4.1 该如何编写程序界面
ConstraintLayout:全新的布局
4.2 常用控件的使用方法
4.2.1 TextView
4.2.2 Button
4.2.3 EditText
4.2.4 ImageView
4.2.5 ProgressBar
# 进度条
# 可见与不可见切换
if (progressBar.visibility == View.VISIBLE){
progressBar.visibility = View.GONE
}else{
progressBar.visibility = View.VISIBLE
}
# 条形进度条
progressBar.progress = progressBar.progress + 10
4.2.6 AlertDialog
AlertDialog.Builder(this).apply {
setTitle("this is Dialog")
setMessage("Something important.")
setCancelable(false)
setPositiveButton("OK"){
dialog, which->
}
setNegativeButton("Cancel"){
dialog,which->
}
show()
}
4.3 详解3种基本布局
4.3.1 LinearLayout
4.3.2 RelativeLayout
4.3.3 FrameLayout
4.4 系统控件不够用，创建自定义控件
4.4.1 引入布局
https://blog.csdn.net/julicliy/article/details/127342207?spm=1001.2014.3001.5502
4.5 最常用和最难用的控件：ListView
4.5.1 ListView的简单用法
for (i in 1 until 20){
fruitList_str.add("str$i")
}
val adapter = ArrayAdapter(this, android.R.layout.simple_list_item_1, fruitList_str)
listView.adapter = adapter
listView.setOnItemClickListener { parent, view, position, id ->
val fruit = fruitList_str[position]
Toast.makeText(this, fruit, Toast.LENGTH_SHORT).show()
}
4.5.2 定制ListView的界面
默认在build.grade添加以下依赖：
apply plugin: 'com.android.application'
apply plugin: 'kotlin-android'
apply plugin: 'kotlin-android-extensions'
第一步：新建fruit_item.xml布局
第二步：创建Fruit类
class Fruit(val name:String, val imageId: Int)
第三步：创建适配器类，FruitAdapter类
class FruitAdapter(activity: Activity, val resourceId: Int, data: List) : ArrayAdapter(activity, resourceId, data) {
override fun getView(position: Int, convertView: View?, parent: ViewGroup): View {
val view: View
val viewHolder: ViewHolder
if (convertView == null) {
view = LayoutInflater.from(context).inflate(resourceId, parent, false)
val fruitImage: ImageView = view.findViewById(R.id.fruitImage)
val fruitName: TextView = view.findViewById(R.id.fruitName)
viewHolder = ViewHolder(fruitImage, fruitName)
view.tag = viewHolder
} else {
view = convertView
viewHolder = view.tag as ViewHolder
}
val fruit = getItem(position) // 获取当前项的Fruit实例
if (fruit != null) {
viewHolder.fruitImage.setImageResource(fruit.imageId)
viewHolder.fruitName.text = fruit.name
}
return view
}
inner class ViewHolder(val fruitImage: ImageView, val fruitName: TextView)
}
第四步：在MainActivity，修改代码如下：
private val fruitList = ArrayList()
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
setContentView(R.layout.activity_main)
initFruits() // 初始化水果数据
val adapter = FruitAdapter(this, R.layout.fruit_item, fruitLi+qq++``` -*-st)
listView.adapter = adapter
listView.setOn+---------+ItemClickListener { parent, view, position, id ->
}
listView.setOnItemClickListener { _, _, position, _ ->
val fruit = fruitList[position]
Toast.makeText(this, fruit.name, Toast.LENGTH_SHORT).show()
}
}
private fun initFruits() {
repeat(2) {
fruitList.add(Fruit("Apple", R.drawable.apple_pic))
fruitList.add(Fruit("Banana", R.drawable.banana_pic))
fruitList.add(Fruit("Orange", R.drawable.orange_pic))
fruitList.add(Fruit("Watermelon", R.drawable.watermelon_pic))
fruitList.add(Fruit("Pear", R.drawable.pear_pic))
fruitList.add(Fruit("Grape", R.drawable.grape_pic))
fruitList.add(Fruit("Pineapple", R.drawable.pineapple_pic))
fruitList.add(Fruit("Strawberry", R.drawable.strawberry_pic))
fruitList.add(Fruit("Cherry", R.drawable.cherry_pic))
fruitList.add(Fruit("Mango", R.drawable.mango_pic))
}
}
4.5.3 提升ListView的运行效率
以上为提升后的代码
4.5.4 ListView的点击事件
以上为实现后的代码
4.6 更加强大的滚动控件：RecyclerView
(图片资源，自己可以替换)
第一步：创建一个Fruit类。
class Fruit(val name:String, val imageId: Int)
第二步：layout创建一个fruit_item.xml文件。
第三步：创建一个FruitAdapter类。
import android.view.View
import android.view.ViewGroup
import android.widget.ImageView
import android.widget.TextView
import androidx.recyclerview.widget.RecyclerView
import android.view.LayoutInflater
import android.widget.Toast
class FruitAdapter(val fruitList: List) : RecyclerView.Adapter() {
inner class ViewHolder(view: View) : RecyclerView.ViewHolder(view) {
val fruitImage: ImageView = view.findViewById(R.id.fruitImage)
val fruitName: TextView = view.findViewById(R.id.fruitName)
}
override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): ViewHolder {
val view = LayoutInflater.from(parent.context).inflate(R.layout.fruit_item, parent, false)
val viewHolder = ViewHolder(view)
viewHolder.itemView.setOnClickListener {
val position = viewHolder.adapterPosition
val fruit = fruitList[position]
Toast.makeText(parent.context, "you clicked view ${fruit.name}", Toast.LENGTH_SHORT).show()
}
viewHolder.fruitImage.setOnClickListener {
val position = viewHolder.adapterPosition
val fruit = fruitList[position]
Toast.makeText(parent.context, "you clicked image ${fruit.name}", Toast.LENGTH_SHORT).show()
}
return viewHolder
}
override fun onBindViewHolder(holder: ViewHolder, position: Int) {
val fruit = fruitList[position]
holder.fruitImage.setImageResource(fruit.imageId)
holder.fruitName.text = fruit.name
}
override fun getItemCount() = fruitList.size
}
第四步：主Activity中修改成如下代码。
import androidx.appcompat.app.AppCompatActivity
import android.os.Bundle
import androidx.recyclerview.widget.LinearLayoutManager
import androidx.recyclerview.widget.StaggeredGridLayoutManager
import kotlinx.android.synthetic.main.activity_main.*
import java.util.*
import kotlin.collections.ArrayList
class MainActivity : AppCompatActivity() {
private val fruitList = ArrayList()
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
setContentView(R.layout.activity_main)
initFruits() // 初始化水果数据
val layoutManager = StaggeredGridLayoutManager(3, StaggeredGridLayoutManager.VERTICAL)
recyclerView.layoutManager = layoutManager
val adapter = FruitAdapter(fruitList)
recyclerView.adapter = adapter
}
private fun initFruits() {
repeat(2) {
fruitList.add(Fruit(getRandomLengthName("Apple"), R.drawable.apple_pic))
fruitList.add(Fruit(getRandomLengthName("Banana"), R.drawable.banana_pic))
fruitList.add(Fruit(getRandomLengthName("Orange"), R.drawable.orange_pic))
fruitList.add(Fruit(getRandomLengthName("Watermelon"), R.drawable.watermelon_pic))
fruitList.add(Fruit(getRandomLengthName("Pear"), R.drawable.pear_pic))
fruitList.add(Fruit(getRandomLengthName("Grape"), R.drawable.grape_pic))
fruitList.add(Fruit(getRandomLengthName("Pineapple"), R.drawable.pineapple_pic))
fruitList.add(Fruit(getRandomLengthName("Strawberry"), R.drawable.strawberry_pic))
fruitList.add(Fruit(getRandomLengthName("Cherry"), R.drawable.cherry_pic))
fruitList.add(Fruit(getRandomLengthName("Mango"), R.drawable.mango_pic))
}
}
private fun getRandomLengthName(name: String): String {
val length = Random().nextInt(20) + 1
val builder = StringBuilder()
for (i in 0 until length) {
builder.append(name)
}
return builder.toString()
}
}
4.6.2 实现横向滚动和瀑布流布局
调线性布局的方式，和主Activity的这行代码。
val layoutManager = StaggeredGridLayoutManager(3, StaggeredGridLayoutManager.VERTICAL)
4.6.3 RecyclerView的点击事件
在FruitAdapter的类当中，onCreateViewHolder内部类中。
4.7 编写界面的最佳实践
4.7.1 制作9-Patch图片
4.7.2 编写精美的聊天界面
具体看www.ituring.com.cn/book/2744网站，下载好，在第4章的项目，
个人见解：就是一个RecyclerView控件的灵活运用。按不同的项，使用不同的布局
