关于长按之后拖动图标的事件监听

先说一下要实现的效果：

1、利用ScrollView来实现可以拖动的动态布局

2、动态添加View来组成视图

3、没有长按时ScrollView有fading的效果（向上隐藏ActionBar，向下展开ActionBar）

4、长按时ScrollView不滑动，被长按的图标跟着手指移动

首先说一下第三点的实现：

<?xml version="1.0" encoding="utf-8"?>
<FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent">

    <include layout="@layout/fab__header_container" />

    <com.manuelpeinado.fadingactionbar.view.ObservableScrollView
        android:id="@+id/fab__scroll_view"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:fillViewport="true"
        android:scrollbars="none">

        <LinearLayout
            android:id="@+id/fab__container"
            android:layout_width="match_parent"
            android:layout_height="match_parent"
            android:orientation="vertical">

            <FrameLayout
                android:id="@+id/fab__content_top_margin"
                android:layout_width="match_parent"
                android:layout_height="wrap_content"
                android:background="@android:color/transparent" />

        </LinearLayout>
    </com.manuelpeinado.fadingactionbar.view.ObservableScrollView>

    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="50dp"
        android:orientation="horizontal"
        android:gravity="center"
        android:id="@+id/action">

        <TextView
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="title" />
    </LinearLayout>
</FrameLayout>

注解：header_container就是头部的布局这里我是用一个ImageView来表示，然后就是ObservableScrollView（重写ScrollView将其OnScrollChange接口暴露出来）里面包含一个fab__content_top_margin（透明的布局，其高度是根据scroll改变的，为了有向上（向下）移动的感觉），ObservableScrollView的主要View是在代码中动态添加的！

下面是header滑动的控制（会比top_margin慢）：

private void addParallaxEffect(int scrollPosition) {
        
        int dampedScroll = (int) (scrollPosition * 0.5);
        int offset = mLastDampedScroll - dampedScroll;
        mHeaderContainer.offsetTopAndBottom(offset);

        if (mFirstGlobalLayoutPerformed) {
            mLastDampedScroll = dampedScroll;
        }
    }

注解：mFirstGlobalLayoutPerformed是判断整个布局树是否布局完成，offsetTopAndBottom(offset)控制headerView上下移动

top_margin的移动：

private void updateHeaderHeight(int headerHeight) {
        ViewGroup.LayoutParams params = (ViewGroup.LayoutParams) mMarginView.getLayoutParams();
        params.height = headerHeight;
        mMarginView.setLayoutParams(params);
        mLastHeaderHeight = headerHeight;
    }

监听OnsrollView的滑动监听：

 private void onNewScroll(int scrollPosition) {

        int currentHeaderHeight = mHeaderContainer.getHeight();
        Log.e("currentHeaderHeight", "" + currentHeaderHeight);
        if (currentHeaderHeight != mLastHeaderHeight) {
            updateHeaderHeight(currentHeaderHeight);
        }

        int headerHeight = currentHeaderHeight - getActionBarHeight();
        float ratio = (float) Math.min(Math.max(scrollPosition, 0), headerHeight) / headerHeight;
        int newAlpha = (int) (ratio * 255);
        mActionBarBackgroundDrawable.setAlpha(newAlpha);
        addParallaxEffect(scrollPosition);
    }

长按之后拖动图标（解决与ScrollChange的冲突）：

1、模拟长按效果：

private Runnable MyTimer = new Runnable() {
        @Override
        public void run() {

            try {
                Thread.sleep(1000);
                isCanMove = true;
                Log.e("isCanMove", "" + "" + isCanMove);
                mVibrator.vibrate(50); //震动一下
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
        }
    };

注解：如果长按事件不到1000mm就触发UP事件，那么MyTimer就会捕捉到InterruptedException，然后就不会执行isCanMove = true;

在ScrollView重写DispatchTouchEvent

 @Override
    public boolean dispatchTouchEvent(MotionEvent ev) {
        boolean isScroll = true;
        switch (ev.getAction()) {
            case MotionEvent.ACTION_DOWN:
                Log.e("dispatchTouchEvent", "" + "ACTION_DOWN");
                timer = new Thread(MyTimer);
                timer.start();
                break;
            case MotionEvent.ACTION_UP:
                Log.e("dispatchTouchEvent", "" + "ACTION_UP");
                if (timer != null && !isCanMove) {
                    timer.interrupt();
                } else {
                    isCanMove = false;
                }
                break;
            case MotionEvent.ACTION_MOVE:
                if (isCanMove) {
                    isScroll = false;
                    Log.e("dispatchTouchEvent", "" + "ACTION_MOVE");
                }
                break;
        }
        if (isScroll) {
            return super.dispatchTouchEvent(ev);
        } else {
            return true;
        }

    }

注解：在长按之后我希望ScrollView不可滑动，所以我设置一个标志值isScroll来判断其是否可以滑动，return true说明ScrollView不可滑动