据我所知，添加标记无法在 UI 线程之外完成。
您可以做的是在后台执行所有准备工作（创建标记、转换为位图等）。为了在添加标记时节省一点 UI 线程，您可以放大并使用 https://code.google.com/p/android-maps-extensions/ 仅显示可见标记或集群标记以降低数量，尽管 250 并不多。
这是关于该主题的 SO 答案：Add markers dynamically on Google Maps v2 for Android
我有一个应用程序，它有大约 4500 个标记，使用第一种方法运行得相当好（只要它没有快速缩小）。需要注意的是，这里我选择制作一个带有进度条的启动画面，在用户打开地图之前准备好所有的标记。
如果您想要一个简单的机制来选择周围标记而不使用第三部分库，您可以执行以下操作：Android Maps v2 - animate camera to include most markers
刚刚想到的一个想法，如果标记的创建真的那么昂贵，那么将 EventBus https://github.com/greenrobot/EventBus 添加到您的项目中。
使用 EventBus，您可以在 onEventAsync() 方法中对标记进行长时间运行准备。在该方法中，每当标记准备好时，将新标记发布到 UI EventBus.getDefault().post(marker) 并在 onEventMainThread(Marker marker) 中捕获它。在这里，您可以将标记保存在所有准备好的标记列表中，如果地图当前打开，请添加它。
以下是我在前面提到的应用程序中用于准备标记的一些代码。它用于在消防部门使用的应用程序中显示消火栓。在第一次启动时，所有的消火栓都是从一组 CSV 文件中读取的，并为所有约 4500 个消火栓创建了 MarkerOptions。毫无疑问，很多代码对你没有用，只是留下它以防万一你可以从中受益：
private List<HydrantHolder> mHydrants;
private Map<HydrantType, List<MarkerOptions>> mMarkers;
private class ReadHydrantsFiles extends
AsyncTask<Void, Integer, List<HydrantHolder>> {
File[] hydrantsFiles = new File[0];
// Before running code in separate thread
@Override protected void onPreExecute() {
loadStarted();
String filepath = paths.PATH_LOCAL_HYDRANTS;
File hydrantsPath = new File(filepath);
hydrantsFiles = hydrantsPath.listFiles(new FilenameFilter() {
@Override public boolean accept(File dir, String filename) {
return filename.toLowerCase(Locale.ENGLISH).contains(
Constants.FILETYPE_CSV);
}
});
int lineCount = 0;
if (hydrantsFiles == null || hydrantsFiles.length == 0) {
if (!preferences.isFirstStartUp()) {
// TODO notify user
}
Log.e(TAG, "Missing hydrants");
if (moduleCallback != null) {
moduleCallback.doneLoadingModule(toString());
}
this.cancel(false);
} else {
for (File file : hydrantsFiles) {
// store linecount for visual progress update
lineCount += Files.lineCount(file);
}
}
}
// The code to be executed in a background thread.
@Override protected List<HydrantHolder> doInBackground(Void... args) {
List<HydrantHolder> all_hydrants = new ArrayList<HydrantHolder>();
// Directory path here
int totalLineProgress = 0;
// // required
int indexLatitude = modulePreferences.indexLatitude();
int indexLongitude = modulePreferences.indexLongitude();
// optional
int indexAddress = modulePreferences.indexAddress();
int indexAddressNumber = modulePreferences.indexAddressNumber();
int indexAddressRemark = modulePreferences.indexAddressRemark();
int indexRemark = modulePreferences.indexRemark();
// decimals
int latitude_decimal = modulePreferences.latitude_decimal();
int longitude_decimal = modulePreferences.longitude_decimal();
if (indexLatitude <= 0 || indexLongitude <= 0)
return all_hydrants;
for (File file : hydrantsFiles) {
BufferedReader in = null;
try {
String hydrantspath = paths.PATH_LOCAL_HYDRANTS;
File hydrantsPath = new File(hydrantspath);
// Read File Line By Line
in = new BufferedReader(new InputStreamReader(
new FileInputStream(file), "windows-1252"));
String strLine;
while ((strLine = in.readLine()) != null) {
totalLineProgress++;
String[] hydrantParts = strLine.split(";", -1);
String errors = "";
final String hydrantType = file.getName().replace(
Constants.FILETYPE_CSV, "");
File[] iconFiles = hydrantsPath
.listFiles(new FilenameFilter() {
@Override public boolean accept(File dir,
String filename) {
if (filename.contains(hydrantType)
&& filename
.contains(Constants.FILETYPE_PNG)) {
return true;
}
return false;
}
});
HydrantHolder.Builder hb = new HydrantHolder.Builder();
if (hydrantParts.length >= 5) {
hb.setHydrantType(hydrantType);
if (iconFiles.length != 0) {
hb.setIconPath(hydrantspath
+ File.separatorChar
+ iconFiles[0].getName());
}
hb.setLatitude(hydrantParts[indexLatitude],
latitude_decimal);
hb.setLongitude(hydrantParts[indexLongitude],
longitude_decimal);
if (indexAddress > 0)
hb.setAddress(hydrantParts[indexAddress]);
if (indexAddressNumber > 0)
hb.setAddressNumber(hydrantParts[indexAddressNumber]);
if (indexAddressRemark > 0)
hb.setAddressRemark(hydrantParts[indexAddressRemark]);
if (indexRemark > 0)
hb.setRemark(hydrantParts[indexRemark]);
if (hb.getErrors().isEmpty()) {
HydrantHolder hydrant = hb.build();
all_hydrants.add(hydrant);
} else {
// TODO write error file to Dropbox if possible,
// otherwise locally
Log.d(TAG, errors);
}
} else {
errors = "Missing information";
}
publishProgress(totalLineProgress);
}
} catch (InvalidPathException e) {
Log.e(TAG, e.getMessage(), e);
} catch (IOException e) {
Log.e(TAG, e.getMessage(), e);
} finally {
if (in != null) {
try {
in.close();
} catch (IOException e) {
}
}
}
}
Log.d(TAG, "" + all_hydrants.size());
return all_hydrants;
}
// Update the progress
@Override protected void onProgressUpdate(Integer... values) {
// set the current progress of the progress dialog
// if (progressDialog != null && values != null && values.length >
// 0) {
// progressDialog.setProgress(values[0]);
// }
}
@Override protected void onPostExecute(List<HydrantHolder> hydrants) {
// Device.releaseOrientation((Activity) context);
Log.d(TAG, "Saved " + hydrants.size() + " hydrants");
mHydrants = hydrants;
new PrepareMarkerOptionsTask(hydrants).execute();
super.onPostExecute(hydrants);
}
}
private class PrepareMarkerOptionsTask extends
AsyncTask<Void, Integer, Map<HydrantType, List<MarkerOptions>>> {
// Before running code in separate thread
List<HydrantHolder> mHydrants;
public PrepareMarkerOptionsTask(List<HydrantHolder> hydrants) {
this.mHydrants = hydrants;
mMarkers = new HashMap<HydrantsModule.HydrantType, List<MarkerOptions>>();
}
@Override protected void onPreExecute() {
}
// The code to be executed in a background thread.
@Override protected Map<HydrantType, List<MarkerOptions>> doInBackground(
Void... arg) {
for (HydrantHolder hydrant : mHydrants) {
final String hydrant_type = hydrant.getHydrantType();
final String hydrant_icon_path = hydrant.getIconPath();
double latitude = hydrant.getLatitude();
double longitude = hydrant.getLongitude();
final LatLng position = new LatLng(latitude, longitude);
final String address = hydrant.getAddress();
final String addressNumber = hydrant.getAddressNumber();
final String addressremark = hydrant.getAddressRemark();
final String remark = hydrant.getRemark();
// Log.d(TAG, hydrant.toString());
BitmapDescriptor icon = BitmapDescriptorFactory
.defaultMarker(BitmapDescriptorFactory.HUE_RED);
if (!hydrant_icon_path.isEmpty()) {
File iconfile = new File(hydrant_icon_path);
if (iconfile.exists()) {
BitmapDescriptor loaded_icon = BitmapDescriptorFactory
.fromPath(hydrant_icon_path);
if (loaded_icon != null) {
icon = loaded_icon;
} else {
Log.e(TAG, "loaded_icon was null");
}
} else {
Log.e(TAG, "iconfile did not exist: "
+ hydrant_icon_path);
}
} else {
Log.e(TAG, "iconpath was empty on hydrant type: "
+ hydrant_type);
}
StringBuffer snippet = new StringBuffer();
if (!address.isEmpty())
snippet.append("\n" + address + " " + addressNumber);
if (addressremark.isEmpty())
snippet.append("\n" + addressremark);
if (!remark.isEmpty())
snippet.append("\n" + remark);
addHydrantMarker(
hydrant_type,
new MarkerOptions().position(position)
.title(hydrant_type)
.snippet(snippet.toString()).icon(icon));
// publishProgress(markers.size());
}
return mMarkers;
}
// Update the progress
@Override protected void onProgressUpdate(Integer... values) {
}
@Override protected void onCancelled() {
}
// after executing the code in the thread
@Override protected void onPostExecute(
Map<HydrantType, List<MarkerOptions>> markers) {
Log.d(TAG, "Prepared " + markers.size() + " hydrantMarkerOptions");
mMarkers = markers;
loadEnded();
super.onPostExecute(markers);
}
}
public Set<HydrantType> getHydrantTypes() {
return new HashSet<HydrantType>(mMarkers.keySet());
}
private void addHydrantMarker(String typeName, MarkerOptions marker) {
HydrantType type = new HydrantType(typeName, marker.getIcon());
if (mMarkers.containsKey(type)) {
List<MarkerOptions> markers = mMarkers.get(type);
markers.add(marker);
} else {
List<MarkerOptions> markers = new ArrayList<MarkerOptions>();
markers.add(marker);
mMarkers.put(type, markers);
enableHydrantType(type);
}
}
public class HydrantType {
private final String name;
private final BitmapDescriptor icon;
public HydrantType(String name, BitmapDescriptor icon) {
this.name = name;
this.icon = icon;
}
public String getName() {
return name;
}
public BitmapDescriptor getIcon() {
return icon;
}
@Override public int hashCode() {
return name.hashCode();
}
@Override public boolean equals(Object o) {
if (o instanceof HydrantType) {
if (((HydrantType) o).name.equals(name)) {
return true;
}
}
return false;
}
}
基于 cmets，我添加了更多文本和代码。
是的，我一次添加了所有 MarkerOptions。不过，因为我在添加所有标记之前放大 GoogleMaps-extensions （第一个链接）只花费 CPU 功率将可见标记添加到地图中。如果用户平移或缩小地图，则会自动添加更多可见标记。
要使地图延迟加载标记：
@Override
public void onMapReady(GoogleMap map) {
Log.i(TAG, "onMapReady");
if (map != null) {
map.setClustering(new ClusteringSettings().enabled(false)
.addMarkersDynamically(true));
}
}
还有我用来添加消火栓的代码（现在在很多情况下都过于复杂，但如果你仔细阅读，它只是简单地缩放到一个地址，并且只有在缩放完成后才添加所有的消火栓）：
public void addHydrantsNearAddress(final AddressHolder addressHolder,
final boolean zoomToAddress) {
final GoogleMap map = googlemaps.getMap();
final OnCameraChangeListener addHydrantsAfterZoom = new OnCameraChangeListener() {
@Override public void onCameraChange(CameraPosition cameraPosition) {
Log.d(TAG, cameraPosition.target.toString());
Log.d(TAG, addressHolder.position.toString());
final GoogleMap map = googlemaps.getMap();
// if (Location.distanceBetween(cameraPosition.tar,
// startLongitude, endLatitude, endLongitude, results)) {
new Handler().postDelayed(new Runnable() {
@Override public void run() {
addAllHydrants();
}
}, 500);
map.setOnCameraChangeListener(null); // unregister
// }
}
};
if (map == null) {
// wait for the map to be ready before adding hydrants
googlemaps.setGoogleMapsCallback(new GoogleMapsCallback() {
@Override public void mapReady(GoogleMap map) {
if (zoomToAddress) {
map.setOnCameraChangeListener(addHydrantsAfterZoom);
googlemaps.zoomTo(addressHolder);
} else {
addAllHydrants();
}
googlemaps.setGoogleMapsCallback(null); // unregister
}
});
} else {
if (zoomToAddress) {
// only setOnCameraChangeListener if cammera needs to move
LatLng cammeraPos = map.getCameraPosition().target;
LatLng addressPos = addressHolder.position;
float[] results = new float[1];
Location.distanceBetween(cammeraPos.latitude,
cammeraPos.longitude, addressPos.latitude,
addressPos.longitude, results);
// Log.d(TAG, "distance " + results[0]);
if (results[0] > 1) {
map.setOnCameraChangeListener(addHydrantsAfterZoom);
googlemaps.zoomTo(addressHolder);
} else {
googlemaps.zoomTo(addressHolder);
addAllHydrants();
}
}
}
}
另一个比示例更复杂的原因是我让用户在消火栓类型之间进行过滤。尽管如此，希望你能看到这个想法。
addAllHydrants() 听起来很简单，迭代 MarkerOptions 并添加它们：
public void addAllHydrants() {
enableAllHydrants();
GoogleMap map = googlemaps.getMap();
map.setTrafficEnabled(modulePreferences.showTraffic());
map.setMapType(modulePreferences.getMapType());
addHydrants(map);
}
private void addHydrants(GoogleMap map) {
Log.d(TAG, "addHydrants");
if (mHydrants == null || mHydrants.isEmpty()) {
Toast.makeText(context,
context.getString(R.string.missing_hydrants),
Toast.LENGTH_LONG).show();
return;
} else {
for (MarkerOptions marker : getEnabledHydrantMarkers()) {
map.addMarker(marker);
}
}
}
我真的认为，如果您自己尝试计算、获取和添加可见标记，而不是仅仅如此，那么您将过于复杂化。
- 准备 MarkerOptions（第一个代码块中的示例）
- 使用 onMapReady 回调等待地图准备就绪（此示例在 Google 的官方示例中）
- 在新创建的地图上设置 addMarkersDynamically(true)
- 放大感兴趣的地址或区域（例如设备位置）
- 添加所有 MarkerOptions
- 查看在您在地图上移动时自动添加的标记
回答关于onMapReady回调的问题
如果您使用 XML 添加地图，那么我怀疑您可能不需要添加回调。尝试直接在您的活动的onCreate() 中使用地图。只要对getExtendedMap() 的调用不为空，就可以了。
我正在代码中创建片段，以便能够将控制器代码与地图放在一起。因此，我的 SupportMapFragment 看起来像这样：
public class GoogleMapFragment extends SupportMapFragment {
private OnGoogleMapFragmentListener mCallback;
public GoogleMapFragment() {
mCallback = null;
}
public static interface OnGoogleMapFragmentListener {
void onMapReady(GoogleMap map);
}
@Override public void onAttach(Activity activity) {
super.onAttach(activity);
try {
mCallback = (OnGoogleMapFragmentListener) activity;
} catch (ClassCastException e) {
throw new ClassCastException(getActivity().getClass().getName()
+ " must implement OnGoogleMapFragmentListener");
}
}
@Override public View onCreateView(LayoutInflater inflater,
ViewGroup container, Bundle savedInstanceState) {
View view = super.onCreateView(inflater, container, savedInstanceState);
if (mCallback != null) {
mCallback.onMapReady(getExtendedMap());
}
return view;
}
}