[英]Drag and Drop in ConstraintLayout
我正在尝试在ConstraintLayout中拖放,如下所示,
override fun onLongClick(v: View?): Boolean {
val dragData = ClipData.newPlainText("", "")
val myShadow = View.DragShadowBuilder(v)
if(Build.VERSION.SDK_INT>= Build.VERSION_CODES.N) {
startDragAndDrop(dragData, myShadow, v, 0)
}else{
startDrag(dragData, myShadow, v, 0)
}
return true
}
我的拖拽听众是
private val mDragListen = View.OnDragListener { v, event ->
val view = event.localState as TextView
when (event.action) {
DragEvent.ACTION_DRAG_STARTED -> {
layoutParams = view.layoutParams as ConstraintLayout.LayoutParams?
true
}
DragEvent.ACTION_DRAG_ENTERED -> {
true
}
DragEvent.ACTION_DRAG_LOCATION ->
true
DragEvent.ACTION_DRAG_EXITED -> {
true
}
DragEvent.ACTION_DROP -> {
layoutParams?.marginStart = event.x.toInt()
layoutParams?.topMargin = event.y.toInt()
view.layoutParams = layoutParams
view.invalidate()
true
}
DragEvent.ACTION_DRAG_ENDED -> {
when (event.result) {
true ->
Toast.makeText(activity, "The drop was handled.", Toast.LENGTH_LONG)
else ->
Toast.makeText(activity, "The drop didn't work.", Toast.LENGTH_LONG)
}.show()
true
}
else -> {
Log.e("DragDrop Example", "Unknown action type received by OnDragListener.")
false
}
}
}
这是我的xml
<android.support.constraint.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
xmlns:app="http://schemas.android.com/apk/res-auto"
android:id="@+id/clContainer"
android:layout_height="match_parent"
tools:context="com.guna.kotlinapplication.BlankFragment">
<com.guna.kotlinapplication.DraggableTextView
android:id="@+id/image"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_marginTop="183dp"
android:layout_marginStart="56dp"
android:paddingStart="5dp"
android:paddingLeft="5dp"
android:text="@string/app_name"
android:paddingEnd="5dp"
android:tag="@string/app_name"
android:textSize="22sp"
android:paddingRight="5dp"
app:layout_constraintTop_toTopOf="parent"
app:layout_constraintStart_toStartOf="parent"
android:src="@drawable/ic_launcher_background" />
</android.support.constraint.ConstraintLayout>
这是有效的,但不是预期的,请参阅输出。
DragEvent方法getX()和getY()返回拖动点的坐标,如此处所示https://developer.android.com/reference/android/view/DragEvent.html#getX()
在您的情况下,只需减去视图高度和宽度的一半即可达到预期效果
layoutParams?.marginStart = event.x.toInt() - (view.width.div(2))
layoutParams?.topMargin = event.y.toInt() - (view.height.div(2))
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