CoordinatorLayout.BehavioronTouchEvent()：处理触摸事件
onDependentViewRemoved()：当被依赖的View移除时回调
onLayoutChild()：确定使用Behavior的View位置
我的练习项目 TestCoordinatorLayoutBehavior
MainActivity
private var dX = 0f
private var dY = 0f
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
setContentView(binding.root)
// 拖拽逻辑
binding.iv.setOnTouchListener { v, event ->
when(event.action){
MotionEvent.ACTION_DOWN -> {
dX = v.x - event.rawX
dY = v.y - event.rawY
}
MotionEvent.ACTION_MOVE -> {
// 平滑过渡
// v.animate()
// .x(event.rawX + dX)
// .y(event.rawY + dY)
// .setDuration(0)
// .start()
// 拖拽更适合使用直接 set 快速响应
v.x = event.rawX + dX
v.y = event.rawY + dY
}
else -> return@setOnTouchListener false
}
true
}
}
class CustomBehavior : Behavior<View> {
constructor() : super()
constructor(context: Context?, attrs: AttributeSet?) : super(context, attrs)
override fun layoutDependsOn(
parent: CoordinatorLayout,
child: View,
dependency: View
): Boolean {
// 指定依赖的 View 类型
return dependency is ImageView
}
override fun onDependentViewChanged(
parent: CoordinatorLayout,
child: View,
dependency: View
): Boolean {
// 这里的逻辑是跟随改变位置
val dX = dependency.x - child.width
val dY = dependency.y - child.height
val translationX =
(dX * 2).coerceIn(0f, ScreenUtils.getScreenWidth().toFloat() - child.width)
val translationY = (dY * 2).coerceIn(
0f,
ScreenUtils.getScreenHeight().toFloat() - child.height - BarUtils.getStatusBarHeight()
)
child.translationX = translationX
child.translationY = translationY
// 这里的逻辑是跟随改变透明度
val dy = dependency.y - child.height
val alpha = 1f - (dy.coerceAtLeast(0f) / ScreenUtils.getScreenHeight())
child.alpha = alpha
return true
}
}
<androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools"
android:id="@+id/main"
android:layout_width="match_parent"
android:layout_height="match_parent"
tools:context=".MainActivity">
<androidx.coordinatorlayout.widget.CoordinatorLayout
android:layout_width="match_parent"
android:layout_height="match_parent"
>
<ImageView
android:id="@+id/iv"
android:layout_width="100dp"
android:layout_height="100dp"
android:src="@mipmap/ic_launcher"
/>
<TextView
android:id="@+id/tv"
android:background="@color/black"
android:textColor="@color/white"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="textView"
app:layout_behavior=".CustomBehavior"
/>
</androidx.coordinatorlayout.widget.CoordinatorLayout>
</androidx.constraintlayout.widget.ConstraintLayout>
MainActivity
// 初始化 rv
binding.rv.adapter = object : Adapter<ViewHolder>() {
override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): ViewHolder {
val textView = TextView(this@MainActivity).apply {
layoutParams = ViewGroup.LayoutParams(ViewGroup.LayoutParams.MATCH_PARENT, 100)
}
return object : ViewHolder(textView) {}
}
override fun getItemCount(): Int {
return 100
}
override fun onBindViewHolder(holder: ViewHolder, position: Int) {
val tv = holder.itemView as TextView
tv.text = "item: ${position}"
}
}
class CustomBehavior2 : Behavior<View> {
constructor() : super()
constructor(context: Context?, attrs: AttributeSet?) : super(context, attrs)
override fun layoutDependsOn(
parent: CoordinatorLayout,
child: View,
dependency: View
): Boolean {
// 指定依赖的 View 类型
return dependency is RecyclerView
}
override fun onStartNestedScroll(
coordinatorLayout: CoordinatorLayout,
child: View,
directTargetChild: View,
target: View,
axes: Int,
type: Int
): Boolean {
// 返回 true 表示处理嵌套滚动事件
return true
}
private var countY = 0
override fun onNestedScroll(
coordinatorLayout: CoordinatorLayout,
child: View,
target: View,
dxConsumed: Int, // 已经消耗的水平滚动距离
dyConsumed: Int,
dxUnconsumed: Int, // 如果 RecyclerView 只能处理部分滚动事件，而剩余的滚动距离是 20 像素，那么 dxUnconsumed 或 dyUnconsumed 就会是 20
dyUnconsumed: Int,
type: Int,
consumed: IntArray // consumed 数组用于指示父视图消耗了多少滚动距离，数组里装x和y
) {
Log.d(
"onNestedScroll",
"dyConsumed: ${dyConsumed} dyUnconsumed: ${dyUnconsumed} consumed[1]: ${consumed[1]}"
)
// dyConsumed 可处理的滑动px。实际滑动的px
// dyUnconsumed 不可处理的滑动px。例如，下拉时到顶了再尝试继续下拉20个px，那么这个值就是20
// 处理嵌套滚动事件
// 例如：根据滚动距离调整 child 的位置
countY += dyConsumed
// child.translationY = countY.toFloat()
val rv = target as RecyclerView
// `computeVerticalScrollRange` rv可滑动的总y
val allY = rv.computeVerticalScrollRange() - ScreenUtils.getScreenHeight() + BarUtils.getStatusBarHeight()
val ratioY = countY.toFloat() / allY
val y = ratioY * ScreenUtils.getScreenHeight() - BarUtils.getStatusBarHeight()
Log.d("onNestedScroll", "y: ${y}, countY: ${countY}, allY: ${allY}")
child.translationY = y.coerceIn(
0f,
ScreenUtils.getScreenHeight().toFloat() - child.height - BarUtils.getStatusBarHeight()
)
// child.translationY += dyConsumed
// child.translationY += dyUnconsumed
}
override fun onNestedPreScroll(
coordinatorLayout: CoordinatorLayout,
child: View,
target: View,
dx: Int,
dy: Int,
consumed: IntArray,
type: Int
) {
// 处理嵌套滚动前的事件
}
}
<androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools"
android:id="@+id/main"
android:layout_width="match_parent"
android:layout_height="match_parent"
tools:context=".MainActivity">
<androidx.coordinatorlayout.widget.CoordinatorLayout
android:layout_width="match_parent"
android:layout_height="match_parent"
>
<androidx.recyclerview.widget.RecyclerView
android:id="@+id/rv"
android:layout_width="match_parent"
android:layout_height="match_parent"
app:layoutManager="androidx.recyclerview.widget.LinearLayoutManager"
android:orientation="vertical"
tools:itemCount="10"
/>
<TextView
android:id="@+id/tv2"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="textView2"
app:layout_behavior=".CustomBehavior2"
/>
</androidx.coordinatorlayout.widget.CoordinatorLayout>
</androidx.constraintlayout.widget.ConstraintLayout>