android - 当我在圆半径内时做点什么

Question

我正在使用 Google Maps API。

我想要的是当我移动到某个特定位置并且我已经在 map 上绘制了一个圆圈时，它会转到另一个 Activity。

所以它就像:

1. 我的位置是 a = (X,Y)

2. 圆的位置是b = (X,Y) radius = 10

3. 当我在 b 半径内时，它将转到另一个 Activity 或做某事。

有什么想法吗？

我已经在使用 distanceTo()，但仍然没有成功。

编辑:这是更新后的代码，但仍然不适合我:

public void onLocationChanged(Location location)
{
float [] distance = new float[];
Location.distanceBetween(location.getLatitude(),location.getLongitude(),-6.xxxxxxx,106.xxxxxxx,distance);

if (distance[0] < 50)
   {
   Intent i = new Intent(student_activity.this,indoor.class);
   student_activity.this,startActivity(i);
   }
}

此方法 setUpMapIfNeeded() 在 onCreate 方法中调用:

public void circle()
{
Circle circle = mMap.addCircle (new CircleOptions()
.center(new LatLng(-6.xxxxxxx,106.xxxxxxx))
.radius(50)
.strokeColor(Color.RED)
.strokeWidth(1)
.fillColor(Color.RED)
}

Answer 1

您可以使用地理围栏，但如果您只是想确定您的当前位置是否在 map 上绘制的圆圈内，则可以使用此技术。

简单比较当前位置到圆心的距离，判断距离是否小于半径。

我回答过类似的问题here ，您可以在其中查看更多信息和屏幕截图示例。

请注意，下面的代码使用了 depricated onMyLocationChangeListener ，但您可以使用任何类型的位置回调来执行此操作，包括 FusedLocationProviderApi。

googleMap.setOnMyLocationChangeListener(new GoogleMap.OnMyLocationChangeListener() {
            @Override
            public void onMyLocationChange(Location location) {
                float[] distance = new float[2];

                Location.distanceBetween( location.getLatitude(), location.getLongitude(),
                        mCircle.getCenter().latitude, mCircle.getCenter().longitude, distance);

                if( distance[0] < mCircle.getRadius() ){
                    //current location is within circle
                    //start new activity
                    Intent i = new Intent(ThisActivity.this, OtherActivity.class);
                    ThisActivity.this.startActivity(i);
                }

            }
        });

编辑:这是一个完全可用且经过测试的类，它使用 FusedLocationApi 获取当前位置:

import android.content.Intent;
import android.graphics.Color;
import android.location.Location;
import android.os.Bundle;
import android.support.v7.app.ActionBarActivity;
import android.util.Log;
import android.widget.Toast;

import com.google.android.gms.common.ConnectionResult;
import com.google.android.gms.common.api.GoogleApiClient;
import com.google.android.gms.location.LocationListener;
import com.google.android.gms.location.LocationRequest;
import com.google.android.gms.location.LocationServices;
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.Circle;
import com.google.android.gms.maps.model.CircleOptions;
import com.google.android.gms.maps.model.LatLng;
import com.google.android.gms.maps.model.LatLngBounds;
import com.google.android.gms.maps.model.MarkerOptions;

public class MapsActivity extends ActionBarActivity implements
        GoogleApiClient.ConnectionCallbacks, GoogleApiClient.OnConnectionFailedListener, LocationListener {

    private GoogleMap mMap;
    LocationRequest mLocationRequest;
    GoogleApiClient mGoogleApiClient;
    Circle mCircle;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_maps);
        setUpMapIfNeeded();

        buildGoogleApiClient();
        mGoogleApiClient.connect();
    }

    @Override
    protected void onResume() {
        super.onResume();
        setUpMapIfNeeded();
    }

    @Override
    protected void onPause(){
        super.onPause();
        if (mGoogleApiClient != null) {
            LocationServices.FusedLocationApi.removeLocationUpdates(mGoogleApiClient, this);
        }
    }


    protected synchronized void buildGoogleApiClient() {
        Toast.makeText(this,"buildGoogleApiClient",Toast.LENGTH_SHORT).show();
        mGoogleApiClient = new GoogleApiClient.Builder(this)
                .addConnectionCallbacks(this)
                .addOnConnectionFailedListener(this)
                .addApi(LocationServices.API)
                .build();
    }

    @Override
    public void onConnected(Bundle bundle) {
        Toast.makeText(this,"onConnected", Toast.LENGTH_SHORT).show();

        mLocationRequest = new LocationRequest();
        mLocationRequest.setInterval(10);
        mLocationRequest.setFastestInterval(10);
        mLocationRequest.setPriority(LocationRequest.PRIORITY_BALANCED_POWER_ACCURACY);
        mLocationRequest.setSmallestDisplacement(0.1F);

        LocationServices.FusedLocationApi.requestLocationUpdates(mGoogleApiClient, mLocationRequest, this);
    }


    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();
            }
        }
    }

    private void setUpMap() {
        mMap.getUiSettings().setMapToolbarEnabled(true);
        mMap.getUiSettings().setZoomControlsEnabled(true);
        mMap.setMyLocationEnabled(true);

        circle();

    }

    public void circle()
    {
        double radiusInMeters = 50.0;
        int strokeColor = 0xffff0000; //red outline
        int shadeColor = 0x44ff0000; //opaque red fill

        mCircle = mMap.addCircle (new CircleOptions()
                .center(new LatLng(37.9614, -122.105))
                .radius(radiusInMeters)
                .fillColor(shadeColor)
                .strokeColor(strokeColor)
                .strokeWidth(1));
    }

    @Override
    public void onConnectionSuspended(int i) {
        Toast.makeText(this,"onConnectionSuspended",Toast.LENGTH_SHORT).show();
    }

    @Override
    public void onConnectionFailed(ConnectionResult connectionResult) {
        Toast.makeText(this,"onConnectionFailed",Toast.LENGTH_SHORT).show();
    }

    @Override
    public void onLocationChanged(Location location) {

        Log.d("locationtesting",  "lat: " + location.getLatitude() + " lon: " + location.getLongitude());

        Toast.makeText(this,"Location Changed",Toast.LENGTH_SHORT).show();

        float[] distance = new float[2];

        Location.distanceBetween( location.getLatitude(), location.getLongitude(),
                mCircle.getCenter().latitude, mCircle.getCenter().longitude, distance);

        if( distance[0] < mCircle.getRadius() ){
            //current location is within circle
            //start new activity
            Intent i = new Intent(this, OtherActivity.class);
            startActivity(i);
        }
    }
}

布局 xml:

<fragment 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:id="@+id/map" tools:context=".MapsActivity"
    android:name="com.google.android.gms.maps.SupportMapFragment" />

build.gradle 中的依赖:

dependencies {
    compile fileTree(dir: 'libs', include: ['*.jar'])
    compile 'com.android.support:appcompat-v7:22.1.1'
    compile 'com.google.android.gms:play-services:7.0.0'
}

首先，我在没有调用 startActivity() 的情况下进行了测试，只是为了确保我的当前位置在圆圈内。正如您在屏幕截图中所见，它是:

然后，我在 onLocationChanged() 回调中添加了对 startActivity() 的调用，它在启动应用程序后立即启动了 OtherActivity .