在旋转和返回时恢复 MapView 的状态 [英] Restoring MapView's state on rotate and on back
问题描述
背景
我有一个更大的应用程序，其中新的 Google Maps API 遇到/遇到了几个问题.我试图在另一个问题中描述它由于看起来太复杂，我决定开始一个新项目，尽可能简单并尝试重现问题.所以就是这里了.
I have a larger application in which I had/have several problems with new Google Maps API. I tried to describe it in a different question but since it seems too complex I decided to start a new project, as simple as possible and try to reproduce problems. So here it is.
情况
我正在使用 Fragments 并且想把 MapView 放在里面.我不想使用 MapFragment.我准备的示例项目可能不是很漂亮，但我试图让它尽可能简单，并且它必须包含来自原始应用程序的一些元素(再次简化).我有一个 Activity 和我的自定义 Fragment，其中包含 MapView，以编程方式添加.Map 包含一些点/Markers.单击 Marker 后，将显示 InfoWindow，单击它会显示下一个 Fragment(使用 replace()> 功能)的内容.
I'm using Fragments and want to put MapView inside. I don't want to use MapFragment. The sample project I prepared may be not very beautiful but I tried to make it as simple as possible and it had to contain some elements (again simplified) from the original app.
I have one Activity and my custom Fragment with MapView in it, added programatically. The Map contains some points/Markers. After clicking on a Marker the InfoWindow is shown and clicking on it causes next Fragment being shown (with replace() function) in content.
问题
我有两个问题:
当显示带有
Markers的Map时，屏幕旋转会导致Class not found when unmarshalling错误与我的自定义MyMapPointclass - 我不知道为什么和它意味着什么.
When the
MapwithMarkersis displayed screen rotation causesClass not found when unmarshallingerror with my customMyMapPointclass - I have no idea why and what it means.
我点击Marker，然后点击InfoWindow.在此之后，我按下硬件后退按钮.现在我可以看到 Map 但没有 Markers 并且以 0,0 点为中心.
I click the Marker and then InfoWindow. After this I press hardware back button. Now I can see the Map but with no Markers and centered in 0,0 point.
代码
主活动
public class MainActivity extends FragmentActivity {
private ArrayList<MyMapPoint> mPoints = new ArrayList<MyMapPoint>();
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
if (savedInstanceState == null) {
mPoints.add(new MyMapPoint(1, new LatLng(20, 10),
"test point", "description", null));
mPoints.add(new MyMapPoint(2, new LatLng(10, 20),
"test point 2", "second description", null));
Fragment fragment = MyMapFragment.newInstance(mPoints);
getSupportFragmentManager().beginTransaction()
.add(R.id.contentPane, fragment).commit();
}
}
}
activity_main.xml
activity_main.xml
<?xml version="1.0" encoding="utf-8"?>
<FrameLayout
xmlns:android="http://schemas.android.com/apk/res/android"
android:id="@+id/contentPane"
android:layout_width="fill_parent"
android:layout_height="fill_parent" />
map_fragment.xml
map_fragment.xml
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout
xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical" >
<com.google.android.gms.maps.MapView
xmlns:map="http://schemas.android.com/apk/res-auto"
android:id="@+id/map"
android:layout_width="match_parent"
android:layout_height="match_parent" />
</LinearLayout>
MyMapFragment
MyMapFragment
public class MyMapFragment extends Fragment implements
OnInfoWindowClickListener {
public static final String KEY_POINTS = "points";
private MapView mMapView;
private GoogleMap mMap;
private HashMap<MyMapPoint, Marker> mPoints =
new HashMap<MyMapPoint, Marker>();
public static MyMapFragment newInstance(ArrayList<MyMapPoint> points) {
MyMapFragment fragment = new MyMapFragment();
Bundle args = new Bundle();
args.putParcelableArrayList(KEY_POINTS, points);
fragment.setArguments(args);
return fragment;
}
@Override
public void onSaveInstanceState(Bundle outState) {
super.onSaveInstanceState(outState);
mMapView.onSaveInstanceState(outState);
MyMapPoint[] points = mPoints.keySet().toArray(
new MyMapPoint[mPoints.size()]);
outState.putParcelableArray(KEY_POINTS, points);
}
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
if (savedInstanceState == null) {
Bundle extras = getArguments();
if ((extras != null) && extras.containsKey(KEY_POINTS)) {
for (Parcelable pointP : extras.getParcelableArrayList(KEY_POINTS)) {
mPoints.put((MyMapPoint) pointP, null);
}
}
} else {
MyMapPoint[] points = (MyMapPoint[]) savedInstanceState
.getParcelableArray(KEY_POINTS);
for (MyMapPoint point : points) {
mPoints.put(point, null);
}
}
}
@Override
public View onCreateView(LayoutInflater inflater,
ViewGroup container, Bundle savedInstanceState) {
View layout = inflater.inflate(R.layout.map_fragment, container, false);
mMapView = (MapView) layout.findViewById(R.id.map);
return layout;
}
@Override
public void onActivityCreated(Bundle savedInstanceState) {
super.onActivityCreated(savedInstanceState);
mMapView.onCreate(savedInstanceState);
setUpMapIfNeeded();
addMapPoints();
}
@Override
public void onPause() {
mMapView.onPause();
super.onPause();
}
@Override
public void onResume() {
super.onResume();
setUpMapIfNeeded();
mMapView.onResume();
}
@Override
public void onDestroy() {
mMapView.onDestroy();
super.onDestroy();
}
public void onLowMemory() {
super.onLowMemory();
mMapView.onLowMemory();
};
private void setUpMapIfNeeded() {
if (mMap == null) {
mMap = ((MapView) getView().findViewById(R.id.map)).getMap();
if (mMap != null) {
setUpMap();
}
}
}
private void setUpMap() {
mMap.setOnInfoWindowClickListener(this);
addMapPoints();
}
private void addMapPoints() {
if (mMap != null) {
HashMap<MyMapPoint, Marker> toAdd =
new HashMap<MyMapPoint, Marker>();
for (Entry<MyMapPoint, Marker> entry : mPoints.entrySet()) {
Marker marker = entry.getValue();
if (marker == null) {
MyMapPoint point = entry.getKey();
marker = mMap.addMarker(point.getMarkerOptions());
toAdd.put(point, marker);
}
}
mPoints.putAll(toAdd);
}
}
@Override
public void onInfoWindowClick(Marker marker) {
Fragment fragment = DetailsFragment.newInstance();
getActivity().getSupportFragmentManager().beginTransaction()
.replace(R.id.contentPane, fragment)
.addToBackStack(null).commit();
}
public static class MyMapPoint implements Parcelable {
private static final int CONTENTS_DESCR = 1;
public int objectId;
public LatLng latLng;
public String title;
public String snippet;
public MyMapPoint(int oId, LatLng point,
String infoTitle, String infoSnippet, String infoImageUrl) {
objectId = oId;
latLng = point;
title = infoTitle;
snippet = infoSnippet;
}
public MyMapPoint(Parcel in) {
objectId = in.readInt();
latLng = in.readParcelable(LatLng.class.getClassLoader());
title = in.readString();
snippet = in.readString();
}
public MarkerOptions getMarkerOptions() {
return new MarkerOptions().position(latLng)
.title(title).snippet(snippet);
}
@Override
public int describeContents() {
return CONTENTS_DESCR;
}
@Override
public void writeToParcel(Parcel dest, int flags) {
dest.writeInt(objectId);
dest.writeParcelable(latLng, 0);
dest.writeString(title);
dest.writeString(snippet);
}
public static final Parcelable.Creator<MyMapPoint> CREATOR =
new Parcelable.Creator<MyMapPoint>() {
public MyMapPoint createFromParcel(Parcel in) {
return new MyMapPoint(in);
}
public MyMapPoint[] newArray(int size) {
return new MyMapPoint[size];
}
};
}
}
如果您需要查看任何其他文件 - 请告诉我.这里你可以找到一个完整的项目，你只需要把自己的Maps API KEY放在<代码>AndroidManifest.xml 文件.
If you need to take a look at any other file - let me know. Here you can find a complete project, you just have to put your own Maps API KEY in AndroidManifest.xml file.
编辑
我设法使示例更加简单并更新了上面的代码.
I managed to make the example even more simple and updated the code above.
推荐答案
这是我对第一个问题的修复:
Here is my fix to the first problem:
当我调用 mMap.onCreate(savedInstanceState) 时，似乎 Map 试图解包所有的包，而不仅仅是它自己的信息，如果它有问题我正在使用我的自定义 Parcelable 类.对我有用的解决方案是在我使用它们后立即从 savedInstanceState 中删除它们 - 在我调用 Map 的 onCreate() 之前.我用 savedInstanceState.remove(MY_KEY) 来做.我必须做的另一件事是在将我自己的信息添加到 Fragment's onSaveInstanceState(BundleoutState) 函数.
It seems that Map is trying to unparcel all the bundle, not just it's own information when I call mMap.onCreate(savedInstanceState) and it has problem with it if I'm using my custom Parcelable class. The solution that worked for me was removing my extras from savedInstanceState as soon as I used them - before I call Map's onCreate(). I do it with savedInstanceState.remove(MY_KEY). Another thing I had to do was to call mMap.onSaveInstanceState() before adding my own information to outState in Fragment's onSaveInstanceState(Bundle outState) function.
这是我处理第二个的方式:
And here's how I handled the second one:
我将示例项目简化为简单的骨架.我正在向地图添加原始 Markers，如果我将 Fragment 替换为另一个地图，然后单击返回"后，我仍然得到空"地图.所以我做了两件事:
I simplified the example project to the bare bones. I was adding raw Markers to the map and if I replace the Fragment with map with another one then after clicking "back" I still got "nulled" map.
So I did two things:
- 在
onPause()函数中保存CameraPosition以在onResume()中恢复它 - 在
onPause()中将mMap设置为 null，以便当Fragment返回时，添加Markers再次通过addMapPoints()函数(因为我正在保存和检查Markersid，所以我不得不稍微改变它).
- saving
CameraPositioninonPause()function to restore it inonResume() - setting
mMapto null inonPause()so when theFragmentcomes back, theMarkersare added again by theaddMapPoints()function (I had to change it a little bit since I was saving and checkingMarkersid's).
以下是代码示例:
private CameraPosition cp;
...
public void onPause() {
mMapView.onPause();
super.onPause();
cp = mMap.getCameraPosition();
mMap = null;
}
...
public void onResume() {
super.onResume();
setUpMapIfNeeded();
mMapView.onResume();
if (cp != null) {
mMap.moveCamera(CameraUpdateFactory.newCameraPosition(cp));
cp = null;
}
}
为了在 onResume() 中更新相机位置，我不得不手动初始化地图.我在 setUpMap() 中做到了:
And to update the camera position in onResume() I had to manually initialize maps. I did it in setUpMap():
private void setUpMap() {
try {
MapsInitializer.initialize(getActivity());
} catch (GooglePlayServicesNotAvailableException e) {
}
mMap.setOnInfoWindowClickListener(this);
mMap.setOnMapLongClickListener(this);
addMapPoints();
}
我意识到这些都不是真正的解决方案 - 只是覆盖，但这是我目前能做的最好的事情，项目必须继续进行.如果有人找到更干净的修复程序，我将不胜感激让我知道.
I realize that those aren't real solutions - just overrides but it's the best I can do for now and the project must go on. If anyone finds cleaner fixes I'll be grateful for letting me know about them.
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