Rxjava +Retrofit 你需要掌握的几个技巧,Retrofit缓存,统一对有无网络处理, 异常处理,返回结果问题
Rxjava +Rterofit 需要掌握的几个技巧
取消订阅
一般我们在视图消亡后,无需RxJava再执行,可以直接取消订阅
observable.unsubscribeOn(Schedulers.io());
可用在activity的 `onDestroy(),` Fragment的 `onDestroyView()`中调用
还有种场景是借助rxJava请求网络数据,需要网络返回后保存数据并更新UI,这种情况视图已经消亡了必定会导致rxJava出错,导致App闪退,这种我们可以判断前的activity/view是否为空,并是否已showing,如果
两者都不存在,即可无须更新UI。只处理保存数据即可。
订阅问题
需要UI绘制后再进行订阅的场景,防止阻塞UI,我们需要延迟订阅执行。
**立即订阅;**
observable
.subscribeOn(Schedulers.io())
.observeOn(AndroidSchedulers.mainThread())
.subscribe(action);
延迟订阅
observable.delay(2, TimeUnit.SECONDS)
.subscribeOn(Schedulers.io())
.observeOn(AndroidSchedulers.mainThread())
.subscribe(action);
基础Subscriber
很多时候我们需要借用RxJava开启多个observable去读取网络,这是我们对不同Subscriber处理起来比较麻烦,因此统一对Subscriber对网络返回进行处理和, 有无网络做判断,甚至可以根据需求显示加载进度等
构建抽象的BaseSubscribe类,只处理`start()`和`onCompleted()` ,上层处理时只处理`onError()`和`onNext()`
public abstract class BaseSubscriber<T> extends Subscriber<T> {
private BaseActivity context;
public BaseSubscriber(BaseActivity context) {
this.context = context;
}
@Override
public void onStart() {
super.onStart();
if (!NetworkUtil.isNetworkAvailable(context)) {
Toast.makeText(context, "当前网络不可用,请检查网络情况", Toast.LENGTH_SHORT).show();
// 一定好主动调用下面这一句
onCompleted();
return;
}
// 显示进度条
showLoadingProgress();
}
@Override
public void onCompleted() {
//关闭等待进度条
closeLoadingProgress();
}
}
这样我们上层调用时只关心成功和失败即可无需关心网络情况
observable..subscribeOn(Schedulers.io())
.observeOn(AndroidSchedulers.mainThread())
.subscribe(new BaseSubscriber<ResponseBody>(MainActivity.this) {
@Override
public void onError(Throwable e) {
Toast.makeText(MainActivity.this, e.getMessage(), Toast.LENGTH_LONG).show();
}
@Override
public void onNext(ResponseBody responseBody) {
Toast.makeText(MainActivity.this, responseBody.toString(), Toast.LENGTH_LONG).show();
}
});
);
如果想对Error错误统一处理,也可以在BaseSubscriber处理onError(), 然后在callback上层,具体看自己项目情况,可以接着往下看
如果对成功结果进行处理,则可以将ResonseBody加入泛型<Response<T>> , Response一般是包含Code,MSg, Data的,在这里你可以中级判断code来进行业务分发,代码很简单,具体看文章结尾源码即可
如果你觉得目前的返回判断麻烦,也可以定义Response基类
public class BaseResponse<T> {
private int code;
private String msg;
private T data;
}
这样我们在onNext() 只需统一判断状态码即可
@Override
public void onNext(BaseResponse<IpResult> responseBody) {
if (responseBody.isOk()) {
IpResult ip = responseBody.getData();
Toast.makeText(MainActivity.this, ip.toString(), Toast.LENGTH_LONG).show();
}
}
错误结果问题
通过RXJva的 Func1来进行对原始的`Throwable` 进行包装转换
我们将原来Throwable 强转成自定义的 ResponeThrowable;
private static class HttpResponseFunc《T》 implements Func1《Throwable, Observable《T》》 {
@Override public Observable<T> call(Throwable t) {
return Observable.error(ExceptionHandle.handleException(t));
}
}
**ResponeThrowable**
public static class ResponeThrowable extends Exception {
public int code;
public String message;
public ResponeThrowable(Throwable throwable, int code) {
super(throwable);
this.code = code;
}
}
我们已经处理好强转工作后 继续把 `Func1`加到`Observable` 中:
因此这样用observable提供的onErrorResumeNext 则可以将你自定义的`Func1` 关联到错误处理类中:
((Observable) observable).onErrorResumeNext(new HttpResponseFunc<T>());
很可能你感觉有点不理解,这前提你需要了解RxJava的转义符和操作符`Observable.Transformer`
还有`Func1`
这样我们对服务器返回的错误状态进行了自我的处理,再稍加翻译下便可以达到用户看懂的语言
这个类我参考**一叶扁舟**同学的案列,我再次做了改进:
**ExceptionHandle 错误处理驱动**
public class ExceptionHandle {
private static final int UNAUTHORIZED = 401;
private static final int FORBIDDEN = 403;
private static final int NOT_FOUND = 404;
private static final int REQUEST_TIMEOUT = 408;
private static final int INTERNAL_SERVER_ERROR = 500;
private static final int BAD_GATEWAY = 502;
private static final int SERVICE_UNAVAILABLE = 503;
private static final int GATEWAY_TIMEOUT = 504;
public static ResponeThrowable handleException(Throwable e) {
ResponeThrowable ex;
if (e instanceof HttpException) {
HttpException httpException = (HttpException) e;
ex = new ResponeThrowable(e, ERROR.HTTP_ERROR);
switch (httpException.code()) {
case UNAUTHORIZED:
case FORBIDDEN:
case NOT_FOUND:
case REQUEST_TIMEOUT:
case GATEWAY_TIMEOUT:
case INTERNAL_SERVER_ERROR:
case BAD_GATEWAY:
case SERVICE_UNAVAILABLE:
default:
ex.message = "网络错误";
break;
}
return ex;
} else if (e instanceof ServerException) {
ServerException resultException = (ServerException) e;
ex = new ResponeThrowable(resultException, resultException.code);
ex.message = resultException.message;
return ex;
} else if (e instanceof JsonParseException
|| e instanceof JSONException
|| e instanceof ParseException) {
ex = new ResponeThrowable(e, ERROR.PARSE_ERROR);
ex.message = "解析错误";
return ex;
} else if (e instanceof ConnectException) {
ex = new ResponeThrowable(e, ERROR.NETWORD_ERROR);
ex.message = "连接失败";
return ex;
} else if (e instanceof javax.net.ssl.SSLHandshakeException) {
ex = new ResponeThrowable(e, ERROR.SSL_ERROR);
ex.message = "证书验证失败";
return ex;
}
else {
ex = new ResponeThrowable(e, ERROR.UNKNOWN);
ex.message = "未知错误";
return ex;
}
}
/**
* 约定异常
*/
class ERROR {
/**
* 未知错误
*/
public static final int UNKNOWN = 1000;
/**
* 解析错误
*/
public static final int PARSE_ERROR = 1001;
/**
* 网络错误
*/
public static final int NETWORD_ERROR = 1002;
/**
* 协议出错
*/
public static final int HTTP_ERROR = 1003;
/**
* 证书出错
*/
public static final int SSL_ERROR = 1005;
}
public static class ResponeThrowable extends Exception {
public int code;
public String message;
public ResponeThrowable(Throwable throwable, int code) {
super(throwable);
this.code = code;
}
}
public class ServerException extends RuntimeException {
public int code;
public String message;
}
}
接着可以在 BaseSubscriber<T>中处理异常拉
public abstract class BaseSubscriber<T> extends Subscriber<T> {
private Context context;
public BaseSubscriber(Context context) {
this.context = context;
}
@Override
public void onError(Throwable e) {
Log.e("Tamic", e.getMessage());
// todo error somthing
if(e instanceof ExceptionHandle.ResponeThrowable){
onError((ExceptionHandle.ResponeThrowable)e);
} else {
onError(new ExceptionHandle.ResponeThrowable(e, ExceptionHandle.ERROR.UNKNOWN));
}
}
}
最后上层调用就是这样了:
RetrofitClient.getInstance(MainActivity.this).createBaseApi().getData(new BaseSubscriber<IpResult>(MainActivity.this) {
@Override
public void onError(ResponeThrowable e) {
// 处理翻译后异常。
Log.e("Tamic", e.code + " "+ e.message);
Toast.makeText(MainActivity.this, e.message, Toast.LENGTH_LONG).show();
}
@Override
public void onNext(IpResult responseBody) {
Toast.makeText(MainActivity.this, responseBody.toString(), Toast.LENGTH_LONG).show();
}
}, "21.22.11.33");
指的注意的是上层使用BaseSubscriber 的实现类和子类即可,如果你要重写BaseSubscriber 的onStat()和onCompleted() 也是可以的
#缓存问题
有时候需要在无网络时增加缓存功能,因此给Retrofit加入基础拦截器,来处理缓存问题
/**
* BaseInterceptor
* Created by Tamic on 2016-7-15.
*/
public class BaseInterceptor implements Interceptor{
private Map<String, String> headers;
private Context context;
public BaseInterceptor(Map<String, String> headers, Context context) {
this.headers = headers;
this.context = context;
}
@Override
public Response intercept(Chain chain) throws IOException {
Request.Builder builder = chain.request()
.newBuilder();
builder.cacheControl(CacheControl.FORCE_CACHE).url(chain.request().url())
.build();
if (!NetworkUtil.isNetworkAvailable(context)) {
((Activity)context).runOnUiThread(new Runnable() {
@Override
public void run() {
Toast.makeText(context, "当前无网络!", Toast.LENGTH_SHORT).show();
}
});
}
if (headers != null && headers.size() > 0) {
Set<String> keys = headers.keySet();
for (String headerKey : keys) {
builder.addHeader(headerKey, headers.get(headerKey)).build();
}
}
if (NetworkUtil.isNetworkAvailable(context)) {
int maxAge = 60; // read from cache for 60 s
builder
.removeHeader("Pragma")
.addHeader("Cache-Control", "public, max-age=" + maxAge)
.build();
} else {
int maxStale = 60 * 60 * 24 * 14; // tolerate 2-weeks stale
builder
.removeHeader("Pragma")
.addHeader("Cache-Control", "public, only-if-cached, max-stale=" + maxStale)
.build();
}
return chain.proceed(builder.build());
}
}
```
okHttpClient加入拦截器
okHttpClient = new OkHttpClient.Builder()
.addInterceptor(new BaseInterceptor(headers, context))
.connectTimeout(DEFAULT_TIMEOUT, TimeUnit.SECONDS)
.build();
Retrofit 加入okhttpClient
```
retrofit = new Retrofit.Builder()
.client(okHttpClient)
.baseUrl(url)
.build();
```
如果你不想用okhttp自带的缓存策略,因为这需要服务端配合处理缓存请求头,不然会抛出: **HTTP 504 Unsatisfiable Request (only-if-cached)**
除了以上修改 Request.cacheControl的方式实现缓存,也可以自定义一个Cahe策略用来实现本地硬缓存。
构建CaheManager,用Url对应Json实现,此类非常简单,你可以自己实现,时间策略可自我加入扩展
在BaseSubscriber进行网络判断,加载缓存数据返回妥妥的;
@Override
public void onStart() {
super.onStart();
Toast.makeText(context, "http is start", Toast.LENGTH_SHORT).show();
// todo some common as show loadding and check netWork is NetworkAvailable
// if NetworkAvailable no ! must to call onCompleted
if (!NetworkUtil.isNetworkAvailable(context)) {
Toast.makeText(context, "无网络", Toast.LENGTH_SHORT).show();
if (isNeedCahe) {
Toast.makeText(context, "无网络,已智能读取缓存!", Toast.LENGTH_SHORT).show();
IpResult ipResult = new Gson().fromJson(CaheManager.getjson(url), IpResult.class);
onNext((T) ipResult);
}
onCompleted();
}
}
总结
通过这次的整理,再进行RxJava和Retrofit中 ,所有坑直接添就行,具体可以点击原文查看
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