我是android地图开发的新手。我试图通过url和get Document type object。它产生了错误。
发生了跟随错误。
这是xml代码。
<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=".MainActivity" >
<fragment
android:id="@+id/map"
android:layout_width="match_parent"
android:layout_height="match_parent"
class="com.google.android.gms.maps.MapFragment" />
<Button
android:id="@+id/button1"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignParentLeft="true"
android:layout_alignParentRight="true"
android:layout_alignParentTop="true"
android:text="Button" />
</RelativeLayout>
这是主要的活动代码。
public class MainActivity extends Activity {
static final LatLng Venushka = new LatLng(6.915861, 79.865368);
static final LatLng venushka2 = new LatLng(6.922763, 79.862053);
public GoogleMap map;
String test;
GMapV2Direction path;
LatLng start=new LatLng(6.915883,79.8654);
LatLng end=new LatLng(6.922784,79.862074);
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
map = ((MapFragment) getFragmentManager().findFragmentById(R.id.map))
.getMap();
Marker hamburg = map.addMarker(new MarkerOptions().position(Venushka) .title("Venushka")
.snippet("Venushka is cool")
.icon(BitmapDescriptorFactory
.fromResource(R.drawable.ic_ven)));
Marker kiel = map.addMarker(new MarkerOptions()
.position(venushka2)
.title("Venushka 2")
.snippet("Venushka is happy")
.icon(BitmapDescriptorFactory
.fromResource(R.drawable.ic_ven)));
// Move the camera instantly to hamburg with a zoom of 15.
map.moveCamera(CameraUpdateFactory.newLatLngZoom(Venushka, 15));
// Zoom in, animating the camera.
map.animateCamera(CameraUpdateFactory.zoomTo(10), 2000, null);
if(map != null)
{
map.setMyLocationEnabled(true);
map.getUiSettings().setCompassEnabled(true);
}
path=new GMapV2Direction();
Document doc=path.getDocument(start,end, "");
String value=doc.toString();
//Toast.makeText(getApplicationContext(), value, Toast.LENGTH_LONG).show();
Log.d(">>>>>>>>",value);
}
}
这是我的GMapV2Direction类代码
public class GMapV2Direction {
public final static String MODE_DRIVING = "driving";
public final static String MODE_WALKING = "walking";
Document doc=null;
public GMapV2Direction() { }
public Document getDocument(LatLng start, LatLng end, String mode) {
String url = "http://maps.googleapis.com/maps/api/directions/xml?"
+ "origin=" + start.latitude + "," + start.longitude
+ "&destination=" + end.latitude + "," + end.longitude
+ "&sensor=false&units=metric&mode=driving";
try {
HttpClient httpClient = new DefaultHttpClient();
HttpContext localContext = new BasicHttpContext();
HttpPost httpPost = new HttpPost(url);
HttpResponse response = httpClient.execute(httpPost, localContext);
InputStream in = response.getEntity().getContent();
DocumentBuilder builder = DocumentBuilderFactory.newInstance().newDocumentBuilder();
Document doc = builder.parse(in);
return doc;
} catch (Exception e) {
e.printStackTrace();
}
return doc;
}
这是清单代码。
<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="com.example.testmaps"
android:versionCode="1"
android:versionName="1.0" >
<uses-sdk
android:minSdkVersion="15"
android:targetSdkVersion="15" />
<permission
android:name="com.example.testmaps.permission.MAPS_RECEIVE"
android:protectionLevel="signature" />
<uses-feature
android:glEsVersion="0x00020000"
android:required="true" />
<uses-permission android:name="com.example.testmaps.permission.MAPS_RECEIVE" />
<uses-permission android:name="android.permission.INTERNET" />
<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />
<uses-permission android:name="com.google.android.providers.gsf.permission.READ_GSERVICES" />
<uses-permission android:name="android.permission.ACCESS_COARSE_LOCATION" />
<uses-permission android:name="android.permission.ACCESS_FINE_LOCATION" />
<uses-permission android:name="android.permission.ACCESS_NETWORK_STATE"/>
<application
android:allowBackup="true"
android:icon="@drawable/ic_launcher"
android:label="@string/app_name"
android:theme="@style/AppTheme" >
<activity
android:name="com.example.testmaps.MainActivity"
android:label="@string/app_name" >
<intent-filter>
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.LAUNCHER" />
</intent-filter>
</activity>
<meta-data
android:name="com.google.android.maps.v2.API_KEY"
android:value="AIzaSyDV5vEA9FdJ4cyINLegzPTGW0twdB83p38" />
</application>
</manifest>
这是我的LogCat
12-19 12:29:34.498: E/AndroidRuntime(16435): FATAL EXCEPTION: main
12-19 12:29:34.498: E/AndroidRuntime(16435): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.testmaps/com.example.testmaps.MainActivity}: java.lang.NullPointerException
12-19 12:29:34.498: E/AndroidRuntime(16435): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1967)
12-19 12:29:34.498: E/AndroidRuntime(16435): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:1992)
12-19 12:29:34.498: E/AndroidRuntime(16435): at android.app.ActivityThread.access$600(ActivityThread.java:127)
12-19 12:29:34.498: E/AndroidRuntime(16435): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1158)
12-19 12:29:34.498: E/AndroidRuntime(16435): at android.os.Handler.dispatchMessage(Handler.java:99)
12-19 12:29:34.498: E/AndroidRuntime(16435): at android.os.Looper.loop(Looper.java:137)
12-19 12:29:34.498: E/AndroidRuntime(16435): at android.app.ActivityThread.main(ActivityThread.java:4511)
12-19 12:29:34.498: E/AndroidRuntime(16435): at java.lang.reflect.Method.invokeNative(Native Method)
12-19 12:29:34.498: E/AndroidRuntime(16435): at java.lang.reflect.Method.invoke(Method.java:511)
12-19 12:29:34.498: E/AndroidRuntime(16435): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:980)
12-19 12:29:34.498: E/AndroidRuntime(16435): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:747)
12-19 12:29:34.498: E/AndroidRuntime(16435): at dalvik.system.NativeStart.main(Native Method)
12-19 12:29:34.498: E/AndroidRuntime(16435): Caused by: java.lang.NullPointerException
12-19 12:29:34.498: E/AndroidRuntime(16435): at com.example.testmaps.MainActivity.onCreate(MainActivity.java:101)
12-19 12:29:34.498: E/AndroidRuntime(16435): at android.app.Activity.performCreate(Activity.java:4470)
12-19 12:29:34.498: E/AndroidRuntime(16435): at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1052)
12-19 12:29:34.498: E/AndroidRuntime(16435): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1931)
12-19 12:29:34.498: E/AndroidRuntime(16435): ... 11 more
12-19 12:29:37.633: D/dalvikvm(16435): GC_CONCURRENT freed 144K, 4% free 13897K/14343K, paused 3ms+2ms
答案 0 :(得分：0)
为什么不参加我在这个主题上写的博客文章：
Google Maps V2 for Android: Draw Driving Direction on Map
在这篇文章的末尾（Section 6），你会发现一个提供这个功能的工作项目，你所要做的就是下载它，在工作环境中导入，生成你自己的Google Maps API V2 key使用API控制台并将其应用于项目。然后运行项目，它应该工作。