英文:
getsupportfragmentmanager().findfragmentbyid(r.id.map) returns null Google map
问题
我试图在我的MainActivity上使用Google地图功能，但我在此处收到空指针错误：
getsupportfragmentmanager().findfragmentbyid(r.id.map); ==> 返回 null
SupportMapFragment mapFragment = (SupportMapFragment) getSupportFragmentManager().findFragmentById(R.id.mapApi);
当我使用 getMapAsync(this); 调用它时，应用在启动之前就崩溃了。
在 content_main.xml 文件中：
<LinearLayout
android:layout_width="match_parent"
android:layout_height="216dp"
android:orientation="horizontal">
<fragment
android:id="@+id/mapApi"
android:name="com.google.android.gms.maps.SupportMapFragment"
android:layout_width="match_parent"
android:layout_height="match_parent">
</fragment>
</LinearLayout>
在 MainActivity 的 onCreate 方法中：
public class MainActivity extends AppCompatActivity
implements NavigationView.OnNavigationItemSelectedListener, OnMapReadyCallback {
private GoogleMap map;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.content_main);
SupportMapFragment mapFragment = (SupportMapFragment) getSupportFragmentManager().findFragmentById(R.id.mapApi);
if (mapFragment != null) {
mapFragment.getMapAsync(this);
}
}
@Override
public void onMapReady(GoogleMap googleMap) {
map = googleMap;
LatLng BordjMenaielGare = new LatLng(36.753162, 3.717716);
LatLng Blida = new LatLng(36.769038, 3.057451);
map.addMarker(new MarkerOptions().position(BordjMenaielGare).title("Gare Bordj Menaiel"));
map.addMarker(new MarkerOptions().position(Blida).title("Gare Agha"));
map.moveCamera(CameraUpdateFactory.newLatLngZoom(BordjMenaielGare, 10));
}
}
你可以看到，地图片段在 content_main.xml 文件中定义，然后在 MainActivity 中使用 getSupportFragmentManager().findFragmentById(R.id.mapApi) 获取该片段，并在获取到片段后，通过 mapFragment.getMapAsync(this) 异步获取地图。
图片链接已被删除，但我可以看到你在问题描述中提到了图片的链接。如果你需要更多帮助，请告诉我。
英文:
I try to use google map functionality on my MainActivity I have this null pointer returned by :
getsupportfragmentmanager().findfragmentbyid(r.id.map); ==> return null
SupportMapFragment mapFragment = (SupportMapFragment) getSupportFragmentManager().findFragmentById(R.id.mapApi);
mapfragment will be null and when I call it using getMapAsync(this); the app shut down before it starts
mapFragment.getMapAsync(this); // null pointer variable call getMapAsync
content_main.xml
<LinearLayout
android:layout_width="match_parent"
android:layout_height="216dp"
android:orientation="horizontal">
<fragment
android:id="@+id/mapApi"
android:name="com.google.android.gms.maps.SupportMapFragment"
android:layout_width="match_parent"
android:layout_height="match_parent">
</fragment>
</LinearLayout>
onCreate inside the MainActivity :
public class MainActivity extends AppCompatActivity
implements NavigationView.OnNavigationItemSelectedListener , OnMapReadyCallback {
private GoogleMap map;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
//setContentView(R.layout.activity_main); didn't work
setContentView(R.layout.content_main); // worked, now i haven't null pointer
System.out.println("************************ mapApi:"+R.id.mapApi);
SupportMapFragment mapFragment = (SupportMapFragment) getSupportFragmentManager().findFragmentById(R.id.mapApi);
System.out.println("************************ mapFragment:"+mapFragment);
if (mapFragment != null) {
mapFragment.getMapAsync(this);
}
}
@Override
public void onMapReady(GoogleMap googleMap) {
map = googleMap;
LatLng BordjMenaielGare = new LatLng(36.753162, 3.717716);
LatLng Blida = new LatLng(36.769038, 3.057451);
map.addMarker(new MarkerOptions().position(BordjMenaielGare).title("Gare Bordj Menaiel "));
map.addMarker(new MarkerOptions().position(Blida).title("Gare Agha"));
map.moveCamera(CameraUpdateFactory.newLatLngZoom(BordjMenaielGare, 10));
}
}
here are the files :
the map fragment is on content_main.xml, I included it in app_bar_main.xml, and app_bar_main included in activity_main.xml and I'm calling the map from MainActivity
I searched a lot in StackOverflow but none of the solutions are valid for my case
can someone help me with this?
答案1
得分: 1
你需要调用：
// 在调用 super.onCreate(savedInstanceState); 之后添加以下代码（为你的活动提供布局）
setContentView(R.layout.activity);
英文:
you need to call:
// add this (supplying the layout for your activity)
setContentView(R.layout.activity);
after your call to super.onCreate(savedInstanceState);
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