[英]Accessing method from a Fragment in Button Click from MainActivity
伙計們,
我試圖通過MainActivity中的按鈕單擊向用戶發送當前緯度和經度到MapFragment(片段)。 我使用fromMainActivity中實現的片段接口,但是當我嘗試從Fragment onButtonClick獲取方法時,我得到了一個
在android.app.ActivityThread.main(ActivityThread.java:5221)的java.lang.reflect.Method.invoke(Native Method),位於com.android的java.lang.reflect.Method.invoke(Method.java:372) .internal.os.ZygoteInit $ MethodAndArgsCaller.run(ZygoteInit.java:899)at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:694)引起:java.lang.NullPointerException:嘗試調用虛方法'com.xtechkid.sudheej.threadingapplication.MainActivity.findLocation(MainActivity.java)上的空對象引用上的'void com.xtechkid.blah.threadingapplication.MapDemoActivity.setupCurrlocation(com.google.android.gms.maps.model.LatLng)' :67)
我的代碼如下
這是Map片段
public class MapDemoActivity extends Fragment {
final LatLng MU = new LatLng(40.8874245, 67.0200729);
private GoogleMap mMap; // Might be null if Google Play services APK is not available.
CommInter mCallback;
public interface CommInter {
public void communicatesWithActivity(double lati,double longi);
}
@Override
public void onAttach(Context context) {
super.onAttach(context);
Activity a;
// if (context instanceof Activity){
a=(Activity) context;
//}
try{
mCallback = (CommInter) a;
}catch (ClassCastException e){
throw new ClassCastException(a.toString());
}
}
@Override
public View onCreateView(LayoutInflater inflater, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState) {
View view = inflater.inflate(R.layout.activity_main, container, false);
//setUpMapIfNeeded();
if (mMap != null) {
mMap.setMyLocationEnabled(true);
}
return view;
}
//This method when called from Main is throwing Exception
public void setupCurrlocation(LatLng MUSEUM) {
makeText(getContext(), "I am inside the function ", Toast.LENGTH_LONG).show();
System.out.println("I am inside the function");
/*CameraPosition cameraPosition = new CameraPosition.Builder()
.target(MUSEUM)
.zoom(10)
.bearing(70)
.tilt(25)
.build();
mMap.animateCamera(CameraUpdateFactory.newCameraPosition(cameraPosition));
*/
}
}
主要活動的代碼
import android.app.FragmentManager;
import android.support.v7.app.AppCompatActivity;
import android.content.Intent;
import android.location.LocationManager;
import android.os.Bundle;
import android.provider.Settings;
import android.view.View;
import android.widget.TextView;
import android.widget.Toast;
import com.google.android.gms.maps.model.LatLng;
public class MainActivity extends AppCompatActivity implements MapDemoActivity.CommInter {
private TextView txtLocation;
private String provider;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
}
@Override
public void communicatesWithActivity(double lati, double longi) {
MapDemoActivity mapFrag = (MapDemoActivity)getSupportFragmentManager().findFragmentById(R.id.map);
final LatLng MUSEU = new LatLng(38.8874245, 77.0200729);
//final LatLng MUSEU = new LatLng(lati, longi);
mapFrag.setupCurrlocation(MUSEU);
}
public void findLocation(View v) {
//final LatLng setLoc = new LatLng(38.8874245, -77.0200729);
//// MapDemoActivity fragment;
// Fragment t = (Fragment)getSupportFragmentManager()findViewById(R.id.map);
// fragment.setupCurrlocation(v,setLoc);
txtLocation = (TextView) findViewById(R.id.textViewLocation);
LocationManager service = (LocationManager) getSystemService(LOCATION_SERVICE);
boolean isLocEnabled = service.isProviderEnabled(LocationManager.GPS_PROVIDER);
if (!isLocEnabled) {
Intent intent = new Intent(Settings.ACTION_LOCATION_SOURCE_SETTINGS);
startActivity(intent);
}
GPSTracker gps = new GPSTracker(MainActivity.this);
// check if GPS enabled
if(gps.canGetLocation()){
double latitude = gps.getLatitude();
double longitude = gps.getLongitude();
// \n is for new line
Toast.makeText(getApplicationContext(), "Your Location is - \nLat: " + latitude + "\nLong: " + longitude, Toast.LENGTH_LONG).show();
txtLocation.setText("Lat: " + latitude + "Long: " + longitude);
//System.out.println(MUS);
//The PROBLEM IS HERE I DONT KNOW THE FIX
communicatesWithActivity(latitude,long);
}else{
// can't get location
// GPS or Network is not enabled
// Ask user to enable GPS/network in settings
gps.showSettingsAlert();
}
}
}
您沒有使用谷歌地圖。 您需要在調用setupcurrlocation的地方擁有所有這些導入。
import com.google.android.gms.maps.CameraUpdateFactory;
import com.google.android.gms.maps.GoogleMap;
import com.google.android.gms.maps.MapFragment;
import com.google.android.gms.maps.model.CameraPosition;
import com.google.android.gms.maps.model.LatLng;
import com.google.android.gms.maps.model.Marker;
import com.google.android.gms.maps.model.MarkerOptions;
// et al...
public void setupCurrlocation(LatLng MUSEUM) {
GoogleMap googleMap = ((MapFragment) fragmentManager.
findFragmentById(R.id.map)).getMap();
googleMap.setMapType(GoogleMap.MAP_TYPE_HYBRID);
Marker marker = googleMap.addMarker(new MarkerOptions().position(latLng).title(null));
CameraPosition cameraPosition = new CameraPosition.Builder().target(MUSEUM).zoom(10).bearing(70).tilt(25)
.build();
googleMap.animateCamera(CameraUpdateFactory.newCameraPosition(cameraPosition));
}
基本上我會在片段附加到的活動中使用此方法。 然后,您需要管理Google地圖的可見性。 因為它將保持在其他片段之上。
通過控制framelayouts的可見性,您可以在其framelayout中控制地圖的可見性。
例:
// your activity layout here:
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
//TO DO/>
<RelativeLayout
android:layout_height="wrap_content"
android:layout_width="match_parent"
android:id="@+id/myrellayout">
// ALL THE THINGS IN YOUR ACTIVTY
</RelativeLayout>
// THE FRAMELAYOUTS MANAGE YOUR MAP FRAGMENT AND OTHER FRAGMENTS VISIBILITY
<FrameLayout
android:id="@+id/firstfrag"
android:layout_below="@+id/myrellayout"
android:layout_height="fill_parent"
android:layout_width="match_parent"
android:visibility="gone"/>
<FrameLayout
android:id="@+id/secondfrag"
android:layout_below="@+id/myrellayout"
android:layout_height="fill_parent"
android:layout_width="match_parent"
android:visibility="gone"/>
<fragment
android:id="@+id/map"
android:layout_height="match_parent"
android:layout_width="match_parent"
android:name="com.google.android.gms.maps.MapFragment"/>
</FrameLayout>
</RelativeLayout>
https://developers.google.com/maps/documentation/android-api/ https://developers.google.com/maps/documentation/javascript/examples/
由於findFragmentById
返回null,因此在Activity中發生異常。 根據您發布的代碼,您已在xml中聲明了Fragment
。 由於您使用的是getSupportFragmentManager
,因此請確保使用com.google.android.gms.maps.SupportMapFragment
聲明它,而不是使用com.google.android.gms.maps.MapFragment
聲明它。 這可能是您獲得null的原因之一。 另一方面,你可以使用transactin
私有的MapDemoActivity mFragment;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
if (savedInstanceState == null) {
mFragment = new MapDemoActivity();
getSupportFragmentManager().beginTransaction().replace(R.id.container, mFragment, "TAG").commit();
}
}
然后你可以使用mFragment
。 在您的xml中,您必須使用普通的ViewGroup替換<fragment
,使用id container
替換FrameLayout
您好,您可以嘗試其他方式,如在您的片段類中創建一個公共靜態方法,並從您的活動類On按鈕單擊調用此方法所需的緯度和經度。
/*
* Get User Desired Location in fragment class */
public static void getLocation(double lati, double longi)
{
try {
CameraUpdate center = CameraUpdateFactory.newLatLng(new LatLng(lati, longi));
CameraUpdate zoom = CameraUpdateFactory.zoomTo(15);
googleMap.moveCamera(center);
googleMap.animateCamera(zoom);
} catch (Exception e) {
e.printStackTrace();
}
}
/* Get Desired Location in your activity class*/
btnCurrentLocation.setOnClickListener(new OnClickListener()
{
@Override
public void onClick(View v)
{
ClassName.getLocation(lati, longi);
}
});
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