先自定義一個Imageview
package com.gode.myapplication.view
import android.content.Context
import android.util.AttributeSet
import android.util.Log
import android.view.MotionEvent
import androidx.appcompat.widget.AppCompatImageView
class ImageViewOnTouch(context: Context?, attrs: AttributeSet?) :
AppCompatImageView(context, attrs) {
override fun onTouchEvent(event: MotionEvent?): Boolean {
Log.e("msg","........ImageViewOnTouch.......onTouchEvent...");
return super.onTouchEvent(event)
}
override fun dispatchTouchEvent(event: MotionEvent?): Boolean {
Log.e("msg","........ImageViewOnTouch.......dispatchTouchEvent...");
return super.dispatchTouchEvent(event)
}
}
很簡單裏面就一個構造和兩個方法，一個是是否分發，一個是處理動作：
繼續接着走，在mainactivity裏面也設置這連個方法：
package com.gode.myapplication
import androidx.appcompat.app.AppCompatActivity
import android.os.Bundle
import android.util.Log
import android.view.MotionEvent
class MainActivity : AppCompatActivity() {
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
setContentView(R.layout.activity_main)
}
override fun dispatchTouchEvent(ev: MotionEvent?): Boolean {
Log.e("msg","........main.......dispatchTouchEvent...");
return super.dispatchTouchEvent(ev)
}
override fun onTouchEvent(event: MotionEvent?): Boolean {
Log.e("msg","........main.......onTouchEvent...");
return super.onTouchEvent(event)
}
}
佈局xml：
<?xml version="1.0" encoding="utf-8"?>
<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:layout_width="match_parent"
android:layout_height="match_parent"
tools:context=".MainActivity">
<com.gode.myapplication.view.ImageViewOnTouch
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:background="@mipmap/ic_launcher"
tools:ignore="MissingConstraints" />
</androidx.constraintlayout.widget.ConstraintLayout>
裏面就一個自定義佈局，當點擊空白處：
2020-07-03 14:23:42.091 15084-15084/com.gode.myapplication E/msg: ........main.......dispatchTouchEvent...
2020-07-03 14:23:42.092 15084-15084/com.gode.myapplication E/msg: ........main.......onTouchEvent...
2020-07-03 14:23:42.131 15084-15084/com.gode.myapplication E/msg: ........main.......dispatchTouchEvent...
2020-07-03 14:23:42.132 15084-15084/com.gode.myapplication E/msg: ........main.......onTouchEvent...
先執行的事件分發方法，這可能是 一個再簡單不過了，繼續接着改點擊imageview了，看看會怎麼執行：
2020-07-03 14:27:05.330 15084-15084/com.gode.myapplication E/msg: ........main.......dispatchTouchEvent...
2020-07-03 14:27:05.331 15084-15084/com.gode.myapplication E/msg: ........ImageViewOnTouch.......dispatchTouchEvent...
2020-07-03 14:27:05.331 15084-15084/com.gode.myapplication E/msg: ........ImageViewOnTouch.......onTouchEvent...
2020-07-03 14:27:05.331 15084-15084/com.gode.myapplication E/msg: ........main.......onTouchEvent...
2020-07-03 14:27:05.353 15084-15084/com.gode.myapplication E/msg: ........main.......dispatchTouchEvent...
2020-07-03 14:27:05.353 15084-15084/com.gode.myapplication E/msg: ........main.......onTouchEvent...
2020-07-03 14:27:05.354 15084-15084/com.gode.myapplication E/msg: ........main.......dispatchTouchEvent...
2020-07-03 14:27:05.354 15084-15084/com.gode.myapplication E/msg: ........main.......onTouchEvent...
先執行了mainactivity裏面的 事件分發再走自定義imageview裏面的事件分發，touch方法，最後回到了main的touch方法。
方法與上面同步：點擊空白處，只是這裏把ACTION_DOWN ACTION_MOVE ACTION_UP 加入進去 比如：
when (event?.action){
MotionEvent.ACTION_DOWN -> {
Log.e("msg","........ImageViewOnTouch...onTouchEvent....ACTION_DOWN...");
}
MotionEvent.ACTION_MOVE -> {
Log.e("msg","........ImageViewOnTouch...onTouchEvent....ACTION_MOVE...");
}
MotionEvent.ACTION_UP -> {
Log.e("msg","........ImageViewOnTouch...onTouchEvent....ACTION_UP...");
}
}
當點擊空白處的時候：
2020-07-03 14:48:06.648 26995-26995/com.gode.myapplication E/msg: ........main...dispatchTouchEvent....ACTION_DOWN...
2020-07-03 14:48:06.648 26995-26995/com.gode.myapplication E/msg: ........main....onTouchEvent...ACTION_DOWN...
2020-07-03 14:48:06.694 26995-26995/com.gode.myapplication E/msg: ........main...dispatchTouchEvent....ACTION_MOVE...
2020-07-03 14:48:06.694 26995-26995/com.gode.myapplication E/msg: ........main...onTouchEvent....ACTION_MOVE...
2020-07-03 14:48:06.695 26995-26995/com.gode.myapplication E/msg: ........main...dispatchTouchEvent....ACTION_UP...
2020-07-03 14:48:06.695 26995-26995/com.gode.myapplication E/msg: ........main..onTouchEvent.....ACTION_UP...
先執行的Down 從事件分發，再touch，不是把dispatchtouchevent方法執行完了才執行ontouchevent方法，而是先執行down再執行move這麼的順序來的
繼續走，現在只操作activity的事件分發方法，在這裏返回true就是攔截；
override fun dispatchTouchEvent(ev: MotionEvent?): Boolean {
when (ev?.action){
MotionEvent.ACTION_DOWN -> {
Log.e("msg","........main...dispatchTouchEvent....ACTION_DOWN...")
}
MotionEvent.ACTION_MOVE -> {
Log.e("msg","........main...dispatchTouchEvent....ACTION_MOVE...")
}
MotionEvent.ACTION_UP -> {
Log.e("msg","........main...dispatchTouchEvent....ACTION_UP...")
}
}
return true
}
執行結果：
2020-07-03 14:59:38.135 3561-3561/com.gode.myapplication E/msg: ........main...dispatchTouchEvent....ACTION_DOWN...
2020-07-03 14:59:38.173 3561-3561/com.gode.myapplication E/msg: ........main...dispatchTouchEvent....ACTION_MOVE...
2020-07-03 14:59:38.176 3561-3561/com.gode.myapplication E/msg: ........main...dispatchTouchEvent....ACTION_UP...
就是ontouchevent方法沒有執行了，已經被消耗了。如果執行攔截down呢那麼結果會怎樣呢？
override fun dispatchTouchEvent(ev: MotionEvent?): Boolean {
when (ev?.action){
MotionEvent.ACTION_DOWN -> {
Log.e("msg","........main...dispatchTouchEvent....ACTION_DOWN...")
return true
}
MotionEvent.ACTION_MOVE -> {
Log.e("msg","........main...dispatchTouchEvent....ACTION_MOVE...")
}
MotionEvent.ACTION_UP -> {
Log.e("msg","........main...dispatchTouchEvent....ACTION_UP...")
}
}
return super.dispatchTouchEvent(ev)
}
2020-07-03 15:03:28.428 5155-5155/com.gode.myapplication E/msg: ........main...dispatchTouchEvent....ACTION_DOWN...
2020-07-03 15:03:28.466 5155-5155/com.gode.myapplication E/msg: ........main...dispatchTouchEvent....ACTION_MOVE...
2020-07-03 15:03:28.466 5155-5155/com.gode.myapplication E/msg: ........main...onTouchEvent....ACTION_MOVE...
2020-07-03 15:03:28.468 5155-5155/com.gode.myapplication E/msg: ........main...dispatchTouchEvent....ACTION_UP...
2020-07-03 15:03:28.468 5155-5155/com.gode.myapplication E/msg: ........main..onTouchEvent.....ACTION_UP...
可以看出，這裏只在down這裏return true了，只有ontouchEvent 的down方法沒有執行。其他move也是一樣的。這裏沒有測試！！最後發現有個奇怪的問題，不管down方法裏面是true還是false都是這樣的結果。其他的move也是如此。
接下來是的，改自定義imageview了，在事件分發dispatchevent裏面做處理：
override fun dispatchTouchEvent(event: MotionEvent?): Boolean {
when (event?.action){
MotionEvent.ACTION_DOWN -> {
Log.e("msg","........ImageViewOnTouch...dispatchTouchEvent....ACTION_DOWN...");
}
MotionEvent.ACTION_MOVE -> {
Log.e("msg","........ImageViewOnTouch....dispatchTouchEvent...ACTION_MOVE...");
}
MotionEvent.ACTION_UP -> {
Log.e("msg","........ImageViewOnTouch....dispatchTouchEvent...ACTION_UP...");
}
}
return true
}
2020-07-03 15:24:18.240 16961-16961/com.gode.myapplication E/msg: ........main...dispatchTouchEvent....ACTION_DOWN...
2020-07-03 15:24:18.241 16961-16961/com.gode.myapplication E/msg: ........ImageViewOnTouch...dispatchTouchEvent....ACTION_DOWN...
2020-07-03 15:24:18.254 16961-16961/com.gode.myapplication E/msg: ........main...dispatchTouchEvent....ACTION_UP...
2020-07-03 15:24:18.254 16961-16961/com.gode.myapplication E/msg: ........ImageViewOnTouch....dispatchTouchEvent...ACTION_UP...
看到這裏心裏其實有點底了，就是從順序一步步來的，先從main裏面執行事件分發DOWN沒有攔截走自定義view的事件分發沒有攔截，回到main裏面執行UP的事件分發沒有攔截走自定義的UP，這樣一個順序，這裏在自定義的事件分發攔截，所以沒有走ontouch方法，更加不會走main裏面ontouch方法l。
繼續在自定義view攔截ontouch方法：
override fun onTouchEvent(event: MotionEvent?): Boolean {
when (event?.action){
MotionEvent.ACTION_DOWN -> {
Log.e("msg","........ImageViewOnTouch...onTouchEvent....ACTION_DOWN...");
}
MotionEvent.ACTION_MOVE -> {
Log.e("msg","........ImageViewOnTouch...onTouchEvent....ACTION_MOVE...");
}
MotionEvent.ACTION_UP -> {
Log.e("msg","........ImageViewOnTouch...onTouchEvent....ACTION_UP...");
}
}
return true
}
2020-07-03 15:33:12.229 19679-19679/com.gode.myapplication E/msg: ........main...dispatchTouchEvent....ACTION_DOWN...
2020-07-03 15:33:12.230 19679-19679/com.gode.myapplication E/msg: ........ImageViewOnTouch...dispatchTouchEvent....ACTION_DOWN...
2020-07-03 15:33:12.230 19679-19679/com.gode.myapplication E/msg: ........ImageViewOnTouch...onTouchEvent....ACTION_DOWN...
2020-07-03 15:33:12.235 19679-19679/com.gode.myapplication E/msg: ........main...dispatchTouchEvent....ACTION_UP...
2020-07-03 15:33:12.235 19679-19679/com.gode.myapplication E/msg: ........ImageViewOnTouch....dispatchTouchEvent...ACTION_UP...
2020-07-03 15:33:12.235 19679-19679/com.gode.myapplication E/msg: ........ImageViewOnTouch...onTouchEvent....ACTION_UP...
這裏可能會忘記剛開始是怎麼的了，這裏重新打印一下；（這裏是什麼都沒有做攔截的）
2020-07-03 15:38:55.754 21208-21208/com.gode.myapplication E/msg: ........main...dispatchTouchEvent....ACTION_DOWN...
2020-07-03 15:38:55.755 21208-21208/com.gode.myapplication E/msg: ........ImageViewOnTouch...dispatchTouchEvent....ACTION_DOWN...
2020-07-03 15:38:55.756 21208-21208/com.gode.myapplication E/msg: ........ImageViewOnTouch...onTouchEvent....ACTION_DOWN...
2020-07-03 15:38:55.756 21208-21208/com.gode.myapplication E/msg: ........main....onTouchEvent...ACTION_DOWN...
2020-07-03 15:38:55.784 21208-21208/com.gode.myapplication E/msg: ........main...dispatchTouchEvent....ACTION_MOVE...
2020-07-03 15:38:55.784 21208-21208/com.gode.myapplication E/msg: ........main...onTouchEvent....ACTION_MOVE...
2020-07-03 15:38:55.785 21208-21208/com.gode.myapplication E/msg: ........main...dispatchTouchEvent....ACTION_UP...
2020-07-03 15:38:55.785 21208-21208/com.gode.myapplication E/msg: ........main..onTouchEvent.....ACTION_UP...
是的你沒看過與上面一樣只是剛開始沒有這麼詳細，這裏沒有走move和up！！！後期會補上。
本來自定義的ontouch方法是沒有執行的，但這裏return true了，表示攔截此方法走到了裏面的方法，Down 和UP，但main裏面的ontouch方法沒有執行。好了，到這裏差不多了。
總結：
執行順序是走main裏的事件分發Down 沒有攔截走自定義的Down ->UP->ontouch (這裏只走了自定義的ontouch 的DOWN）
哪裏攔截，哪裏就行自己的ontouch:
圖有點醜！！