes in UI thread, after the execution of
// doInBackground()
@Override
protected void onPostExecute(String result) {
super.onPostExecute(result);
ParserTask parserTask = new ParserTask();
// Invokes the thread for parsing the JSON data
parserTask.execute(result);
}
}
/** A class to parse the Google Places in JSON format */
private class ParserTask extends AsyncTask<String, Integer, List<List<HashMap<String,String>>> >{
// Parsing the data in non-ui thread
@Override
protected List<List<HashMap<String, String>>> doInBackground(String... jsonData) {
JSONObject jObject;
List<List<HashMap<String, String>>> routes = null;
try{
jObject = new JSONObject(jsonData[0]);
DirectionsJSONParser parser = new DirectionsJSONParser();
// Starts parsing data
routes = parser.parse(jObject);
}catch(Exception e){
e.printStackTrace();
}
return routes;
}
// Executes in UI thread, after the parsing process
@Override
protected void onPostExecute(List<List<HashMap<String, String>>> result) {
ArrayList<LatLng> points = null;
PolylineOptions lineOptions = null;
MarkerOptions markerOptions = new MarkerOptions();
String distance = "";
String duration = "";
if(result.size()<1){
Toast.makeText(getBaseContext(), "No Points", Toast.LENGTH_SHORT).show();
return;
}
// Traversing through all the routes
for(int i=0;i<result.size();i++){
points = new ArrayList<LatLng>();
lineOptions = new PolylineOptions();
// Fetching i-th route
List<HashMap<String, String>> path = result.get(i);
// Fetching all the points in i-th route
for(int j=0;j<path.size();j++){
HashMap<String,String> point = path.get(j);
if(j==0){ // Get distance from the list
distance = (String)point.get("distance");
continue;
}else if(j==1){ // Get duration from the list
duration = (String)point.get("duration");
continue;
}
double lat = Double.parseDouble(point.get("lat"));
double lng = Double.parseDouble(point.get("lng"));
LatLng position = new LatLng(lat, lng);
points.add(position);
}
// Adding all the points in the route to LineOptions
lineOptions.addAll(points);
lineOptions.width(2);
lineOptions.color(Color.RED);
}
tvDistanceDuration.setText("Distance:"+distance + ", Duration:"+duration);
// Drawing polyline in the Google Map for the i-th route
map.addPolyline(lineOptions);
}
}
我在这里找不到可能为空的内容。课堂上没有错误。可以请人帮助我吗？谢谢。这是我的日志：
FATAL EXCEPTION: main
java.lang.RuntimeException: Unable to start activity ComponentInfo{com.synergy88studios.quezoncityguide/com.synergy88studios.quezoncityguide.QuezonCityMap}: java.lang.NullPointerException
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2211)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2261)
at android.app.ActivityThread.access$600(ActivityThread.java:141)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1256)
at android.os.Handler.dispatchMessage(Handler.java:99)
at android.os.Looper.loop(Looper.java:137)
at android.app.ActivityThread.main(ActivityThread.java:5103)
at java.lang.reflect.Method.invokeNative(Native Method)
at java.lang.reflect.Method.invoke(Method.java:525)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:737)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:553)
at dalvik.system.NativeStart.main(Native Method)
Caused by: java.lang.NullPointerException
at com.synergy88studios.quezoncityguide.QuezonCityMap.onCreate(QuezonCityMap.java:83)
at android.app.Activity.performCreate(Activity.java:5133)
at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1087)
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2175)
... 11 more
我的 XML
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
tools:context=".QuezonCityMap" >
<TextView
android:id="@+id/tv_distance_time"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="@string/hello_world"
android:layout_alignParentTop="true" />
<fragment
android:id="@+id/map"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_below="@id/tv_distance_time"
class="com.google.android.gms.maps.SupportMapFragment"
android:name="com.google.android.gms.maps.SupportMapFragment"
/>
<Button
android:id="@+id/buttonRoutes"
style="?android:attr/buttonStyleSmall"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignTop="@+id/map"
android:layout_alignParentLeft="true"
android:layout_marginTop="7dp"
android:layout_marginLeft="9dp"
/>