Question

我想在Android谷歌地图活动中显示多个位置，但不能因为应用程序崩溃的原因。在Logcat中显示错误，*

可以使用适用于Android的JSON API解决问题或提供任何多个Google地图位置

java.lang.RuntimeException: Unable to start activity ComponentInfo{daffodilvarsity.edu.bd.studentportal/daffodilvarsity.edu.bd.studentportal.MapsActivity}: java.lang.NullPointerException: Attempt to invoke virtual method 'void com.google.android.gms.maps.MapFragment.getMapAsync(com.google.android.gms.maps.OnMapReadyCallback)' on a null object reference

以下是Logcat的错误：

08-18 11:30:47.044 4324-4324/daffodilvarsity.edu.bd.studentportal D/ChimeraFileApk: Primary ABI of requesting process is x86_64
08-18 11:30:47.044 4324-4324/daffodilvarsity.edu.bd.studentportal D/ChimeraFileApk: Classloading successful. Optimized code found.
08-18 11:30:47.055 4324-4324/daffodilvarsity.edu.bd.studentportal I/Google Maps Android API: Google Play services client version: 9452000
08-18 11:30:47.056 4324-4324/daffodilvarsity.edu.bd.studentportal I/Google Maps Android API: Google Play services package version: 9452480
08-18 11:30:47.089 4324-4324/daffodilvarsity.edu.bd.studentportal I/c: Token loaded from file. Expires in: 370172650 ms.
08-18 11:30:47.089 4324-4324/daffodilvarsity.edu.bd.studentportal I/c: Scheduling next attempt in 369872 seconds.
08-18 11:30:47.136 4324-4324/daffodilvarsity.edu.bd.studentportal D/AndroidRuntime: Shutting down VM
08-18 11:30:47.137 4324-4324/daffodilvarsity.edu.bd.studentportal E/AndroidRuntime: FATAL EXCEPTION: main
                                                                                  Process: daffodilvarsity.edu.bd.studentportal, PID: 4324
                                                                                   java.lang.RuntimeException: Unable to start activity  ComponentInfo{daffodilvarsity.edu.bd.studentportal/daffodilvarsity.edu.bd. studentportal.MapsActivity}: java.lang.NullPointerException: Attempt to invoke virtual method 'void com.google.android.gms.maps.MapFragment.getMapAsync(com.google.android.gms.maps.OnMapReadyCallback)' on a null object reference
                                                                                     at  android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2416)
                                                                                    at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2476)
                                                                                    at android.app.ActivityThread.-wrap11(ActivityThread.java)
                                                                                    at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1344)
                                                                                    at android.os.Handler.dispatchMessage(Handler.java:102)
                                                                                    at android.os.Looper.loop(Looper.java:148)
                                                                                    at android.app.ActivityThread.main(ActivityThread.java:5417)
                                                                                    at java.lang.reflect.Method.invoke(Native Method)
                                                                                    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:726)
                                                                                    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:616)
                                                                                  Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'void com.google.android.gms.maps.MapFragment.getMapAsync(com.google.android.gms.maps.OnMapReadyCallback)' on a null object reference
                                                                                    at daffodilvarsity.edu.bd.studentportal.MapsActivity.onCreate(MapsActivity.java:53)
                                                                                    at android.app.Activity.performCreate(Activity.java:6237)
                                                                                    at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1107)
                                                                                    at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2369)
                                                                                    at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2476) 
                                                                                    at android.app.ActivityThread.-wrap11(ActivityThread.java) 
                                                                                    at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1344) 
                                                                                    at android.os.Handler.dispatchMessage(Handler.java:102) 
                                                                                    at android.os.Looper.loop(Looper.java:148) 
                                                                                    at android.app.ActivityThread.main(ActivityThread.java:5417) 
                                                                                    at java.lang.reflect.Method.invoke(Native Method) 
                                                                                    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:726) 
                                                                                    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:616)

以下是我的XML文件： activity_maps.xml

<fragment xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:map="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools"
android:id="@+id/map"
android:name="com.google.android.gms.maps.SupportMapFragment"
android:layout_width="match_parent"
android:layout_height="match_parent"
 tools:context="daffodilvarsity.edu.bd.studentportal.LocationShareMapsActivity" />

这是 AndroidManifest.xml 文件

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="daffodilvarsity.edu.bd.studentportal">

<uses-feature
    android:glEsVersion="0x00020000"
    android:required="true" /> 
<uses-permission android:name="android.permission.INTERNET" />
<uses-permission  android:name="android.permission.ACCESS_NETWORK_STATE" />
<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />
<uses-permission android:name="android.permission.ACCESS_FINE_LOCATION" />
<uses-permission android:name="android.permission.ACCESS_COARSE_LOCATION" />
<uses-permission  android:name="com.google.android.providers.gsf.permission.READ_GSERVICES" />
<uses-permission android:name="android.permission.READ_EXTERNAL_STORAGE" />
<uses-permission android:name="android.permission.GET_ACCOUNTS" />
<uses-permission android:name="android.permission.READ_CONTACTS" />
<uses-permission android:name="android.permission.READ_PROFILE" />

<application
    android:name="android.support.multidex.MultiDexApplication"
    android:allowBackup="true"
    android:icon="@mipmap/ic_launcher"
    android:label="@string/app_name"
    android:supportsRtl="true"
    android:theme="@style/AppTheme">
    <activity
        android:name=".MapsActivity"
        android:label="@string/app_name">
        <intent-filter>
            <action android:name="android.intent.action.MAIN" />

            <category android:name="android.intent.category.LAUNCHER" />
        </intent-filter>
    </activity>

</application>

</manifest>

这是 Build.gradle 文件

apply plugin: 'com.android.application'

android {
compileSdkVersion 23
buildToolsVersion "24.0.1"
useLibrary 'org.apache.http.legacy'

dexOptions {
    incremental true
    javaMaxHeapSize "2048M"
}

defaultConfig {
    applicationId "daffodilvarsity.edu.bd.studentportal"
    minSdkVersion 14
    targetSdkVersion 23
    versionCode 1
    versionName "1.0"

    // Enabling multidex support.
    multiDexEnabled true

}
packagingOptions {
    exclude 'META-INF/XXX'
    exclude 'META-INF/DEPENDENCIES.txt'
    exclude 'META-INF/NOTICE'
    exclude 'META-INF/NOTICE.txt'
    exclude 'META-INF/LICENSE'
    exclude 'META-INF/LICENSE.txt'
}

buildTypes {
    release {
        minifyEnabled false
        proguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.pro'
    }
}
}

dependencies {
compile fileTree(dir: 'libs', include: ['*.jar'])
testCompile 'junit:junit:4.12'

compile 'com.android.support:multidex:1.0.1'
compile 'com.android.support:appcompat-v7:23.4.0'
compile 'com.android.support:design:23.4.0'
compile 'com.google.android.gms:play-services:9.4.0'
compile 'com.google.android.gms:play-services-maps:9.4.0'
}

这是java文件： MapsActivity.java 文件

package daffodilvarsity.edu.bd.studentportal;

import android.support.v4.app.FragmentActivity;
import android.os.Bundle;
import android.util.Log;
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.model.LatLng;
import com.google.android.gms.maps.model.MarkerOptions;
import org.json.JSONArray;
import org.json.JSONException;
import org.json.JSONObject;
import java.io.IOException;
import java.io.InputStreamReader;
import java.net.HttpURLConnection;
import java.net.URL;

public class MapsActivity extends FragmentActivity implements OnMapReadyCallback {
private static final String LOG_TAG = "ExampleApp";

private static final String SERVICE_URL = "https://api.myjson.com/bins/4jb09";

protected GoogleMap map;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_maps);
    if (map == null) {

        MapFragment mapFragment = (MapFragment) getFragmentManager().findFragmentById(R.id.map);
        mapFragment.getMapAsync(this);

        if (map != null) {
            setUpMap();
        }
    }
    //setUpMapIfNeeded();
 }

 private void setUpMap() {
    // Retrieve the city data from the web service
    // In a worker thread since it's a network operation.
    new Thread(new Runnable() {
        public void run() {
            try {
                retrieveAndAddCities();
            } catch (IOException e) {
                Log.e(LOG_TAG, "Cannot retrive cities", e);
                return;
            }
        }
    }).start();
 }

 protected void retrieveAndAddCities() throws IOException {
    HttpURLConnection conn = null;
    final StringBuilder json = new StringBuilder();
    try {
        // Connect to the web service
        URL url = new URL(SERVICE_URL);
        conn = (HttpURLConnection) url.openConnection();
        InputStreamReader in = new InputStreamReader(conn.getInputStream());

        // Read the JSON data into the StringBuilder
        int read;
        char[] buff = new char[1024];
        while ((read = in.read(buff)) != -1) {
            json.append(buff, 0, read);
        }
    } catch (IOException e) {
        Log.e(LOG_TAG, "Error connecting to service", e);
        throw new IOException("Error connecting to service", e);
    } finally {
        if (conn != null) {
            conn.disconnect();
        }
    }

    // Create markers for the city data.
    // Must run this on the UI thread since it's a UI operation.
    runOnUiThread(new Runnable() {
        public void run() {
            try {
                createMarkersFromJson(json.toString());
            } catch (JSONException e) {
                Log.e(LOG_TAG, "Error processing JSON", e);
            }
        }
    });
  }

 void createMarkersFromJson(String json) throws JSONException {
    // De-serialize the JSON string into an array of city objects
    JSONArray jsonArray = new JSONArray(json);
    for (int i = 0; i < jsonArray.length(); i++) {
        // Create a marker for each city in the JSON data.
        JSONObject jsonObj = jsonArray.getJSONObject(i);
        map.addMarker(new MarkerOptions()
                .title(jsonObj.getString("name"))
                .snippet(Integer.toString(jsonObj.getInt("population")))
                .position(new LatLng(
                        jsonObj.getJSONArray("latlng").getDouble(0),
                        jsonObj.getJSONArray("latlng").getDouble(1)
                ))
        );
    }
 }

@Override
public void onMapReady(GoogleMap googleMap) {

    try {
        createMarkersFromJson(SERVICE_URL);
    } catch (JSONException e) {
        e.printStackTrace();
    }

}
}

Answer 1

你正在调用方法，即使你的地图还没有准备好在onMapReady

这样做

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_maps);  
        MapFragment mapFragment = (MapFragment) getFragmentManager().findFragmentById(R.id.map);
        mapFragment.getMapAsync(this);
 }

@Override
public void onMapReady(GoogleMap googleMap) {

    try {
        setUpMap();
    } catch (JSONException e) {
        e.printStackTrace();
    }

}

Answer 2

我认为只需更改此行即可解决您的问题

 MapFragment mapFragment = (MapFragment) getFragmentManager().findFragmentById(R.id.map);

到

  SupportMapFragment mapFragment =
                (SupportMapFragment) getSupportFragmentManager().findFragmentById(R.id.map);

Answer 3

谢谢，我已经解决了我的问题，项目运行正常。这是我的MapsActivity.jave文件

package daffodilvarsity.edu.bd.studentportal;

import android.support.v4.app.FragmentActivity;
import android.os.Bundle;
import android.util.Log;
import com.google.android.gms.maps.CameraUpdateFactory;
import com.google.android.gms.maps.GoogleMap;
import com.google.android.gms.maps.OnMapReadyCallback;
import com.google.android.gms.maps.SupportMapFragment;
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 org.json.JSONArray;
import org.json.JSONException;
import org.json.JSONObject;
import java.io.IOException;
import java.io.InputStreamReader;
import java.net.HttpURLConnection;
import java.net.URL;

public class MapsActivity extends FragmentActivity {
private static final String LOG_TAG = "ExampleApp";

private static final String SERVICE_URL = "https://api.myjson.com/bins/4jb09";

protected GoogleMap map;

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

    setUpMapIfNeeded();
}

 @Override
protected void onResume() {
    super.onResume();
    setUpMapIfNeeded();
}

  private void setUpMapIfNeeded() {
    if (map == null) {

        SupportMapFragment mapFragment = (SupportMapFragment) getSupportFragmentManager().findFragmentById(R.id.map);
        mapFragment.getMapAsync(new OnMapReadyCallback() {

            @Override
            public void onMapReady(GoogleMap googlemap) {
                map = googlemap;
                if (map != null) {
                    setUpMap();

                    LatLng norway = new LatLng(62.455102,17.345599);

                    CameraPosition target = CameraPosition.builder().target(norway).zoom(14).build();
                        map.moveCamera(CameraUpdateFactory.newCameraPosition(target));

                }
            }
        });
    }
}

private void setUpMap() {
    new Thread(new Runnable() {
        public void run() {
            try {
                retrieveAndAddCities();
            } catch (IOException e) {
                Log.e(LOG_TAG, "Cannot retrive cities", e);
                return;
            }
        }
    }).start();
}

protected void retrieveAndAddCities() throws IOException {
    HttpURLConnection conn = null;
    final StringBuilder json = new StringBuilder();
    try {
        URL url = new URL(SERVICE_URL);
        conn = (HttpURLConnection) url.openConnection();
        InputStreamReader in = new InputStreamReader(conn.getInputStream());
        int read;
        char[] buff = new char[1024];
        while ((read = in.read(buff)) != -1) {
            json.append(buff, 0, read);
        }
    } catch (IOException e) {
        Log.e(LOG_TAG, "Error connecting to service", e);
        throw new IOException("Error connecting to service", e);
    } finally {
        if (conn != null) {
            conn.disconnect();
        }
    }

    runOnUiThread(new Runnable() {
        public void run() {
            try {
                createMarkersFromJson(json.toString());
            } catch (JSONException e) {
                Log.e(LOG_TAG, "Error processing JSON", e);
            }
        }
    });
}

void createMarkersFromJson(String json) throws JSONException {
    JSONArray jsonArray = new JSONArray(json);
    for (int i = 0; i < jsonArray.length(); i++) {
        // Create a marker for each city in the JSON data.
        JSONObject jsonObj = jsonArray.getJSONObject(i);
        map.addMarker(new MarkerOptions()
                .title(jsonObj.getString("name"))
                .snippet(Integer.toString(jsonObj.getInt("population")))
                .position(new LatLng(
                        jsonObj.getJSONArray("latlng").getDouble(0),
                        jsonObj.getJSONArray("latlng").getDouble(1)
                ))
        );
    }
}

}

我想在Android Google地图活动中显示多个位置

3 个答案: