Three types: relay type/matching type/individual type
Single touch
package com.example.myapplication.view
import android.content.Context
import android.graphics.Canvas
import android.graphics.Paint
import android.util.AttributeSet
import android.view.MotionEvent
import android.view.View
import com.example.myapplication.dp
class MultiTouchView1(context: Context, attrs: AttributeSet) : View(context, attrs) {
private val bitmap = getBitmap()
private val paint = Paint(Paint.ANTI_ALIAS_FLAG)
private var offsetX = 0f //Initial position
private var offsetY = 0f
private var downX = 0f //Pressed position
private var downY = 0f
private var originalOffsetX = 0f //Offset position
private var originalOffsetY = 0f
override fun onDraw(canvas: Canvas) {
super.onDraw(canvas)
canvas.drawBitmap(bitmap, offsetX, offsetY, paint)
}
override fun onTouchEvent(event: MotionEvent): Boolean {
when (event.actionMasked) {
MotionEvent.ACTION_DOWN -> {
downX = event.x
downY = event.y
originalOffsetX = offsetX
originalOffsetY = offsetY
}
MotionEvent.ACTION_MOVE -> {
offsetX = event.x - downX + originalOffsetX
offsetY = event.y - downY + originalOffsetY
invalidate()
}
}
return true
}
}
The touch event sequence is for the View rather than the finger
x, y, index, id belong to a point, a sequence, getX gets the finger position with index 0
public final float getX() {
return nativeGetAxisValue(mNativePtr, AXIS_X, 0, HISTORY_CURRENT);
}
point_move two points, when the second finger is up, the index will be set to 0 instead of 1. Sometimes the 0th finger down with an index of 0 will be pressed, and then 0 will become 1
The function of index is to traverse each Point through index when a MotionEvent occurs.
getX(),getX(index),index is obtained through event.pointCount
for traverses event.point through getX(index). If a certain point is raised, an error will be reported and the Index cannot be found. In this case, you can search by id
MotionEvent.ACTION_MOVE -> {
event.getX(event.actionIndex) //The ID of the finger being pressed
event.getX(event.findPointerIndex(downId)) //Get by ID
}
action_move is not suitable for this method, because when moving and updating in real time, there is no so-called Point, that is, index and id, which only make sense in down/up
Relay type
package com.example.myapplication.view
import android.content.Context
import android.graphics.Canvas
import android.graphics.Paint
import android.util.AttributeSet
import android.view.MotionEvent
import android.view.View
import com.example.myapplication.dp
class MultiTouchView1(context: Context, attrs: AttributeSet) : View(context, attrs) {
private val bitmap =getBitmap()
private val paint = Paint(Paint.ANTI_ALIAS_FLAG)
private var offsetX = 0f //Initial position
private var offsetY = 0f
private var downX = 0f //Pressed position
private var downY = 0f
private var originalOffsetX = 0f //Offset position
private var originalOffsetY = 0f
private var trackingPointerId = 0 //Currently pressed finger ID
override fun onDraw(canvas: Canvas) {
super.onDraw(canvas)
canvas.drawBitmap(bitmap, offsetX, offsetY, paint)
}
override fun onTouchEvent(event: MotionEvent): Boolean {
when (event.actionMasked) {
MotionEvent.ACTION_DOWN -> {
trackingPointerId = event.getPointerId(0)
downX = event.x
downY = event.y
originalOffsetX = offsetX
originalOffsetY = offsetY
}
//Multiple
MotionEvent.ACTION_POINTER_DOWN -> {
val actionIndex = event.actionIndex
trackingPointerId = event.getPointerId(actionIndex) //Get the ID of the pressed finger number
//update takeover
downX = event.getX(actionIndex)
downY = event.getY(actionIndex)
originalOffsetX = offsetX
originalOffsetY = offsetY
}
MotionEvent.ACTION_POINTER_UP -> {
val actionIndex = event.actionIndex
val pointerId = event.getPointerId(actionIndex)
if (pointerId == trackingPointerId) {
//If it is the finger being tracked, replace it
val newIndex = if (actionIndex == event.pointerCount - 1) {
event.pointerCount - 2
} else {
event.pointerCount - 1
}
trackingPointerId = event.getPointerId(newIndex) //Get the ID of the pressed finger number
//update takeover
downX = event.getX(newIndex)
downY = event.getY(newIndex)
originalOffsetX = offsetX
originalOffsetY = offsetY
}
}
MotionEvent.ACTION_MOVE -> {
val index = event.findPointerIndex(trackingPointerId)
offsetX = event.getX(index) - downX + originalOffsetX
offsetY = event.getY(index) - downY + originalOffsetY
invalidate()
}
}
return true
}
}
Matching type:
package com.example.myapplication.view
import android.content.Context
import android.graphics.Canvas
import android.graphics.Paint
import android.util.AttributeSet
import android.view.MotionEvent
import android.view.View
import com.example.myapplication.dp
import com.example.myapplication.getAvatar
//Swipe with two fingers
class MultiTouchView2(context: Context, attrs: AttributeSet) : View(context, attrs) {
private val bitmap = getAvatar(resources, 200.dp.toInt())
private val paint = Paint(Paint.ANTI_ALIAS_FLAG)
private var offsetX = 0f //Initial position
private var offsetY = 0f
private var downX = 0f //Pressed position
private var downY = 0f
private var originalOffsetX = 0f //Offset position
private var originalOffsetY = 0f
override fun onDraw(canvas: Canvas) {
super.onDraw(canvas)
canvas.drawBitmap(bitmap, offsetX, offsetY, paint)
}
override fun onTouchEvent(event: MotionEvent): Boolean {
val focusX: Float//Add the two focus values /2
val focusY : Float
var pointerCount = event.pointerCount
var sumX = 0f
var sumY = 0f
val inPointerUp = event.actionMasked == MotionEvent.ACTION_POINTER_UP //If it is lifted
for (i in 0 until pointerCount){
if (!(inPointerUp & amp; & amp; i == event.actionIndex)){ //The current position is not lifted, then calculate
sumX + = event.getX(i) //Get the coordinates of each point
sumY + = event.getY(i)
}
}
if (inPointerUp){
pointerCount -- //Handle additional offsets
}
focusX = sumX / pointerCount //Get the focus value. When lifted, the count will change
focusY = sumY /pointerCount
when (event.actionMasked) {
MotionEvent.ACTION_DOWN,MotionEvent.ACTION_POINTER_DOWN, MotionEvent.ACTION_POINTER_UP -> {
downX = focusX
downY = focusY
originalOffsetX = offsetX
originalOffsetY = offsetY
}
MotionEvent.ACTION_MOVE -> {
offsetX = focusX - downX + originalOffsetX
offsetY = focusY - downY + originalOffsetY
invalidate()
}
}
return true
}
}
Polydactyly
package com.example.myapplication.view
import android.content.Context
import android.graphics.Canvas
import android.graphics.Paint
import android.graphics.Path
import android.util.AttributeSet
import android.util.SparseArray
import android.view.MotionEvent
import android.view.View
import androidx.core.util.isEmpty
import com.example.myapplication.dp
class MultiTouchView3(context: Context, attrs: AttributeSet) : View(context, attrs) {
private val paint = Paint(Paint.ANTI_ALIAS_FLAG)
private var paths = SparseArray<Path>()
init {
paint.style = Paint.Style.STROKE
paint.strokeWidth = 4.dp
paint.strokeCap = Paint.Cap.ROUND
paint.strokeJoin = Paint.Join.ROUND
}
override fun onDraw(canvas: Canvas) {
super.onDraw(canvas)
for (i in 0 until paths.size()){
val path = paths.valueAt(i)
canvas.drawPath(path,paint)
}
}
override fun onTouchEvent(event: MotionEvent): Boolean {
when(event.actionMasked){
MotionEvent.ACTION_DOWN,MotionEvent.ACTION_POINTER_DOWN ->{
val actionIndex = event.actionIndex
val path = Path()
path.moveTo(event.getX(actionIndex),event.getY(actionIndex))
paths.append(event.getPointerId(actionIndex),path)
invalidate()
}
MotionEvent.ACTION_MOVE ->{
if (!paths.isEmpty()){
for (i in 0 until paths.size()){
val pointerId = event.getPointerId(i)
val path = paths.get(pointerId)
path.lineTo(event.getX(i),event.getY(i))
}
invalidate()
}
}
MotionEvent.ACTION_UP,MotionEvent.ACTION_POINTER_UP -> {
val actionIndex = event.actionIndex
val pointerId = event.getPointerId(actionIndex)
paths.remove(pointerId)
invalidate()
}
}
return true
}
}