1、数据项点击事件，针对的是ListView每个数据项的点击事件
listView.setOnItemClickListener { _, _, position, _ -> Toast.makeText(this, "position: $position", Toast.LENGTH_LONG).show()}
2、ListView组件焦点事件（不是指单个item，是整个ListView）
listView.setOnFocusChangeListener { _, hasFocus -> if (hasFocus) { Log.d("MainActivity", "has focus ... ") } else { Log.d("MainActivity", "lose focus ...") }}
3、ListView中数据项被选中事件监听
bind.listView.onItemSelectedListener = object: AdapterView.OnItemSelectedListener{ override fun onItemSelected(parent: AdapterView<*>?,view: View?,position: Int,id: Long) { Log.d("MainActivity", "position: $position") } override fun onNothingSelected(parent: AdapterView<*>?) { Log.d("MainActivity", "onNothingSelected ...") }}
AdapterView.OnItemSelectedListener中有两个方法，onItemSelected在数据项被选中时触发，onNothingSelected在LiveView没有任何数据项被选中时触发。
4、监听ListView中item焦点的变化
假设有一个需求，item获取焦点背景颜色为blue，没有焦点的背景颜色为white，则伪代码如下：
Adapter中代码
class FruitAdapter(activity: Activity, private val resourceId: Int, data: List
ArrayAdapter
var position: Int = 0
override fun getView(position: Int, convertView: View?, parent: ViewGroup): View {
Log.d("FruitAdapter", "position: $position convertView: $convertView")
val view = ... //加载布局伪代码
if (this.position == position) {
view.setBackgroundColor(Color.BLUE)
} else {
view.setBackgroundColor(Color.WHITE)
}
return view
}
}
Adapter中定义了一个position，用来记录当前哪个item被选中，数值由Activity那边监听更新
MainActivity中代码
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
val bind = ActivityMainBinding.inflate(layoutInflater)
setContentView(bind.root)
val fruitAdapter = FruitAdapter(this, R.layout.fruit_item, fruitList)
bind.listView.adapter = fruitAdapter
bind.listView.onItemSelectedListener = object: AdapterView.OnItemSelectedListener{
override fun onItemSelected(parent: AdapterView<*>?,view: View?,position: Int,id: Long) {
Log.d("MainActivity", "position: $position")
fruitAdapter.position = position
fruitAdapter.notifyDataSetChanged()
}
override fun onNothingSelected(parent: AdapterView<*>?) {
Log.d("MainActivity", "onNothingSelected ...")
}
}
}
看红色代码即可，获取ListView对象后，添加onItemSelectedListener 监听，然后把选中的item下标传递给Adapter。这时调用Adapter的方法notifyDataSetChanged()来通知Adapter刷新数据，再次执行Adapter中getView()方法，在getView方法中对下标进行了比较，相等下标的view背景色变为blue，否则变为while，这样就实现了ListView中item焦点变化事件的监听。