尝试学习如何使用google maps api ，我正在关注youtube上的教程。当我运行给定代码时，应用程序关闭＆amp;按摩＆＃34; ...已停止响应＆＃34; 显示。请帮助。
以下是代码：
import com.google.android.gms.maps.*;
import com.google.android.gms.maps.model.BitmapDescriptorFactory;
import com.google.android.gms.maps.model.LatLng;
import com.google.android.gms.maps.model.Marker;
import com.google.android.gms.maps.model.MarkerOptions;
import android.app.Activity;
import android.location.Criteria;
import android.location.Location;
import android.location.LocationManager;
import android.os.Bundle;
import android.support.v4.app.FragmentActivity;
import android.view.Menu;
import android.view.MenuItem;
public class MainActivity extends FragmentActivity {
private GoogleMap mainMap;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
setUpMap(); //line 27
}
private void setUpMap() {
if(mainMap == null) {
mainMap = ((SupportMapFragment) getSupportFragmentManager().findFragmentById(R.id.map)).getMap(); //line 34
if(mainMap != null) {
startMap();
}
}
}
private void startMap() {
mainMap.setMyLocationEnabled(true);
mainMap.setMapType(GoogleMap.MAP_TYPE_HYBRID);
LocationManager locationManager = (LocationManager) getSystemService(LOCATION_SERVICE);
Criteria criteria = new Criteria(); //retrieve provider
String provider = locationManager.getBestProvider(criteria, true); //name of best provider
Location myLocation = locationManager.getLastKnownLocation(provider);
double myLat = myLocation.getLatitude();
double myLong = myLocation.getLongitude();
LatLng latLng = new LatLng(myLat, myLong);
mainMap.moveCamera(CameraUpdateFactory.newLatLng(latLng));
mainMap.animateCamera(CameraUpdateFactory.zoomTo(20));
mainMap.addMarker(new MarkerOptions().position(new LatLng(myLat, myLong)).title("You are here"));
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.main, menu);
return true;
}
@Override
public boolean onOptionsItemSelected(MenuItem item) {
// Handle action bar item clicks here. The action bar will
// automatically handle clicks on the Home/Up button, so long
// as you specify a parent activity in AndroidManifest.xml.
int id = item.getItemId();
if (id == R.id.action_settings) {
return true;
}
return super.onOptionsItemSelected(item);
}
}
这是logcat：
01-18 12:16:20.915: E/AndroidRuntime(5163): FATAL EXCEPTION: main
01-18 12:16:20.915: E/AndroidRuntime(5163): Process: com.example.map, PID: 5163
01-18 12:16:20.915: E/AndroidRuntime(5163): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.map/com.example.map.MainActivity}: java.lang.NullPointerException
01-18 12:16:20.915: E/AndroidRuntime(5163): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2205)
01-18 12:16:20.915: E/AndroidRuntime(5163): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2255)
01-18 12:16:20.915: E/AndroidRuntime(5163): at android.app.ActivityThread.access$800(ActivityThread.java:142)
01-18 12:16:20.915: E/AndroidRuntime(5163): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1203)
01-18 12:16:20.915: E/AndroidRuntime(5163): at android.os.Handler.dispatchMessage(Handler.java:102)
01-18 12:16:20.915: E/AndroidRuntime(5163): at android.os.Looper.loop(Looper.java:136)
01-18 12:16:20.915: E/AndroidRuntime(5163): at android.app.ActivityThread.main(ActivityThread.java:5118)
01-18 12:16:20.915: E/AndroidRuntime(5163): at java.lang.reflect.Method.invokeNative(Native Method)
01-18 12:16:20.915: E/AndroidRuntime(5163): at java.lang.reflect.Method.invoke(Method.java:515)
01-18 12:16:20.915: E/AndroidRuntime(5163): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:794)
01-18 12:16:20.915: E/AndroidRuntime(5163): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:610)
01-18 12:16:20.915: E/AndroidRuntime(5163): at dalvik.system.NativeStart.main(Native Method)
01-18 12:16:20.915: E/AndroidRuntime(5163): Caused by: java.lang.NullPointerException
01-18 12:16:20.915: E/AndroidRuntime(5163): at com.example.map.MainActivity.setUpMap(MainActivity.java:34)
01-18 12:16:20.915: E/AndroidRuntime(5163): at com.example.map.MainActivity.onCreate(MainActivity.java:27)
01-18 12:16:20.915: E/AndroidRuntime(5163): at android.app.Activity.performCreate(Activity.java:5275)
01-18 12:16:20.915: E/AndroidRuntime(5163): at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1087)
01-18 12:16:20.915: E/AndroidRuntime(5163): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2169)
01-18 12:16:20.915: E/AndroidRuntime(5163): ... 11 more
这是layout.xml
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
xmlns:map="http://schemas.android.com/apk/res-auto"
android:id="@+id/LinearLayout1"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical" >
<fragment
android:id="@+id/map"
android:name="com.google.android.gms.maps.MapFragment"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:layout_marginBottom="5dp" />
</LinearLayout>
答案 0 :(得分：1)
或者：
getSupportFragmentManager()正在返回null，这不太可能，或者
findFragmentById()正在返回null
如果R.id.map文件中没有名为res/layout/activity_main.xml的片段，则可能会发生后者。
<强>更新
您的布局正在使用com.google.android.gms.maps.MapFragment。这不适用于FragmentActivity。如果您要使用com.google.android.gms.maps.SupportMapFragment和片段反向移植，请使用FragmentActivity。
答案 1 :(得分：0)
您正在尝试使用首先未初始化的方法getMap（）。没有它就试试吧。
mainMap = ((SupportMapFragment) getSupportFragmentManager().findFragmentById(R.id.map)); //line 34
答案 2 :(得分：0)
因为您使用onCreate设置了地图。我可以看到任何导致该应用无法显示的内容，然后Android会报告它已停止响应等等。
尝试在onStart中抛出setUpMap（）调用，将其包装在Try Catch中，看看会发生什么。为了获得更好的性能，请将该调用放在它自己的线程上。这样就不会影响启动时间。
@Override
protected void onStart() {
setUpMap();
}
private void setUpMap() {
try {
// your code here
} catch (Exception e) {
}
}