谷歌地图 Android API 错误

Question

使用示例https://www.youtube.com/watch?v=awX5T-EwLPc https://developers.google.com/maps/documentation/android/start

AVD 目标：Google API（API 级别 17）

MainActivity 第 28 行：

map.addMarker(new MarkerOptions().position(LOCATION_SURRREY).title("Find me here!"));

这就是我的 AndroidManifest.xml 的样子：

 <?xml version="1.0" encoding="utf-8"?>
    <manifest xmlns:android="http://schemas.android.com/apk/res/android"
        package="ca.sfu.cmpt276.bfraser"
        android:versionCode="1"
        android:versionName="1.0" >

        <uses-sdk
            android:minSdkVersion="11"
            android:targetSdkVersion="17" />

        <permission
            android:name="ca.sfu.cmpt276.bfraser.permission.MAPS_RECEIVE"
            android:protectionLevel="signature"/>
        <uses-permission android:name="ca.sfu.cmpt276.bfraser.permission.MAPS_RECEIVE"/>

        <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="com.google.android.providers.gsf.permission.READ_GSERVICES"/>
        <!-- The following two permissions are not required to use
             Google Maps Android API v2, but are recommended. -->
        <uses-permission android:name="android.permission.ACCESS_COARSE_LOCATION"/>
        <uses-permission android:name="android.permission.ACCESS_FINE_LOCATION"/>

        <uses-feature
            android:glEsVersion="0x00020000"
            android:required="true"/>   


        <application
            android:allowBackup="true"
            android:icon="@drawable/ic_launcher"
            android:label="@string/app_name"
            android:theme="@style/AppTheme" >

            <meta-data 
           android:name="com.google.android.gms.version" 
           android:value="@integer/google_play_services_version" />

            <meta-data
                android:name="com.google.android.maps.v2.API_KEY"
                android:value="AIzaSyDCqcB_u_mPRdCa4N9wCrw2cX6LY9iWxEk"/>

            <activity
                android:name="ca.sfu.cmpt276.bfraser.MainActivity"
                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>

MainActivity:-

package ca.sfu.cmpt276.bfraser;

import android.app.Activity;
import android.os.Bundle;
import android.view.Menu;
import android.view.View;

import com.google.android.gms.maps.CameraUpdate;
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.LatLng;
import com.google.android.gms.maps.model.MarkerOptions;

public class MainActivity extends Activity {
    private final LatLng LOCATION_BURNABY = new LatLng(49.27645, -122.917587);
    private final LatLng LOCATION_SURRREY = new LatLng(49.187500, -122.849000);

    private GoogleMap map;

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

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

        map.addMarker(new MarkerOptions().position(LOCATION_SURRREY).title("Find me here!"));
    }

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

    public void onClick_City(View v) {
//      CameraUpdate update = CameraUpdateFactory.newLatLng(LOCATION_BURNABY);
        map.setMapType(GoogleMap.MAP_TYPE_SATELLITE);
        CameraUpdate update = CameraUpdateFactory.newLatLngZoom(LOCATION_BURNABY, 9);
        map.animateCamera(update);
    }
    public void onClick_Burnaby(View v) {
        map.setMapType(GoogleMap.MAP_TYPE_TERRAIN);
        CameraUpdate update = CameraUpdateFactory.newLatLngZoom(LOCATION_BURNABY, 14);
        map.animateCamera(update);

    }
    public void onClick_Surrey(View v) {
        map.setMapType(GoogleMap.MAP_TYPE_NORMAL);
        CameraUpdate update = CameraUpdateFactory.newLatLngZoom(LOCATION_SURRREY, 16);
        map.animateCamera(update);

    }

}

日志：-

08-22 20:13:49.078: E/AndroidRuntime(1068): FATAL EXCEPTION: main
08-22 20:13:49.078: E/AndroidRuntime(1068): java.lang.RuntimeException: Unable to start activity ComponentInfo{ca.sfu.cmpt276.bfraser/ca.sfu.cmpt276.bfraser.MainActivity}: java.lang.NullPointerException
08-22 20:13:49.078: E/AndroidRuntime(1068):   at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2180)
08-22 20:13:49.078: E/AndroidRuntime(1068):   at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2230)
08-22 20:13:49.078: E/AndroidRuntime(1068):   at android.app.ActivityThread.access$600(ActivityThread.java:141)
08-22 20:13:49.078: E/AndroidRuntime(1068):   at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1234)
08-22 20:13:49.078: E/AndroidRuntime(1068):   at android.os.Handler.dispatchMessage(Handler.java:99)
08-22 20:13:49.078: E/AndroidRuntime(1068):   at android.os.Looper.loop(Looper.java:137)
08-22 20:13:49.078: E/AndroidRuntime(1068):   at android.app.ActivityThread.main(ActivityThread.java:5041)
08-22 20:13:49.078: E/AndroidRuntime(1068):   at java.lang.reflect.Method.invokeNative(Native Method)
08-22 20:13:49.078: E/AndroidRuntime(1068):   at java.lang.reflect.Method.invoke(Method.java:511)
08-22 20:13:49.078: E/AndroidRuntime(1068):   at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:793)
08-22 20:13:49.078: E/AndroidRuntime(1068):   at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:560)
08-22 20:13:49.078: E/AndroidRuntime(1068):   at dalvik.system.NativeStart.main(Native Method)
08-22 20:13:49.078: E/AndroidRuntime(1068): Caused by: java.lang.NullPointerException
08-22 20:13:49.078: E/AndroidRuntime(1068):   at ca.sfu.cmpt276.bfraser.MainActivity.onCreate(MainActivity.java:28)
08-22 20:13:49.078: E/AndroidRuntime(1068):   at android.app.Activity.performCreate(Activity.java:5104)
08-22 20:13:49.078: E/AndroidRuntime(1068):   at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1080)
08-22 20:13:49.078: E/AndroidRuntime(1068):   at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2144)
08-22 20:13:49.078: E/AndroidRuntime(1068):   ... 11 more

Answer 1

onCreate 方法上的map 变量为空。
这意味着您的activity_main 布局中没有片段的map 标识符。

Answer 2

问题：

((MapFragment) getFragmentManager().findFragmentById(R.id.map)).getMap();

您使用的是 Google 多年前实施的旧地图片段，

我建议使用较新的地图类型，即SupportMapFragment。

解决方案：

改变这个：

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

到：

map  = ((SupportMapFragment) getFragmentManager().findFragmentById(R.id.map)).getMap();

还将您的 xml 更改为：

<fragment
android:id="@+id/map"
android:name="com.example.test.HomeFragment"
android:layout_width="match_parent"
android:layout_height="match_parent"
class="com.google.android.gms.maps.SupportMapFragment" />