Switching from Map fragment to another Fragment an

问题:

I have a fragment activity that switches fragments on button click.
The two fragments that I switch are:

1. Google map android v2 fragment
2. Another fragment with a text view

This is how I switch the fragments:

public void onClick(View v) {
    FragmentManager fm = getSupportFragmentManager();
    if(tv.getText().toString().equalsIgnoreCase("Click ME!!")){
        tv.setText("MAP");
        if (fm != null) {
            if(map == null){    
                map = new Map();
            }
            FragmentTransaction ft = fm.beginTransaction();
            ft.replace(R.id.lay_contaier, map);
            ft.commit();

        }
    }
    else{
        tv.setText("Click ME!!");
        if (fm != null ){
            FragmentTransaction ft = fm.beginTransaction();
            ft.replace(R.id.lay_contaier,new empty());
            ft.commit();

        }
    }
}

This s my Maps Fagment code

  public class Map extends Fragment implements OnMarkerClickListener,    OnInfoWindowClickListener, OnMarkerDragListener {

private static final LatLng PERTH = new LatLng(-31.952854, 115.857342);
private static final LatLng SYDNEY = new LatLng(-33.87365, 151.20689);


  private GoogleMap mMap;

private Marker mPerth;
  private Marker mSydney;
  @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
        View view = inflater.inflate(R.layout.activity_main,null);

        return view;
  }

activity_mail.xml

<?xml version="1.0" encoding="utf-8"?>


<fragment xmlns:android="http://schemas.android.com/apk/res/android"
 android:id="@+id/map"
 android:layout_width="fill_parent"
 android:layout_height="fill_parent"
 class="com.google.android.gms.maps.SupportMapFragment"/>

But every time I swich back to the Map fragment the Application crashes. How should I make this code right?

回答1:

I suspect this is happening to you because you have your map fragment defined in your XML layout file. In order to swap fragments in this way, you will need to instantiate your map in code, something like the following:

private void initializeMap() {

    mMapFragment = SupportMapFragment.newInstance();
    FragmentTransaction fragmentTransaction = getSupportFragmentManager().beginTransaction();
    fragmentTransaction.add(R.id.fragment_container, mMapFragment, "map");
    fragmentTransaction.commit();

    handler.post(new Runnable() {
        @Override
        public void run() {
            mMap = mMapFragment.getMap();

            mMap.setOnCameraChangeListener(new GoogleMap.OnCameraChangeListener() {
                @Override
                public void onCameraChange(CameraPosition cameraPosition) {
                    // Do something here
                }
            });
        }
    });
}

I found that mMapFragment.getMap() was returning null, so that's why you'll need to schedule the rest of the setup through a Handler instance. My layout XML looks like the following:

<android.support.v4.widget.DrawerLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:id="@+id/drawer_layout"
android:layout_width="match_parent"
android:layout_height="match_parent"
tools:context=".LauncherActivity">

<RelativeLayout
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:id="@+id/fragment_container">

    <!-- The fragments will go here -->
</RelativeLayout>

<RelativeLayout
    android:layout_gravity="start"
    android:layout_height="match_parent"
    android:layout_width="wrap_content"
    android:background="@color/drawer_background">
...
</RelativeLayout>
</android.support.v4.widget.DrawerLayout>

I hope this helps.

回答2:

you are making FragmentManager Null. remove fm=null. Also in the else loop you are replacing two fragments. Don't do double replacements at a time. before calling commit(), you do only one replacement