Android OkHttp的基本用法

OkHttp可以说是如今最为流行的网络请求框架之一，今天来探究下OkHttp 的使用方法，包括Get 请求、Post 请求、上传下载文件、上传下载图片等功能

在使用OKHttp之前，首先要先了解如下几个比较核心的类：

- OkHttpClient：客户端对象

- Request：访问请求，Post请求中需要包含RequestBody

- RequestBody：请求数据，在Post请求中用到

- Response：即网络请求的响应结果

- MediaType：数据类型，用来表明数据是json，image，pdf等一系列格式

- client.newCall(request).execute()：同步的请求方法

- client.newCall(request).enqueue(Callback callBack)：异步的请求方法，但Callback是执行在子线程中的，因此不能在此进行UI更新操作

在使用前需要先在项目中添加OkHttp的依赖库，在对应的Module的gradle中添加如下语句

compile 'com.squareup.okhttp3:okhttp:3.6.0'

此外，OkHttp内部依赖另一个开源库OkIo，所以也要将它导入进来

compile 'com.squareup.okio:okio:1.11.0'

然后同步项目即可

OkHttp的GitHub地址是：OkHttp

OkIo的GitHub地址是：OkIo

一、Get 请求

最常见的网络请求方式可以说就是Get请求了，这里来获取我在简书的个人主页的网页内容

public void get(View view) {
OkHttpClient client = new OkHttpClient();
//构造Request对象
//采用建造者模式，链式调用指明进行Get请求,传入Get的请求地址
Request request = new Request.Builder().get().url("http://www.jianshu.com/u/9df45b87cfdf").build();
Call call = client.newCall(request);
//异步调用并设置回调函数
call.enqueue(new Callback() {
@Override
public void onFailure(Call call, IOException e) {
ToastUtil.showToast(GetActivity.this, "Get 失败");
}

@Override
public void onResponse(Call call, final Response response) throws IOException {
final String responseStr = response.body().string();
runOnUiThread(new Runnable() {
@Override
public void run() {
tv_result.setText(responseStr);
}
});
}
});
}

需要注意的是，异步调用的回调函数是在子线程当中的，因为需要用Handler或者runOnUiThread来更新UI

这里使用到了一个Toast工具类，用户判断当前线程是否是主线程，是的话则直接弹出Toast，否则利用runOnUiThread来弹出Toast

/**
* 作者： 叶应是叶
* 时间： 2017/4/2 15:41
* 描述：
*/
public class ToastUtil {

public static void showToast(final Activity activity, final String message) {
if ("main".equals(Thread.currentThread().getName())) {
Log.e("ToastUtil", "在主线程");
Toast.makeText(activity, message, Toast.LENGTH_SHORT).show();
} else {
activity.runOnUiThread(new Runnable() {
@Override
public void run() {
Log.e("ToastUtil", "不在主线程");
Toast.makeText(activity, message, Toast.LENGTH_SHORT).show();
}
});
}
}

}

此外，在回调函数的以下方法中

public void onResponse(Call call, final Response response)

如果希望获得返回的是字符串，则可以使用

response.body().string()

如果需要的是字节数组，则使用

response.body().bytes()

如果需要的是输入流，则使用

response.body().byteStream()

二、Post 类型

在OkHttp中用Post方法向服务器发送一个请求体时，请求体需要是一个RequestBody。这个请求体可以是：

- key-value：键值对类型

- String：字符串类型

- Form：类似于Html的表单数据提交

- Stream：流类型

- File：文件类型

三、Post 键值对

public void postParameter(View view) {
OkHttpClient client = new OkHttpClient();
//构建FormBody，传入要提交的参数
FormBody formBody = new FormBody
.Builder()
.add("username", "initObject")
.add("password", "initObject")
.build();
final Request request = new Request.Builder()
.url("http://www.jianshu.com/")
.post(formBody)
.build();
Call call = client.newCall(request);
call.enqueue(new Callback() {
@Override
public void onFailure(Call call, IOException e) {
ToastUtil.showToast(PostParameterActivity.this, "Post Parameter 失败");
}

@Override
public void onResponse(Call call, Response response) throws IOException {
final String responseStr = response.body().string();
ToastUtil.showToast(PostParameterActivity.this, "Code：" + String.valueOf(response.code()));
runOnUiThread(new Runnable() {
@Override
public void run() {
tv_result.setText(responseStr);
}
});
}
});
}

这里来向简书的网站主页提交两个参数值，可以通过Post来实现模拟登录的功能。当然这里只是模拟了Post操作而已，提交参数后会跳转到404页面

在

public void onResponse(Call call, Response response)

方法中通过

response.code()

可以得到整数类型的结果码：404

四、Post 字符串

在上面的例子中Post传递的是参数对，有时候我们会有要传送字符串的需要，比如向服务器发送一个JSON字符串。那么就可以用如下方法：

public void postString(View view) {
OkHttpClient client = new OkHttpClient();
//RequestBody中的MediaType指定为纯文本，编码方式是utf-8
RequestBody requestBody = RequestBody.create(MediaType.parse("text/plain;charset=utf-8"),
"{username:admin;password:admin}");
final Request request = new Request.Builder()
.url("http://www.jianshu.com/")
.post(requestBody)
.build();
Call call = client.newCall(request);
call.enqueue(new Callback() {
@Override
public void onFailure(Call call, IOException e) {
ToastUtil.showToast(PostStringActivity.this, "Post String 失败");
}

@Override
public void onResponse(Call call, Response response) throws IOException {
final String responseStr = response.body().string();
ToastUtil.showToast(PostStringActivity.this, "Code：" + String.valueOf(response.code()));
runOnUiThread(new Runnable() {
@Override
public void run() {
tv_result.setText(responseStr);
}
});
}
});
}

五、Post 表单

通过查看网站登录页的Html源代码，通常都可以查看到如下格式的登录表单

<form id="fm1" action="" method="post">
<input id="username" name="username" type="text"/>
<input id="password" name="password" type="password"/>
</form>

这里使用到 MuiltipartBody 来构建一个RequestBody，这是 RequestBody 的一个子类，提交表单数据就是利用这个类来实现的

public void postForm(View view) {
OkHttpClient client = new OkHttpClient();
RequestBody requestBody = new MultipartBody.Builder()
.setType(MultipartBody.FORM)
.addFormDataPart("username", "叶应是叶")
.addFormDataPart("password", "叶应是叶")
.build();
final Request request = new Request.Builder()
.url("http://www.jianshu.com/")
.post(requestBody)
.build();
Call call = client.newCall(request);
call.enqueue(new Callback() {
@Override
public void onFailure(Call call, IOException e) {
ToastUtil.showToast(PostFormActivity.this, "Post Form 失败");
}

@Override
public void onResponse(Call call, Response response) throws IOException {
final String responseStr = response.body().string();
ToastUtil.showToast(PostFormActivity.this, "Code：" + String.valueOf(response.code()));
runOnUiThread(new Runnable() {
@Override
public void run() {
tv_result.setText(responseStr);
}
});
}
});
}

六、Post 流

public void postStreaming(View view) {
final MediaType MEDIA_TYPE_MARKDOWN = MediaType.parse("text/x-markdown; charset=utf-8");
OkHttpClient client = new OkHttpClient();
RequestBody requestBody = new RequestBody() {
@Override
public MediaType contentType() {
return MEDIA_TYPE_MARKDOWN;
}

@Override
public void writeTo(BufferedSink sink) throws IOException {
sink.writeUtf8("Numbers\n");
sink.writeUtf8("-------\n");
for (int i = 2; i <= 997; i++) {
sink.writeUtf8(String.format(" * %s = %s\n", i, factor(i)));
}
}

private String factor(int n) {
for (int i = 2; i < n; i++) {
int x = n / i;
if (x * i == n) return factor(x) + " × " + i;
}
return Integer.toString(n);
}
};
Request request = new Request.Builder()
.url("https://api.github.com/markdown/raw")
.post(requestBody)
.build();
Call call = client.newCall(request);
call.enqueue(new Callback() {
@Override
public void onFailure(Call call, IOException e) {
ToastUtil.showToast(PostStreamingActivity.this, "Post Streaming 失败");
}

@Override
public void onResponse(Call call, Response response) throws IOException {
final String responseStr = response.body().string();
ToastUtil.showToast(PostStreamingActivity.this, "Code：" + String.valueOf(response.code()));
runOnUiThread(new Runnable() {
@Override
public void run() {
tv_result.setText(responseStr);
}
});
}
});
}

七、Post 文件

public void postFile(View view) {
OkHttpClient client = new OkHttpClient();
final MediaType MEDIA_TYPE_MARKDOWN = MediaType.parse("text/x-markdown; charset=utf-8");
File file = new File("README.md");
Request request = new Request.Builder()
.url("https://api.github.com/markdown/raw")
.post(RequestBody.create(MEDIA_TYPE_MARKDOWN, file))
.build();
Call call = client.newCall(request);
call.enqueue(new Callback() {
@Override
public void onFailure(Call call, IOException e) {
ToastUtil.showToast(PostFileActivity.this, "Post File 失败");
}

@Override
public void onResponse(Call call, Response response) throws IOException {
final String responseStr = response.body().string();
ToastUtil.showToast(PostFileActivity.this, "Code：" + String.valueOf(response.code()));
runOnUiThread(new Runnable() {
@Override
public void run() {
tv_result.setText(responseStr);
}
});
}
});
}

八、下载图片

public void downImage(View view) {
OkHttpClient client = new OkHttpClient();
final Request request = new Request
.Builder()
.get()
.url("http://avatar.csdn.net/B/0/1/1_new_one_object.jpg")
.build();
Call call = client.newCall(request);
call.enqueue(new Callback() {
@Override
public void onFailure(Call call, IOException e) {
ToastUtil.showToast(DownImageActivity.this, "下载图片失败");
}

@Override
public void onResponse(Call call, Response response) throws IOException {
InputStream inputStream = response.body().byteStream();
//将图片显示到ImageView中
final Bitmap bitmap = BitmapFactory.decodeStream(inputStream);
runOnUiThread(new Runnable() {
@Override
public void run() {
iv_result.setImageBitmap(bitmap);
}
});
//将图片保存到本地存储卡中
File file = new File(Environment.getExternalStorageDirectory(), "image.png");
FileOutputStream fileOutputStream = new FileOutputStream(file);
byte[] temp = new byte[128];
int length;
while ((length = inputStream.read(temp)) != -1) {
fileOutputStream.write(temp, 0, length);
}
fileOutputStream.flush();
fileOutputStream.close();
inputStream.close();
}
});
}

指定图片地址并下载成功后，获取图片的输入流，先用

Bitmap decodeStream(InputStream is)

方法将输入流转为Bitmap然后显示出来，然后将图片保存到本地存储卡根目录下

记得要申请存储卡的写权限

<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />

九、解析Json

这里来通过Gson将response的内容解析为Java Bean

首先需要先去将Gson.jar文件导入工程

这里来通过OkHttp访问接口“http://news-at.zhihu.com/api/4/themes”，获取Json数据然后将之解析为JavaBean实体



首先根据Json格式建立一个JavaBean

/**
* 作者： 叶应是叶
* 时间： 2017/4/2 22:27
* 描述：
*/
public class Bean {

private String date;

private List<StoriesBean> stories;

public String getDate() {
return date;
}

public void setDate(String date) {
this.date = date;
}

public List<StoriesBean> getStories() {
return stories;
}

public void setStories(List<StoriesBean> stories) {
this.stories = stories;
}

public static class StoriesBean {

private int type;

private int id;

private String ga_prefix;

private String title;

private boolean multipic;

private List<String> images;

public int getType() {
return type;
}

public void setType(int type) {
this.type = type;
}

public int getId() {
return id;
}

public void setId(int id) {
this.id = id;
}

public String getGa_prefix() {
return ga_prefix;
}

public void setGa_prefix(String ga_prefix) {
this.ga_prefix = ga_prefix;
}

public String getTitle() {
return title;
}

public void setTitle(String title) {
this.title = title;
}

public boolean isMultipic() {
return multipic;
}

public void setMultipic(boolean multipic) {
this.multipic = multipic;
}

public List<String> getImages() {
return images;
}

public void setImages(List<String> images) {
this.images = images;
}

@Override
public String toString() {
return "标题='" + title + '\'' + "图片链接=" + images;
}
}

}

获取Json数据并解析

public void parseJson(View view) {
OkHttpClient client = new OkHttpClient();
final Gson gson = new Gson();
Request request = new Request.Builder()
.url("http://news-at.zhihu.com/api/4/news/before/20131119")
.build();

Call call = client.newCall(request);
call.enqueue(new Callback() {
@Override
public void onFailure(Call call, IOException e) {
ToastUtil.showToast(ParseJsonActivity.this, "parse Json 失败");
}

@Override
public void onResponse(Call call, Response response) throws IOException {
ToastUtil.showToast(ParseJsonActivity.this, "Code：" + String.valueOf(response.code()));
final Bean bean = gson.fromJson(response.body().charStream(), Bean.class);
List<Bean.StoriesBean> stories = bean.getStories();
final StringBuilder stringBuilder = new StringBuilder();
for (Bean.StoriesBean storiesBean : stories) {
stringBuilder.append(storiesBean);
stringBuilder.append("\n\n\n");
}
runOnUiThread(new Runnable() {
@Override
public void run() {
tv_result.setText(stringBuilder.toString());
}
});
}
});
}

解析结果：

这里提供上述示例代码下载：Android OkHttp的基本用法