Anko
Anko 是一个 DSL (Domain-Specific Language)， 它是JetBrains出品的，用 Kotlin 开发的安卓框架。它主要的目的是用来替代以前XML的方式来使用代码生成UI布局。
先来看一个直观的例子
<LinearLayout
xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_height="match_parent"
android:layout_width="match_parent">
<EditText
android:id="@+id/todo_title"
android:layout_width="match_parent"
android:layout_heigh="wrap_content"
android:hint="@string/title_hint" />
<!-- Cannot directly add an inline click listener as onClick delegates implementation to the activity -->
<Button
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:text="@string/add_todo" />
</LinearLayout>使用Anko之后，可以用代码实现布局，并且button还绑定了点击事件。
verticalLayout {
var title = editText {
id = R.id.todo_title
hintResource = R.string.title_hint
}
button {
textResource = R.string.add_todo
onClick { view -> {
// do something here
title.text = "Foo"
}
}
}
}可以看到 DSL 的一个主要优点在于，它需要很少的时间即可理解和传达某个领域的详细信息。
简单封装OkHttp
OkHttp是一个成熟且强大的网络库，在Android源码中已经使用OkHttp替代原先的HttpURLConnection。很多著名的框架例如Picasso、Retrofit也使用OkHttp作为底层框架。在这里我对OkHttp做一下简单的封装，其实封装得有点粗暴只是为了演示如何实现dsl。
import io.reactivex.BackpressureStrategy
import io.reactivex.Flowable
import io.reactivex.schedulers.Schedulers
import okhttp3.OkHttpClient
import okhttp3.Request
import okhttp3.RequestBody
import okhttp3.Response
import java.util.concurrent.TimeUnit
/**
* Created by Tony Shen on 2017/6/1.
*/
class RequestWrapper {
var url:String? = null
var method:String? = null
var body: RequestBody? = null
var timeout:Long = 10
internal var _success: (String) -> Unit = { }
internal var _fail: (Throwable) -> Unit = {}
fun onSuccess(onSuccess: (String) -> Unit) {
_success = onSuccess
}
fun onFail(onError: (Throwable) -> Unit) {
_fail = onError
}
}
fun http(init: RequestWrapper.() -> Unit) {
val wrap = RequestWrapper()
wrap.init()
executeForResult(wrap)
}
private fun executeForResult(wrap:RequestWrapper) {
Flowable.create<Response>({
e -> e.onNext(onExecute(wrap))
}, BackpressureStrategy.BUFFER)
.subscribeOn(Schedulers.io())
.subscribe(
{ resp ->
wrap._success(resp.body()!!.string())
},
{ e -> wrap._fail(e) })
}
private fun onExecute(wrap:RequestWrapper): Response? {
var req:Request? = null
when(wrap.method) {
"get","Get","GET" -> req =Request.Builder().url(wrap.url).build()
"post","Post","POST" -> req = Request.Builder().url(wrap.url).post(wrap.body).build()
"put","Put","PUT" -> req = Request.Builder().url(wrap.url).put(wrap.body).build()
"delete","Delete","DELETE" -> req = Request.Builder().url(wrap.url).delete(wrap.body).build()
}
val http = OkHttpClient.Builder().connectTimeout(wrap.timeout, TimeUnit.SECONDS).build()
val resp = http.newCall(req).execute()
return resp
}封装完OkHttp之后，看看如何来编写get请求
http {
url = "http://www.163.com/"
method = "get"
onSuccess {
string -> L.i(string)
}
onFail {
e -> L.i(e.message)
}
}是不是很像以前用jquery来写ajax？
post请求也是类似的，只不过多了body
var json = JSONObject()
json.put("xxx","yyyy")
....
val postBody = RequestBody.create(MediaType.parse("application/json; charset=utf-8"),json.toString())
http {
url = "https://......"
method = "post"
body = postBody
onSuccess {
string -> L.json(string)
}
onFail {
e -> L.i(e.message)
}
}封装自己的图像处理框架
cv4j 是我们开发的实时图像处理框架。最早使用滤镜的方式如下：
CV4JImage cv4jImage = new CV4JImage(bitmap);
CommonFilter filter = new NatureFilter();
Bitmap newBitMap = filter.filter(cv4jImage.getProcessor()).getImage().toBitmap();
image.setImageBitmap(newBitMap);后来增加了RxJava封装的版本
RxImageData.bitmap(bitmap).addFilter(new NatureFilter()).into(image);现在Kotlin项目除了可以使用上述两种方式之外，还多了一种方式。
cv4j {
bitmap = BitmapFactory.decodeResource(resources, R.drawable.test_io)
filter = NatureFilter()
imageView = image
}这个dsl是如何封装的呢？其实是对RxJava版本进一步封装。
/**
* Copyright (c) 2017-present, CV4J Contributors.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package com.cv4j.rxjava
import android.app.Dialog
import android.graphics.Bitmap
import android.widget.ImageView
import com.cv4j.core.datamodel.CV4JImage
import com.cv4j.core.filters.CommonFilter
/**
* only for Kotlin code,this class provides the DSL style for cv4j
*/
class Wrapper {
var bitmap:Bitmap? = null
var cv4jImage: CV4JImage? = null
var bytes:ByteArray? = null
var useCache:Boolean = true
var imageView: ImageView? = null
var filter: CommonFilter? = null
var dialog: Dialog? = null
}
fun cv4j(init: Wrapper.() -> Unit) {
val wrap = Wrapper()
wrap.init()
render(wrap)
}
private fun render(wrap: Wrapper) {
if (wrap.bitmap!=null) {
if (wrap.filter!=null) {
RxImageData.bitmap(wrap.bitmap).dialog(wrap.dialog).addFilter(wrap.filter).isUseCache(wrap.useCache).into(wrap.imageView)
} else {
RxImageData.bitmap(wrap.bitmap).dialog(wrap.dialog).isUseCache(wrap.useCache).into(wrap.imageView)
}
} else if (wrap.cv4jImage!=null) {
if (wrap.filter!=null) {
RxImageData.image(wrap.cv4jImage).dialog(wrap.dialog).addFilter(wrap.filter).isUseCache(wrap.useCache).into(wrap.imageView)
} else {
RxImageData.image(wrap.cv4jImage).dialog(wrap.dialog).isUseCache(wrap.useCache).into(wrap.imageView)
}
} else if (wrap.bytes!=null) {
if (wrap.filter!=null) {
RxImageData.bytes(wrap.bytes).dialog(wrap.dialog).addFilter(wrap.filter).isUseCache(wrap.useCache).into(wrap.imageView)
} else {
RxImageData.bytes(wrap.bytes).dialog(wrap.dialog).isUseCache(wrap.useCache).into(wrap.imageView)
}
}
}来看一下程序的最终效果图
cv4j 目前已经支持了几十种滤镜，当然除了滤镜还有其他功能，感兴趣的童鞋可以看我们的源码：）。
总结
使用dsl的代码风格，可以让程序更加直观和简洁。如果使用Kotlin来开发项目的话，完全可以尝试一下。
公司的sdk项目我也考虑引入Kotlin，我已经写了一个module用于封装原先的sdk，这个module只适用于Kotlin项目。用于简化初始化sdk和实现deep link的注册服务。
可以感受一下，使用dsl是不是比原先的代码更加简洁和直观呢？
另外，众所周知的Gradle也是基于DSL的Java构建工具。
参考资料：
