Android Google Maps v2 API在我返回地图活动时显示世界地图

我第一次进入“地图”活动时，它会正确显示我想要的一切—我的位置、工具以及放大到我所在位置的地图：

然后，当我走出这项活动，回到这里，我看到：

这是我的活动代码： @凌驾 公共无效启动{ super.onStart； }

为什么它第一次工作得很好，但第二次和以后的每一次都不行

我已经记录了所有内容-没有抛出异常或是零或空的东西

这是我的舱单：

---

请帮忙？

我已经解决了这个问题，但我不确定这是否是最好的方法

在onPause、onDestroy、onBackPressed中，在我声明类变量的活动开始时，我将googleMap设置为null

这样，googleMap总是空的，并且总是需要重新实例化

现在，我的地图每次都可以完美地加载我的位置和所有其他内容

---

我愿意听取关于如何做得更好的建议，因为我确实觉得这有点不妥

谢谢你这么快的回复。我已经添加了清单代码。清单看起来很好。退出这项活动是什么意思？你的意思是在上面完成或开始另一项活动？@marienke你解决了这个问题吗？是的，请看下面我的答案。但这是2015年的，所以它可能不再有效了。另外，我不再做Android编程了，所以我不能告诉你是否是。祝你好运

@Override
public void onStop() {
    super.onStop();
}

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

@Override
protected void onPause() {
    super.onPause();
}

@Override
protected void onDestroy() {
    super.onDestroy();
}

@Override
public void onBackPressed() {

    Intent intent = new Intent();
    setResult(RESULT_CANCELED, intent);
    finish();

}

@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_settings_my_location);

    //...

    Log.d(TAG, "Get user's location in a variable");
    userLocation = new LatLng(MainActivity.CURRENT_LATITUDE, MainActivity.CURRENT_LONGITUDE);
    Log.d(TAG, "Set user's location to "+MainActivity.CURRENT_LATITUDE+", "+MainActivity.CURRENT_LONGITUDE);
    // I've tested for this to be 0.0 or null or something - it's perfectly captured every time.

    //... 

    setUpMapIfNeeded();


}

private void setUpMapIfNeeded() {
    // Do a null check to confirm that we have not already instantiated the map.
    if (googleMap == null) {
        // Try to obtain the map from the SupportMapFragment.
        googleMap = ((SupportMapFragment) getSupportFragmentManager().findFragmentById(R.id.map)).getMap();
        // Check if we were successful in obtaining the map.
        if (googleMap != null) {
            setUpMap();
        }
    }else{
        setUpMap();
    }
}

private void setUpMap() {
    try {
        // Loading map

        googleMap.setOnCameraChangeListener(this);
        googleMap.setOnMapClickListener(this);

        Log.d(TAG, "Changing map type");
        googleMap.setMapType(GoogleMap.MAP_TYPE_NORMAL);

        Log.d(TAG, "Showing / hiding your current location");
        googleMap.setMyLocationEnabled(true);

        Log.d(TAG, "Enable / Disable zooming controls");
        googleMap.getUiSettings().setZoomControlsEnabled(false);

        Log.d(TAG, "Enable / Disable my location button");
        googleMap.getUiSettings().setMyLocationButtonEnabled(true);

        Log.d(TAG, "Enable / Disable Compass icon");
        googleMap.getUiSettings().setCompassEnabled(true);

        Log.d(TAG, "Enable / Disable Rotate gesture");
        googleMap.getUiSettings().setRotateGesturesEnabled(true);

        Log.d(TAG, "Enable / Disable zooming functionality");
        googleMap.getUiSettings().setZoomGesturesEnabled(true);

        googleMap.getUiSettings().setTiltGesturesEnabled(true);
        googleMap.setPadding(0, 0, 0, (int) getResources().getDimension(R.dimen.height_button_dialog));

        Log.d(TAG, "Move map camera to user's location");
        googleMap.moveCamera(CameraUpdateFactory.newLatLngZoom(userLocation, 13));

    } catch (Exception e) {
        e.printStackTrace();
    }
}

<uses-permission android:name="android.permission.INTERNET" />
<uses-permission android:name="android.permission.ACCESS_NETWORK_STATE"/>
<uses-permission android:name="android.permission.READ_CONTACTS" />
<uses-permission android:name="android.permission.CALL_PHONE" />
<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />

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

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

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

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

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

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

<!-- Required OpenGL ES 2.0. for Maps V2 -->
<uses-feature
    android:glEsVersion="0x00020000"
    android:required="true" />

<!-- Service wakelock -->
<uses-permission android:name="android.permission.WAKE_LOCK" />

<permission
    android:name="my.package.name.permission.C2D_MESSAGE"
    android:protectionLevel="signature" />

<uses-permission android:name="my.package.name.permission.C2D_MESSAGE" />
<!-- ...App receives GCM messages. -->
<uses-permission android:name="com.google.android.c2dm.permission.RECEIVE" />

<!-- Deprecated
http://stackoverflow.com/a/17937382/956975
This permission is now completely unnecessary. The latest update of Google Play Services 3.1.59 made it useless. As a result, it can be removed.

<permission
    android:name="my.package.name.permission.MAPS_RECEIVE"
    android:protectionLevel="signature" />
<uses-permission android:name="my.package.name.permission.MAPS_RECEIVE" />-->

<application
    tools:replace="android:icon"
    android:name="@string/app_name"
    android:allowBackup="true"
    android:icon="@drawable/ic_launcher"
    android:label="@string/app_name"
    android:theme="@style/AppTheme"
    android:hardwareAccelerated="true"
    android:installLocation="preferExternal"
     >

    <activity
        android:name=".activities.MainActivity"
        android:label="@string/app_name"
        android:screenOrientation="portrait"
        android:windowSoftInputMode="stateHidden" >
        <intent-filter>
            <action android:name="android.intent.action.MAIN" />

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

    <!-- Goolge Maps API Key -->
    <meta-data
        android:name="com.google.android.maps.v2.API_KEY"
        android:value="my_API_key" />
    <meta-data
        android:name="com.google.android.gms.version"
        android:value="@integer/google_play_services_version" />

    <uses-library
        android:name="com.google.android.maps"
        android:required="false" />

</application>

buildscript {
    repositories {
        maven { url 'http://download.crashlytics.com/maven' }
    }

    dependencies {
        classpath 'com.crashlytics.tools.gradle:crashlytics-gradle:1.+'
    }
}
apply plugin: 'com.android.application'
apply plugin: 'crashlytics'

repositories {
    maven { url 'http://download.crashlytics.com/maven' }
}


android {
    compileSdkVersion 'Google Inc.:Google APIs:14'
    buildToolsVersion "21.1.2"

    defaultConfig {
        applicationId "my.package.name"
        minSdkVersion 14
        targetSdkVersion 21

        versionCode 46
        versionName "2.0"
    }

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

    packagingOptions{
        exclude 'META-INF/LICENSE'
        exclude 'META-INF/NOTICE'
    }
}

dependencies {
    compile project(':countryPicker')
    compile files('libs/apache-mime4j-core-0.7.2.jar')

    compile 'org.apache.commons:commons-lang3:3.3.2'

    compile files('libs/FlurryAnalytics_3.3.1.jar')
    compile files('libs/httpmime-4.1.2.jar')

    compile 'com.fasterxml.jackson.core:jackson-annotations:2.4.4'
    compile 'com.fasterxml.jackson.core:jackson-core:2.4.4'
    compile 'com.fasterxml.jackson.core:jackson-databind:2.4.4'

    compile 'com.googlecode.libphonenumber:libphonenumber:7.0.1'

    compile files('libs/log-1.0.4.jar')

    compile files('libs/universal-image-loader-1.8.4-with-sources.jar')

    compile 'com.google.android.gms:play-services:6.5.87'
    compile 'com.android.support:support-v4:21.0.3'

    compile 'com.crashlytics.android:crashlytics:1.+'

    //https://github.com/square/picasso
    compile 'com.squareup.picasso:picasso:2.3.2'

    /*For animation ease*/
    compile 'com.nineoldandroids:library:2.4.0'
    compile 'com.daimajia.easing:library:1.0.0@aar'
}