android retrofit 从无知到入门

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前言

本文会从零开始介绍retrofit的一些简单使用和封装，基于retrofit:2.3.0

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一、初识retrofit

1.retrofit是什么？

retrofit官方文档的介绍非常的简洁明了，俗话说得好，字越少越牛逼，它是一个适用于Android和Java的类型安全HTTP客户端，它的底层是基于okhttp的，用了各种各样的设计模式封装起来的，在这里我们不多赘述，至于也不了解okhttp的，emmm，懂的都懂

2.一些配置和数据准备

既然是用于通信的，就不要忘记添加网络权限，在项目的Androidmanifest中添加

<!-- 访问网络的权限 -->
<uses-permission android:name="android.permission.INTERNET"></uses-permission>

当然也少不了添加依赖，为了不过多赘述这些，我们一次添加齐全，在build.gradle中添加

//retrofit
api 'com.squareup.retrofit2:retrofit:2.3.0'
api 'com.squareup.retrofit2:converter-gson:2.3.0'
api 'com.squareup.retrofit2:adapter-rxjava2:2.3.0'
api 'com.trello.rxlifecycle2:rxlifecycle-components:2.2.1'
api 'com.facebook.stetho:stetho:1.5.0'
api 'com.facebook.stetho:stetho-okhttp3:1.5.0'

我们来一个请求的返回体
“为了规范我们写的规范一点”

import io.swagger.annotations.ApiModel;
import io.swagger.annotations.ApiModelProperty;
import java.io.Serializable;
import java.util.HashMap;
import java.util.Map;

@ApiModel(
    value = "DataResponse",
    description = "请求返回值"
)
public abstract class DataResponse<T> implements Serializable {
    private static final long serialVersionUID = -7574544066074667453L;
    @ApiModelProperty(
        value = "错误编码,0代表无错误",
        name = "errorCode"
    )
    private int errorCode = 0;
    @ApiModelProperty(
        value = "结果编码",
        name = "resultCode"
    )
    private String resultCode = "";
    @ApiModelProperty(
        value = "结果信息",
        name = "message"
    )
    private String message;
    @ApiModelProperty(
        value = "附加信息",
        name = "extInfo"
    )
    private Map<String, Object> extInfo = new HashMap();
    @ApiModelProperty(
        value = "请求返回数据",
        name = "data"
    )
    private T data;
    private String requestId;

    public DataResponse() {
    }

    public DataResponse(T data) {
        this.data = data;
    }

    public DataResponse(T data, int errorCode) {
        this.data = data;
        this.errorCode = errorCode;
    }

    public int getErrorCode() {
        return this.errorCode;
    }

    public void setErrorCode(int errorCode) {
        this.errorCode = errorCode;
    }

    public T getData() {
        return this.data;
    }

    public void setData(T data) {
        this.data = data;
    }

    public String getMessage() {
        return this.message;
    }

    public void setMessage(String message) {
        this.message = message;
    }

    public Map<String, Object> getExtInfo() {
        return this.extInfo;
    }

    public void setExtInfo(Map<String, Object> extInfo) {
        this.extInfo = extInfo;
    }

    public String getResultCode() {
        return this.resultCode;
    }

    public void setResultCode(String resultCode) {
        this.resultCode = resultCode;
    }

    public boolean isError() {
        return this.errorCode != 0;
    }

    public String getRequestId() {
        return this.requestId;
    }

    public void setRequestId(String requestId) {
        this.requestId = requestId;
    }

    public String toString() {
        StringBuilder builder = new StringBuilder();
        builder.append("DataResponse [errorCode=");
        builder.append(this.errorCode);
        builder.append(", ");
        if (this.resultCode != null) {
            builder.append("resultCode=");
            builder.append(this.resultCode);
            builder.append(", ");
        }

        if (this.message != null) {
            builder.append("message=");
            builder.append(this.message);
            builder.append(", ");
        }

        if (this.extInfo != null) {
            builder.append("extInfo=");
            builder.append(this.extInfo);
            builder.append(", ");
        }

        if (this.data != null) {
            builder.append("data=");
            builder.append(this.data);
            builder.append(", ");
        }

        if (this.requestId != null) {
            builder.append("requestId=");
            builder.append(this.requestId);
        }

        builder.append("]");
        return builder.toString();
    }
}

自然我们也需要个请求头

import io.swagger.annotations.ApiModel;
import io.swagger.annotations.ApiModelProperty;
import java.io.Serializable;
import java.util.Date;
import java.util.HashMap;
import java.util.Map;

@ApiModel(
    value = "DataRequest",
    description = "请求"
)
public abstract class DataRequest<T> implements Serializable {
    private static final long serialVersionUID = -7574544066074667453L;
    @ApiModelProperty(
        value = "请求数据",
        name = "data"
    )
    private T data;
    @ApiModelProperty(
        value = "附加信息",
        name = "extInfo"
    )
    private Map<String, String> extInfo = new HashMap();
    @ApiModelProperty(
        value = "附加动作",
        name = "action"
    )
    private String action;
    private String username;
    private String requestId;
    private Date requestTime;
    private String security;

    public DataRequest() {
    }

    public T getData() {
        return this.data;
    }

    public void setData(T data) {
        this.data = data;
    }

    public Map<String, String> getExtInfo() {
        return this.extInfo;
    }

    public void setExtInfo(Map<String, String> extInfo) {
        this.extInfo = extInfo;
    }

    public String getAction() {
        return this.action;
    }

    public void setAction(String action) {
        this.action = action;
    }

    public String toString() {
        StringBuilder builder = new StringBuilder();
        builder.append("DataRequest [");
        if (this.data != null) {
            builder.append("data=");
            builder.append(this.data);
            builder.append(", ");
        }

        if (this.extInfo != null) {
            builder.append("extInfo=");
            builder.append(this.extInfo);
            builder.append(", ");
        }

        if (this.action != null) {
            builder.append("action=");
            builder.append(this.action);
        }

        builder.append("]");
        return builder.toString();
    }

    public String getUsername() {
        return this.username;
    }

    public void setUsername(String username) {
        this.username = username;
    }

    public String getSecurity() {
        return this.security;
    }

    public void setSecurity(String security) {
        this.security = security;
    }

    public String getRequestId() {
        return this.requestId;
    }

    public void setRequestId(String requestId) {
        this.requestId = requestId;
    }

    public Date getRequestTime() {
        return this.requestTime;
    }

    public void setRequestTime(Date requestTime) {
        this.requestTime = requestTime;
    }
}

3.快速上手retrofit

如果你学习过springboot，那么你对接下来这一套不要太熟悉，我们先来一个最简单的不带参get请求熟悉一下

a.接口

首先我们来一个Retrofit标准的接口

public interface ITestService {
    @GET("/test")
    Call<DefaultResponse<Object>> get();
}

其中
“/test”
代表我们与后台约定的路径；
DefaultResponse