添加边界以避免在特定区域外滑动

Question

我的应用程序显示了一张地图,我希望用户无法滑过某个区域.所以我试图添加边界,但它会使应用程序崩溃.这是工作代码:

public class MapViewer extends Activity implements OnInfoWindowClickListener {
    private LatLng defaultLatLng = new LatLng(42.564241, 12.22759);
    private GoogleMap map;
    private int zoomLevel = 5;
    private Database db = new Database(this);

    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.mapviewer);

        try {
            map = ((MapFragment) getFragmentManager().findFragmentById(R.id.map)).getMap();
            if (map != null) {
                map.setMyLocationEnabled(true);
                map.setMapType(GoogleMap.MAP_TYPE_NORMAL);
                map.getUiSettings().setRotateGesturesEnabled(false);

                map.moveCamera(CameraUpdateFactory.newLatLngZoom(defaultLatLng, zoomLevel));

                this.addMerchantMarkers(new MarkerOptions());

                map.setOnInfoWindowClickListener(this);
            }
        } catch (NullPointerException e) {
            e.printStackTrace();
        }
    }

    @Override
    public void onPause() {
        if (map != null) {
            map.setMyLocationEnabled(false);
            map.setTrafficEnabled(false);
        }
        super.onPause();
    }

    public void addMerchantMarkers(MarkerOptions mo) {
        SQLiteDatabase dbRead = db.getReadableDatabase();
        String[] columns = {"title", "addr", "lat", "lon"};
        Cursor result = dbRead.query("merchants", columns, null, null, null, null, null);

        while(result.moveToNext()) {
            String merchant = result.getString(0);
            String address = result.getString(1);
            float lat = result.getFloat(2);
            float lon = result.getFloat(3);

            LatLng pos = new LatLng(lat, lon);

            map.addMarker(mo.position(pos)
                    .title(merchant)
                    .snippet(address)
                    .icon(BitmapDescriptorFactory.fromResource(R.drawable.marker_50)));;
        }
    }
}

这是我在onCreate方法中添加的导致崩溃的代码:

    LatLngBounds.Builder builder = new LatLngBounds.Builder();
    builder.include(new LatLng(47.09194444, 18.52166666));
    builder.include(new LatLng(36.448311, 6.62555555));
    LatLngBounds bounds = builder.build();

    CameraUpdate cu = CameraUpdateFactory.newLatLngBounds(bounds, 30);

    map.animateCamera(cu);

这是LogCat:

08-10 20:59:41.689: E/AndroidRuntime(6304): FATAL EXCEPTION: main
08-10 20:59:41.689: E/AndroidRuntime(6304): Process: com.example.myapp, PID: 6304
08-10 20:59:41.689: E/AndroidRuntime(6304): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.myapp/com.example.myapp.MapViewer}: java.lang.IllegalStateException: Error using newLatLngBounds(LatLngBounds, int): Map size can't be 0. Most likely, layout has not yet occured for the map view.  Either wait until layout has occurred or use newLatLngBounds(LatLngBounds, int, int, int) which allows you to specify the map's dimensions.
08-10 20:59:41.689: E/AndroidRuntime(6304):     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2215)
08-10 20:59:41.689: E/AndroidRuntime(6304):     at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2264)
08-10 20:59:41.689: E/AndroidRuntime(6304):     at android.app.ActivityThread.access$800(ActivityThread.java:144)
08-10 20:59:41.689: E/AndroidRuntime(6304):     at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1205)
08-10 20:59:41.689: E/AndroidRuntime(6304):     at android.os.Handler.dispatchMessage(Handler.java:102)
08-10 20:59:41.689: E/AndroidRuntime(6304):     at android.os.Looper.loop(Looper.java:136)
08-10 20:59:41.689: E/AndroidRuntime(6304):     at android.app.ActivityThread.main(ActivityThread.java:5139)
08-10 20:59:41.689: E/AndroidRuntime(6304):     at java.lang.reflect.Method.invokeNative(Native Method)
08-10 20:59:41.689: E/AndroidRuntime(6304):     at java.lang.reflect.Method.invoke(Method.java:515)
08-10 20:59:41.689: E/AndroidRuntime(6304):     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:796)
08-10 20:59:41.689: E/AndroidRuntime(6304):     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:612)
08-10 20:59:41.689: E/AndroidRuntime(6304):     at dalvik.system.NativeStart.main(Native Method)
08-10 20:59:41.689: E/AndroidRuntime(6304): Caused by: java.lang.IllegalStateException: Error using newLatLngBounds(LatLngBounds, int): Map size can't be 0. Most likely, layout has not yet occured for the map view.  Either wait until layout has occurred or use newLatLngBounds(LatLngBounds, int, int, int) which allows you to specify the map's dimensions.
08-10 20:59:41.689: E/AndroidRuntime(6304):     at mut.b(Unknown Source)
08-10 20:59:41.689: E/AndroidRuntime(6304):     at oxp.a(Unknown Source)
08-10 20:59:41.689: E/AndroidRuntime(6304):     at oxi.a(Unknown Source)
08-10 20:59:41.689: E/AndroidRuntime(6304):     at oyf.b(Unknown Source)
08-10 20:59:41.689: E/AndroidRuntime(6304):     at grl.onTransact(SourceFile:92)
08-10 20:59:41.689: E/AndroidRuntime(6304):     at android.os.Binder.transact(Binder.java:361)
08-10 20:59:41.689: E/AndroidRuntime(6304):     at com.google.android.gms.maps.internal.IGoogleMapDelegate$a$a.animateCamera(Unknown Source)
08-10 20:59:41.689: E/AndroidRuntime(6304):     at com.google.android.gms.maps.GoogleMap.animateCamera(Unknown Source)
08-10 20:59:41.689: E/AndroidRuntime(6304):     at com.example.myapp.MapViewer.onCreate(MapViewer.java:59)
08-10 20:59:41.689: E/AndroidRuntime(6304):     at android.app.Activity.performCreate(Activity.java:5231)
08-10 20:59:41.689: E/AndroidRuntime(6304):     at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1087)
08-10 20:59:41.689: E/AndroidRuntime(6304):     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2169)
08-10 20:59:41.689: E/AndroidRuntime(6304):     ... 11 more

Answer 1

你可以使用MapLoadedCallBack;

map.setOnMapLoadedCallback(new GoogleMap.OnMapLoadedCallback() {
  @Override
  public void onMapLoaded() {
      map.moveCamera(CameraUpdateFactory.newLatLngBounds(bounds, 30));
  }
});

而且你也可以使用这个事件发生在上面.

  map.setOnCameraChangeListener(new GoogleMap.OnCameraChangeListener() {
        @Override
        public void onCameraChange(CameraPosition arg0) {
        map.moveCamera(CameraUpdateFactory.newLatLngBounds(bounds, 30));
  }
});

Answer 2

您可以通过遵循日志中的建议来防止错误发生:

"...使用newLatLngBounds(LatLngBounds,int,int,int),它允许您指定地图的尺寸​​."

额外的参数是屏幕的宽度和高度.以下是更新代码的外观:

LatLngBounds.Builder builder = new LatLngBounds.Builder();
builder.include(new LatLng(47.09194444, 18.52166666));
builder.include(new LatLng(36.448311, 6.62555555));
LatLngBounds bounds = builder.build();

// begin new code:
int width = getResources().getDisplayMetrics().widthPixels;
int height = getResources().getDisplayMetrics().heightPixels;
int padding = (int) (width * 0.12); // offset from edges of the map 12% of screen

CameraUpdate cu = CameraUpdateFactory.newLatLngBounds(bounds, width, height, padding);
// end of new code

map.animateCamera(cu);

Answer 3

onMapReady()的文档明确指出你必须等待onMapReadyCallback和ViewTreeObserver.OnGlobalLayoutListener:

请注意,这并不能保证地图已经过布局.因此,可能尚未通过调用回调方法确定映射的大小.如果您需要知道维度或在API中调用需要知道维度的方法,请获取地图的视图并注册ViewTreeObserver.OnGlobalLayoutListener.

这是非常不方便的,但一种方法是使用RxJava.您可以发出两个observable,第一个在onMapReady中,第二个在onGlobalLayout中,然后将它们压缩在一起并执行您需要做的任何操作.这样你可以确定两个回调都被触发了.

Answer 4

Caused by: java.lang.IllegalStateException: Map size should not be 0. Most likely, layout has not yet occured for the map view.

这个错误背后的原因是因为地图布局还没有完成，你应该在你的调用中实现 OnMapReadyCallback ，这将确保你的代码只有在你的布局完成后才会运行或者实现下面的回调

map.setOnCameraChangeListener(new GoogleMap.OnCameraChangeListener() {
    @Override
    public void onCameraChange(CameraPosition arg0) {
    map.moveCamera(CameraUpdateFactory.newLatLngBounds(bounds, 30));
}
});

重复链接

带有 CameraUpdateFactory.newLatLngBounds 的 moveCamera 崩溃

IllegalStateException 地图大小不应为 0

如果有办法合并此链接，我不知道。我希望我有所帮助