android View中如何判断长按事件

一、如果用户在获得焦点的VIEW上按KEYCODE_DPAD_CENTER或KEYCODE_ENTER键，即OK键后，在VIEW的onKeyDown方法中会开启一个延迟线程，在延迟线程中会去回调onLongClick()方法，代码如下：

在如下代码中开始延迟线程：

[java]
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public boolean onKeyDown(int keyCode, KeyEvent event) {
boolean result = false;

switch (keyCode) {
case KeyEvent.KEYCODE_DPAD_CENTER:
case KeyEvent.KEYCODE_ENTER: {
if ((mViewFlags & ENABLED_MASK) == DISABLED) {
return true;
}
// Long clickable items don't necessarily have to be clickable

if (((mViewFlags & CLICKABLE) == CLICKABLE ||
(mViewFlags & LONG_CLICKABLE) == LONG_CLICKABLE) &&
(event.getRepeatCount() == 0)) {
setPressed(true);
if ((mViewFlags & LONG_CLICKABLE) == LONG_CLICKABLE) {
postCheckForLongClick(0);//在这里开启延迟线程

}
return true;
}
break;
}
}
return result;
}

public boolean onKeyDown(int keyCode, KeyEvent event) {
        boolean result = false;

        switch (keyCode) {
            case KeyEvent.KEYCODE_DPAD_CENTER:
            case KeyEvent.KEYCODE_ENTER: {
                if ((mViewFlags & ENABLED_MASK) == DISABLED) {
                    return true;
                }
                // Long clickable items don't necessarily have to be clickable
                if (((mViewFlags & CLICKABLE) == CLICKABLE ||
                        (mViewFlags & LONG_CLICKABLE) == LONG_CLICKABLE) &&
                        (event.getRepeatCount() == 0)) {
                    setPressed(true);
                    if ((mViewFlags & LONG_CLICKABLE) == LONG_CLICKABLE) {
                        postCheckForLongClick(0);//在这里开启延迟线程
                    }
                    return true;
                }
                break;
            }
        }
        return result;
    }

延迟线程代码如下：

[java]
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class CheckForLongPress implements Runnable {

private int mOriginalWindowAttachCount;

public void run() {
if (isPressed() && (mParent != null)
&& mOriginalWindowAttachCount == mWindowAttachCount) {
if (performLongClick()) { //这里回调onLongClick()方法

mHasPerformedLongPress = true;
}
}
}

public void rememberWindowAttachCount() {
mOriginalWindowAttachCount = mWindowAttachCount;
}
}

class CheckForLongPress implements Runnable {

        private int mOriginalWindowAttachCount;

        public void run() {
            if (isPressed() && (mParent != null)
                    && mOriginalWindowAttachCount == mWindowAttachCount) {
                if (performLongClick()) { //这里回调onLongClick()方法
                    mHasPerformedLongPress = true;
                }
            }
        }

        public void rememberWindowAttachCount() {
            mOriginalWindowAttachCount = mWindowAttachCount;
        }
    }

二、如果用户在触摸屏上长按某个VIEW，VIEW中首先会检测在这个触摸点移动没，如果没有移动再开启一个延迟线程去回调onLongClick()方法，代码如下：

在View中的onTouchEvent中的DOWN事件中：

[java]
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case MotionEvent.ACTION_DOWN:
if (mPendingCheckForTap == null) {
mPendingCheckForTap = new CheckForTap();
}
mPrivateFlags |= PREPRESSED;
mHasPerformedLongPress = false;
postDelayed(mPendingCheckForTap, ViewConfiguration.getTapTimeout());//开始延迟线程检测触摸点移动没

break;

case MotionEvent.ACTION_DOWN:
                    if (mPendingCheckForTap == null) {
                        mPendingCheckForTap = new CheckForTap();
                    }
                    mPrivateFlags |= PREPRESSED;
                    mHasPerformedLongPress = false;
                    postDelayed(mPendingCheckForTap, ViewConfiguration.getTapTimeout());//开始延迟线程检测触摸点移动没
                    break;

如果没有移动，则会开启一个延迟线程回调onLongClick()方法：

[java]
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private final class CheckForTap implements Runnable {
public void run() {
mPrivateFlags &= ~PREPRESSED;
mPrivateFlags |= PRESSED;
refreshDrawableState();
if ((mViewFlags & LONG_CLICKABLE) == LONG_CLICKABLE) {
postCheckForLongClick(ViewConfiguration.getTapTimeout());//开启延迟线程回调onLongClick()方法

}
}
}

private final class CheckForTap implements Runnable {
        public void run() {
            mPrivateFlags &= ~PREPRESSED;
            mPrivateFlags |= PRESSED;
            refreshDrawableState();
            if ((mViewFlags & LONG_CLICKABLE) == LONG_CLICKABLE) {
                postCheckForLongClick(ViewConfiguration.getTapTimeout());//开启延迟线程回调onLongClick()方法
            }
        }
    }

剩下来就和按键长按一样的处理了。

在其中要注意二个参数：

ViewConfiguration.getTapTimeout() 是用于检测触摸点有没有移动的时间，默认为115毫秒

ViewConfiguration.getLongPressTimeout() 是用于检测是不是长按的时间，默认为500毫秒