更换片段时，应用程序会不断崩溃

时间：2017-03-01 23:24:32

标签： android google-maps android-fragments

我正在尝试创建一个基本的Android应用程序。我有一个导航抽屉活动，一个地图片段和一个配置文件片段。在实现地图片段之前，应用程序运行顺利，但现在它一直在崩溃。我之前通过实现nameOfFragment.OnFragmentInteractionListener方法解决了这个问题。但地图上没有这样的东西。我该如何解决这个问题？

这是我的主要活动代码：

package georgia.languagelandscape;

//import android.app.FragmentManager;
import android.net.Uri;
import android.os.Bundle;
import android.support.design.widget.FloatingActionButton;
import android.support.design.widget.NavigationView;
import android.support.design.widget.Snackbar;
import android.support.v4.app.FragmentManager;
import android.support.v4.app.FragmentTransaction;
import android.support.v4.view.GravityCompat;
import android.support.v4.widget.DrawerLayout;
import android.support.v7.app.ActionBarDrawerToggle;
import android.support.v7.app.AppCompatActivity;
import android.support.v7.widget.Toolbar;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;

public class NavigationDrawerActivity extends AppCompatActivity
        implements NavigationView.OnNavigationItemSelectedListener, ProfileFragment.OnFragmentInteractionListener {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_navigation_drawer);
        Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
        setSupportActionBar(toolbar);

        FloatingActionButton fab = (FloatingActionButton) findViewById(R.id.fab);
        fab.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                Snackbar.make(view, "Replace with your own action", Snackbar.LENGTH_LONG)
                        .setAction("Action", null).show();
            }
        });

        DrawerLayout drawer = (DrawerLayout) findViewById(R.id.drawer_layout);
        ActionBarDrawerToggle toggle = new ActionBarDrawerToggle(
                this, drawer, toolbar, R.string.navigation_drawer_open, R.string.navigation_drawer_close);
        drawer.setDrawerListener(toggle);
        toggle.syncState();

        NavigationView navigationView = (NavigationView) findViewById(R.id.nav_view);
        navigationView.setNavigationItemSelectedListener(this);

        //me
        navigationView.setItemIconTintList(null);
        getSupportActionBar().setDisplayShowTitleEnabled(false);
    }

    @Override
    public void onBackPressed() {
        DrawerLayout drawer = (DrawerLayout) findViewById(R.id.drawer_layout);
        if (drawer.isDrawerOpen(GravityCompat.START)) {
            drawer.closeDrawer(GravityCompat.START);
        } else {
            super.onBackPressed();
        }
    }

    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        // Inflate the menu; this adds items to the action bar if it is present.
        getMenuInflater().inflate(R.menu.navigation_drawer, 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();

        //noinspection SimplifiableIfStatement
        if (id == R.id.action_settings) {
            return true;
        }

        return super.onOptionsItemSelected(item);
    }

    @SuppressWarnings("StatementWithEmptyBody")
    @Override
    public boolean onNavigationItemSelected(MenuItem item) {
        // Handle navigation view item clicks here.
        int id = item.getItemId();

        FragmentManager fm = getSupportFragmentManager();

        FragmentTransaction ft = fm.beginTransaction();
        MapFragment mapFragment= new MapFragment();
        ft.replace(R.id.content_replace, mapFragment);
        ft.commit();

        if (id == R.id.nav_feed) {
            // Handle the camera action
        } else if (id == R.id.nav_my_profile) {

            ProfileFragment profileFragment= new ProfileFragment();
            ft.replace(R.id.content_replace, profileFragment);
            ft.commit();

        } else if (id == R.id.nav_my_projects) {

        } else if (id == R.id.nav_seetings) {

        } else if (id == R.id.nav_log_out) {

        }

        DrawerLayout drawer = (DrawerLayout) findViewById(R.id.drawer_layout);
        drawer.closeDrawer(GravityCompat.START);
        return true;
    }

    @Override
    public void onFragmentInteraction(Uri uri) {

    }
}

和我的地图片段代码：

package georgia.languagelandscape;

//import android.app.Fragment;

import android.support.v4.app.Fragment;
import android.os.Bundle;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;

import com.google.android.gms.maps.CameraUpdateFactory;
import com.google.android.gms.maps.GoogleMap;
import com.google.android.gms.maps.MapView;
import com.google.android.gms.maps.MapsInitializer;
import com.google.android.gms.maps.OnMapReadyCallback;
import com.google.android.gms.maps.SupportMapFragment;
import com.google.android.gms.maps.model.BitmapDescriptorFactory;
import com.google.android.gms.maps.model.CameraPosition;
import com.google.android.gms.maps.model.LatLng;
import com.google.android.gms.maps.model.MarkerOptions;

//import android.support.v4.app.Fragment;


/**
 * A simple {@link Fragment} subclass.
 * Activities that contain this fragment must implement the
 * {@link MapFragment.OnFragmentInteractionListener} interface
 * to handle interaction events.
 * Use the {@link MapFragment#newInstance} factory method to
 * create an instance of this fragment.
 */
public class MapFragment extends SupportMapFragment implements OnMapReadyCallback {

    MapView mMapView;
    private GoogleMap googleMap;

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
                             Bundle savedInstanceState) {
        // inflate and return the layout
        View v = inflater.inflate(R.layout.fragment_map, container,
                false);
        mMapView = (MapView) v.findViewById(R.id.mapView);
        mMapView.onCreate(savedInstanceState);

        mMapView.onResume();// needed to get the map to display immediately

        try {
            MapsInitializer.initialize(getActivity().getApplicationContext());
        } catch (Exception e) {
            e.printStackTrace();
        }

        SupportMapFragment mapFragment = ((SupportMapFragment) getChildFragmentManager()
                .findFragmentById(R.id.mapView));
        mapFragment.getMapAsync(this);
        // latitude and longitude
        double latitude = 17.385044;
        double longitude = 78.486671;

        // create marker
        MarkerOptions marker = new MarkerOptions().position(
                new LatLng(latitude, longitude)).title("Hello Maps");

        // Changing marker icon
        marker.icon(BitmapDescriptorFactory
                .defaultMarker(BitmapDescriptorFactory.HUE_ROSE));

        // adding marker
        googleMap.addMarker(marker);
        CameraPosition cameraPosition = new CameraPosition.Builder()
                .target(new LatLng(17.385044, 78.486671)).zoom(12).build();
        googleMap.animateCamera(CameraUpdateFactory
                .newCameraPosition(cameraPosition));

        // Perform any camera updates here
        return v;
    }

    @Override
    public void onResume() {
        super.onResume();
        mMapView.onResume();
    }

    @Override
    public void onPause() {
        super.onPause();
        mMapView.onPause();
    }

    @Override
    public void onDestroy() {
        super.onDestroy();
        mMapView.onDestroy();
    }

    @Override
    public void onLowMemory() {
        super.onLowMemory();
        mMapView.onLowMemory();
    }

    @Override
    public void onMapReady(GoogleMap googleMap) {

    }
}

我的崩溃日志：

java.lang.NullPointerException: Attempt to invoke virtual method 'void com.google.android.gms.maps.SupportMapFragment.getMapAsync(com.google.android.gms.maps.OnMapReadyCallback)' on a null object reference
                                                                               at georgia.languagelandscape.MapFragment.onCreateView(MapFragment.java:57)
                                                                               at android.support.v4.app.Fragment.performCreateView(Fragment.java:2184)
                                                                               at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:1298)
                                                                               at android.support.v4.app.FragmentManagerImpl.moveFragmentsToInvisible(FragmentManager.java:2323)
                                                                               at android.support.v4.app.FragmentManagerImpl.executeOpsTogether(FragmentManager.java:2136)
                                                                               at android.support.v4.app.FragmentManagerImpl.optimizeAndExecuteOps(FragmentManager.java:2092)
                                                                               at android.support.v4.app.FragmentManagerImpl.execPendingActions(FragmentManager.java:1998)
                                                                               at android.support.v4.app.FragmentManagerImpl$1.run(FragmentManager.java:709)
                                                                               at android.os.Handler.handleCallback(Handler.java:739)
                                                                               at android.os.Handler.dispatchMessage(Handler.java:95)
                                                                               at android.os.Looper.loop(Looper.java:148)
                                                                               at android.app.ActivityThread.main(ActivityThread.java:5451)
                                                                               at java.lang.reflect.Method.invoke(Native Method)
                                                                               at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:726)
                                                                               at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:616)

谢谢！

3 个答案:

答案 0 :(得分：0)

 SupportMapFragment mapFragment = ((SupportMapFragment) getChildFragmentManager()
            .findFragmentById(R.id.mapView));
    mapFragment.getMapAsync(this);

没有找到视图，因此mapFragment为null。

答案 1 :(得分：0)

我无法看到其余的错误日志。通常，如果您进一步向下滚动，会有一个链接指向您代码中产生问题的行。

但是，您似乎对您的片段使用与MapView相同的ID。这些应该是不同的。

答案 2 :(得分：0)

由于Fragment扩展了SupportMapFragment，因此无需对任何xml布局进行扩充。

您的整个Fragment类可以简化为：

import ctypes
p = (ctypes.c_char).from_address(0)
while True:
  p[0] = 0
  p = p + 1
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