我使用makeServiceCall从TheMovieDB API获取JSON数据。
由于他们没有电影ID列表，我必须循环播放ID。
String JSONString = httpHandler.makeServiceCall("https://api.themoviedb.org/3/movie/" +
i +
"?api_key=" + API_KEY);
i = id
API_KEY =我的API密钥。
当我循环访问URL时，我会收到部分呼叫的IOExceptions。
I/System.out: ID: 152
I/System.out: ID: 160
I/System.out: ID: 165
I/System.out: ID: 168
I/System.out: ID: 171
E/HttpHandler: IOException: https://api.themoviedb.org/3/movie/181?api_key=b692b9da86f1cf0c1b623ea6e2770101
E/HttpHandler: IOException: https://api.themoviedb.org/3/movie/184?api_key=b692b9da86f1cf0c1b623ea6e2770101
E/HttpHandler: IOException: https://api.themoviedb.org/3/movie/185?api_key=b692b9da86f1cf0c1b623ea6e2770101
E/HttpHandler: IOException: https://api.themoviedb.org/3/movie/186?api_key=b692b9da86f1cf0c1b623ea6e2770101
E/HttpHandler: IOException: https://api.themoviedb.org/3/movie/187?api_key=b692b9da86f1cf0c1b623ea6e2770101
E/HttpHandler: IOException: https://api.themoviedb.org/3/movie/188?api_key=b692b9da86f1cf0c1b623ea6e2770101
E/HttpHandler: IOException: https://api.themoviedb.org/3/movie/189?api_key=b692b9da86f1cf0c1b623ea6e2770101
E/HttpHandler: IOException: https://api.themoviedb.org/3/movie/190?api_key=b692b9da86f1cf0c1b623ea6e2770101
E/HttpHandler: IOException: https://api.themoviedb.org/3/movie/191?api_key=b692b9da86f1cf0c1b623ea6e2770101
E/HttpHandler: IOException: https://api.themoviedb.org/3/movie/192?api_key=b692b9da86f1cf0c1b623ea6e2770101
某些IOExceptions只是返回null的URL，如
{"status_code":34,"status_message":"The resource you requested could not be found."}
如何减慢for循环以不超过API调用限制？
HttpHandler的：
package com.example.zdroa.yplex;
import android.util.Log;
import java.io.BufferedInputStream;
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.net.HttpURLConnection;
import java.net.MalformedURLException;
import java.net.ProtocolException;
import java.net.URL;
public class HttpHandler {
private static final String TAG = HttpHandler.class.getSimpleName();
public HttpHandler() {
}
public String makeServiceCall(String reqUrl) {
String response = null;
try {
URL url = new URL(reqUrl);
HttpURLConnection conn = (HttpURLConnection) url.openConnection();
conn.setRequestMethod("GET");
// read the response
InputStream in = new BufferedInputStream(conn.getInputStream());
response = convertStreamToString(in);
} catch (MalformedURLException e) {
Log.e(TAG, "MalformedURLException: " + e.getMessage());
} catch (ProtocolException e) {
Log.e(TAG, "ProtocolException: " + e.getMessage());
} catch (IOException e) {
Log.e(TAG, "IOException: " + e.getMessage());
} catch (Exception e) {
Log.e(TAG, "Exception: " + e.getMessage());
}
return response;
}
private String convertStreamToString(InputStream is) {
BufferedReader reader = new BufferedReader(new InputStreamReader(is));
StringBuilder sb = new StringBuilder();
String line;
try {
while ((line = reader.readLine()) != null) {
sb.append(line).append('\n');
}
} catch (IOException e) {
e.printStackTrace();
} finally {
try {
is.close();
} catch (IOException e) {
e.printStackTrace();
}
}
return sb.toString();
}
}
我的调用是在AsyncTask中进行的
class getWorkingIdsFromAPI extends AsyncTask<Void, Void, Void> {
ArrayList<String> alPersonType;
public getWorkingIdsFromAPI(ArrayList<String> arrayList) {
alPersonType = new ArrayList<>(arrayList);
}
@Override
protected Void doInBackground(Void... params) {
final HttpHandler httpHandler = new HttpHandler();
Timer timer = new Timer();
timer.schedule(new TimerTask() {
@Override
public void run() {
for (int i = 0; i < 200; i++) { //20000
String JSONString = httpHandler.makeServiceCall("https://api.themoviedb.org/3/movie/" + i + "?api_key=" + API_KEY);
if (JSONString != null) {
try {
JSONObject jsonObject = new JSONObject(JSONString);
JSONArray jsonArray = jsonObject.getJSONArray("genres");
boolean cont = true;
for (int a = 0; a < jsonArray.length(); a++) {
JSONObject jsonObject1 = jsonArray.getJSONObject(a);
String string = jsonObject1.getString("name");
for (int b = 0; b < alPersonType.size(); b++) {
if (string.equals(alPersonType.get(b))) {
cont = false;
}
}
}
if (cont) {
String id = String.valueOf(jsonObject.getInt("id"));
System.out.println("ID: " + id);
switch (id.length()) {
case 1:
id = "0000" + id;
break;
case 2:
id = "000" + id;
break;
case 3:
id = "00" + id;
break;
case 4:
id = "0" + id;
break;
}
switch (i) {
case 1:
STRING_LIST_OF_IDS = STRING_LIST_OF_IDS + id;
break;
default:
STRING_LIST_OF_IDS = ", " + STRING_LIST_OF_IDS + id;
break;
}
}
} catch (JSONException e) {
e.printStackTrace();
}
}
}
}
}
, 3000);
return null;
}
@Override
protected void onPostExecute(Void aVoid) {
super.onPostExecute(aVoid);
//add STRING_LIST_OF_IDS
getStringOfIdsFromDB();
}
}
答案 0 :(得分：1)
你做错了，因为计时器任务将在每3000毫秒后重复，它将在循环中执行所有请求。你可以改变这样的代码。
ArrayList<String> alPersonType;
i=0; // initialise your variable once instead of each time in task
public getWorkingIdsFromAPI(ArrayList<String> arrayList) {
alPersonType = new ArrayList<>(arrayList);
}
@Override
protected Void doInBackground(Void... params) {
final HttpHandler httpHandler = new HttpHandler();
Timer timer = new Timer();
timer.schedule(new TimerTask() {
@Override
public void run() {
if(i < 200) { String JSONString = httpHandler.makeServiceCall("https://api.themoviedb.org/3/movie/" + i + "?api_key=" + API_KEY);
if (JSONString != null) {
try {
JSONObject jsonObject = new JSONObject(JSONString);
JSONArray jsonArray = jsonObject.getJSONArray("genres");
boolean cont = true;
for (int a = 0; a < jsonArray.length(); a++) {
JSONObject jsonObject1 = jsonArray.getJSONObject(a);
String string = jsonObject1.getString("name");
for (int b = 0; b < alPersonType.size(); b++) {
if (string.equals(alPersonType.get(b))) {
cont = false;
}
}
}
if (cont) {
String id = String.valueOf(jsonObject.getInt("id"));
System.out.println("ID: " + id);
switch (id.length()) {
case 1:
id = "0000" + id;
break;
case 2:
id = "000" + id;
break;
case 3:
id = "00" + id;
break;
case 4:
id = "0" + id;
break;
}
switch (i) {
case 1:
STRING_LIST_OF_IDS = STRING_LIST_OF_IDS + id;
break;
default:
STRING_LIST_OF_IDS = ", " + STRING_LIST_OF_IDS + id;
break;
}
}
} catch (JSONException e) {
e.printStackTrace();
}i++;//increase the counter
}
}
}
}
, 3000);return null;
}
你也可以使用Thread.sleep（）改变你的doin背景，如下面的
@Override
protected Void doInBackground(Void... params) {
final HttpHandler httpHandler = new HttpHandler();
for (int i = 0; i < 200; i++) {try {
Thread.sleep(400);} catch (InterruptedException e) {
e.printStackTrace();}
String JSONString = httpHandler.makeServiceCall("https://api.themoviedb.org/3/movie/" + i + "?api_key=" + API_KEY);
if (JSONString != null) {
try {
JSONObject jsonObject = new JSONObject(JSONString);
JSONArray jsonArray = jsonObject.getJSONArray("genres");
boolean cont = true;
for (int a = 0; a < jsonArray.length(); a++) {
JSONObject jsonObject1 = jsonArray.getJSONObject(a);
String string = jsonObject1.getString("name");
for (int b = 0; b < alPersonType.size(); b++) {
if (string.equals(alPersonType.get(b))) {
cont = false;
}
}
}
if (cont) {
String id = String.valueOf(jsonObject.getInt("id"));
System.out.println("ID: " + id);
switch (id.length()) {
case 1:
id = "0000" + id;
break;
case 2:
id = "000" + id;
break;
case 3:
id = "00" + id;
break;
case 4:
id = "0" + id;
break;
}
switch (i) {
case 1:
STRING_LIST_OF_IDS = STRING_LIST_OF_IDS + id;
break;
default:
STRING_LIST_OF_IDS = ", " + STRING_LIST_OF_IDS + id;
break;
}
}
} catch (JSONException e) {
e.printStackTrace();
}
}
}
;
return null;
}
答案 1 :(得分：0)
放一个Thread.sleep（持续时间）;在循环开始之后。
try {
Thread.sleep(400);
} catch (InterruptedException e) {
e.printStackTrace();
}
需要400毫秒。每个循环周期都会睡眠。