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android - Android，mapFragment.getMapAsync 错误发生空对象引用

问题描述

我试图在这里通过片段使用谷歌地图。我使用了 SupportMapFragment，并通过 R.id.map 获取了该片段。最后我使用了 mapFragment.GetMapAsync(this)。

但是，它一直在犯错误。不知道为什么……请来人帮帮我。

// MainActivity.java
package com.example.fleago;

import androidx.annotation.NonNull;

import androidx.appcompat.app.AppCompatActivity;
import androidx.core.content.ContextCompat;
import androidx.fragment.app.Fragment;
import androidx.fragment.app.FragmentActivity;
import androidx.fragment.app.FragmentTransaction;

import android.Manifest;
import android.app.Activity;
import android.content.pm.PackageManager;
import android.location.Location;
import android.location.LocationListener;
import android.location.LocationManager;
import android.os.Build;
import android.os.Bundle;
import android.util.Log;
import android.view.View;
import android.widget.AdapterView;
import android.widget.ListView;

import com.daimajia.swipe.SwipeLayout;
import com.daimajia.swipe.util.Attributes;
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.OnMapReadyCallback;
import com.google.android.gms.maps.SupportMapFragment;
import com.google.android.gms.maps.model.LatLng;
import com.google.android.gms.maps.model.MarkerOptions;
import com.google.firebase.database.DataSnapshot;
import com.google.firebase.database.DatabaseError;
import com.google.firebase.database.DatabaseReference;
import com.google.firebase.database.FirebaseDatabase;
import com.google.firebase.database.ValueEventListener;
import com.sothree.slidinguppanel.SlidingUpPanelLayout;

import net.daum.android.map.MapView;

import java.util.ArrayList;
import java.util.Collections;
import java.util.Comparator;

import adapter.ListViewAdapter;

import static com.example.fleago.ARActivity.REQUEST_LOCATION_PERMISSIONS_CODE;

public class MainActivity extends AppCompatActivity implements OnMapReadyCallback {
    private GoogleMap mMap;
    private static final String TAG = "MarketListView";

    private SlidingUpPanelLayout mLayout;
    private ListViewAdapter mAdapter;
    private ArrayList<Market> list;

    private Location currentLocation;
    private LocationManager locationManager;
    boolean isGPSEnabled;
    boolean isNetworkEnabled;
    boolean locationServiceAvailable;
    private static final long MIN_DISTANCE_CHANGE_FOR_UPDATES = 1; // 10 meters
    private static final long MIN_TIME_BW_UPDATES = 100;//1000 * 60 * 1; // 1 minute
    private static final int MAX_DISTANCE = Integer.MAX_VALUE;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        SupportMapFragment mapFragment = (SupportMapFragment) getSupportFragmentManager()
                .findFragmentById(R.id.map);
        mapFragment.getMapAsync(this);
    }
    @Override
    public void onMapReady(GoogleMap googleMap) {
        mMap = googleMap;
        LatLng SEOUL = new LatLng(37.56, 126.97);

        MarkerOptions markerOptions = new MarkerOptions();
        markerOptions.position(SEOUL);
        markerOptions.title("Seoul");
        markerOptions.snippet("Korea's Center");
        mMap.addMarker(markerOptions);

        mMap.moveCamera(CameraUpdateFactory.newLatLng(SEOUL));
        mMap.animateCamera(CameraUpdateFactory.zoomTo(10));
    }
}

这是 XML 布局代码

//activity_main.xml
<LinearLayout
    xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:sothree="http://schemas.android.com/apk/res-auto"
    android:layout_height="match_parent"
    android:layout_width="match_parent"
    android:orientation="vertical">

    <com.sothree.slidinguppanel.SlidingUpPanelLayout
        android:id="@+id/sliding_layout"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:gravity="bottom"

        sothree:umanoDragView="@+id/btn_handle"
        sothree:umanoPanelHeight="@dimen/default_small_list_height"
        sothree:umanoShadowHeight="0dp"
        sothree:umanoParallaxOffset="100dp">

        <!-- MAIN CONTENT -->
        <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
            xmlns:tools="http://schemas.android.com/tools"
            android:layout_width="match_parent"
            android:layout_height="match_parent"
            tools:context=".MainActivity" >

            <fragment
                android:layout_width="match_parent"
                android:layout_height="match_parent"
                android:id="@+id/map"
                tools:context=".MapsActivity"
                android:name="com.google.android.gms.maps.SupportMapFragment" />

        </LinearLayout>
        <!-- SLIDING LAYOUT -->
        <LinearLayout
            android:layout_width="match_parent"
            android:layout_height="@dimen/default_full_list_height"
            android:background="@color/seoul_default_light"
            android:orientation="vertical"
            android:focusable="false"
            android:clickable="false">

            <!--- 손잡이 -->
            <Button
                android:id="@+id/btn_handle"
                android:background="#00ff0000"
                android:layout_width="match_parent"
                android:layout_height="40dp"
                android:layout_gravity="right"
                android:layout_marginRight="10dp"
                android:clickable="true"    >
            </Button>

            <ListView
                android:id="@+id/marketList"
                android:layout_width="match_parent"
                android:layout_height="match_parent" >
            </ListView>
        </LinearLayout>
    </com.sothree.slidinguppanel.SlidingUpPanelLayout>
</LinearLayout>

这是来自 Logcat 的错误

2019-09-28 17:35:13.911 18564-18564/com.example.fleago E/AndroidRuntime: FATAL EXCEPTION: main
    Process: com.example.fleago, PID: 18564
    java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.fleago/com.example.fleago.MainActivity}: 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 android.app.ActivityThread.performLaunchActivity(ActivityThread.java:3114)
        at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:3257)
        at android.app.servertransaction.LaunchActivityItem.execute(LaunchActivityItem.java:78)
        at android.app.servertransaction.TransactionExecutor.executeCallbacks(TransactionExecutor.java:108)
        at android.app.servertransaction.TransactionExecutor.execute(TransactionExecutor.java:68)
        at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1948)
        at android.os.Handler.dispatchMessage(Handler.java:106)
        at android.os.Looper.loop(Looper.java:214)
        at android.app.ActivityThread.main(ActivityThread.java:7050)
        at java.lang.reflect.Method.invoke(Native Method)
        at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:493)
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:965)
     Caused by: 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 com.example.fleago.MainActivity.onCreate(MainActivity.java:74)
        at android.app.Activity.performCreate(Activity.java:7327)
        at android.app.Activity.performCreate(Activity.java:7318)
        at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1271)
        at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:3094)
        at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:3257) 
        at android.app.servertransaction.LaunchActivityItem.execute(LaunchActivityItem.java:78) 
        at android.app.servertransaction.TransactionExecutor.executeCallbacks(TransactionExecutor.java:108) 
        at android.app.servertransaction.TransactionExecutor.execute(TransactionExecutor.java:68) 
        at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1948) 
        at android.os.Handler.dispatchMessage(Handler.java:106) 
        at android.os.Looper.loop(Looper.java:214) 
        at android.app.ActivityThread.main(ActivityThread.java:7050) 
        at java.lang.reflect.Method.invoke(Native Method) 
        at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:493) 
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:965) 

我不明白为什么getMapAsync(this)在这里为空请任何人都可以告诉我为什么会发生这种情况？

标签： androidgoogle-mapsandroid-studio

解决方案

像这样设置支持片段

<fragment android:layout_width="match_parent" android:layout_height="match_parent" android:id="@+id/map" tools:context=".MapsActivity" class="com.google.android.gms.maps.SupportMapFragment" />

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