Android Google Map api v2 返回 null？

Question

我有下面的代码，它工作得很好，tvTitle 不返回 null，但是

RelativeLayout relmain = (RelativeLayout) findViewById(R.id.mainview);
LayoutInflater inflater = LayoutInflater.from(this);

RelativeLayout contents = (RelativeLayout) inflater
            .inflate(R.layout.placedetail, null);
relmain.addView(contents);

TextView tvTitle = (TextView) contents.findViewById(R.id.tvdealtitle);
                               ^^^^^^  

但谷歌地图返回 null...检查下面的代码...

GoogleMap googleMap = ((SupportMapFragment) getSupportFragmentManager()
                .findFragmentById(R.id.map2)).getMap();


System.out.println("Google map is :: " + googleMap);

placedetail.xml

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

<RelativeLayout
    android:id="@+id/rel1"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:background="@drawable/banner"
    android:onClick="onClickBack" >

    <ImageView
        android:id="@+id/img"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignParentRight="true"
        android:layout_centerVertical="true"
        android:layout_marginRight="5dp"
        android:background="@drawable/directions"
        android:onClick="onClickImage" />
</RelativeLayout>

<RelativeLayout
    android:id="@+id/reldetail"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_below="@+id/rel1"
    android:layout_marginTop="10dp" >

    <TextView
        android:id="@+id/tvdealtitle"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignParentTop="true"
        android:layout_marginLeft="5dp"
        android:layout_marginRight="5dp"
        android:layout_marginTop="8dp"
        android:ellipsize="end"
        android:singleLine="true"
        android:text="Title"
        android:textColor="@android:color/black"
        android:textSize="16sp"
        android:textStyle="bold" />

    <TextView
        android:id="@+id/tvdealoffertext"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignLeft="@+id/tvdealtitle"
        android:layout_below="@+id/tvdealtitle"
        android:layout_marginTop="2dp"
        android:ellipsize="end"
        android:maxLines="2"
        android:text="offertext"
        android:textColor="#696969"
        android:textStyle="bold" />

    <TextView
        android:id="@+id/tvdealdesc"
        android:layout_width="wrap_content"
        android:layout_height="100dp"
        android:layout_alignLeft="@+id/tvdealtitle"
        android:layout_below="@+id/tvdealoffertext"
        android:layout_marginTop="2dp"
        android:scrollbars="vertical"
        android:text="desc"
        android:textColor="#696969"
        android:textStyle="bold" />
</RelativeLayout>

<fragment
    android:id="@+id/map2"
    android:name="com.google.android.gms.maps.SupportMapFragment"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:layout_below="@+id/reldetail" /> 

</RelativeLayout>

Answer 1

取自 SupportMapFragment documentation :

A GoogleMap can only be acquired using getMap() when the underlying maps system is loaded and the underlying view in the fragment exists. This class automatically initializes the maps system and the view; however you cannot be guaranteed when it will be ready because this depends on the availability of the Google Play services APK. If a GoogleMap is not available, getMap() will return null.

然后，在您的 Activity 中您可以使用 GooglePlayServicesUtil检查可用性:

// 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) {
    // Setup your map...
} else {
    int isEnabled = GooglePlayServicesUtil.isGooglePlayServicesAvailable(this);
    if (isEnabled != ConnectionResult.SUCCESS) {
        GooglePlayServicesUtil.getErrorDialog(isEnabled, this, 0);
    }
}

Here in method setUpMapIfNeeded您已经获得了我的一个应用程序的工作示例:Tureame .