我现在正在编写一个简单的应用程序并且一切正常，除非我添加了mapType更改。
package com.example.preset19;
import android.os.Bundle;
import android.support.v4.app.FragmentActivity;
import android.support.v7.widget.Toolbar;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.view.animation.Animation;
import android.view.animation.AnimationUtils;
import android.widget.Toast;
import com.google.android.gms.maps.CameraUpdateFactory;
import com.google.android.gms.maps.GoogleMap;
import com.google.android.gms.maps.OnMapReadyCallback;
import com.google.android.gms.maps.SupportMapFragment;
import com.google.android.gms.maps.model.LatLng;
import com.google.android.gms.maps.model.Marker;
import com.google.android.gms.maps.model.MarkerOptions;
public class MapsActivity extends FragmentActivity implements OnMapReadyCallback {
private GoogleMap mMap;
static final LatLng MELBOURNE = new LatLng(-37.81319, 144.96298);
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_maps);
// Obtain the SupportMapFragment and get notified when the map is ready to be used.
SupportMapFragment mapFragment = (SupportMapFragment) getSupportFragmentManager()
.findFragmentById(R.id.map);
mapFragment.getMapAsync(this);
mMap.setMapType(GoogleMap.MAP_TYPE_SATELLITE);
}
/**
* Manipulates the map once available.
* This callback is triggered when the map is ready to be used.
* This is where we can add markers or lines, add listeners or move the camera. In this case,
* we just add a marker near Sydney, Australia.
* If Google Play services is not installed on the device, the user will be prompted to install
* it inside the SupportMapFragment. This method will only be triggered once the user has
* installed Google Play services and returned to the app.
*/
@Override
public void onMapReady(GoogleMap googleMap) {
mMap = googleMap;
// Add a marker in Sydney and move the camera
LatLng sydney = new LatLng(-34, 151);
mMap.addMarker(new MarkerOptions().position(sydney).title("Marker in Sydney"));
mMap.moveCamera(CameraUpdateFactory.newLatLng(sydney));
LatLng Bern = new LatLng(46, 56);
mMap.addMarker(new MarkerOptions().position(Bern).title("Marker in Bern"));
mMap.moveCamera(CameraUpdateFactory.newLatLng(Bern));
Marker melbourne = mMap.addMarker(new MarkerOptions()
.position(MELBOURNE)
.title("Melbourne")
.snippet("Population: 4'137'400"));
googleMap.addMarker(new MarkerOptions()
.position(new LatLng(10, 10))
.title("Hello World"));
}
}
如果我想启动应用程序，它会在之前没有显示地图时崩溃。 Android Studio没有检测到任何错误，但这是我的启动协议：
E/AndroidRuntime: FATAL EXCEPTION: main
Process: com.example.preset19, PID: 13639
Theme: themes:{default=overlay:com.cyngn.hexo, iconPack:system, fontPkg:com.cyngn.hexo, com.android.systemui=overlay:com.cyngn.hexo, com.android.systemui.navbar=overlay:com.cyngn.hexo}
java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.preset19/com.example.preset19.MapsActivity}: java.lang.NullPointerException: Attempt to invoke virtual method 'void com.google.android.gms.maps.GoogleMap.setMapType(int)' on a null object reference
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2450)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2510)
at android.app.ActivityThread.-wrap11(ActivityThread.java)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1363)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:148)
at android.app.ActivityThread.main(ActivityThread.java:5461)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:726)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:616)
Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'void com.google.android.gms.maps.GoogleMap.setMapType(int)' on a null object reference
at com.example.preset19.MapsActivity.onCreate(MapsActivity.java:35)
at android.app.Activity.performCreate(Activity.java:6251)
at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1108)
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2403)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2510)
at android.app.ActivityThread.-wrap11(ActivityThread.java)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1363)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:148)
at android.app.ActivityThread.main(ActivityThread.java:5461)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:726)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:616)
W/DynamiteModule: Local module descriptor class for com.google.android.gms.googlecertificates not found.
I/DynamiteModule: Considering local module com.google.android.gms.googlecertificates:0 and remote module com.google.android.gms.googlecertificates:3
I/DynamiteModule: Selected remote version of com.google.android.gms.googlecertificates, version >= 3
W/System: ClassLoader referenced unknown path: /data/data/com.google.android.gms/app_chimera/m/00000023/n/armeabi-v7a
W/System: ClassLoader referenced unknown path: /data/data/com.google.android.gms/app_chimera/m/00000023/n/armeabi
I/Process: Sending signal. PID: 13639 SIG: 9
Application terminated.
答案 0 :(得分：1)
这是因为您在初始化之前使用了mMap变量，在mMap.setMapType(GoogleMap.MAP_TYPE_SATELLITE);方法中移动了这行代码onMapReady
如果你仔细阅读了这里写的例外
java.lang.NullPointerException：尝试调用虚方法＆＃39; void com.google.android.gms.maps.GoogleMap.setMapType（INT）＆＃39;在null 对象参考
答案 1 :(得分：0)
你可以在里面添加（或）改变maptype设置为onMapReady以使其正常工作。
map.setMapType(GoogleMap.MAP_TYPE_HYBRID);
答案 2 :(得分：0)
设置mMap.setMapType（GoogleMap.MAP_TYPE_SATELLITE）; on onMapReady方法。在准备好之前，您无法使用地图。您正试图在Go上设置地图。 所以改变这样的代码
@Override
public void onMapReady(GoogleMap googleMap) {
mMap = googleMap;
mMap.setMapType(GoogleMap.MAP_TYPE_SATELLITE);
--------
}
答案 3 :(得分：0)
只需写下：
googleMap.setMapType(GoogleMap.MAP_TYPE_HYBRID);