一. 簡介
Retrofit是Square公司開發的一款針對Android網絡請求的框架,Retrofit2底層基於OkHttp實現的,OkHttp現在已經得到Google官方認可,大量的app都採用OkHttp做網絡請求。[Retrofit github地址](https://github.com/square/retrofit)。[Retrofit官網](http://square.github.io/retrofit/)。
二. 這裏主要介紹get、post、上傳、下載
1.get方法
1. @Query
Get方法請求參數都會以key=value的方式拼接在url後面,Retrofit提供了兩種方式設置請求參數。第一種就是像上文提到的直接在interface中添加@Query註解,還有一種方式是通過Interceptor實現,直接看如何通過Interceptor實現請求參數的添加。
public class CustomInterceptor implements Interceptor {
@Override
public Response intercept(Chain chain) throws IOException {
Request request = chain.request();
HttpUrl httpUrl = request.url().newBuilder()
.addQueryParameter("token", "tokenValue")
.build();
request = request.newBuilder().url(httpUrl).build();
return chain.proceed(request);
}
}
addQueryParameter就是添加請求參數的具體代碼,這種方式比較適用於所有的請求都需要添加的參數,一般現在的網絡請求都會添加token作爲用戶標識,那麼這種方式就比較適合。
addInterceptor(new CustomInterceptor())
2. @QueryMap
如果Query參數比較多,那麼可以通過@QueryMap方式將所有的參數集成在一個Map統一傳遞,還以上文中的get請求方法爲例
public interface BlueService {
@GET("book/search")
Call<BookSearchResponse> getSearchBooks(@QueryMap Map<String, String> options);
}
調用的時候將所有的參數集合在統一的map中即可
Map<String, String> options = new HashMap<>();
map.put("q", "小王子");
map.put("tag", null);
map.put("start", "0");
map.put("count", "3");
Call<BookSearchResponse> call = mBlueService.getSearchBooks(options);
3. Query集合
假如你需要添加相同Key值,但是value卻有多個的情況,一種方式是添加多個@Query參數,還有一種簡便的方式是將所有的value放置在列表中,然後在同一個@Query下完成添加,實例代碼如下:
public interface BlueService {
@GET("book/search")
Call<BookSearchResponse> getSearchBooks(@Query("q") List<String> name);
}
最後得到的url地址爲
https://api.douban.com/v2/book/search?q=leadership&q=beyond%20feelings
1
4. Query非必填
如果請求參數爲非必填,也就是說即使不傳該參數,服務端也可以正常解析,請求方法定義處還是需要完整的Query註解,某次請求如果不需要傳該參數的話,只需填充null即可。
針對文章開頭提到的get的請求,加入按以下方式調用
Call<BookSearchResponse> call = mBlueService.getSearchBooks("小王子", null, 0, 3);
那麼得到的url地址爲
https://api.douban.com/v2/book/search?q=%E5%B0%8F%E7%8E%8B%E5%AD%90&start=0&count=3
5. @Path
如果請求的相對地址也是需要調用方傳遞,那麼可以使用@Path註解,示例代碼如下:
@GET("book/{id}")
Call<BookResponse> getBook(@Path("id") String id);
業務方想要在地址後面拼接書籍id,那麼通過Path註解可以在具體的調用場景中動態傳遞,具體的調用方式如下:
Call<BookResponse> call = mBlueService.getBook("1003078");
此時的url地址爲
https://api.douban.com/v2/book/1003078
@Path可以用於任何請求方式,包括Post,Put,Delete等等
Post請求
1. @field
Post請求需要把請求參數放置在請求體中,而非拼接在url後面,先來看一個簡單的例子
@FormUrlEncoded
@POST("book/reviews")
Call<String> addReviews(@Field("book") String bookId, @Field("title") String title,
@Field("content") String content, @Field("rating") String rating);
這裏有幾點需要說明的
1. @FormUrlEncoded將會自動將請求參數的類型調整爲application/x-www-form-urlencoded,假如content傳遞的參數爲Good Luck,那麼最後得到的請求體就是content=Good+Luck
2. @Field註解將每一個請求參數都存放至請求體中,還可以添加encoded參數,該參數爲boolean型,具體的用法爲
@Field(value = "book", encoded = true) String book
encoded參數爲true的話,key-value-pair將會被編碼,即將中文和特殊字符進行編碼轉換
2.@FieldMap
上述Post請求有4個請求參數,假如說有更多的請求參數,那麼通過一個一個的參數傳遞就顯得很麻煩而且容易出錯,這個時候就可以用FieldMap
3. @Body
如果Post請求參數有多個,那麼統一封裝到類中應該會更好,這樣維護起來會非常方便
@FormUrlEncoded
@POST("book/reviews")
Call<String> addReviews(@Body Reviews reviews);
public class Reviews {
public String book;
public String title;
public String content;
public String rating;
}
除了Get和Post請求,Http請求還包括Put,Delete等等,用法和Post相似,所以就不再單獨介紹了。
文件上傳
上傳因爲需要用到Multipart,所以需要單獨拿出來介紹,先看一個具體上傳的例子
首先還是需要新建一個interface用於定義上傳方法
public interface FileUploadService {
// 上傳單個文件
@Multipart
@POST("upload")
Call<ResponseBody> uploadFile(
@Part("description") RequestBody description,
@Part MultipartBody.Part file);
// 上傳多個文件
@Multipart
@POST("upload")
Call<ResponseBody> uploadMultipleFiles(
@Part("description") RequestBody description,
@Part MultipartBody.Part file1,
@Part MultipartBody.Part file2);
}
接下來我們還需要在Activity和Fragment中實現兩個工具方法,代碼如下:
public static final String MULTIPART_FORM_DATA = "multipart/form-data";
@NonNull
private RequestBody createPartFromString(String descriptionString) {
return RequestBody.create(
MediaType.parse(MULTIPART_FORM_DATA), descriptionString);
}
@NonNull
private MultipartBody.Part prepareFilePart(String partName, Uri fileUri) {
File file = FileUtils.getFile(this, fileUri);
// 爲file建立RequestBody實例
RequestBody requestFile =
RequestBody.create(MediaType.parse(MULTIPART_FORM_DATA), file);
// MultipartBody.Part藉助文件名完成最終的上傳
return MultipartBody.Part.createFormData(partName, file.getName(), requestFile);
}
好了,接下來就是最終的上傳文件代碼了
Uri file1Uri = ... // 從文件選擇器或者攝像頭中獲取
Uri file2Uri = ...
// 創建上傳的service實例
FileUploadService service =
ServiceGenerator.createService(FileUploadService.class);
// 創建文件的part (photo, video, ...)
MultipartBody.Part body1 = prepareFilePart("video", file1Uri);
MultipartBody.Part body2 = prepareFilePart("thumbnail", file2Uri);
// 添加其他的part
RequestBody description = createPartFromString("hello, this is description speaking");
// 最後執行異步請求操作
Call<ResponseBody> call = service.uploadMultipleFiles(description, body1, body2);
call.enqueue(new Callback<ResponseBody>() {
@Override
public void onResponse(Call<ResponseBody> call,
Response<ResponseBody> response) {
Log.v("Upload", "success");
}
@Override
public void onFailure(Call<ResponseBody> call, Throwable t) {
Log.e("Upload error:", t.getMessage());
}
});
文件下載
文件下載我們需要使用@Url和 @Streaming ,@Url動態Url正好非常適合我們的場景,而使用@Streaming註解可以讓我們下載非常大的文件時,避免Retrofit將整個文件讀進內存,否則可能造成OOM現象。
@Streaming
@GET
Call<ResponseBody> downloadFileByDynamicUrlAsync(@Url String downloadUrl);
需要注意的是我們需要使用Retrofitcall.execute同步獲取ResponseBody,那麼我們就需要放進一個單獨的工作線程中:
new AsyncTask<Void, Long, Void>() {
@Override
protected Void doInBackground(Void... voids) {
Call<ResponseBody> call = myTestApiService.downloadFileByDynamicUrlAsync(API_BASE_URL.concat("/res/atom-amd64.deb"));
try {
Response<ResponseBody> response = call.execute();
boolean writtenToDisk = writeResponseBodyToDisk(response.body());
Log.d(TAG, "下載文件 " + writtenToDisk);
} catch (IOException e) {
e.printStackTrace();
}
return null;
}
@Override
protected void onPreExecute() {
super.onPreExecute();
}
}.execute();
最後我們需要將文件寫入磁盤根目錄中:
//寫入到磁盤根目錄
private boolean writeResponseBodyToDisk(ResponseBody body) {
try {
File futureStudioIconFile = new File(Environment.getExternalStorageDirectory() + File.separator + "atom.deb");
InputStream inputStream = null;
OutputStream outputStream = null;
try {
byte[] fileReader = new byte[4096];
final long fileSize = body.contentLength();
long fileSizeDownloaded = 0;
inputStream = body.byteStream();
outputStream = new FileOutputStream(futureStudioIconFile);
while (true) {
int read = inputStream.read(fileReader);
if (read == -1) {
break;
}
outputStream.write(fileReader, 0, read);
fileSizeDownloaded += read;
Log.d(TAG, "file download: " + fileSizeDownloaded + " of " + fileSize);
final long finalFileSizeDownloaded = fileSizeDownloaded;
runOnUiThread(new Runnable() {
@Override
public void run() {
resultTextView.setText("file download: " + finalFileSizeDownloaded + " of " + fileSize);
}
});
}
outputStream.flush();
return true;
} catch (IOException e) {
return false;
} finally {
if (inputStream != null) {
inputStream.close();
}
if (outputStream != null) {
outputStream.close();
}
}
} catch (IOException e) {
return false;
}
}
這樣我們就可以非常高效的下載大文件了,最後友情提醒(如果是6.0以上另外再申請權限):
<uses-permission android:name="android.permission.INTERNET" />
<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />
其它註解
1. @Headers
@Headers:用於在方法添加請求頭:
@POST("test/sayHi")
@Headers("Accept-Encoding: application/json")
Call<ResultBean> postSayHi(@Body UserBean userBean, @Header("city") String city);
2. @Streaming
如果您正在下載一個大文件,Retrofit2將嘗試將整個文件移動到內存中。爲了避免這種,我們必須向請求聲明中添加一個特殊的註解@Streaming
@Streaming
@GET
Call<ResponseBody> downloadFileByDynamicUrlAsync(@Url String fileUrl);
3.@Header
用於在方法參數裏動態添加請求頭:
Call<ResultBean> postSayHi(@Header("city") String city);
public class RequestInterceptor implements Interceptor {
@Override
public Response intercept(Chain chain) throws IOException {
Request original = chain.request();
Request request = original.newBuilder()
.header("User-Agent", "Your-App-Name")
.header("Accept", "application/vnd.yourapi.v1.full+json")
.method(original.method(), original.body())
.build();
return chain.proceed(request);
}
}
4. @Url
使用動態的請求的網址,會複寫之前的baseUrl,值得注意的是@Url需要在所有參數之前:
@POST
Call<ResultBean> postSayHelloByURL(@Url String url,@Query("username") String username, @Query("age") String age);
5. @Part
6. @PartMap
這兩個用於上傳文件,與@MultiPart註解結合使用
@Multipart
@POST("test/upload")
Call<ResultBean> upload(@Part("file\"; filename=\"launcher_icon.png") RequestBody file);
添加日誌
調試網絡請求的時候經常需要關注一下請求參數和返回值,以便判斷和定位問題出在哪裏,Retrofit官方提供了一個很方便查看日誌的Interceptor,你可以控制你需要的打印信息類型,使用方法也很簡單。
首先需要在build.gradle文件中引入logging-interceptor
compile 'com.squareup.okhttp3:logging-interceptor:3.4.1'
同上文提到的CustomInterceptor和RequestInterceptor一樣,添加到OkHttpClient創建處即可,完整的示例代碼如下:
private static OkHttpClient getNewClient(){
HttpLoggingInterceptor logging = new HttpLoggingInterceptor();
logging.setLevel(HttpLoggingInterceptor.Level.BODY);
return new OkHttpClient.Builder()
.addInterceptor(new CustomInterceptor())
.addInterceptor(logging)
.connectTimeout(DEFAULT_TIMEOUT, TimeUnit.SECONDS)
.build();
}
HttpLoggingInterceptor提供了4中控制打印信息類型的等級,分別是NONE,BASIC,HEADERS,BODY,接下來分別來說一下相應的打印信息類型。
-NONE
沒有任何日誌信息
-Basic
打印請求類型,URL,請求體大小,返回值狀態以及返回值的大小
D/HttpLoggingInterceptor$Logger: --> POST /upload HTTP/1.1 (277-byte body)
D/HttpLoggingInterceptor$Logger: <-- HTTP/1.1 200 OK (543ms, -1-byte body)
-Headers
打印返回請求和返回值的頭部信息,請求類型,URL以及返回值狀態碼
<-- 200 OK https://api.douban.com/v2/book/search?q=%E5%B0%8F%E7%8E%8B%E5%AD%90&start=0&count=3&token=tokenValue (3787ms)
D/OkHttp: Date: Sat, 06 Aug 2016 14:26:03 GMT
D/OkHttp: Content-Type: application/json; charset=utf-8
D/OkHttp: Transfer-Encoding: chunked
D/OkHttp: Connection: keep-alive
D/OkHttp: Keep-Alive: timeout=30
D/OkHttp: Vary: Accept-Encoding
D/OkHttp: Expires: Sun, 1 Jan 2006 01:00:00 GMT
D/OkHttp: Pragma: no-cache
D/OkHttp: Cache-Control: must-revalidate, no-cache, private
D/OkHttp: Set-Cookie: bid=D6UtQR5N9I4; Expires=Sun, 06-Aug-17 14:26:03 GMT; Domain=.douban.com; Path=/
D/OkHttp: X-DOUBAN-NEWBID: D6UtQR5N9I4
D/OkHttp: X-DAE-Node: dis17
D/OkHttp: X-DAE-App: book
D/OkHttp: Server: dae
D/OkHttp: <-- END HTTP
-Body
打印請求和返回值的頭部和body信息
<-- 200 OK https://api.douban.com/v2/book/search?q=%E5%B0%8F%E7%8E%8B%E5%AD%90&tag=&start=0&count=3&token=tokenValue (3583ms)
D/OkHttp: Connection: keep-alive
D/OkHttp: Date: Sat, 06 Aug 2016 14:29:11 GMT
D/OkHttp: Keep-Alive: timeout=30
D/OkHttp: Content-Type: application/json; charset=utf-8
D/OkHttp: Vary: Accept-Encoding
D/OkHttp: Expires: Sun, 1 Jan 2006 01:00:00 GMT
D/OkHttp: Transfer-Encoding: chunked
D/OkHttp: Pragma: no-cache
D/OkHttp: Connection: keep-alive
D/OkHttp: Cache-Control: must-revalidate, no-cache, private
D/OkHttp: Keep-Alive: timeout=30
D/OkHttp: Set-Cookie: bid=ESnahto1_Os; Expires=Sun, 06-Aug-17 14:29:11 GMT; Domain=.douban.com; Path=/
D/OkHttp: Vary: Accept-Encoding
D/OkHttp: X-DOUBAN-NEWBID: ESnahto1_Os
D/OkHttp: Expires: Sun, 1 Jan 2006 01:00:00 GMT
D/OkHttp: X-DAE-Node: dis5
D/OkHttp: Pragma: no-cache
D/OkHttp: X-DAE-App: book
D/OkHttp: Cache-Control: must-revalidate, no-cache, private
D/OkHttp: Server: dae
D/OkHttp: Set-Cookie: bid=5qefVyUZ3KU; Expires=Sun, 06-Aug-17 14:29:11 GMT; Domain=.douban.com; Path=/
D/OkHttp: X-DOUBAN-NEWBID: 5qefVyUZ3KU
D/OkHttp: X-DAE-Node: dis17
D/OkHttp: X-DAE-App: book
D/OkHttp: Server: dae
D/OkHttp: {"count":3,"start":0,"total":778,"books":[{"rating":{"max":10,"numRaters":202900,"average":"9.0","min":0},"subtitle":"","author":["[法] 聖埃克蘇佩裏"],"pubdate":"2003-8","tags":[{"count":49322,"name":"小王子","title":"小王子"},{"count":41381,"name":"童話","title":"童話"},{"count":19773,"name":"聖埃克蘇佩裏","title":"聖埃克蘇佩裏"}
D/OkHttp: <-- END HTTP (13758-byte body)