java.lang.NullPointerException GoogleMaps V2

Question

我只是学习有关显示地图的android编程。但是当我运行这段代码时，出现了一些错误。谁能解释为什么会发生此错误？我该如何解决这个问题？非常感谢你。

堆栈跟踪：

12-01 02:58:27.324: E/AndroidRuntime(1360): FATAL EXCEPTION: main
12-01 02:58:27.324: E/AndroidRuntime(1360): java.lang.NullPointerException
12-01 02:58:27.324: E/AndroidRuntime(1360):     at android.app.Instrumentation.execStartActivity(Instrumentation.java:1417)
12-01 02:58:27.324: E/AndroidRuntime(1360):     at android.app.Activity.startActivityForResult(Activity.java:3390)
12-01 02:58:27.324: E/AndroidRuntime(1360):     at android.app.Activity.startActivityForResult(Activity.java:3351)
12-01 02:58:27.324: E/AndroidRuntime(1360):     at android.support.v4.app.FragmentActivity.startActivityForResult(FragmentActivity.java:839)
12-01 02:58:27.324: E/AndroidRuntime(1360):     at android.app.Activity.startActivity(Activity.java:3587)
12-01 02:58:27.324: E/AndroidRuntime(1360):     at android.app.Activity.startActivity(Activity.java:3555)
12-01 02:58:27.324: E/AndroidRuntime(1360):     at com.google.android.gms.dynamic.a$5.onClick(Unknown Source)
12-01 02:58:27.324: E/AndroidRuntime(1360):     at android.view.View.performClick(View.java:4240)
12-01 02:58:27.324: E/AndroidRuntime(1360):     at android.view.View$PerformClick.run(View.java:17721)
12-01 02:58:27.324: E/AndroidRuntime(1360):     at android.os.Handler.handleCallback(Handler.java:730)
12-01 02:58:27.324: E/AndroidRuntime(1360):     at android.os.Handler.dispatchMessage(Handler.java:92)
12-01 02:58:27.324: E/AndroidRuntime(1360):     at android.os.Looper.loop(Looper.java:137)
12-01 02:58:27.324: E/AndroidRuntime(1360):     at android.app.ActivityThread.main(ActivityThread.java:5103)
12-01 02:58:27.324: E/AndroidRuntime(1360):     at java.lang.reflect.Method.invokeNative(Native Method)
12-01 02:58:27.324: E/AndroidRuntime(1360):     at java.lang.reflect.Method.invoke(Method.java:525)
12-01 02:58:27.324: E/AndroidRuntime(1360):     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:737)
12-01 02:58:27.324: E/AndroidRuntime(1360):     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:553)
12-01 02:58:27.324: E/AndroidRuntime(1360):     at dalvik.system.NativeStart.main(Native Method)
12-01 02:58:29.088: I/Process(1360): Sending signal. PID: 1360 SIG: 9

MainActivity.java

package unai.skripsi.mymaps;

import com.google.android.gms.maps.CameraUpdateFactory;
import com.google.android.gms.maps.GoogleMap;
import com.google.android.gms.maps.SupportMapFragment;
import com.google.android.gms.maps.model.BitmapDescriptorFactory;
import com.google.android.gms.maps.model.LatLng;
import com.google.android.gms.maps.model.Marker;
import com.google.android.gms.maps.model.MarkerOptions;

import android.os.Bundle;
import android.support.v4.app.FragmentActivity;
import android.view.Menu;

public class MainActivity extends FragmentActivity {

    static final LatLng RAGUNAN = new LatLng(-6.3039, 106.8267);
    static final LatLng TAMANMINI = new LatLng(-6.29436, 106.8859);
    private GoogleMap map;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    map= ((SupportMapFragment) getSupportFragmentManager().findFragmentById(R.id.map)).getMap();
    if (map!=null){
    Marker ragunan = map.addMarker(new MarkerOptions().position(RAGUNAN)
        .title("Ragunan"));
    Marker tamanmini = map.addMarker(new MarkerOptions().position(TAMANMINI)
        .title("Taman mini")
        .snippet("Taman mini itu indah")
        .icon(BitmapDescriptorFactory.fromResource(R.drawable.ic_launcher)));

    map.moveCamera(CameraUpdateFactory.newLatLngZoom(RAGUNAN, 15));
    map.animateCamera(CameraUpdateFactory.zoomTo(10), 2000, null);

    }
}


@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;
}

 }

布局

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

</RelativeLayout>

表现

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="unai.skripsi.mymaps"
android:versionCode="1"
android:versionName="1.0" >

<uses-sdk
    android:minSdkVersion="8"
    android:targetSdkVersion="17" />

<permission
    android:name="unai.skripsi.mymaps.permission.MAPS_RECEIVE"
    android:protectionLevel="signature" />

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

<uses-permission android:name="android.permission.ACCESS_NETWORK_STATE"/>
<uses-permission android:name="unai.skripsi.mymaps.permission.MAPS_RECEIVE" />
<uses-permission android:name="android.permission.INTERNET" />
<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />
<uses-permission   android:name="com.google.android.providers.gsf.permission.READ_GSERVICES" />
<uses-permission android:name="android.permission.ACCESS_COARSE_LOCATION" />
<uses-permission android:name="android.permission.ACCESS_FINE_LOCATION" />

<application
    android:allowBackup="true"
    android:icon="@drawable/ic_launcher"
    android:label="@string/app_name"
    android:theme="@style/AppTheme" >
    <activity
        android:name="unai.skripsi.mymaps.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>
    <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="My API KEY" />
</application>

</manifest>

Answer 1

在您的xml文件中，将其更改 class="com.google.android.gms.maps.MapFragment" 为
android:name="com.google.android.gms.maps.SupportMapFragment"

将您的活动扩展到FragmentActivty并进行更改

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

还要检查

if (map== null) 
            {
          map= ((SupportMapFragment) getSupportFragmentManager()
                    .findFragmentById(R.id.map)).getMap();}

希望这可以帮助。