Android Google Map api v2 返回空值？

Question

我有下面的代码，它的工作很好 tvTitle 没有返回 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);
                               ^^^^^^  

但是 google map 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你有我的一个应用程序的工作示例:Tureame .