android - 如何包含谷歌地图的交通图层？

Question

我是使用 Google Maps API 在 android 中进行开发的新手。我已经能够设置 map 并测试基本功能，但是我无法将文档中显示的逻辑实现到我自己的代码中。

我通过 google 的文档进行了研究并发现，您必须使用 map 检查交通数据是否可用:

public final boolean isTrafficEnabled() 

然后调用方法:

public final boolean isTrafficEnabled() {
   return mMap.isTrafficEnabled();

}
public final void setTrafficEnabled(boolean enabled) {
   mMap.setTrafficEnabled(enabled);
}

我不完全确定如何实现这一点，因为我完全是开发新手。我在另一个文档来源中找到了以下示例:

var map = new google.maps.Map(document.getElementById('map-canvas'), mapOptions);

var trafficLayer = new google.maps.TrafficLayer();
 trafficLayer.setMap(map);

}

google.maps.event.addDomListener(window, 'load', initialize);

但我似乎无法弄清楚如何正确地做到这一点。我是否必须以任何方式编辑 list XML，或者这一切都是从 mainActivity 完成的？这是我的完整 Activity 代码:

package example.testdevice;

import android.app.Dialog;
import android.support.v4.app.FragmentActivity;
import android.os.Bundle;
import android.view.Menu;
import android.view.MenuItem;
import android.widget.Toast;

import com.google.android.gms.common.ConnectionResult;
import com.google.android.gms.common.GooglePlayServicesUtil;
import com.google.android.gms.maps.GoogleMap;
import com.google.android.gms.maps.SupportMapFragment;


public class MainActivity extends FragmentActivity {

private static final int GPS_ERRORDIALOG_REQUEST = 9001;
GoogleMap mMap;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);

    if (servicesOK()) {                                                         //checks if APK is available; if it is, display Map
        setContentView(R.layout.activity_map);

        if (initMap()){
            Toast.makeText(this, "Ready to Map", Toast.LENGTH_SHORT).show();
        }
    else {
            Toast.makeText(this, "Map not available!", Toast.LENGTH_SHORT).show();
        }
    }
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
    // Inflate the menu; this adds items to the action bar if it is present.
    getMenuInflater().inflate(R.menu.menu_main, menu);
    return true;
}

public boolean servicesOK() {
    int isAvailable = GooglePlayServicesUtil.isGooglePlayServicesAvailable(this); //pass this as context

    if (isAvailable == ConnectionResult.SUCCESS) {
        return true;
    }
    else if (GooglePlayServicesUtil.isUserRecoverableError(isAvailable)) {
        Dialog dialog = GooglePlayServicesUtil.getErrorDialog(isAvailable, this, GPS_ERRORDIALOG_REQUEST); //error code, activity, request code
        dialog.show();
    }
    else {
        Toast.makeText(this, "Can't connect to Google Play Services", Toast.LENGTH_SHORT).show();
    }
    return false;
    }

@Override
public boolean onOptionsItemSelected(MenuItem item) {
    // Handle action bar item clicks here. The action bar will
    // automatically handle clicks on the Home/Up button, so long
    // as you specify a parent activity in AndroidManifest.xml.
    int id = item.getItemId();

    //noinspection SimplifiableIfStatement
    if (id == R.id.action_settings) {
        return true;
    }

    return super.onOptionsItemSelected(item);
}

private boolean initMap() {
    if (mMap == null) {
        SupportMapFragment mapFrag =
                (SupportMapFragment) getSupportFragmentManager().findFragmentById(R.id.map); // reference to support map fragment
        mMap = mapFrag.getMap();
    }
    return (mMap != null);
}

public final boolean isTrafficEnabled() {
    return mMap.isTrafficEnabled();

}
public final void setTrafficEnabled(boolean enabled) {
    mMap.setTrafficEnabled(enabled);
}

}

map 已加载，但未显示任何类型的交通。任何和所有的帮助将不胜感激；提前谢谢你。

Answer 1

为了能够显示流量数据，您应该考虑以下问题，

1. 确保在 Google map 中检测到您的当前位置

2. 确保您的 Google map 有您当前位置的路况数据。

您也可以尝试以下代码。它会正确初始化 map ，然后在检测到您的当前位置后设置交通数据。

  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();
                mMap.setMyLocationEnabled(true);
                // Check if we were successful in obtaining the map.
                if (mMap != null) {


                 mMap.setOnMyLocationChangeListener(new GoogleMap.OnMyLocationChangeListener() {

               @Override
               public void onMyLocationChange(Location arg0) {
                // TODO Auto-generated method stub

                 mMap.addMarker(new MarkerOptions().position(new LatLng(arg0.getLatitude(), arg0.getLongitude())).title("It's Me!"));

                 //load the traffic now
                  googleMap.setTrafficEnabled(true);
               }
              });

                }
            }
        }