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Retrofit的优点

时间:2019-12-08 10:23:02      阅读:438      评论:0      收藏:0      [点我收藏+]

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Retrofit的优点

  1. 可以配置不同HTTP client来实现网络请求,如okhttp、httpclient等
  2. 将接口的定义与使用分离开来,实现结构。
  3. 支持多种返回数据解析的Converter可以快速进行数据转换。
  4. 和RxJava集成的很好
  5. 因为容易和RxJava结合使用,所以对于异步请求,同步请求也不需要做额外的工作。
  6. Retrofit是基于OKHttp

简单使用

配置依赖

在module的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"
    
// OkHttp3
api "com.squareup.okhttp3:okhttp:3.10.0"
api "com.squareup.okhttp3:logging-interceptor:3.10.0"

// RxJava2
api "io.reactivex.rxjava2:rxjava:2.1.9"
api "io.reactivex.rxjava2:rxandroid:2.0.2"

// RxLifecycle
api "com.trello.rxlifecycle2:rxlifecycle:2.2.1"
api "com.trello.rxlifecycle2:rxlifecycle-android:2.2.1"
api "com.trello.rxlifecycle2:rxlifecycle-components:2.2.1"
定义Retrofit单例

在Application中初始化Retrofit,因为一个Retrofit对象本身就包含一个线程池,所以我们可以初始化一个Retrofit对象,并将其做成一个全局单例对象

/**
 * Retrofit单例管理
 * Created by Leon.W on 2019/4/28
 */
public class RetrofitManager {
    private final String BASE_URL = "https://api.github.com";
    private static RetrofitManager sInstance;
    private Retrofit mRetrofit;
    public static RetrofitManager getInstance() {
        if (null == sInstance) {
            synchronized (RetrofitManager.class) {
                if (null == sInstance) {
                    sInstance = new RetrofitManager();
                }
            }
        }
        return sInstance;
    }

    public void init() {
        if(mRetrofit == null) {
            //初始化一个OkHttpClient
            OkHttpClient.Builder builder = new OkHttpClient.Builder()
                    .connectTimeout(30000, TimeUnit.MILLISECONDS)
                    .readTimeout(30000, TimeUnit.MILLISECONDS)
                    .writeTimeout(30000, TimeUnit.MILLISECONDS);
            builder.addInterceptor(new LoggingInterceptor());
            OkHttpClient okHttpClient = builder.build();

            //使用该OkHttpClient创建一个Retrofit对象
            mRetrofit = new Retrofit.Builder()
                    //添加Gson数据格式转换器支持
                    .addConverterFactory(GsonConverterFactory.create())
                    //添加RxJava语言支持
                    .addCallAdapterFactory(RxJava2CallAdapterFactory.create())
                    //指定网络请求client
                    .client(okHttpClient)
                    .baseUrl(BASE_URL)
                    .build();
        }
    }

    public Retrofit getRetrofit() {
        if(mRetrofit == null) {
            throw  new IllegalStateException("Retrofit instance hasn‘t init!");
        }
        return mRetrofit;
    }
}
定义ApiService
//ApiService.java
public interface ApiService {
    @GET("/TP_S/BookList")
    Observable<JsonArrayBase<Book>> queryBookList();
}
定义接口方法实现方法
//GithubAPI.java
public class GithubAPI {
    Observable<GithubUserInfo> queryJakeWhartonInfo() {
        return RetrofitManager.getInstance().getRetrofit()
                //动态代理创建GithubAPI对象
                .create(ApiService.class)
                .queryJakeWhartonInfo()
                //指定上游发送事件线程
                .subscribeOn(Schedulers.computation())
                //指定下游接收事件线程
                .observeOn(AndroidSchedulers.mainThread());
    }
}
定义返回数据实体类
public class GithubUserInfo {
    String login,url,name,company;
    int id,public_repos,followers;

    @Override
    public String toString() {
        return "GithubUserInfo{" +
                "login=‘" + login + ‘\‘‘ +
                ", url=‘" + url + ‘\‘‘ +
                ", name=‘" + name + ‘\‘‘ +
                ", company=‘" + company + ‘\‘‘ +
                ", id=" + id +
                ", public_repos=" + public_repos +
                ", followers=" + followers +
                ‘}‘;
    }
}
调用接口
new GithubAPI().queryJakeWhartonInfo().subscribe(new Observer<GithubUserInfo>() {
    @Override
    public void onSubscribe(Disposable d) {
    }
    @Override
    public void onNext(GithubUserInfo githubUserInfo) {
        Log.d(TAG,githubUserInfo.toString());
    }
    @Override
    public void onError(Throwable e) {
        e.printStackTrace();
        Log.e(TAG,e.getMessage());
    }
    @Override
    public void onComplete() {
    }
});

>>>输出:
D/TestRetrofit: GithubUserInfo{login=‘JakeWharton‘, url=‘https://api.github.com/users/JakeWharton‘, name=‘Jake Wharton‘, company=‘Google, Inc.‘, id=66577, public_repos=102, followers=52467}

异常处理

请求过程中的异常一般分为2种类型,一种是类似网络异常、服务器这种环境问题;另一种比如请求参数错误、登录超时、Token失效等异常。分别做如下处理

环境问题

环境异常诸如404、500、502等服务器状态异常,或者设备本身网路异常造成的,这种时候的Exception会在onError方法中得到响应。

数据问题

数据问题诸如请求参数异常、对象为空、登录超时等数据相关异常,这种情况Response还是会走onNext方法,只是我们需要在里面根据自定义的code,来处理各种数据异常。
下面是一个具体的基础Observer类,在其onNext中解析
一般服务器接口返回数据会约定一个简单的格式:

{
    code:int,
    msg:String,
    data:{} //可能是对象,有可能是数组data:[]
}

对应的建议解析类,一般当接口返回先解析其code是否为成功,如果不是,那看看是否是特定的错误码,把错误码code和错误信息msg包装成一个自定义的Exception进行处理。如果成功,则对返回结果进行进一步的解析,针对不同的接口解析成“对象”或者“数组”。

//JsonBase.java,解析code和msg
public class JsonBase implements Serializable{
    private static final long serialVersionUID = -6182189632617616248L;
    @SerializedName("msg")
    private String msg;
    private int code = -1;

    public int getCode() {
        return code;
    }
    public void setCode(int code) {
        this.code = code;
    }
    public String getMsg() {
        return msg;
    }
    public void setMsg(String msg) {
        this.msg = msg;
    }
}
//JsonArrayBase.java,解析数组类型
public class JsonArrayBase<T> extends JsonBase {
    @SerializedName("data")
    List<T> data;
    public List<T> getData() {
        return data;
    }
    public void setData(List<T> data) {
        this.data = data;
    }

    @Override
    public String toString() {
        StringBuilder sb = new StringBuilder();
        for(int i = 0; i< data.size(); i++) {
            sb.append(data.get(i).toString());
        }
        return sb.toString();
    }
}
//JsonObjBase.java,解析对象类型
public class JsonObjBase<T> extends JsonBase {
    @SerializedName("data")
    T data;
    public T getData() {
        return data;
    }
    public void setData(T data) {
        this.data = data;
    }
}

基础Observer,用于处理数据异常(即code不是SUCC的情况);网络异常(在onError方法中进行toast提示),具体使用界面可以通过重写onError来得到回调(比如分页加载失败,需要隐藏加载进度条,此时需要得到失败回调)

//BaseObserver.java
public abstract class BaseObserver<T> implements Observer<T> {
    private String TAG = "BaseObserver";

    @Override
    public void onNext(T t) {
        if (t == null) {
            onError(HttpCode.ERROR_EMPTY_OBJ, getErrorMessage(HttpCode.ERROR_EMPTY_OBJ));
        } else {
            onSuccess(t);
        }
    }

    /**
     * 外部想要处理异常(比如分页加载失败,需要隐藏加载中效果)时,可以重写该方法
     */
    public void onError(int errorCode, String message) {
    }

    /**
     * 外部重写,接受数据
     * @param t
     */
    public abstract void onSuccess(T t);

    /**
     * 不显示服务器返回错误信息(部分接口返回不规范)
     */
    public boolean isShowErrorToast() {
        return true;
    }
    @Override
    public void onError(Throwable e) {
        int errorCode = -1;
        String errMsg = "";
        //自定义异常
        if (e instanceof MyException) {
            MyException exception = (MyException) e;
            errorCode = exception.getErrorCode();
            errMsg = exception.getMessage();
            handleIybErrorCode(errorCode);
            if (isShowErrorToast()) {
                Toast.makeText(TestAPP.getInstance().getApplicationContext(), errMsg,Toast.LENGTH_LONG).show();
            }
        } else if (e instanceof NullPointerException) { // RxJava2 发送值为null时,不执行 onNext,直接走 onError
            errorCode = HttpCode.ERROR_EMPTY_OBJ;
            errMsg = getErrorMessage(HttpCode.ERROR_EMPTY_OBJ);
        } else if (e instanceof SocketTimeoutException) {
            errorCode = HttpCode.ERROR_TIMEOUT;
            errMsg = getErrorMessage(HttpCode.ERROR_TIMEOUT);
            Toast.makeText(TestAPP.getInstance().getApplicationContext(), errMsg,Toast.LENGTH_LONG).show();
        } else if (e instanceof NetworkErrorException) {
            errorCode = HttpCode.ERROR_NETWORK;
            errMsg = getErrorMessage(HttpCode.ERROR_NETWORK);
            Toast.makeText(TestAPP.getInstance().getApplicationContext(), errMsg,Toast.LENGTH_LONG).show();
        } else if (e instanceof HttpException) {
            HttpException httpException = (HttpException) e;
            errMsg = httpException != null ? httpException.getMessage() : getErrorMessage(HttpCode.ERROR_SERVER_EXCEPTION);
            int httpErrorCode = httpException != null ? httpException.code() : HttpCode.ERROR_UNKNOWN;
            Log.d(TAG, "Http request error:" + "message=" + errMsg + " :::: " + "httpErrorCode=" + httpErrorCode);
            Toast.makeText(TestAPP.getInstance().getApplicationContext(), getErrorMessage(HttpCode.ERROR_SERVER_EXCEPTION),Toast.LENGTH_LONG).show(); // 统一提示服务器异常
        } else {
            errMsg = e != null ? e.getMessage() : getErrorMessage(HttpCode.ERROR_UNKNOWN);
        }
        onError(errorCode, errMsg);
    }

    /**
     * 处理数据异常code
     * @param errorCode
     */
    private void handleIybErrorCode(int errorCode) {
        if (errorCode == HttpCode.ERROR_ALREADY_REGISTER) {
            //已注册处理逻辑
        } else if (errorCode == HttpCode.ERROR_LOGIN_EXPIRED ) {
            //登录超时处理逻辑
        }
    }
    
    private String getErrorMessage(int errorCode) {
        String message = HttpCode.ERRORS.get(errorCode);
        if (TextUtils.isEmpty(message)) {
            message = HttpCode.ERRORS.get(HttpCode.ERROR_UNKNOWN);
        }
        return message;
    }
}
public abstract class BaseObserver<T> implements Observer<T> {
    private String TAG = "BaseObserver";

    @Override
    public void onNext(T t) {
        if (t == null) {
            onError(HttpCode.ERROR_EMPTY_OBJ, getErrorMessage(HttpCode.ERROR_EMPTY_OBJ));
        } else {
            onSuccess(t);
        }
    }
    /**外部想要处理异常时(比如分页加载失败,需要隐藏加载中效果),可以重写该方法*/
    public void onError(int errorCode, String message) {
    }

    public abstract void onSuccess(T t);

    /** 不显示服务器返回错误信息(部分接口返回不规范) */
    public boolean isShowErrorToast() {
        return true;
    }

    @Override
    public void onError(Throwable e) {
        int errorCode = -1;
        String errMsg = "";
        //自定义异常
        if (e instanceof MyException) {
            MyException exception = (MyException) e;
            errorCode = exception.getErrorCode();
            errMsg = exception.getMessage();
            handleErrorCode(errorCode);
            if (isShowErrorToast()) {
                Toast.makeText(TestAPP.getInstance().getApplicationContext(), errMsg,Toast.LENGTH_LONG).show();
            }
        } else if (e instanceof NullPointerException) { // RxJava2 发送值为null时,不执行 onNext,直接走 onError
            errorCode = HttpCode.ERROR_EMPTY_OBJ;
            errMsg = getErrorMessage(HttpCode.ERROR_EMPTY_OBJ);
        } else if (e instanceof SocketTimeoutException) {
            errorCode = HttpCode.ERROR_TIMEOUT;
            errMsg = getErrorMessage(HttpCode.ERROR_TIMEOUT);
            Toast.makeText(TestAPP.getInstance().getApplicationContext(), errMsg,Toast.LENGTH_LONG).show();
        } else if (e instanceof NetworkErrorException) {
            errorCode = HttpCode.ERROR_NETWORK;
            errMsg = getErrorMessage(HttpCode.ERROR_NETWORK);
            Toast.makeText(TestAPP.getInstance().getApplicationContext(), errMsg,Toast.LENGTH_LONG).show();
        } else if (e instanceof HttpException) {
            HttpException httpException = (HttpException) e;
            errMsg = httpException != null ? httpException.getMessage() : getErrorMessage(HttpCode.ERROR_SERVER_EXCEPTION);
            int httpErrorCode = httpException != null ? httpException.code() : HttpCode.ERROR_UNKNOWN;
            Log.d(TAG, "Http request error:" + "message=" + errMsg + " :::: " + "httpErrorCode=" + httpErrorCode);
            Toast.makeText(TestAPP.getInstance().getApplicationContext(), getErrorMessage(HttpCode.ERROR_SERVER_EXCEPTION),Toast.LENGTH_LONG).show(); // 统一提示服务器异常
        } else {
            errMsg = e != null ? e.getMessage() : getErrorMessage(HttpCode.ERROR_UNKNOWN);
            Toast.makeText(TestAPP.getInstance().getApplicationContext(), e.getMessage(),Toast.LENGTH_LONG).show(); // 统一提示服务器异常
        }
        onError(errorCode, errMsg);
    }

    /**
     * 处理数据异常code
     * @param errorCode
     */
    private void handleErrorCode(int errorCode) {
        if (errorCode == HttpCode.ERROR_ALREADY_REGISTER) {
            //已注册处理逻辑
        } else if (errorCode == HttpCode.ERROR_LOGIN_EXPIRED ) {
            //登录超时处理逻辑
        }
    }
    private String getErrorMessage(int errorCode) {
        String message = HttpCode.ERRORS.get(errorCode);
        if (TextUtils.isEmpty(message)) {
            message = HttpCode.ERRORS.get(HttpCode.ERROR_UNKNOWN);
        }
        return message;
    }
}
//MyException.java
public class MyException extends Exception {
    private int mErrorCode;
    private String mMessage;

    public MyException(int errorCode, String message) {
        super();
        mErrorCode = errorCode;
        mMessage = message;
    }
    public int getErrorCode() {
        return mErrorCode;
    }
    public void setErrorCode(int mErrorCode) {
        this.mErrorCode = mErrorCode;
    }
    public String getMessage() {
        return mMessage;
    }
    public void setMessage(String message) {
        this.mMessage = message;
    }
}
public class HttpCode {
    public static final int ERROR_UNKNOWN = -1;
    public static final int ERROR_SUCCESS = 0;
    // 1000~1099 自定义错误码
    public static final int ERROR_NETWORK = 1000;
    public static final int ERROR_TIMEOUT = 1001;
    public static final int ERROR_SERVER_EXCEPTION = 1002;
    public static final int ERROR_EMPTY_OBJ = 1011;
    public static final int ERROR_ALREADY_REGISTER = 100001; // 已经注册过
    public static final int ERROR_LOGIN_EXPIRED = 100002; // 登录cookie超时,需要重新登录
    public static final SparseArray<String> ERRORS = new SparseArray<>();

    static {
        ERRORS.append(ERROR_UNKNOWN, "未知错误");
        ERRORS.append(ERROR_SUCCESS, "请求成功");
        ERRORS.append(ERROR_NETWORK, "网络错误");
        ERRORS.append(ERROR_TIMEOUT, "连接超时");
        ERRORS.append(ERROR_SERVER_EXCEPTION, "服务器异常");
        ERRORS.append(ERROR_ALREADY_REGISTER, "您的手机号已经注册过i云保帐号");
        ERRORS.append(ERROR_LOGIN_EXPIRED, "登录超时,需要重新登录");
        ERRORS.append(ERROR_EMPTY_OBJ, "返回对象为空!");
    }
}

生命周期绑定

有时我们关闭一个页面时,希望该页面上正在进行以及准备开始进行的请求能够及时关闭、取消掉。以免造成内存溢出或空指针异常等问题。此时就需要将请求与页面的生命周期相关联。因为Retrofit和RxJava2集成,由RxJava2控制上下游的时间分发,所以处理RxJava2的生命周期问题就是处理Retrofit请求的声明周期问题。可以看到在上面的”依赖配置“段落中导入了三个rxlifiecycle相关的依赖,其中rxliftcycle-components包含我们将要使用到的RxAppCompatActivity,而他有依赖另外两个依赖,可以查看RxAppCompatActivity的源码验证:

//RxAppCompatActivity.java
import com.trello.rxlifecycle2.LifecycleProvider;
import com.trello.rxlifecycle2.LifecycleTransformer;
//来自基础包rxlifecycle
import com.trello.rxlifecycle2.RxLifecycle; 
//来自android包rxlifecycle-android
import com.trello.rxlifecycle2.android.ActivityEvent; 
//来自android包rxlifecycle-android
import com.trello.rxlifecycle2.android.RxLifecycleAndroid;
import io.reactivex.Observable;
import io.reactivex.subjects.BehaviorSubject;

public abstract class RxAppCompatActivity extends AppCompatActivity implements LifecycleProvider<ActivityEvent> { 
        ......
}

下面开始声明周期相关的Demo,演示一下未绑定页面生命周期导致内存溢出的问题,假设有一个Activity中有一个operator每隔1秒发送一个事件:

public class TestMemLeakActivity extends Activity {
    private String TAG = "TestMemLeak";
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.rx_act_test_leak);
        Observable.interval(1000l, TimeUnit.MILLISECONDS)
                .subscribeOn(Schedulers.computation())
                .observeOn(AndroidSchedulers.mainThread())
                .subscribe(new Observer<Long>() {
                    @Override
                    public void onSubscribe(Disposable d) {
                    }
                    @Override
                    public void onNext(Long aLong) {
                        Log.d(TAG,aLong + "");
                    }
                    @Override
                    public void onError(Throwable e) {
                        Log.d(TAG,e.getMessage());
                    }
                    @Override
                    public void onComplete() {
                        Log.d(TAG,"onComplete");
                    }
                });
    }

    @Override
    protected void onDestroy() {
        super.onDestroy();
        Log.d(TAG,"onDestory------");
    }
}
>>>输出:
04-29 19:38:00.102 18964-18964/com.ebm.rxjava D/TestMemLeak: 0
04-29 19:38:01.101 18964-18964/com.ebm.rxjava D/TestMemLeak: 1
04-29 19:38:02.101 18964-18964/com.ebm.rxjava D/TestMemLeak: 2
04-29 19:38:03.102 18964-18964/com.ebm.rxjava D/TestMemLeak: 3
04-29 19:38:04.102 18964-18964/com.ebm.rxjava D/TestMemLeak: 4
04-29 19:38:05.102 18964-18964/com.ebm.rxjava D/TestMemLeak: 5
04-29 19:38:05.110 18964-18964/com.ebm.rxjava D/TestMemLeak: onDestory------
04-29 19:38:06.105 18964-18964/com.ebm.rxjava D/TestMemLeak: 6
04-29 19:38:07.102 18964-18964/com.ebm.rxjava D/TestMemLeak: 7
04-29 19:38:08.102 18964-18964/com.ebm.rxjava D/TestMemLeak: 8
04-29 19:38:09.102 18964-18964/com.ebm.rxjava D/TestMemLeak: 9

从Log可以看出,TestMemLeakActivity关闭调用onDestory()之后,事件没有随着界面关闭而停止发送,这样会导致Activity无法回收,进而导致内存泄露。下面使用RxAppCompatActivity进行将RxJava绑定到Activity的声明周期。

//1.继承自RxAppCompatActivity
public class TestMemLeakActivity extends RxAppCompatActivity {
    private String TAG = "TestMemLeak";
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.rx_act_test_leak);
        Observable.interval(1000l, TimeUnit.MILLISECONDS)
                .subscribeOn(Schedulers.computation())
                .observeOn(AndroidSchedulers.mainThread())
                //2.绑定声明周期
                .compose(this.<Long>bindToLifecycle())
                .subscribe(new Observer<Long>() {
                    @Override
                    public void onSubscribe(Disposable d) {
                    }
                    @Override
                    public void onNext(Long aLong) {
                        Log.d(TAG,aLong + "");
                    }
                    @Override
                    public void onError(Throwable e) {
                        Log.d(TAG,e.getMessage());
                    }
                    @Override
                    public void onComplete() {
                        Log.d(TAG,"onComplete");
                    }
                });
    }

    @Override
    protected void onDestroy() {
        super.onDestroy();
        Log.d(TAG,"onDestory------");
    }
}
>>>输出:
04-29 19:41:41.254 20080-20080/com.ebm.rxjava D/TestMemLeak: 0
04-29 19:41:42.254 20080-20080/com.ebm.rxjava D/TestMemLeak: 1
04-29 19:41:43.254 20080-20080/com.ebm.rxjava D/TestMemLeak: 2
04-29 19:41:44.253 20080-20080/com.ebm.rxjava D/TestMemLeak: 3
04-29 19:41:44.762 20080-20080/com.ebm.rxjava D/TestMemLeak: onComplete
04-29 19:41:44.762 20080-20080/com.ebm.rxjava D/TestMemLeak: onDestory------

从上面的Log可以看出,界面关闭之前先发送了onComplete事件,关闭了事件流的发送。

 

Retrofit的优点

标签:nts   查看   lang   就是   类型   toast   nbsp   lis   exce   

原文地址:https://www.cnblogs.com/endv/p/12004439.html

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