我正在使用android studio编写googlemap活动
mMap = ((SupportMapFragment) getSupportFragmentManager().findFragmentById(R.id.**map**))
.getMap();
＆＃34; map＆＃34;在我运行程序之后变为红色（之前没有错误）
这是我的代码
主要活动：
package com.example.albert.lab_assignment2;
import android.support.v4.app.FragmentActivity;
import android.os.Bundle;
import android.view.View;
import android.widget.AdapterView;
import android.widget.ArrayAdapter;
import android.widget.Button;
import android.widget.Spinner;
import android.widget.Toast;
import com.google.android.gms.maps.CameraUpdateFactory;
import com.google.android.gms.maps.GoogleMap;
import com.google.android.gms.maps.SupportMapFragment;
import com.google.android.gms.maps.model.LatLng;
import com.google.android.gms.maps.model.Marker;
import com.google.android.gms.maps.model.MarkerOptions;
import java.util.ArrayList;
import java.util.List;
public class MapsActivity extends FragmentActivity {
private GoogleMap mMap; // Might be null if Google Play services APK is not available.
Marker markerParis, markerLondon, markerNewYork, markerTokyo, markerHongKong;
LatLng HongKong, Paris, London, NewYork, Tokyo;
private Spinner spinner2;
Button btnParis, btnLondon, btnNewYork;
private void addItemOnSpinner2() {
spinner2 = (Spinner) findViewById(R.id.spinner2);
List list = new ArrayList();
list.add("Hong Kong");
list.add("London");
list.add("New York");
list.add("Paris");
list.add("Tokyo");
ArrayAdapter dataAdapter = new ArrayAdapter(this, android.R.layout.simple_spinner_item, list);
dataAdapter.setDropDownViewResource(
android.R.layout.simple_spinner_dropdown_item);
spinner2.setAdapter(dataAdapter);
String.valueOf(spinner2.getSelectedItem());
spinner2.setOnItemSelectedListener(new AdapterView.OnItemSelectedListener() {
@Override
public void onItemSelected(AdapterView<?> parent, View view, int position, long id) {
String message = "Selected place:" + parent.getItemAtPosition(position).toString();
Toast.makeText(parent.getContext(),message,Toast.LENGTH_LONG).show();
String place = parent.getItemAtPosition(position).toString();
if (place.equals("Hong Kong")){
goHongKong();
}
else if (place.equals("Paris")){
goParis();
}
else if (place.equals("New York")){
goNewYork();
}
else if (place.equals("London")){
goLondon();
}
else if (place.equals("Tokyo")){
goTokyo();
}
}
@Override
public void onNothingSelected(AdapterView<?> parent) {
}
});
}
private void goTokyo() {
mMap.clear();
double distance = computeDistance(Tokyo);
String distMsg = "Distance from HK:" + Math.round(distance) + "km";
Toast.makeText(getApplicationContext(), distMsg, Toast.LENGTH_LONG).show();
markerTokyo = mMap.addMarker(new MarkerOptions()
.position(Tokyo)
.title("Tokyo")
.snippet("Population"));
mMap.animateCamera(CameraUpdateFactory.newLatLngZoom(NewYork, 10));
}
private void goHongKong() {
mMap.clear();
double distance = computeDistance(HongKong);
String distMsg = "Distance from HK:" + Math.round(distance) + "km";
Toast.makeText(getApplicationContext(), distMsg, Toast.LENGTH_LONG).show();
markerHongKong = mMap.addMarker(new MarkerOptions()
.position(HongKong)
.title("Hong Kong")
.snippet("Population"));
mMap.animateCamera(CameraUpdateFactory.newLatLngZoom(HongKong, 10));
}
private void goLondon() {
mMap.clear();
double distance = computeDistance(London);
String distMsg = "Distance from HK:" + Math.round(distance) + "km";
Toast.makeText(getApplicationContext(), distMsg, Toast.LENGTH_LONG).show();
markerLondon = mMap.addMarker(new MarkerOptions()
.position(London)
.title("London")
.snippet("Population"));
mMap.animateCamera(CameraUpdateFactory.newLatLngZoom(London, 10));
}
private void goNewYork() {
mMap.clear();
double distance = computeDistance(NewYork);
String distMsg = "Distance from HK:" + Math.round(distance) + "km";
Toast.makeText(getApplicationContext(), distMsg, Toast.LENGTH_LONG).show();
markerNewYork = mMap.addMarker(new MarkerOptions()
.position(NewYork)
.title("New York")
.snippet("Population"));
mMap.animateCamera(CameraUpdateFactory.newLatLngZoom(NewYork, 10));
}
private void goParis() {
mMap.clear();
double distance = computeDistance(Paris);
String distMsg = "Distance from HK:" + Math.round(distance) + "km";
Toast.makeText(getApplicationContext(), distMsg, Toast.LENGTH_LONG).show();
markerParis = mMap.addMarker(new MarkerOptions()
.position(Paris)
.title("Paris")
.snippet("Population"));
mMap.animateCamera(CameraUpdateFactory.newLatLngZoom(Paris, 10));
}
private double computeDistance(LatLng dest) {
int R = 6371; //Earth's radius in km
double dLat = Math.toRadians(HongKong.latitude - dest.latitude) ;
double dLon = Math.toRadians(HongKong.longitude - dest.longitude);
double lat1 = Math.toRadians(dest.latitude);
double lat2 = Math.toRadians(HongKong.latitude);
double a = Math.sin(dLat/2) * Math.sin(dLat/2) + Math.sin(dLon/2) *
Math.sin(dLon/2) * Math.cos(lat1) * Math.cos(lat2);
double c = 2 * Math.atan2(Math.sqrt(a), Math.sqrt(1-a));
return R * c;
}
private void HomeLocation() {
mMap.setOnMyLocationButtonClickListener(new GoogleMap.OnMyLocationButtonClickListener() {
@Override
public boolean onMyLocationButtonClick() {
mMap.animateCamera(CameraUpdateFactory.newLatLngZoom(HongKong, 14));
return false;
}
});
}
private void initializingCity() {
HongKong = new LatLng(22.2783, 114.1747);
Paris = new LatLng(48.8567, 2.3508);
London = new LatLng(51.518815, -0.1275);
NewYork = new LatLng(40.713723, -74.002640);
Tokyo = new LatLng(35.6833, 139.6833);
}
@Override
protected void onResume() {
super.onResume();
setUpMapIfNeeded();
}
/**
* Sets up the map if it is possible to do so (i.e., the Google Play services APK is correctly
* installed) and the map has not already been instantiated.. This will ensure that we only ever
* call {@link #setUpMap()} once when {@link #mMap} is not null.
* <p/>
* If it isn't installed {@link SupportMapFragment} (and
* {@link com.google.android.gms.maps.MapView MapView}) will show a prompt for the user to
* install/update the Google Play services APK on their device.
* <p/>
* A user can return to this FragmentActivity after following the prompt and correctly
* installing/updating/enabling the Google Play services. Since the FragmentActivity may not
* have been completely destroyed during this process (it is likely that it would only be
* stopped or paused), {@link #onCreate(Bundle)} may not be called again so we should call this
* method in {@link #onResume()} to guarantee that it will be called.
*/
private void setUpMapIfNeeded() {
// Do a null check to confirm that we have not already instantiated the map.
if (mMap == null) {
// 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) {
setUpMap();
}
}
}
/**
* This is where we can add markers or lines, add listeners or move the camera. In this case, we
* just add a marker near Africa.
* <p/>
* This should only be called once and when we are sure that {@link #mMap} is not null.
*/
private void setUpMap() {
mMap.addMarker(new MarkerOptions().position(HongKong).title("Marker"));
mMap.animateCamera(CameraUpdateFactory.newLatLng(HongKong));
mMap.getUiSettings().setZoomControlsEnabled(true);
mMap.getUiSettings().setScrollGesturesEnabled(true);
mMap.getUiSettings().setTiltGesturesEnabled(true);
mMap.getUiSettings().setRotateGesturesEnabled(true);
mMap.setMyLocationEnabled(true);
mMap.setMapType(GoogleMap.MAP_TYPE_NORMAL);
}
}
activity_maps.xml：
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout
xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
android:orientation="vertical" >
<Spinner
android:id="@+id/spinner2"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:prompt="@string/select2" />
</LinearLayout>
string.xml
<?xml version="1.0" encoding="utf-8"?>
<resources xmlns:android="http://schemas.android.com/apk/res/android">
<string name="app_name">Lab_Assignment2</string>
<string name="title_activity_maps">Map</string>
<string name="select2">Choose an item</string> //spinner
</resources>
请帮忙
答案 0 :(得分：1)
您的fragment中没有任何xml地图标记。
在相关的xml中添加以下内容：
<fragment
android:layout_width="match_parent"
android:layout_height="400dp"
android:id="@+id/map"
android:name="com.google.android.gms.maps.MapFragment" />
答案 1 :(得分：0)
尝试将其放在gradle.properties中
android.enableJetifier=true