所以我遇到了一个问题，我需要一些帮助。
为了让你们更好地了解我的应用是什么，我会写下我希望我的应用做的事情。
1.启动GooglePlayServices并开始获取用户的位置。 2.给定位置后，对网址发出一个Volley请求并获取一些数据并将其放入JSONArray中。 3.获取JSONArray，并将其内容存储在db中， 4.一旦成功，请显示我的viewPager适配器，我将有一个listfragment和另一个片段。
我测试了我的Volley请求并且它有效，我尝试将其插入数据库中，因此这两个功能完美运行。我正在尝试运行异步任务来执行这两个功能，同时显示一条说明“获取数据...”的ProgressDialog消息。
这是我遇到麻烦的地方。当我获取我的数据库中的项目总数时，它显示0，所以我不知道最近发生了什么。我认为postExecute在我的数据被放入数据库之前以某种方式运行。
*我现在不担心位置为空的情况，所以不用担心。
问题：在我的AsyncTask中没有正确调用我的retrieveFeed（）（Volley Task）和insertToDB（）调用。
我将在我的代码下面发布，然后我会在日志声明下面发布作为参考，看看发生了什么。
import...
public class MainActivity extends AppCompatActivity implements ConnectionCallbacks,
OnConnectionFailedListener, LocationListener {
private ViewPager mViewPager;
private BaseTabAdapter mAdapter;
private JSONArray jsonArray;
private JSONObject jsonObject;
private List<Model> mList;
private ProgressDialog mDialog;
private DBHandler handler;
boolean fetchedData = false;
private static final String TAG = MainActivity.class.getSimpleName();
private final static int PLAY_SERVICES_RESOLUTION_REQUEST = 1000;
private Location mLastLocation;
// Google client to interact with Google API
private GoogleApiClient mGoogleApiClient;
private LocationRequest mLocationRequest;
// Location updates intervals in sec
private static int UPDATE_INTERVAL = 10000; // 10 sec
private static int FATEST_INTERVAL = 5000; // 5 sec
private static int DISPLACEMENT = 10; // 10 meters
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
setSupportActionBar(toolbar);
handler = new DBHandler(this);
mDialog = new ProgressDialog(this);
mDialog.setCancelable(false);
// First we need to check availability of play services
if (checkPlayServices()) {
// Building the GoogleApi client
buildGoogleApiClient();
createLocationRequest();
}
}
/***
* Initialize SlidingTabLayout
*/
private void initViews() {
SlidingTabLayout mSlidingTabLayout = (SlidingTabLayout) findViewById(R.id.tabs);
mSlidingTabLayout.setCustomTabView(R.layout.tab_txt_layout, R.id.tab_name_txt);
mSlidingTabLayout.setCustomTabColorizer(new SlidingTabLayout.TabColorizer() {
@Override
public int getIndicatorColor(int position) {
return ContextCompat.getColor(getApplicationContext(), R.color.white);
}
});
mSlidingTabLayout.setViewPager(mViewPager);
}
/***
* Starting a volley request to get JSON from URL
*/
private void retrieveFeed() {
String url = "...json";
StringRequest stringRequest = new StringRequest(Request.Method.GET,
url, new Response.Listener<String>() {
@Override
public void onResponse(String response) {
// Get the JSONObject and JSONArray
try {
jsonObject = new JSONObject(response);
jsonArray = jsonObject.getJSONArray("...");
// Insert values to database
insertToDB();
} catch (JSONException e) {
e.printStackTrace();
}
}
}, new Response.ErrorListener() {
@Override
public void onErrorResponse(VolleyError error) {
// TODO Auto-generated method stub
Toast.makeText(MainActivity.this, "Cant fetch data right now", Toast.LENGTH_LONG).show();
}
});
// Access the RequestQueue through your singleton class.
MySingleton.getInstance(this).addToRequestQueue(stringRequest);
}
private void insertToDB() {
try {
for (int i = 0; i < jsonArray.length(); i++) {
JSONObject object = jsonArray.getJSONObject(i);
... creating a new model and setting data parsed from the json
// Inserting into DB
handler.add(model...);
}
} catch (JSONException e) {
e.printStackTrace();
}
Log.i("Finished", "inserting db");
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.menu_main, menu);
return true;
}
@Override
public boolean onOptionsItemSelected(MenuItem item) {
// Handle action bar item clicks here. The action bar will
// automatically handle clicks on the Home/Up button, so long
// as you specify a parent activity in AndroidManifest.xml.
int id = item.getItemId();
if (id == R.id.action_settings) {
return true;
}
return super.onOptionsItemSelected(item);
}
@Override
protected void onStart() {
super.onStart();
Log.d(TAG, "onStart:");
if (mGoogleApiClient != null) {
Log.d(TAG, "onStart: Connecting Google API Client");
mGoogleApiClient.connect();
}
}
@Override
protected void onResume() {
super.onResume();
Log.d(TAG, "onResume:");
checkPlayServices();
// Resuming the periodic location updates
if (mGoogleApiClient.isConnected()) {
startLocationUpdates();
}
}
@Override
protected void onStop() {
super.onStop();
Log.d(TAG, "onStop:");
if (mGoogleApiClient.isConnected()) {
Log.d(TAG, "onStop: Disconnecting Google API Client");
mGoogleApiClient.disconnect();
}
}
@Override
protected void onPause() {
super.onPause();
Log.d(TAG, "onPause:");
stopLocationUpdates();
}
/**
* Creating google api client object
* */
protected synchronized void buildGoogleApiClient() {
Log.d(TAG, "buildGoogleApiClient:");
mGoogleApiClient = new GoogleApiClient.Builder(this)
.addConnectionCallbacks(this)
.addOnConnectionFailedListener(this)
.addApi(LocationServices.API).build();
}
/**
* Creating location request object
* */
protected void createLocationRequest() {
Log.d(TAG, "createLocationRequest:");
mLocationRequest = new LocationRequest();
mLocationRequest.setInterval(UPDATE_INTERVAL);
mLocationRequest.setFastestInterval(FATEST_INTERVAL);
mLocationRequest.setPriority(LocationRequest.PRIORITY_HIGH_ACCURACY);
mLocationRequest.setSmallestDisplacement(DISPLACEMENT);
}
/**
* Method to verify google play services on the device
* */
private boolean checkPlayServices() {
Log.d(TAG, "checkPlayServices:");
int resultCode = GooglePlayServicesUtil
.isGooglePlayServicesAvailable(this);
if (resultCode != ConnectionResult.SUCCESS) {
if (GooglePlayServicesUtil.isUserRecoverableError(resultCode)) {
GooglePlayServicesUtil.getErrorDialog(resultCode, this,
PLAY_SERVICES_RESOLUTION_REQUEST).show();
} else {
Toast.makeText(getApplicationContext(),
"This device is not supported.", Toast.LENGTH_LONG)
.show();
finish();
}
return false;
}
return true;
}
/**
* Starting the location updates
* */
protected void startLocationUpdates() {
Log.d(TAG, "startLocationUpdates:");
LocationServices.FusedLocationApi.requestLocationUpdates(
mGoogleApiClient, mLocationRequest, this);
// Runnign the asyn task when i get a location, not worring about the case when if i dont get a location
if (!fetchedData) {
new FetchData().execute();
fetchedData = true;
Log.i("FetchData", "true");
}
}
/**
* Stopping location updates
*/
protected void stopLocationUpdates() {
Log.d(TAG, "stopLocationUpdates:");
LocationServices.FusedLocationApi.removeLocationUpdates(
mGoogleApiClient, this);
}
/**
* Google api callback methods
*/
@Override
public void onConnectionFailed(ConnectionResult result) {
Log.i(TAG, "Connection failed: ConnectionResult.getErrorCode() = " + result.getErrorCode());
}
@Override
public void onConnected(Bundle arg0) {
Log.d(TAG, "onConnected:");
// Once connected with google api, get the location
getLocation();
startLocationUpdates();
}
@Override
public void onConnectionSuspended(int arg0) {
Log.d(TAG, "onConnectionSuspended:");
mGoogleApiClient.connect();
}
@Override
public void onLocationChanged(Location location) {
Log.d(TAG, "onLocationChanged:");
// Assign the new location
mLastLocation = location;
Toast.makeText(getApplicationContext(), "Location changed!", Toast.LENGTH_LONG).show();
Toast.makeText(getApplicationContext(), String.valueOf(mLastLocation.getLatitude()) + " - " +String.valueOf(mLastLocation.getLongitude()), Toast.LENGTH_LONG).show();
getLocation();
}
private void getLocation() {
Log.d(TAG, "displayLocation:");
mLastLocation = LocationServices.FusedLocationApi
.getLastLocation(mGoogleApiClient);
}
private class FetchData extends AsyncTask<Void, Void, Void> {
ProgressDialog mDialog = new ProgressDialog(MainActivity.this);
@Override
protected void onPreExecute() {
super.onPreExecute();
mDialog.setMessage("Fetching data...");
mDialog.show();
Log.i("onPreExecute", "started");
}
@Override
protected Void doInBackground(Void... params) {
Log.i("doInBackground", "started");
if (mLastLocation != null) {
Log.i("mLastLocation", "notnull");
retrieveFeed();
Log.i("Finished", "retrieving feed");
} else {
Log.i("mLastLocation", "null");
}
return null;
}
@Override
protected void onPostExecute(Void result) {
super.onPostExecute(result);
Log.i("onPostExecute", "started");
Log.i("COUNT", Integer.toString(handler.getTotalModels()));
if (handler.getTotalModels() > 0) {
Log.i("getTotalModels", "not zero");
mAdapter = new BaseTabAdapter(MainActivity.this);
mViewPager = (ViewPager) findViewById(R.id.pager);
mViewPager.setAdapter(mAdapter);
initViews();
}
mDialog.dismiss();
}
}
}
日志：
D/MainActivity: checkPlayServices:
D/MainActivity: buildGoogleApiClient:
D/MainActivity: createLocationRequest:
D/MainActivity: onStart:
D/MainActivity: onStart: Connecting Google API Client
D/MainActivity: onResume:
D/MainActivity: checkPlayServices:
D/MainActivity: onConnected:
D/MainActivity: displayLocation:
D/MainActivity: startLocationUpdates:
I/onPreExecute: **started**
I/FetchRoadAsync: **true**
I/doInBackground: **started**
I/mLastLocation: **notnull**
I/Finished: **retrieving feed**
I/onPostExecute: **started**
I/COUNT: 0
I/Finished: **inserting db**
D/MainActivity: onLocationChanged:
D/MainActivity: displayLocation:
asynctak位于底部，我从startLocationUpdates（）调用它;
答案 0 :(得分：0)
这种情况正在发生，因为Volley已经在另一个线程上执行您的请求，并且在主线程上的回调方法中异步调用您。因此，无需在AsyncTask中包含截击请求。