使用GoogleMap V2時，Android App不斷崩潰

Question

我在使用GoogleMap時遇到麻煩的問題。 我已經測試過了，地圖顯示正常。 但是現在我要設置“我的位置已啟用”，以便地圖自動在手機所在的位置啟動。 現在，每次我運行該應用程序時，它都會崩潰。 而且我注意到，當我使用語法GoogleMap時，應用程序崩潰了。 我試圖找出這個問題，並在網上四處尋找結果。

這是我的Maps.java文件：

package test.test;

import com.google.android.gms.maps.GoogleMap;
import com.google.android.gms.maps.SupportMapFragment;

import android.location.Location;
import android.location.LocationListener;
import android.os.Bundle;
import android.support.v4.app.FragmentActivity;

public class Maps extends FragmentActivity implements LocationListener{

    GoogleMap googlemap;

    @Override
    public void onCreate(Bundle savedInstanceState) {
        // TODO Auto-generated method stub
        super.onCreate(savedInstanceState);
        setContentView(R.layout.maps);
        SupportMapFragment mf = (SupportMapFragment)     getSupportFragmentManager().findFragmentById(R.id.map);
        googlemap = mf.getMap();

        googlemap.setMyLocationEnabled(true);
        googlemap.setMapType(GoogleMap.MAP_TYPE_NORMAL);

    }

Maps.xml：

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical" >

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

</LinearLayout>

最后是我的androidmanifest：

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

        <uses-sdk
            android:minSdkVersion="8"
            android:targetSdkVersion="16" />

        <permission
            android:name="test.test.permission.MAPS_RECEIVE"
            android:protectionLevel="signature" />

        <uses-permission android:name="test.test.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" />

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

        <application

....
<meta-data
            android:name="com.google.android.maps.v2.API_KEY"
            android:value="my key is here" />
    </application>

這是錯誤日志：

FATAL EXCEPTION: main
java.lang.RuntimeException: Unable to start activity ComponentInfo{test.test/test.test.Maps}: java.lang.NullPointerException
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2180)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2230)
at android.app.ActivityThread.access$600(ActivityThread.java:141)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1234)
at android.os.Handler.dispatchMessage(Handler.java:99)
at android.os.Looper.loop(Looper.java:137)
at android.app.ActivityThread.main(ActivityThread.java:5039)
at java.lang.reflect.Method.invokeNative(Native Method)
at java.lang.reflect.Method.invoke(Method.java:511)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:793)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:560)
at dalvik.system.NativeStart.main(Native Method)
Caused by: java.lang.NullPointerException
at test.test.Maps.onCreate(Maps.java:23)
at android.app.Activity.performCreate(Activity.java:5104)
at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1080)
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2144)
... 11 more

Answer 1

該片段尚未准備就緒，或者設備上的Google Play服務出現問題。

從文檔 （添加重點）：

退貨
GoogleMap。 如果片段的視圖尚未准備好，則為null。 如果片段生命周期尚未通過onCreateView(LayoutInflater, ViewGroup, Bundle)則會發生這種情況。 如果Google Play服務不可用，也會發生這種情況。 如果此后可以使用Google Play服務，並且該片段已通過onCreateView(LayoutInflater, ViewGroup, Bundle) ，則再次調用此方法將初始化並返回GoogleMap。

“地圖”演示應用程序顯示了一種處理此問題的模式，嘗試在創建和恢復時根據需要設置地圖：

/**
 * This shows how to create a simple activity with a map and a marker on the map.
 * <p>
 * Notice how we deal with the possibility that the Google Play services APK is not
 * installed/enabled/updated on a user's device.
 */
public class BasicMapActivity extends FragmentActivity {
    /**
     * Note that this may be null if the Google Play services APK is not available.
     */
    private GoogleMap mMap;

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

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

    /**
     * Sets up the map if it is possible to do so (i.e., the Google Play services APK is correctly
     * installed) and the map has not already been instantiated.. This will ensure that we only ever
     * call {@link #setUpMap()} once when {@link #mMap} is not null.
     * <p>
     * If it isn't installed {@link SupportMapFragment} (and
     * {@link com.google.android.gms.maps.MapView MapView}) will show a prompt for the user to
     * install/update the Google Play services APK on their device.
     * <p>
     * A user can return to this FragmentActivity after following the prompt and correctly
     * installing/updating/enabling the Google Play services. Since the FragmentActivity may not have been
     * completely destroyed during this process (it is likely that it would only be stopped or
     * paused), {@link #onCreate(Bundle)} may not be called again so we should call this method in
     * {@link #onResume()} to guarantee that it will be called.
     */
    private void setUpMapIfNeeded() {
        // Do a null check to confirm that we have not already instantiated the map.
        if (mMap == null) {
            // Try to obtain the map from the SupportMapFragment.
            mMap = ((SupportMapFragment) getSupportFragmentManager().findFragmentById(R.id.map))
                    .getMap();
            // Check if we were successful in obtaining the map.
            if (mMap != null) {
                setUpMap();
            }
        }
    }

    /**
     * This is where we can add markers or lines, add listeners or move the camera. In this case, we
     * just add a marker near Africa.
     * <p>
     * This should only be called once and when we are sure that {@link #mMap} is not null.
     */
    private void setUpMap() {
        mMap.addMarker(new MarkerOptions().position(new LatLng(0, 0)).title("Marker"));
    }
}