android - MapView 中的致命和 NullPointerException

Question

这是我的 MainActivity.java 代码:

public class MainActivity extends Activity {

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    FragmentManager fr_mgr = getFragmentManager();
    MapFragment map_frag = (MapFragment) fr_mgr.findFragmentById(R.id.map);
    map = ((MapFragment) getFragmentManager().findFragmentById(R.id.map))
            .getMap();
    map = map_frag.getMap();
    map.setMyLocationEnabled(true);
    LatLng Bhopal = new LatLng(23.233243200000000000, 77.434339400000000000);
    map.addMarker(new MarkerOptions()
            .position(new LatLng(23.233243200000000000, 77.434339400000000000))
            .title("Hello Bhopal")
            .icon(BitmapDescriptorFactory.defaultMarker(BitmapDescriptorFactory.HUE_AZURE)));
    Polygon polygon = map.addPolygon(new PolygonOptions()
            .add(new LatLng(23.226834, 77.355309),
                    new LatLng(23.214845, 77.42672),
                    new LatLng(23.187707, 77.388954),
                    new LatLng(23.200961, 77.31411)).strokeColor(Color.RED)
            .fillColor(Color.parseColor("#51000000")).strokeWidth(2));
}
}

这是我的布局文件“activity_main.xml”:

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
tools:context=".MainActivity" >

    <fragment
        android:id="@+id/map"
        android:layout_width="fill_parent"
        android:layout_height="fill_parent"
        class="com.google.android.gms.maps.MapFragment" />

</RelativeLayout>

Answer 1

已解决的问题:

XML:

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
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"
    class="com.google.android.gms.maps.SupportMapFragment" />

</LinearLayout>

代码:

import android.graphics.Color;
import android.os.Bundle;
import android.os.StrictMode;
import android.support.v4.app.FragmentActivity;
import android.view.Menu;

import com.google.android.gms.maps.GoogleMap;
import com.google.android.gms.maps.SupportMapFragment;
import com.google.android.gms.maps.model.BitmapDescriptorFactory;
import com.google.android.gms.maps.model.LatLng;  
import com.google.android.gms.maps.model.MarkerOptions;
import com.google.android.gms.maps.model.Polygon;
import com.google.android.gms.maps.model.PolygonOptions;

public class MapAPIV2DemoActivity extends FragmentActivity
{
    GoogleMap mMap;
    @Override
    protected void onCreate(Bundle savedInstanceState)
    {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_map_apiv2_demo);

        mMap = ((SupportMapFragment) getSupportFragmentManager().findFragmentById(R.id.map)).getMap();

    mMap.setMyLocationEnabled(true);
    LatLng Bhopal = new LatLng(23.233243200000000000, 77.434339400000000000);
    mMap.addMarker(new MarkerOptions()
            .position(new LatLng(23.233243200000000000, 77.434339400000000000))
            .title("Hello Bhopal")
            .icon(BitmapDescriptorFactory.defaultMarker(BitmapDescriptorFactory.HUE_AZURE)));
    Polygon polygon = mMap.addPolygon(new PolygonOptions()
            .add(new LatLng(23.226834, 77.355309),
                    new LatLng(23.214845, 77.42672),
                    new LatLng(23.187707, 77.388954),
                    new LatLng(23.200961, 77.31411)).strokeColor(Color.RED)
            .fillColor(Color.parseColor("#51000000")).strokeWidth(2));
}
}