我已经编写了这个用于搜索的应用程序：输入源名称并在列表视图中显示行程，起始位置与用户源名称相同。它在模拟器上工作正常但在我尝试在真实设备上运行应用程序时选择源名称后它停止工作。
MainActivity.java
public class MainActivity extends AppCompatActivity {
private static final String ITEM_TITLE = "Item title";
private static final String ITEM_SOURCE = "Source";
private static final String ITEM_DESTINATION = "Destination";
static int no = 0;
static int y = 0;
PlaceAutocompleteFragment sourceAutocompleteFragment;
PlaceAutocompleteFragment destinationAutocompleteFragment;
PlaceObj sourcePlace = null;
PlaceObj destination = null;
ArrayList<PlaceObj> p = new ArrayList<PlaceObj>();
String sourceName = "";
String destinationName = "";
ArrayList<Ride> rides = new ArrayList<>();
private ListView lsv_main;
private ListAdapter mListAdapter;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
lsv_main = (ListView) findViewById(R.id.listView);
//Source
sourceAutocompleteFragment = (PlaceAutocompleteFragment)
getFragmentManager().findFragmentById(R.id.place_source);
AutocompleteFilter typeFilter = new AutocompleteFilter.Builder()
.setTypeFilter(AutocompleteFilter.TYPE_FILTER_ADDRESS)
.build();
sourceAutocompleteFragment.setFilter(typeFilter);
actionSource();
//Destination
//Source
destinationAutocompleteFragment = (PlaceAutocompleteFragment)
getFragmentManager().findFragmentById(R.id.place_destination);
typeFilter = new AutocompleteFilter.Builder()
.setTypeFilter(AutocompleteFilter.TYPE_FILTER_ADDRESS)
.build();
destinationAutocompleteFragment.setFilter(typeFilter);
actionDestination();
}
public void actionSource() {
final ArrayList<Ride> rideTemp = new ArrayList<Ride>();
sourceAutocompleteFragment.setOnPlaceSelectedListener(new PlaceSelectionListener() {
@Override
public void onPlaceSelected(com.google.android.gms.location.places.Place place) {
// TODO: Get info about the selected place.
Toast.makeText(getApplicationContext(), "Place:" + place.getName(), Toast.LENGTH_SHORT).show();
sourceName = (String) place.getName();
Double latitude = place.getLatLng().latitude;
Double longitude = place.getLatLng().longitude;
String address = (String) place.getAddress();
API.getInstance(getApplicationContext()).getRideByStartPlace(latitude, longitude, new ResponseListener() { //get ride
@Override
public void onResponse(String str) {
super.onResponse(str);
JSONArray jsonArray = null;
System.out.println(str);
try {
jsonArray = new JSONArray(str);
JSONObject jsonData = jsonArray.getJSONObject(0); //{}->1 object
if (jsonData.has("msg")) {
if (jsonData.getString("msg").equals("No exist ride with the entered start point.")) {
Toast.makeText(getApplicationContext(), "No exist ride with the entered start point.", Toast.LENGTH_SHORT).show();
}
} else { //get the ride info and store to ride Object
for (int i = 0; i < jsonArray.length(); i++) {
jsonData = jsonArray.getJSONObject(i);
System.out.println(jsonData);
int rideId = Integer.parseInt(jsonData.getString("rideId"));
SimpleDateFormat format = new SimpleDateFormat("yyyy-MM-dd");
Date createOn = format.parse(jsonData.getString("create_on"));
System.out.println(createOn);
String travelDateTime = jsonData.getString("travel_start_time");
int sourceId = Integer.parseInt(jsonData.getString("source_place_id"));
// String sourceName = source.getName();
getPlace(sourceId, new VolleyCallback() {
@Override
public void onSuccessResponse(String result) {
SharedPreferences sharedPreferences = getSharedPreferences("place", MODE_PRIVATE);
String json = sharedPreferences.getString("placeObj", "");
sourcePlace = new Gson().fromJson(json, PlaceObj.class);
}
});
int destinationId = Integer.parseInt(jsonData.getString("destination_place_id"));
getPlace(destinationId, new VolleyCallback() {
@Override
public void onSuccessResponse(String result) {
SharedPreferences sharedPreferences = getSharedPreferences("place", MODE_PRIVATE);
String json = sharedPreferences.getString("placeObj", "");
destination = new Gson().fromJson(json, PlaceObj.class);
}
});
int seats = Integer.parseInt(jsonData.getString("seats_offered"));
String remark = jsonData.getString("remark");
Ride ride = new Ride(rideId, createOn, travelDateTime, sourcePlace, destination, seats, remark, sourceId, destinationId);
rideTemp.add(ride);
}
System.out.println("myArry " + rideTemp);
showRide(rideTemp);
}
} catch (JSONException e) {
e.printStackTrace();
} catch (ParseException e) {
e.printStackTrace();
}
System.out.println(str);
}
@Override
public void onError(VolleyError error) {
super.onError(error);
}
}
);
}
@Override
public void onError(Status status) {
// TODO: Handle the error.
Toast.makeText(getApplicationContext(), "error" + status, Toast.LENGTH_SHORT).show();
}
});
System.out.println("Rides array:" + rides);
}
public void actionDestination() {
final ArrayList<Ride> rideTemp = new ArrayList<Ride>();
destinationAutocompleteFragment.setOnPlaceSelectedListener(new PlaceSelectionListener() {
@Override
public void onPlaceSelected(com.google.android.gms.location.places.Place place) {
// TODO: Get info about the selected place.
Toast.makeText(getApplicationContext(), "Place:" + place.getName(), Toast.LENGTH_SHORT).show();
destinationName = (String) place.getName();
System.out.println("rSource: " + sourceName);
Double latitude = place.getLatLng().latitude;
Double longitude = place.getLatLng().longitude;
String address = (String) place.getAddress();
API.getInstance(getApplicationContext()).getRideByStartDestinationPlace(sourceName, latitude, longitude, new ResponseListener() { //get ride
@Override
public void onResponse(String str) {
super.onResponse(str);
JSONArray jsonArray = null;
System.out.println(str);
try {
jsonArray = new JSONArray(str);
JSONObject jsonData = jsonArray.getJSONObject(0); //{}->1 object
if (jsonData.has("msg")) {
if (jsonData.getString("msg").equals("No exist ride with the entered start point.")) {
Toast.makeText(getApplicationContext(), "No exist ride with the entered start point.", Toast.LENGTH_SHORT).show();
}
} else { //get the ride info and store to ride Object
for (int i = 0; i < jsonArray.length(); i++) {
jsonData = jsonArray.getJSONObject(i);
System.out.println(jsonData);
int rideId = Integer.parseInt(jsonData.getString("rideId"));
SimpleDateFormat format = new SimpleDateFormat("yyyy-MM-dd");
Date createOn = format.parse(jsonData.getString("create_on"));
System.out.println(createOn);
String travelDateTime = jsonData.getString("travel_start_time");
int sourceId = Integer.parseInt(jsonData.getString("source_place_id"));
getPlace(sourceId, new VolleyCallback() {
@Override
public void onSuccessResponse(String result) {
SharedPreferences sharedPreferences = getSharedPreferences("place", MODE_PRIVATE);
String json = sharedPreferences.getString("placeObj", "");
sourcePlace = new Gson().fromJson(json, PlaceObj.class);
}
});
int destinationId = Integer.parseInt(jsonData.getString("destination_place_id"));
getPlace(destinationId, new VolleyCallback() {
@Override
public void onSuccessResponse(String result) {
SharedPreferences sharedPreferences = getSharedPreferences("place", MODE_PRIVATE);
String json = sharedPreferences.getString("placeObj", "");
destination = new Gson().fromJson(json, PlaceObj.class);
}
});
int seats = Integer.parseInt(jsonData.getString("seats_offered"));
String remark = jsonData.getString("remark");
Ride ride = new Ride(rideId, createOn, travelDateTime, sourcePlace, destination, seats, remark, sourceId, destinationId);
rideTemp.add(ride);
}
System.out.println("myArry " + rideTemp);
showRide(rideTemp);
}
} catch (JSONException e) {
e.printStackTrace();
} catch (ParseException e) {
e.printStackTrace();
}
System.out.println(str);
}
@Override
public void onError(VolleyError error) {
super.onError(error);
}
}
);
}
@Override
public void onError(Status status) {
// TODO: Handle the error.
Toast.makeText(getApplicationContext(), "error" + status, Toast.LENGTH_SHORT).show();
}
});
System.out.println("Rides array:" + rides);
}
public void getPlace(int id, final VolleyCallback callback) {
SharedPreferences pref = getSharedPreferences("place", MODE_PRIVATE);
final SharedPreferences.Editor editor = pref.edit();
final PlaceObj[] placeBean = new PlaceObj[1];
API.getInstance(getApplicationContext()).getPlaceById(id, new ResponseListener() {
@Override
public void onResponse(String str) {
super.onResponse(str);
JSONArray jsonArray = null;
try {
jsonArray = new JSONArray(str);
JSONObject jsonData = jsonArray.getJSONObject(0);
int placeId = Integer.parseInt(jsonData.getString("placeId"));
String name = jsonData.getString("name");
double latitude = Double.parseDouble(jsonData.getString("latitude"));
double longitude = Double.parseDouble(jsonData.getString("longitude"));
String address = jsonData.getString("address");
System.out.println("address" + name);
PlaceObj placeObj = new PlaceObj(placeId, name, latitude, longitude, address);
Gson gson = new Gson();
String json = gson.toJson(placeObj);
editor.putString("placeObj" + placeId, json);
editor.commit();
no++;
callback.onSuccessResponse(str);
} catch (JSONException e) {
e.printStackTrace();
}
System.out.println(str);
}
@Override
public void onError(VolleyError error) {
super.onError(error);
}
});
}
public void showRide(final ArrayList<Ride> rides) {
final String[] myarray = new String[10];
List<Map<String, Object>> itemList = new ArrayList<Map<String, Object>>();
for (int i = 0; i < rides.size(); i++) {
final Ride ride = rides.get(i);
final Map<String, Object> item = new HashMap<String, Object>();
item.put(ITEM_TITLE, rides.get(i).getTravelDateTime());
System.out.println("sourceid: " + rides.get(i).getSourceID());
SharedPreferences sharedPreferences = getSharedPreferences("place", MODE_PRIVATE); //test as login info
String json = sharedPreferences.getString("placeObj" + rides.get(i).getSourceID(), "");
PlaceObj a = new Gson().fromJson(json, PlaceObj.class);
String creator_id = a.getName();
System.out.println("Name:" + creator_id);
item.put(ITEM_SOURCE, creator_id);
json = sharedPreferences.getString("placeObj" + rides.get(i).getDestinationID(), "");
a = new Gson().fromJson(json, PlaceObj.class);
creator_id = a.getName();
System.out.println("Name:" + creator_id);
item.put(ITEM_DESTINATION, creator_id);
itemList.add(item);
}
mListAdapter = new ListAdapter(MainActivity.this, itemList);
lsv_main.setAdapter(mListAdapter);
}
}
activity_main.xml中
<?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">
<TableLayout
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:paddingLeft="10px"
android:paddingRight="10px"
android:shrinkColumns="0"
android:stretchColumns="1">
<TableRow>
<TextView
android:id="@+id/tv_start"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="@string/start" />
<fragment
android:id="@+id/place_source"
android:name="com.google.android.gms.location.places.ui.PlaceAutocompleteFragment"
android:layout_width="match_parent"
android:layout_height="wrap_content" />
</TableRow>
<TableRow>
<TextView
android:id="@+id/tv_destination"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="@string/destination" />
<fragment
android:id="@+id/place_destination"
android:name="com.google.android.gms.location.places.ui.PlaceAutocompleteFragment"
android:layout_width="match_parent"
android:layout_height="wrap_content" />
</TableRow>
<TableRow>
<Button
android:id="@+id/btn_date"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="@string/pick_date" />
<TextView
android:id="@+id/tv_date"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_span="2" />
</TableRow>
<TableRow>
<Button
android:id="@+id/btn_time"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="@string/pick_time" />
<TextView
android:id="@+id/tv_time"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_span="2" />
</TableRow>
</TableLayout>
<ListView
android:id="@+id/listView"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:layout_alignParentLeft="true"
android:layout_alignParentStart="true"
android:layout_alignParentTop="true" />
</LinearLayout>
logcat的
05-18 15:44:22.237 7813-7813/fyp.wcm.shareourride I/System.out: [{"rideId":1,"create_on":"2018-03-07","travel_start_time":"2018-03-07 17:17:00","source_place_id":1,"destination_place_id":2,"seats_offered":2,"creator_id":1,"remark":"music taxi","placeId":1,"name":"Harbour Heights Ko Fung Court","latitude":22.2882477,"longitude":114.1907985,"address":"Harbour Heights Ko Fung Court, 5 Fook Yum Rd, Causeway Bay, Hong Kong"},{"rideId":2,"create_on":"2018-03-10","travel_start_time":"2018-03-10 18:54:00","source_place_id":1,"destination_place_id":3,"seats_offered":3,"creator_id":1,"remark":"good as","placeId":1,"name":"Harbour Heights Ko Fung Court","latitude":22.2882477,"longitude":114.1907985,"address":"Harbour Heights Ko Fung Court, 5 Fook Yum Rd, Causeway Bay, Hong Kong"}]
05-18 15:44:22.238 7813-7813/fyp.wcm.shareourride I/System.out: {"rideId":1,"create_on":"2018-03-07","travel_start_time":"2018-03-07 17:17:00","source_place_id":1,"destination_place_id":2,"seats_offered":2,"creator_id":1,"remark":"music taxi","placeId":1,"name":"Harbour Heights Ko Fung Court","latitude":22.2882477,"longitude":114.1907985,"address":"Harbour Heights Ko Fung Court, 5 Fook Yum Rd, Causeway Bay, Hong Kong"}
05-18 15:44:22.238 7813-7813/fyp.wcm.shareourride I/System.out: Wed Mar 07 00:00:00 GMT+08:00 2018
05-18 15:44:22.240 7813-7813/fyp.wcm.shareourride I/System.out: {"rideId":2,"create_on":"2018-03-10","travel_start_time":"2018-03-10 18:54:00","source_place_id":1,"destination_place_id":3,"seats_offered":3,"creator_id":1,"remark":"good as","placeId":1,"name":"Harbour Heights Ko Fung Court","latitude":22.2882477,"longitude":114.1907985,"address":"Harbour Heights Ko Fung Court, 5 Fook Yum Rd, Causeway Bay, Hong Kong"}
05-18 15:44:22.241 7813-7813/fyp.wcm.shareourride I/System.out: Sat Mar 10 00:00:00 GMT+08:00 2018
05-18 15:44:22.241 7813-7813/fyp.wcm.shareourride I/System.out: myArry [fyp.wcm.shareourride.Ride@c945316, fyp.wcm.shareourride.Ride@57c4497]
05-18 15:44:22.243 7813-7813/fyp.wcm.shareourride I/System.out: sourceid: 1
05-18 15:44:22.249 7813-7813/fyp.wcm.shareourride D/AndroidRuntime: Shutting down VM
--------- beginning of crash
05-18 15:44:22.250 7813-7813/fyp.wcm.shareourride E/AndroidRuntime: FATAL EXCEPTION: main
Process: fyp.wcm.shareourride, PID: 7813
java.lang.NullPointerException: Attempt to invoke virtual method 'java.lang.String fyp.wcm.shareourride.PlaceObj.getName()' on a null object reference
at fyp.wcm.shareourride.MainActivity.showRide(MainActivity.java:401)
at fyp.wcm.shareourride.MainActivity$2$1.onResponse(MainActivity.java:212)
at fyp.wcm.shareourride.CustomJsonObjectRequest$1.onResponse(CustomJsonObjectRequest.java:25)
at fyp.wcm.shareourride.CustomJsonObjectRequest$1.onResponse(CustomJsonObjectRequest.java:22)
at com.android.volley.toolbox.StringRequest.deliverResponse(StringRequest.java:60)
at com.android.volley.toolbox.StringRequest.deliverResponse(StringRequest.java:30)
at com.android.volley.ExecutorDelivery$ResponseDeliveryRunnable.run(ExecutorDelivery.java:99)
at android.os.Handler.handleCallback(Handler.java:751)
at android.os.Handler.dispatchMessage(Handler.java:95)
at android.os.Looper.loop(Looper.java:159)
at android.app.ActivityThread.main(ActivityThread.java:6097)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:865)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:755)
05-18 15:44:22.252 1622-2345/? W/ActivityManager: Force finishing activity fyp.wcm.shareourride/.MainActivity
05-18 15:44:22.256 1622-2345/? I/InputDispatcher: Window 'Window{8721876 u0 fyp.wcm.shareourride/fyp.wcm.shareourride.MainActivity}' spent 0.0ms processing input events on average(0/0). Monitor spent 0.0ms processing input events on average(0/0).
05-18 15:44:22.258 1622-2345/? D/ActivityTrigger: ActivityTrigger activityPauseTrigger
仿真器API级别：23：5554
Real Device API等级：24
答案 0 :(得分：0)
API级别24中有一个功能是android:allowBackup
是否允许应用程序参与备份和 恢复基础架构如果此属性设置为false，则不进行备份 或者，即使是通过a，也可以执行应用程序的恢复 全系统备份，否则会导致所有应用程序数据 通过adb保存。该属性的默认值为true。
简而言之，如果清单中android:allowBackup为真，则您的Sharedpreferences数据将被恢复，即如果您登录并将userId存储在Sharedpreferences中，无论您是卸载还是安装新应用程序，它都将保留存储。
因此，只需在android:allowBackup="false"代码下添加<application>即可。