Android设置GoolgeMap从点数据库边界

Question

使用谷歌地图Android API v2,我试图使用LatLngBounds.Builder()数据库中的点设置地图的边界.我认为我很接近,但活动正在崩溃,因为我认为我没有正确加载积分.我可能只是几行之遥.

//setup map
private void setUpMap() {

    //get all cars from the datbase with getter method
    List<Car> K = db.getAllCars();

    //loop through cars in the database
    for (Car cn : K) {

        //add a map marker for each car, with description as the title using getter methods
        mapView.addMarker(new MarkerOptions().position(new LatLng(cn.getLatitude(), cn.getLongitude())).title(cn.getDescription()));

        //use .include to put add each point to be included in the bounds   
        bounds = new LatLngBounds.Builder().include(new LatLng(cn.getLatitude(), cn.getLongitude())).build();

       //set bounds with all the map points
       mapView.moveCamera(CameraUpdateFactory.newLatLngBounds(bounds, 50));
    }
}

我认为在安排for循环以获取所有汽车时可能会出现错误,如果我删除了边界语句,地图点正确地按照我的预期绘制,但没有正确地限制地图.

Answer 1

你每次都在循环中创建一个新的LatLngBounds.Builder().试试这个

private LatLngBounds.Builder bounds;
//setup map
private void setUpMap() {

    bounds = new LatLngBounds.Builder();   
    //get all cars from the datbase with getter method
    List<Car> K = db.getAllCars();

    //loop through cars in the database
    for (Car cn : K) {

        //add a map marker for each car, with description as the title using getter methods
        mapView.addMarker(new MarkerOptions().position(new LatLng(cn.getLatitude(), cn.getLongitude())).title(cn.getDescription()));

        //use .include to put add each point to be included in the bounds   
        bounds.include(new LatLng(cn.getLatitude(), cn.getLongitude()));


    }
    //set bounds with all the map points
    mapView.moveCamera(CameraUpdateFactory.newLatLngBounds(bounds.build(), 50));
}