需要按顺序发送多个 Volley 请求
Need to send multiple Volley Requests - in a sequence
我需要使用 volley 发送请求以检索 membershipid，然后将该会员 id 传递到第二个 volley 请求以检索该成员的统计信息。
我的第一个请求完美运行时遇到问题，但第二个请求似乎在变量返回传递之前就开始了。任何人都知道如何防止第二个请求在返回值之前启动？
您不能只按顺序编写每个请求并在每次成功响应后等待执行每个请求...您必须在第一个服务响应中调用第二个请求...即
public void firstServiceCall(String url)
{
JsonObjectRequest jsonObjReq = new JsonObjectRequest(
Request.Method.GET, url, null,
new Response.Listener<JSONObject>() {
@Override
public void onResponse(JSONObject response) {
int membershipid=response.getInt("membershipid");
//suppose the membershipid comes under main json with key "membershipid"
secondServiceCall(membershipid,<url2>);
// on the response of first service ... call to the second service ... and continue so on... if required
}
}, new Response.ErrorListener() {
@Override
public void onErrorResponse(VolleyError error) {
}
});
Volley.newRequestQueue(getApplicationContext()).add(jsonObjReq);
}
public void secondServiceCall(int membershipid,String url)
{
// use this var membershipid acc to your need ...
JsonObjectRequest jsonObjReq = new JsonObjectRequest(
Request.Method.GET, url, null,
new Response.Listener<JSONObject>() {
@Override
public void onResponse(JSONObject response) {
}
}, new Response.ErrorListener() {
@Override
public void onErrorResponse(VolleyError error) {
}
});
Volley.newRequestQueue(getApplicationContext()).add(jsonObjReq);
}
also the request call is asynchronous hence... the other process won't wait for service call to finish...hence your second service starts before the first service response
用于链接异步 Volley 请求的代码。重要的是：
a) 在 mJsonResp 侦听器中调用 nextRequest()。
nextRequest() 将链中的每个 link 连接在一起，并由侦听器调用。
b) 成员 mLinkedRequest.
c) 需要覆盖 getRequest() 的抽象函数。
d) 如何实例化("usage")个HTTP注册请求：
// 1) POST registrations -> 2) PATCH registrations -> 3) GET devices
pkRequest ChainReg3 = new LinkedRequest(pkURL.devices, null ) {
@Override public JSONObject getRequest( final JSONObject response ){
JSONObject retVal = new JSONObject();
retVal.put( "MyAwesomeString", "This is the final request string in the chain" );
return retVal;
}
} ;
pkRequest ChainReg2 = new LinkedRequest(pkURL.registrations2, ChainReg3 ){
//pkRequest ChainReg2 = new pkRequest(pkURL.registrations2, null ){
@Override public JSONObject getRequest( final JSONObject response ){
JSONObject retVal = new JSONObject();
retVal.put( "MyAwesomeInt", 99 );
return retVal;
};
JSONObject firstRequestBodyTest = new JSONObject( "test" );
pkRequest ChainReg1 = new LinkedRequest(pkURL.registrations, firstRequestBodyTest , ChainReg2 ){
@Override public JSONObject getRequest( final JSONObject response ){ return null; }
};
ChainReg1.submit();
}
/* 仅供参考：我创建了一个枚举来处理所有 URL。你可以用其他方式与他们交易。 post 的目的是展示如何将异步截击请求链接在一起。
package org.Somepackage;
import android.support.annotation.NonNull;
import android.widget.Toast;
import com.android.volley.*;
import com.android.volley.Request.*;
import com.android.volley.Response.ErrorListener;
import com.android.volley.toolbox.JsonObjectRequest;
import org.json.*;
import org.peacekeeper.util.pkUtility;
import java.net.*;
import java.util.*;
public abstract class LinkedRequest{
protected static org.slf4j.Logger mLog;
protected final static pkUtility mUtility = pkUtility.getInstance();
protected final static RequestQueue mRequestQueue = mUtility.getRequestQueue();
protected final static Toast mToast = Toast.makeText( mUtility.getBaseContext(), "", Toast.LENGTH_LONG );
static private HashMap< String, String > newHeader(){
HashMap< String, String > newHeader = new HashMap<>();
final String applicationjson = "application/json";
newHeader.put( "Accept", applicationjson );
newHeader.put( "Content-Type", applicationjson );
return newHeader;
}
static private HashMap<String, String> mHeaders = newHeader()
, registrations2Hdr = newHeader();
static{
//
registrations2Hdr.put( "X-HTTP-Method-Override", "PATCH" );
}
//end static
private UUID msg_id = UUID.randomUUID();
//each enum needs priority and method, url, request, response, errlsnr
protected final Response.Listener< JSONObject > mJsonResp = new Response.Listener< JSONObject >(){
@Override public void onResponse( JSONObject response ){
String respStr = "response:\t" + ((response == null)? "NULL" : response.toString() );
mToast.setText( respStr );
mToast.show();
mLog.debug( "onResponse\t url:\t" + mPkURL.toString() + "\t:Response:\t" + respStr );
nextRequest( response );
}
};
protected final ErrorListener mErrLsnr = new ErrorListener(){
@Override public void onErrorResponse( VolleyError error ){
mToast.setText( "Error:\t" + error.getMessage() );
mToast.show();
mLog.error( "Error!:\t" + error.getMessage() );
if( error.networkResponse != null){
NetworkResponse response = error.networkResponse;
int statusCode = error.networkResponse.statusCode;
mLog.error( "statuscode:\t" + statusCode + ":\t" + new String(response.data) );
}
}
};
private HashMap< String, String > getAuthorizationHeader(){
HashMap< String, String > newHeader = newHeader();
//newHeader.put( "Authorization", SecurityGuard.getAuthToken() );
newHeader.put( "Authorization", "test getAuthToken()" );
mLog.debug( newHeader.toString() );
return newHeader;
}
//PLACE ALL URL NAMES HERE
public enum pkURL{
//each link in the chain should be of ever increasing priority to reflect its progression.
devices(Method.GET, Priority.IMMEDIATE)
//
// java.net.ProtocolException: Unknown method 'PATCH'; must be one of [OPTIONS, GET, HEAD, POST, PUT, DELETE, TRACE]
//
, registrations2( Method.POST, Priority.HIGH, LinkedRequest.registrations2Hdr)
, registrations(Method.POST, Priority.NORMAL )
, status
;
//each enum needs priority and method, url, request, response, errlsnr
protected Priority mPriority;
protected int mMethod;
public HashMap< String, String > mHeader;
protected String URLstr;
pkURL(){
mMethod = Method.GET;
mPriority = Priority.LOW;
mHeader = LinkedRequest.mHeaders;
}
pkURL(int aMethod, Priority aPriority ){
mMethod = aMethod;
mPriority = aPriority;
mHeader = LinkedRequest.mHeaders;
}
pkURL(int aMethod,
Priority aPriority,
HashMap< String, String > aHeader){
this(aMethod, aPriority);
mHeader = aHeader;
}
}//enum pkURL
public pkURL mPkURL;
private JsonObjectRequest mJsonRequest = null;//The current request of this link. For future Request override getRequest().
private LinkedRequest mLinkedRequest = null;
//This constructor is only used for intermediate and last links in the chain.
public LinkedRequest( @NonNull pkURL aPkURL, LinkedRequest aLinkedRequest ){
mLog = org.slf4j.LoggerFactory.getLogger( getClass() );
mPkURL = aPkURL;
if ( aLinkedRequest != null ){
mLinkedRequest = aLinkedRequest;
mLinkedRequest.msg_id = this.msg_id;
}
}//cstr
//This constructor is only used for the first link in the chain or singleton requests.
public LinkedRequest( @NonNull final pkURL aPkURL, @NonNull JSONObject aRequestBody, LinkedRequest aLinkedRequest ){
this( aPkURL, aLinkedRequest );
try{ aRequestBody.put( "_id", msg_id.toString() ); } catch ( Exception ignore ){}
mJsonRequest = //this is the current request of this link. For future Requests override getRequest().
new JsonObjectRequest( aPkURL.mMethod, toURL(), aRequestBody, mJsonResp, mErrLsnr ){
@Override public Priority getPriority() { return mPkURL.mPriority; }
@Override public Map<String, String> getHeaders() throws AuthFailureError{ return aPkURL.mHeader; }
};
mJsonRequest.setShouldCache( false );
}//cstr
private static final String URLhead = "http://192.168.1.156/";
private String toURL(){ //} throws JSONException{
//private < E extends Enum< E > > URL toURL( E URLPostOrGet ){
URL url;
switch ( mPkURL){
case registrations2:
this.mPkURL.URLstr = "registrations/" + this.msg_id;
this.mPkURL.mHeader = registrations2Hdr;
break;
case devices:
final String deviceID = "testdeviceId" //SecurityGuard.getEntry( entryType.deviceId )
, keeperID = "testkeeperId" //SecurityGuard.getEntry( entryType.keeperId )
;
//GET http://192.168.1.156:80/devices/bbdef07b-9360-4d7b-8448-21c4daca4711?where=keeperId=="b0c486e5-13b1-4555-ba5f-d54bb1f0a6f7"
this.mPkURL.URLstr = new StringBuilder( "devices/" )
.append( deviceID )
.append( "?where=keeperId==\"" )
.append( keeperID + "\"" )
.toString();
this.mHeaders = getAuthorizationHeader();
break;
default: this.mPkURL.URLstr = mPkURL.name();
}//switch
try{
url = new URL(URLhead + this.mPkURL.URLstr + "/" );
}
catch ( MalformedURLException e ){
mLog.error( "Error!:\t" + e.getMessage() );
url = null;
}
return url.toString();
}//toURL
@Override public String toString(){
String toURL = toURL();
if (mJsonRequest == null) return "toString() NULL mJsonRequest:\t" + toURL;
String hdrs;
try{ hdrs = this.mJsonRequest.getHeaders().toString(); }
catch ( AuthFailureError aAuthFailureError ){ hdrs = "ERROR: getHeaders()"; }
return new StringBuilder( "\nmethod:\t:" + mJsonRequest.getMethod() )
.append( "\nheaders:\t" + hdrs )
.append( "\nbody:\t" + new String( mJsonRequest.getBody()) )
.append( "\nBodyContentType:\t" + mJsonRequest.getBodyContentType() )
.append( "\nPriority:\t" + mJsonRequest.getPriority() )
.append( "\ngetUrl():\t" + mJsonRequest.getUrl() )
.append( "\ntoURL():\t" + toURL )
.append( "\n" )
.toString();
}//toString()
//getRequest is used for the FUTURE request of mLinkedRequest.
//for CURRENT request of this() use the constructor
abstract public JSONObject getRequest( final JSONObject response );
private Request nextRequest(final JSONObject aResponse ){//nextRequest() ties each link in the chain together and is called by the listener.
mLog.debug( "nextRequest:\t" + aResponse.toString() );
Request retVal = null;
// * * * * * * This is how and where the the "future" request must be called/constructed. * * * * * *
if ( mLinkedRequest != null ){
final int mMethod = mLinkedRequest.mPkURL.mMethod;
final String aURL = mLinkedRequest.toURL();
final JSONObject requestBody = mLinkedRequest.getRequest( aResponse );
final Priority priority = mLinkedRequest.mPkURL.mPriority;
final Map<String, String> header = mLinkedRequest.mPkURL.mHeader;
this.mJsonRequest = new JsonObjectRequest( mMethod, aURL,
requestBody,
mJsonResp, mErrLsnr ){
@Override public Priority getPriority() { return priority; }
@Override public Map<String, String> getHeaders() throws AuthFailureError{ return header; }
};
mJsonRequest.setShouldCache( false );
this.mLinkedRequest = mLinkedRequest.mLinkedRequest;
retVal = submit();
}//if
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *
return retVal;
}//nextRequest()
public Request submit(){
mLog.debug( "submit:\n" );
mLog.debug( this.toString() );
if ( mLinkedRequest != null ) mLog.debug( "mLinkedRequest:\t" + mLinkedRequest.toString() );
if ( mJsonRequest!= null ) return mRequestQueue.add( mJsonRequest );
return null;
}//submit()
}//class LinkedRequest
我需要使用 volley 发送请求以检索 membershipid，然后将该会员 id 传递到第二个 volley 请求以检索该成员的统计信息。
我的第一个请求完美运行时遇到问题，但第二个请求似乎在变量返回传递之前就开始了。任何人都知道如何防止第二个请求在返回值之前启动？
您不能只按顺序编写每个请求并在每次成功响应后等待执行每个请求...您必须在第一个服务响应中调用第二个请求...即
public void firstServiceCall(String url)
{
JsonObjectRequest jsonObjReq = new JsonObjectRequest(
Request.Method.GET, url, null,
new Response.Listener<JSONObject>() {
@Override
public void onResponse(JSONObject response) {
int membershipid=response.getInt("membershipid");
//suppose the membershipid comes under main json with key "membershipid"
secondServiceCall(membershipid,<url2>);
// on the response of first service ... call to the second service ... and continue so on... if required
}
}, new Response.ErrorListener() {
@Override
public void onErrorResponse(VolleyError error) {
}
});
Volley.newRequestQueue(getApplicationContext()).add(jsonObjReq);
}
public void secondServiceCall(int membershipid,String url)
{
// use this var membershipid acc to your need ...
JsonObjectRequest jsonObjReq = new JsonObjectRequest(
Request.Method.GET, url, null,
new Response.Listener<JSONObject>() {
@Override
public void onResponse(JSONObject response) {
}
}, new Response.ErrorListener() {
@Override
public void onErrorResponse(VolleyError error) {
}
});
Volley.newRequestQueue(getApplicationContext()).add(jsonObjReq);
}
also the request call is asynchronous hence... the other process won't wait for service call to finish...hence your second service starts before the first service response
用于链接异步 Volley 请求的代码。重要的是：
a) 在 mJsonResp 侦听器中调用 nextRequest()。
nextRequest() 将链中的每个 link 连接在一起，并由侦听器调用。
b) 成员 mLinkedRequest.
c) 需要覆盖 getRequest() 的抽象函数。
d) 如何实例化("usage")个HTTP注册请求：
// 1) POST registrations -> 2) PATCH registrations -> 3) GET devices
pkRequest ChainReg3 = new LinkedRequest(pkURL.devices, null ) {
@Override public JSONObject getRequest( final JSONObject response ){
JSONObject retVal = new JSONObject();
retVal.put( "MyAwesomeString", "This is the final request string in the chain" );
return retVal;
}
} ;
pkRequest ChainReg2 = new LinkedRequest(pkURL.registrations2, ChainReg3 ){
//pkRequest ChainReg2 = new pkRequest(pkURL.registrations2, null ){
@Override public JSONObject getRequest( final JSONObject response ){
JSONObject retVal = new JSONObject();
retVal.put( "MyAwesomeInt", 99 );
return retVal;
};
JSONObject firstRequestBodyTest = new JSONObject( "test" );
pkRequest ChainReg1 = new LinkedRequest(pkURL.registrations, firstRequestBodyTest , ChainReg2 ){
@Override public JSONObject getRequest( final JSONObject response ){ return null; }
};
ChainReg1.submit();
}
/* 仅供参考：我创建了一个枚举来处理所有 URL。你可以用其他方式与他们交易。 post 的目的是展示如何将异步截击请求链接在一起。
package org.Somepackage;
import android.support.annotation.NonNull;
import android.widget.Toast;
import com.android.volley.*;
import com.android.volley.Request.*;
import com.android.volley.Response.ErrorListener;
import com.android.volley.toolbox.JsonObjectRequest;
import org.json.*;
import org.peacekeeper.util.pkUtility;
import java.net.*;
import java.util.*;
public abstract class LinkedRequest{
protected static org.slf4j.Logger mLog;
protected final static pkUtility mUtility = pkUtility.getInstance();
protected final static RequestQueue mRequestQueue = mUtility.getRequestQueue();
protected final static Toast mToast = Toast.makeText( mUtility.getBaseContext(), "", Toast.LENGTH_LONG );
static private HashMap< String, String > newHeader(){
HashMap< String, String > newHeader = new HashMap<>();
final String applicationjson = "application/json";
newHeader.put( "Accept", applicationjson );
newHeader.put( "Content-Type", applicationjson );
return newHeader;
}
static private HashMap<String, String> mHeaders = newHeader()
, registrations2Hdr = newHeader();
static{
//
registrations2Hdr.put( "X-HTTP-Method-Override", "PATCH" );
}
//end static
private UUID msg_id = UUID.randomUUID();
//each enum needs priority and method, url, request, response, errlsnr
protected final Response.Listener< JSONObject > mJsonResp = new Response.Listener< JSONObject >(){
@Override public void onResponse( JSONObject response ){
String respStr = "response:\t" + ((response == null)? "NULL" : response.toString() );
mToast.setText( respStr );
mToast.show();
mLog.debug( "onResponse\t url:\t" + mPkURL.toString() + "\t:Response:\t" + respStr );
nextRequest( response );
}
};
protected final ErrorListener mErrLsnr = new ErrorListener(){
@Override public void onErrorResponse( VolleyError error ){
mToast.setText( "Error:\t" + error.getMessage() );
mToast.show();
mLog.error( "Error!:\t" + error.getMessage() );
if( error.networkResponse != null){
NetworkResponse response = error.networkResponse;
int statusCode = error.networkResponse.statusCode;
mLog.error( "statuscode:\t" + statusCode + ":\t" + new String(response.data) );
}
}
};
private HashMap< String, String > getAuthorizationHeader(){
HashMap< String, String > newHeader = newHeader();
//newHeader.put( "Authorization", SecurityGuard.getAuthToken() );
newHeader.put( "Authorization", "test getAuthToken()" );
mLog.debug( newHeader.toString() );
return newHeader;
}
//PLACE ALL URL NAMES HERE
public enum pkURL{
//each link in the chain should be of ever increasing priority to reflect its progression.
devices(Method.GET, Priority.IMMEDIATE)
//
// java.net.ProtocolException: Unknown method 'PATCH'; must be one of [OPTIONS, GET, HEAD, POST, PUT, DELETE, TRACE]
//
, registrations2( Method.POST, Priority.HIGH, LinkedRequest.registrations2Hdr)
, registrations(Method.POST, Priority.NORMAL )
, status
;
//each enum needs priority and method, url, request, response, errlsnr
protected Priority mPriority;
protected int mMethod;
public HashMap< String, String > mHeader;
protected String URLstr;
pkURL(){
mMethod = Method.GET;
mPriority = Priority.LOW;
mHeader = LinkedRequest.mHeaders;
}
pkURL(int aMethod, Priority aPriority ){
mMethod = aMethod;
mPriority = aPriority;
mHeader = LinkedRequest.mHeaders;
}
pkURL(int aMethod,
Priority aPriority,
HashMap< String, String > aHeader){
this(aMethod, aPriority);
mHeader = aHeader;
}
}//enum pkURL
public pkURL mPkURL;
private JsonObjectRequest mJsonRequest = null;//The current request of this link. For future Request override getRequest().
private LinkedRequest mLinkedRequest = null;
//This constructor is only used for intermediate and last links in the chain.
public LinkedRequest( @NonNull pkURL aPkURL, LinkedRequest aLinkedRequest ){
mLog = org.slf4j.LoggerFactory.getLogger( getClass() );
mPkURL = aPkURL;
if ( aLinkedRequest != null ){
mLinkedRequest = aLinkedRequest;
mLinkedRequest.msg_id = this.msg_id;
}
}//cstr
//This constructor is only used for the first link in the chain or singleton requests.
public LinkedRequest( @NonNull final pkURL aPkURL, @NonNull JSONObject aRequestBody, LinkedRequest aLinkedRequest ){
this( aPkURL, aLinkedRequest );
try{ aRequestBody.put( "_id", msg_id.toString() ); } catch ( Exception ignore ){}
mJsonRequest = //this is the current request of this link. For future Requests override getRequest().
new JsonObjectRequest( aPkURL.mMethod, toURL(), aRequestBody, mJsonResp, mErrLsnr ){
@Override public Priority getPriority() { return mPkURL.mPriority; }
@Override public Map<String, String> getHeaders() throws AuthFailureError{ return aPkURL.mHeader; }
};
mJsonRequest.setShouldCache( false );
}//cstr
private static final String URLhead = "http://192.168.1.156/";
private String toURL(){ //} throws JSONException{
//private < E extends Enum< E > > URL toURL( E URLPostOrGet ){
URL url;
switch ( mPkURL){
case registrations2:
this.mPkURL.URLstr = "registrations/" + this.msg_id;
this.mPkURL.mHeader = registrations2Hdr;
break;
case devices:
final String deviceID = "testdeviceId" //SecurityGuard.getEntry( entryType.deviceId )
, keeperID = "testkeeperId" //SecurityGuard.getEntry( entryType.keeperId )
;
//GET http://192.168.1.156:80/devices/bbdef07b-9360-4d7b-8448-21c4daca4711?where=keeperId=="b0c486e5-13b1-4555-ba5f-d54bb1f0a6f7"
this.mPkURL.URLstr = new StringBuilder( "devices/" )
.append( deviceID )
.append( "?where=keeperId==\"" )
.append( keeperID + "\"" )
.toString();
this.mHeaders = getAuthorizationHeader();
break;
default: this.mPkURL.URLstr = mPkURL.name();
}//switch
try{
url = new URL(URLhead + this.mPkURL.URLstr + "/" );
}
catch ( MalformedURLException e ){
mLog.error( "Error!:\t" + e.getMessage() );
url = null;
}
return url.toString();
}//toURL
@Override public String toString(){
String toURL = toURL();
if (mJsonRequest == null) return "toString() NULL mJsonRequest:\t" + toURL;
String hdrs;
try{ hdrs = this.mJsonRequest.getHeaders().toString(); }
catch ( AuthFailureError aAuthFailureError ){ hdrs = "ERROR: getHeaders()"; }
return new StringBuilder( "\nmethod:\t:" + mJsonRequest.getMethod() )
.append( "\nheaders:\t" + hdrs )
.append( "\nbody:\t" + new String( mJsonRequest.getBody()) )
.append( "\nBodyContentType:\t" + mJsonRequest.getBodyContentType() )
.append( "\nPriority:\t" + mJsonRequest.getPriority() )
.append( "\ngetUrl():\t" + mJsonRequest.getUrl() )
.append( "\ntoURL():\t" + toURL )
.append( "\n" )
.toString();
}//toString()
//getRequest is used for the FUTURE request of mLinkedRequest.
//for CURRENT request of this() use the constructor
abstract public JSONObject getRequest( final JSONObject response );
private Request nextRequest(final JSONObject aResponse ){//nextRequest() ties each link in the chain together and is called by the listener.
mLog.debug( "nextRequest:\t" + aResponse.toString() );
Request retVal = null;
// * * * * * * This is how and where the the "future" request must be called/constructed. * * * * * *
if ( mLinkedRequest != null ){
final int mMethod = mLinkedRequest.mPkURL.mMethod;
final String aURL = mLinkedRequest.toURL();
final JSONObject requestBody = mLinkedRequest.getRequest( aResponse );
final Priority priority = mLinkedRequest.mPkURL.mPriority;
final Map<String, String> header = mLinkedRequest.mPkURL.mHeader;
this.mJsonRequest = new JsonObjectRequest( mMethod, aURL,
requestBody,
mJsonResp, mErrLsnr ){
@Override public Priority getPriority() { return priority; }
@Override public Map<String, String> getHeaders() throws AuthFailureError{ return header; }
};
mJsonRequest.setShouldCache( false );
this.mLinkedRequest = mLinkedRequest.mLinkedRequest;
retVal = submit();
}//if
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *
return retVal;
}//nextRequest()
public Request submit(){
mLog.debug( "submit:\n" );
mLog.debug( this.toString() );
if ( mLinkedRequest != null ) mLog.debug( "mLinkedRequest:\t" + mLinkedRequest.toString() );
if ( mJsonRequest!= null ) return mRequestQueue.add( mJsonRequest );
return null;
}//submit()
}//class LinkedRequest