Android 中触摸事件与点击事件分析

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触摸事件

两种检测触摸事件的方式:

设置触摸监听 setOnTouchListener

返回 true: 表示消费事件 , 可以检测到 down/move/up 事件
返回 false: 不消费事件, 只能检测到 down 事件

重写onTouchEvent()

必须继承自系统的一个View,才能重写 onTouchEvent()方法;
如 MyImageView extends ImageView ,才能重写onTouchEvent
返回 true: 消费事件,能检测到 down/move/up 事件
返回 false: 不消费事件,只能检测到 down 事件

如果两种触摸事件都存在,并且都返回true,结果如何?

setOnTouchListener 有效
onTouchEvent() 无效

另外:一个View能否消费事件,关键看 dispatchTouchEvent(),我们来看下 android-10的源码(为什么要看这个版本的源码呢?因为低版本的源码中,原理性的知识点都是一样的,高版本的源码中,加入了非常多的逻辑判断)
View.java事件是怎么分发的

    /**     * Pass the touch screen motion event down to the target view, or this     * view if it is the target.     *     * @param event The motion event to be dispatched.     * @return True if the event was handled by the view, false otherwise.     */    public boolean dispatchTouchEvent(MotionEvent event) {        if (mOnTouchListener != null && (mViewFlags & ENABLED_MASK) == ENABLED &&                mOnTouchListener.onTouch(this, event)) {            return true;        }        return onTouchEvent(event);    }

我们可以看到如果两种方式都设置的话,每次这个if条件判断都会走,所以 onTouchListener 可以拿到所有事件(down/move/up事件);只有onTouchListener返回false时,onTouchEvent()方法才会走,才能拿到(down/move/up)所有事件;

如何让两种方式同时生效呢?

setOnTouchListener 返回false
onTouchEvent() 返回true

下面我们上代码:

<?xml version="1.0" encoding="utf-8"?><RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"    xmlns:tools="http://schemas.android.com/tools"    android:layout_width="match_parent"    android:layout_height="match_parent"    android:paddingBottom="@dimen/activity_vertical_margin"    android:paddingLeft="@dimen/activity_horizontal_margin"    android:paddingRight="@dimen/activity_horizontal_margin"    android:paddingTop="@dimen/activity_vertical_margin"    tools:context="com.xialm.touchdemo.MainActivity">    <ImageView        android:id="@+id/iv"        android:layout_width="100dp"        android:layout_height="100dp"        android:src="@mipmap/ic_launcher" /></RelativeLayout>

修改返回true,所有事件都能拿到;返回false,只能拿到down事件;

true时:

04-28 01:44:13.515 1471-1471/com.xialm.touchdemo E/MainActivity: onTouch: 004-28 01:44:18.266 1471-1471/com.xialm.touchdemo E/MainActivity: onTouch: 204-28 01:44:18.283 1471-1471/com.xialm.touchdemo E/MainActivity: onTouch: 204-28 01:44:18.333 1471-1471/com.xialm.touchdemo E/MainActivity: onTouch: 204-28 01:44:19.555 1471-1471/com.xialm.touchdemo E/MainActivity: onTouch: 1

false时:

04-28 01:44:13.515 1471-1471/com.xialm.touchdemo E/MainActivity: onTouch: 0

同理,我们创建 CustomImageView,继承自ImageView,同时修改布局文件中的ImageView为 CustomImageView

public class CustomImageView extends ImageView {    private static final String TAG = "CustomImageView";    public CustomImageView(Context context) {        super(context);    }    public CustomImageView(Context context, AttributeSet attrs) {        super(context, attrs);    }    public CustomImageView(Context context, AttributeSet attrs, int defStyleAttr) {        super(context, attrs, defStyleAttr);    }    /**     * 返回false:只能拿到down事件     * 返回true: 能拿到down/move/up事件     * @param event     * @return     */    @Override    public boolean onTouchEvent(MotionEvent event) {        Log.e(TAG, "onTouchEvent: "+event.getAction() );        return true; //super.onTouchEvent(event);    }}

同时设置,同时返回true的情况,可以看到跟我们的分析是一样的

04-28 01:47:54.060 5005-5005/com.xialm.touchdemo E/MainActivity: onTouch: 004-28 01:47:54.434 5005-5005/com.xialm.touchdemo E/MainActivity: onTouch: 204-28 01:47:54.450 5005-5005/com.xialm.touchdemo E/MainActivity: onTouch: 204-28 01:47:54.817 5005-5005/com.xialm.touchdemo E/MainActivity: onTouch: 204-28 01:47:54.850 5005-5005/com.xialm.touchdemo E/MainActivity: onTouch: 204-28 01:47:55.188 5005-5005/com.xialm.touchdemo E/MainActivity: onTouch: 1

同时设置setOnTouchListener返回false,onTouchEvent()返回true

04-28 01:49:55.452 6978-6978/com.xialm.touchdemo E/MainActivity: onTouch: 004-28 01:49:55.452 6978-6978/com.xialm.touchdemo E/CustomImageView: onTouchEvent: 004-28 01:49:58.850 6978-6978/com.xialm.touchdemo E/MainActivity: onTouch: 204-28 01:49:58.850 6978-6978/com.xialm.touchdemo E/CustomImageView: onTouchEvent: 204-28 01:49:58.866 6978-6978/com.xialm.touchdemo E/MainActivity: onTouch: 204-28 01:49:58.866 6978-6978/com.xialm.touchdemo E/CustomImageView: onTouchEvent: 204-28 01:49:59.926 6978-6978/com.xialm.touchdemo E/MainActivity: onTouch: 104-28 01:49:59.926 6978-6978/com.xialm.touchdemo E/CustomImageView: onTouchEvent: 1

Touch事件处理流程分析

我们自定义一个MyLinearLayout 继承自系统的LinearLayout,然后在布局文件中包裹 CustomImageView,

public class MyLinearLayout extends LinearLayout {    private static final String TAG = "MyLinearLayout";    public MyLinearLayout(Context context) {        super(context);    }    public MyLinearLayout(Context context, AttributeSet attrs) {        super(context, attrs);    }    public MyLinearLayout(Context context, AttributeSet attrs, int defStyleAttr) {        super(context, attrs, defStyleAttr);    }    @Override    public boolean onTouchEvent(MotionEvent event) {        Log.e(TAG, "onTouchEvent: "+event.getAction() );        return true;//super.onTouchEvent(event);   返回true    }}

<com.xialm.touchdemo.MyLinearLayout        android:layout_width="match_parent"        android:layout_height="wrap_content"        android:background="#ccc"        android:padding="10dp">        <com.xialm.touchdemo.CustomImageView            android:id="@+id/iv"            android:layout_width="100dp"            android:layout_height="100dp"            android:src="@mipmap/ic_launcher" />    </com.xialm.touchdemo.MyLinearLayout>

我们只研究onTouchEvent()

CustomImageView的onTouchEvent()也返回true

04-28 02:37:15.952 14101-14101/com.xialm.touchdemo E/CustomImageView: onTouchEvent: 004-28 02:37:16.350 14101-14101/com.xialm.touchdemo E/CustomImageView: onTouchEvent: 204-28 02:37:16.367 14101-14101/com.xialm.touchdemo E/CustomImageView: onTouchEvent: 204-28 02:37:16.700 14101-14101/com.xialm.touchdemo E/CustomImageView: onTouchEvent: 204-28 02:37:17.367 14101-14101/com.xialm.touchdemo E/CustomImageView: onTouchEvent: 204-28 02:37:17.648 14101-14101/com.xialm.touchdemo E/CustomImageView: onTouchEvent: 1

当父View和子view都有处理触摸事件的逻辑时,子view可以接收到所有的事件;

这是因为事件传递是由外向内,而事件的消费是由内向外的;

只有子View不处理触摸事件时,父View才能处理消费事件(即CustomImageView的onTouchEvent()返回false,MyLinearLayout的onTouchEvent()返回true)
使用下面示意图来解释,再好不过了:

父View想要消费事件,有没有办法呢?

办法是有的,只需重写onInterceptTouchEvent()方法,返回true,把事件中断掉,则事件就不能往下传递了,我们处理消费逻辑即可:

public class CustomImageView extends ImageView {   ...省略代码...    /**     * 返回false:只能拿到down事件     * 返回true: 能拿到down/move/up事件     * @param event     * @return     */    @Override    public boolean onTouchEvent(MotionEvent event) {        Log.e(TAG, "onTouchEvent: "+event.getAction() );        return true; //super.onTouchEvent(event);    }}

public class MyLinearLayout extends LinearLayout {    ...省略代码...    private int count = 0;    @Override    public boolean onInterceptTouchEvent(MotionEvent ev) {        count++;        if (count > 4) {            return true;        }        return false; // 中断事件    }    @Override    public boolean onTouchEvent(MotionEvent event) {        Log.e(TAG, "onTouchEvent: "+event.getAction() );        return true;//super.onTouchEvent(event);    }}

04-28 02:52:30.948 28332-28332/com.xialm.touchdemo E/CustomImageView: onTouchEvent: 004-28 02:52:31.250 28332-28332/com.xialm.touchdemo E/CustomImageView: onTouchEvent: 204-28 02:52:31.266 28332-28332/com.xialm.touchdemo E/CustomImageView: onTouchEvent: 204-28 02:52:31.783 28332-28332/com.xialm.touchdemo E/CustomImageView: onTouchEvent: 204-28 02:52:31.800 28332-28332/com.xialm.touchdemo E/CustomImageView: onTouchEvent: 304-28 02:52:31.867 28332-28332/com.xialm.touchdemo E/MyLinearLayout: onTouchEvent: 204-28 02:52:31.933 28332-28332/com.xialm.touchdemo E/MyLinearLayout: onTouchEvent: 204-28 02:52:31.950 28332-28332/com.xialm.touchdemo E/MyLinearLayout: onTouchEvent: 204-28 02:52:32.033 28332-28332/com.xialm.touchdemo E/MyLinearLayout: onTouchEvent: 204-28 02:52:32.050 28332-28332/com.xialm.touchdemo E/MyLinearLayout: onTouchEvent: 204-28 02:52:32.167 28332-28332/com.xialm.touchdemo E/MyLinearLayout: onTouchEvent: 204-28 02:52:35.396 28332-28332/com.xialm.touchdemo E/MyLinearLayout: onTouchEvent: 1

由下面流程示意图来说明:

触摸事件与点击事件

onTouchEvent() 与 onClickListener

点击事件是由 down 和 up 事件组成的,系统一直检测 up事件是否发生,如果有up事件,就会判断 onClickListener监听是否存在,存在就回调onClick()方法

触摸事件和点击事件同时存在时:

系统是怎么区分点击事件还是触摸事件呢?不知道你有没有注意到我们重写onTouchEvent()时有一句话
super.onTouchEvent(event); // 在内部处理了,点击事件的逻辑

查看android-10 View.java源码我们着重留意一下 up事件

 /**     * Implement this method to handle touch screen motion events.     *     * @param event The motion event.     * @return True if the event was handled, false otherwise.     */    public boolean onTouchEvent(MotionEvent event) {        final int viewFlags = mViewFlags;        if ((viewFlags & ENABLED_MASK) == DISABLED) {            // A disabled view that is clickable still consumes the touch            // events, it just doesn't respond to them.            return (((viewFlags & CLICKABLE) == CLICKABLE ||                    (viewFlags & LONG_CLICKABLE) == LONG_CLICKABLE));        }        if (mTouchDelegate != null) {            if (mTouchDelegate.onTouchEvent(event)) {                return true;            }        }        if (((viewFlags & CLICKABLE) == CLICKABLE ||                (viewFlags & LONG_CLICKABLE) == LONG_CLICKABLE)) {            switch (event.getAction()) {                case MotionEvent.ACTION_UP:    // 着重研究up事件                    if ((mPrivateFlags & PRESSED) != 0) {                        // take focus if we don't have it already and we should in                        // touch mode.                        boolean focusTaken = false;                        if (isFocusable() && isFocusableInTouchMode() && !isFocused()) {                            focusTaken = requestFocus();                        }                        if (!mHasPerformedLongPress) {                            // This is a tap, so remove the longpress check                            if (mPendingCheckForLongPress != null) {                                removeCallbacks(mPendingCheckForLongPress);                            }                            // Only perform take click actions if we were in the pressed state                            if (!focusTaken) {                                performClick();  // 执行点击监听回调                            }                        }                        if (mUnsetPressedState == null) {                            mUnsetPressedState = new UnsetPressedState();                        }                        if (!post(mUnsetPressedState)) {                            // If the post failed, unpress right now                            mUnsetPressedState.run();                        }                    }                    break;                case MotionEvent.ACTION_DOWN:                    mPrivateFlags |= PRESSED;                    refreshDrawableState();                    if ((mViewFlags & LONG_CLICKABLE) == LONG_CLICKABLE) {                        postCheckForLongClick();                    }                    break;                case MotionEvent.ACTION_CANCEL:                    mPrivateFlags &= ~PRESSED;                    refreshDrawableState();                    break;                case MotionEvent.ACTION_MOVE:                    final int x = (int) event.getX();                    final int y = (int) event.getY();                    // Be lenient about moving outside of buttons                    int slop = ViewConfiguration.get(mContext).getScaledTouchSlop();                    if ((x < 0 - slop) || (x >= getWidth() + slop) ||                            (y < 0 - slop) || (y >= getHeight() + slop)) {                        // Outside button                        if ((mPrivateFlags & PRESSED) != 0) {                            // Remove any future long press checks                            if (mPendingCheckForLongPress != null) {                                removeCallbacks(mPendingCheckForLongPress);                            }                            // Need to switch from pressed to not pressed                            mPrivateFlags &= ~PRESSED;                            refreshDrawableState();                        }                    } else {                        // Inside button                        if ((mPrivateFlags & PRESSED) == 0) {                            // Need to switch from not pressed to pressed                            mPrivateFlags |= PRESSED;                            refreshDrawableState();                        }                    }                    break;            }            return true;        }        return false;    }

    /**     * Call this view's OnClickListener, if it is defined.     *     * @return True there was an assigned OnClickListener that was called, false     *         otherwise is returned.     */    public boolean performClick() {        sendAccessibilityEvent(AccessibilityEvent.TYPE_VIEW_CLICKED);        if (mOnClickListener != null) {  // 点击监听回调不为null,就执行回调,并返回true            playSoundEffect(SoundEffectConstants.CLICK);            mOnClickListener.onClick(this);            return true;        }        return false;    }

如果我们想要同时处理点击事件和触摸事件,super.onTouchEvent(event); 就不可少

  @Override    public boolean onTouchEvent(MotionEvent event) {        super.onTouchEvent(event);        Log.e(TAG, "onTouchEvent: "+event.getAction() );        return true;    }

04-28 03:40:08.296 8330-8330/com.xialm.touchdemo E/CustomImageView: onTouchEvent: 004-28 03:40:08.392 8330-8330/com.xialm.touchdemo E/CustomImageView: onTouchEvent: 104-28 03:40:08.393 8330-8330/com.xialm.touchdemo E/MainActivity: onClick:

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