简介
主要会通过安卓实战来讲解kotlin语法和实际应用，本教程设及知识点包括框架模式mvp+mvvm, Databinding(数据绑定框架),Dagger2(依赖注入框架)，DeepLink（页面路由框架），Rxjava,RxAndroid(异步操作框架)，Retrofit,Okhtttp等，不过本教程重点在kotlin所以这些框架需要了解可自行百度。
针对人群：Android中级以上，kotlin入门
我们马上开始完成第一个kotlin代码实现的fragment
首先先看一下代码
/**
*
* Created by bigman on 18-05-18.
*/
class AndroidFragment : BaseBingingFragment(), AndroidContract.View {
private var mList = ArrayList()
private lateinit var mAdapter: AndroidAdapter
private var mPage = 1
@Inject lateinit var mPresenter: AndroidPresenter
override fun createDataBinding(inflater: LayoutInflater?, container: ViewGroup?,
savedInstanceState: Bundle?): ViewRecyclerBinding {
return ViewRecyclerBinding.inflate(inflater!!, container, false)
}
override fun initView() {
mAdapter = AndroidAdapter(mList)
context.getMainComponent().plus(AndroidModule(this)).inject(this)
with(mBinding) {
recyclerView.adapter = mAdapter
recyclerView.layoutManager = LinearLayoutManager(context)
recyclerView.addOnScrollListener(object : RecyclerView.OnScrollListener() {
override fun onScrolled(recyclerView: RecyclerView?, dx: Int, dy: Int) {
super.onScrolled(recyclerView, dx, dy)
//是否滚动到底部
if (!recyclerView?.canScrollVertically(1)!!) {
mPresenter.getData(++mPage, ANDROID)
}
}
override fun onScrollStateChanged(recyclerView: RecyclerView?, newState: Int) {
super.onScrollStateChanged(recyclerView, newState)
}
})
}
//请求数据
mPresenter.getData(mPage, ANDROID)
mAdapter.setOnItemClickListener {
pos ->
val url = URLEncoder.encode(mList[pos].url)
GankRouter.router(context, GankClientUri.DETAIL + url)
}
}
override fun setData(results: List) {
mList.addAll(results)
mAdapter.notifyDataSetChanged()
}
override fun onDestroy() {
super.onDestroy()
mPresenter.unSubscribe()
}
companion object {
val ANDROID = "ANDROID"
fun newInstance(): AndroidFragment {
val fragment = AndroidFragment()
val bundle = Bundle()
fragment.arguments = bundle
return fragment
}
}
}
AndroidFragment 代码结构其实和MainActivity的差不多，首先是两个主要方法createDataBinding和initView,他同样是基类声明的两个抽象方法，我们看看基类 BaseBingingFragment的代码：
/**
* Created by bigman on 18-05-17.
*/
abstract class BaseBingingFragment : Fragment(){
lateinit var mBinding : B
override fun onCreateView(inflater: LayoutInflater?, container: ViewGroup?, savedInstanceState: Bundle?): View {
mBinding = createDataBinding(inflater,container,savedInstanceState)
initView()
return mBinding.root
}
override fun onViewCreated(view: View?, savedInstanceState: Bundle?) {
super.onViewCreated(view, savedInstanceState)
}
abstract fun createDataBinding(inflater: LayoutInflater?, container: ViewGroup?, savedInstanceState: Bundle?): B
abstract fun initView()
}
当然它的实现和activity的基类一样，就是实现了databinding框架的页面绑定，不记得的同学可以翻看一下前面，我们再看基类提供的抽象方法的具体实现
override fun createDataBinding(inflater: LayoutInflater?, container: ViewGroup?,
savedInstanceState: Bundle?): ViewRecyclerBinding {
return ViewRecyclerBinding.inflate(inflater!!, container, false)
}
这里就是把view_recycler.xml由Databinding自动生成类ViewRecyclerBinding和页面绑定起来
然后再看看initView方法实现代码
override fun initView() {
mAdapter = AndroidAdapter(mList)
context.getMainComponent().plus(AndroidModule(this)).inject(this)
with(mBinding) {
recyclerView.adapter = mAdapter
recyclerView.layoutManager = LinearLayoutManager(context)
recyclerView.addOnScrollListener(object : RecyclerView.OnScrollListener() {
override fun onScrolled(recyclerView: RecyclerView?, dx: Int, dy: Int) {
super.onScrolled(recyclerView, dx, dy)
//是否滚动到底部
if (!recyclerView?.canScrollVertically(1)!!) {
mPresenter.getData(++mPage, ANDROID)
}
}
override fun onScrollStateChanged(recyclerView: RecyclerView?, newState: Int) {
super.onScrollStateChanged(recyclerView, newState)
}
})
}
//请求数据
mPresenter.getData(mPage, ANDROID)
mAdapter.setOnItemClickListener {
pos ->
val url = URLEncoder.encode(mList[pos].url)
GankRouter.router(context, GankClientUri.DETAIL + url)
}
}
首先是实例化了一个adapter适配器，然后把通过context.getMainComponent().plus(AndroidModule(this)).inject(this)实现了依赖注入，然后是通过一个with函数包含的代码块实现了 recyclerView的初始化和滚动监听
语法点: with函数
- with函数是将某对象作为函数的参数，在函数块内可以通过 this 指代该对象。返回值为函数块的最后一行或指定return表达式。
- 意思就是说如果要操作with的对象参数直接调用就行，不用多余的修饰符，比如这里的
recyclerView就是mBinding对象的成员变量，完整写法应该是mBinding . recyclerView
剩下的需要注意这段代码
companion object {
val ANDROID = "ANDROID"
fun newInstance(): AndroidFragment {
val fragment = AndroidFragment()
val bundle = Bundle()
fragment.arguments = bundle
return fragment
}
}
这个伴生对象我们前面说过，这里再说一次，它相当于java的静态成员变量，这里的代码大家可以对比一下java的写法，相信java的写法大家都很熟悉了
欢迎一起交流，有问题加群交流
kotlin实战交流群群二维码.png