放大标记谷歌地图V2

我有一个ArrayList具有lat和long属性的自定义对象.

我已设法在地图上放置标记.我想要的是能够在地图加载时放大这些标记.

我在下面尝试的内容导致应用程序崩溃.

这是加载地图的代码:

public void getBridgeData() {
    db = new DbHelperClass(this);
    bridges = db.getAllBridges();
    DecimalFormat dc = new DecimalFormat("#.000");
    Builder builder = new LatLngBounds.Builder();

    for (int i= 0;i

这里也是代码的一部分

public class MainActivity extends FragmentActivity {
    private GoogleMap map;
    private DbHelperClass db;
    private List bridges = new ArrayList();
    CameraUpdate cu;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main_map);
        //AddSomeData();
        map = ((SupportMapFragment) getSupportFragmentManager().findFragmentById(R.id.map))
        .getMap();

        if(map!=null) {
            getBridgeData();
        }
    }
}


这是错误日志:

05-30 22:19:28.894: E/AndroidRuntime(5593): FATAL EXCEPTION: main
05-30 22:19:28.894: E/AndroidRuntime(5593): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.bridge.bridgeinventory/com.bridge.bridgeinventory.MainActivity}: java.lang.IllegalStateException: Error using newLatLngBounds(LatLngBounds, int): Map size can't be 0. Most likely, layout has not yet occured for the map view.  Either wait until layout has occurred or use newLatLngBounds(LatLngBounds, int, int, int) which allows you to specify the map's dimensions.
05-30 22:19:28.894: E/AndroidRuntime(5593):     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1755)
05-30 22:19:28.894: E/AndroidRuntime(5593):     at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:1774)
05-30 22:19:28.894: E/AndroidRuntime(5593):     at android.app.ActivityThread.access$1500(ActivityThread.java:157)
05-30 22:19:28.894: E/AndroidRuntime(5593):     at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1001)
05-30 22:19:28.894: E/AndroidRuntime(5593):     at android.os.Handler.dispatchMessage(Handler.java:130)
05-30 22:19:28.894: E/AndroidRuntime(5593):     at android.os.Looper.loop(SourceFile:351)
05-30 22:19:28.894: E/AndroidRuntime(5593):     at android.app.ActivityThread.main(ActivityThread.java:3841)
05-30 22:19:28.894: E/AndroidRuntime(5593):     at java.lang.reflect.Method.invokeNative(Native Method)
05-30 22:19:28.894: E/AndroidRuntime(5593):     at java.lang.reflect.Method.invoke(Method.java:538)
05-30 22:19:28.894: E/AndroidRuntime(5593):     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:969)
05-30 22:19:28.894: E/AndroidRuntime(5593):     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:727)
05-30 22:19:28.894: E/AndroidRuntime(5593):     at dalvik.system.NativeStart.main(Native Method)
05-30 22:19:28.894: E/AndroidRuntime(5593): Caused by: java.lang.IllegalStateException: Error using newLatLngBounds(LatLngBounds, int): Map size can't be 0. Most likely, layout has not yet occured for the map view.  Either wait until layout has occurred or use newLatLngBounds(LatLngBounds, int, int, int) which allows you to specify the map's dimensions.
05-30 22:19:28.894: E/AndroidRuntime(5593):     at kbh.b(Unknown Source)
05-30 22:19:28.894: E/AndroidRuntime(5593):     at mas.a(Unknown Source)
05-30 22:19:28.894: E/AndroidRuntime(5593):     at mal.a(Unknown Source)
05-30 22:19:28.894: E/AndroidRuntime(5593):     at mbi.a(Unknown Source)
05-30 22:19:28.894: E/AndroidRuntime(5593):     at fms.onTransact(SourceFile:83)
05-30 22:19:28.894: E/AndroidRuntime(5593):     at android.os.Binder.transact(Binder.java:310)
05-30 22:19:28.894: E/AndroidRuntime(5593):     at com.google.android.gms.maps.internal.IGoogleMapDelegate$a$a.moveCamera(Unknown Source)
05-30 22:19:28.894: E/AndroidRuntime(5593):     at com.google.android.gms.maps.GoogleMap.moveCamera(Unknown Source)
05-30 22:19:28.894: E/AndroidRuntime(5593):     at com.bridge.bridgeinventory.MainActivity.getBridgeData(MainActivity.java:148)
05-30 22:19:28.894: E/AndroidRuntime(5593):     at com.bridge.bridgeinventory.MainActivity.onCreate(MainActivity.java:44)
05-30 22:19:28.894: E/AndroidRuntime(5593):     at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1082)
05-30 22:19:28.894: E/AndroidRuntime(5593):     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1719)
05-30 22:19:28.894: E/AndroidRuntime(5593):     ... 11 more


我怎样才能使它工作？