Android 如何使用 Retrofit 从异步回调中返回 String 或 JSONObject？
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How can I return String or JSONObject from asynchronous callback using Retrofit?
提问by lordmegamax
For example, calling
例如，调用
api.getUserName(userId, new Callback<String>() {...});
cause:
原因：
retrofit.RetrofitError: retrofit.converter.ConversionException:
com.google.gson.JsonSyntaxException: java.lang.IllegalStateException:
Expected a string but was BEGIN_OBJECT at line 1 column 2
I think I must disable gson parsing into POJOs but can't figure out how to do it.
我想我必须禁用 gson 解析成 POJO，但不知道如何去做。
回答by lordmegamax
I figured it out. It's embarrassing but it was very simple... Temporary solutionmay be like this:
我想到了。这很尴尬，但很简单......临时解决方案可能是这样的：
public void success(Response response, Response ignored) {
TypedInput body = response.getBody();
try {
BufferedReader reader = new BufferedReader(new InputStreamReader(body.in()));
StringBuilder out = new StringBuilder();
String newLine = System.getProperty("line.separator");
String line;
while ((line = reader.readLine()) != null) {
out.append(line);
out.append(newLine);
}
// Prints the correct String representation of body.
System.out.println(out);
} catch (IOException e) {
e.printStackTrace();
}
}
But if you want to get directly Callback the Better wayis to use Converter.
但是如果你想直接获得回调，更好的方法是使用Converter。
public class Main {
public interface ApiService {
@GET("/api/")
public void getJson(Callback<String> callback);
}
public static void main(String[] args) {
RestAdapter restAdapter = new RestAdapter.Builder()
.setClient(new MockClient())
.setConverter(new StringConverter())
.setEndpoint("http://www.example.com").build();
ApiService service = restAdapter.create(ApiService.class);
service.getJson(new Callback<String>() {
@Override
public void success(String str, Response ignored) {
// Prints the correct String representation of body.
System.out.println(str);
}
@Override
public void failure(RetrofitError retrofitError) {
System.out.println("Failure, retrofitError" + retrofitError);
}
});
}
static class StringConverter implements Converter {
@Override
public Object fromBody(TypedInput typedInput, Type type) throws ConversionException {
String text = null;
try {
text = fromStream(typedInput.in());
} catch (IOException ignored) {/*NOP*/ }
return text;
}
@Override
public TypedOutput toBody(Object o) {
return null;
}
public static String fromStream(InputStream in) throws IOException {
BufferedReader reader = new BufferedReader(new InputStreamReader(in));
StringBuilder out = new StringBuilder();
String newLine = System.getProperty("line.separator");
String line;
while ((line = reader.readLine()) != null) {
out.append(line);
out.append(newLine);
}
return out.toString();
}
}
public static class MockClient implements Client {
@Override
public Response execute(Request request) throws IOException {
URI uri = URI.create(request.getUrl());
String responseString = "";
if (uri.getPath().equals("/api/")) {
responseString = "{result:\"ok\"}";
} else {
responseString = "{result:\"error\"}";
}
return new Response(request.getUrl(), 200, "nothing", Collections.EMPTY_LIST,
new TypedByteArray("application/json", responseString.getBytes()));
}
}
}
If you know how to improve this code - please feel free to write about it.
如果您知道如何改进此代码 - 请随时写下它。
回答by TPoschel
A possible solution would be to use JsonElementas the Callbacktype (Callback<JsonElement>). In your original example:
一种可能的解决方案是使用JsonElementasCallback类型 ( Callback<JsonElement>)。在您的原始示例中：
api.getUserName(userId, new Callback<JsonElement>() {...});
In the success method you can convert the JsonElementto either a Stringor a JsonObject.
在成功方法中，您可以将 转换JsonElement为 aString或 a JsonObject。
JsonObject jsonObj = element.getAsJsonObject();
String strObj = element.toString();
回答by floating cat
Retrofit 2.0.0-beta3 adds a
converter-scalarsmodule provides aConverter.Factoryfor convertingString, the 8 primitive types, and the 8 boxed primitive types astext/plainbodies. Install this before your normal converter to avoid passing these simple scalars through, for example, a JSON converter.
Retrofit 2.0.0-beta3 添加了一个
converter-scalars模块，提供了一个Converter.Factory用于转换String的 8 种原始类型和 8 种装箱原始类型作为text/plain主体。在您的普通转换器之前安装它，以避免通过例如 JSON 转换器传递这些简单的标量。
So, first add converter-scalarsmodule to build.gradlefile for your application.
因此，首先将converter-scalars模块添加到build.gradle您的应用程序的文件中。
dependencies {
...
// use your Retrofit version (requires at minimum 2.0.0-beta3) instead of 2.0.0
// also do not forget to add other Retrofit module you needed
compile 'com.squareup.retrofit2:converter-scalars:2.0.0'
}
Then, create your Retrofitinstance like this:
然后，Retrofit像这样创建你的实例：
new Retrofit.Builder()
.baseUrl(BASE_URL)
// add the converter-scalars for coverting String
.addConverterFactory(ScalarsConverterFactory.create())
.addConverterFactory(GsonConverterFactory.create())
.addCallAdapterFactory(RxJavaCallAdapterFactory.create())
.build()
.create(Service.class);
Now you can use API declaration like this:
现在您可以像这样使用 API 声明：
interface Service {
@GET("/users/{id}/name")
Call<String> userName(@Path("userId") String userId);
// RxJava version
@GET("/users/{id}/name")
Observable<String> userName(@Path("userId") String userId);
}
回答by bgplaya
The answer may be much shorter than already mentioned and doesn't require any additional libraries:
答案可能比已经提到的要短得多，并且不需要任何额外的库：
In declaration use Responseas follows:
在声明中使用Response如下：
... Callback<Response> callback);
And while handling response:
在处理响应时：
@Override
public void success(Response s, Response response) {
new JSONObject(new String(((TypedByteArray) response.getBody()).getBytes()))
}
回答by ar-g
When @lordmegamax answer completely work there is much nicer solution which is come from
当@lordmegamax 回答完全有效时，有更好的解决方案来自
Okio is a new library that complements java.io and java.nio
Okio 是一个补充 java.io 和 java.nio 的新库
other squares project which already tight with retrofitand therefore you don't need to add any new dependency and it's have to be reliable:
其他 squares 项目已经很紧密了retrofit，因此您不需要添加任何新的依赖项，并且它必须是可靠的：
ByteString.read(body.in(), (int) body.length()).utf8();
ByteString is an immutable sequence of bytes. For character data, String is fundamental. ByteString is String's long-lost brother, making it easy to treat binary data as a value. This class is ergonomic: it knows how to encode and decode itself as hex, base64, and UTF-8.
ByteString 是一个不可变的字节序列。对于字符数据，String 是基础。ByteString 是 String 失散已久的兄弟，可以轻松地将二进制数据视为值。这个类是符合人体工程学的：它知道如何将自己编码和解码为十六进制、base64 和 UTF-8。
Full example:
完整示例：
public class StringConverter implements Converter {
@Override public Object fromBody(TypedInput body, Type type) throws ConversionException {
try {
return ByteString.read(body.in(), (int) body.length()).utf8();
} catch (IOException e) {
throw new ConversionException("Problem when convert string", e);
}
}
@Override public TypedOutput toBody(Object object) {
return new TypedString((String) object);
}
}
回答by styler1972
Here is what I did, after poking around in the debugger. Note: this is for actually getting it inside an error callback, not the success callback.
这是我在调试器中闲逛后所做的。注意：这是为了在错误回调中实际获取它，而不是成功回调。
You'll see that the success type is found by calling retrofitError.getSuccessType()and returns and object of type Type
你会看到成功类型是通过调用retrofitError.getSuccessType()和返回类型的对象找到的Type
You can then call retrofitError.getBodyAs(YourType.class)which is all I needed to do because for me its always the class I expect it to be.
然后你可以调用retrofitError.getBodyAs(YourType.class)我需要做的所有事情，因为对我来说它总是我期望的类。
Here is the one-liner answer:
这是单行答案：
retrofitError.getBodyAs(retrofitError.getSuccessType())
Now, I'll note that I dont have to do anything like this regarding the success callback because it's already working magically.
现在，我会注意到我不必对成功回调做任何类似的事情，因为它已经神奇地工作了。
回答by oziem
To get Call JSONObject or JSONArray
获取调用 JSONObject 或 JSONArray
you can create custom factory or copy it from here : https://github.com/marcinOz/Retrofit2JSONConverterFactory
您可以创建自定义工厂或从这里复制它：https: //github.com/marcinOz/Retrofit2JSONConverterFactory
