Android 自定义底部上拉控件的实现方法

allprojects {
 repositories {
  ...
  maven { url 'https://jitpack.io' }
 }
}

dependencies {
   compile 'com.github.qingmei2:SlideBottomLayout-Android:1.2.3'
}

<com.qingmei2.library.SlideBottomLayout
    android:id="@+id/slideLayout"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:layout_alignParentBottom="true"
    android:layout_marginTop="200dp"
    app:handler_height="50dp" 
    <!--app:handler_height:该属性就是您要暴露出来Handle的高度，详见下方的TextView(id=handle)-- 
    <!--Just one child-- 
    <LinearLayout
      android:layout_width="match_parent"
      android:layout_height="wrap_content"
      android:orientation="vertical" 
      <TextView
        android:id="@+id/handle"
        android:layout_width="match_parent"
        android:layout_height="50dp"
        android:background="#d95858"
        android:gravity="center"
        android:text="handle"
        android:textColor="@android:color/white"
        android:textSize="16sp" / 
      <android.support.v7.widget.RecyclerView
        android:id="@+id/recycler_view"
        android:layout_width="match_parent"
        android:layout_height="wrap_content" 
      </android.support.v7.widget.RecyclerView 
    </LinearLayout 
  </com.qingmei2.library.SlideBottomLayout 

<?xml version="1.0" encoding="utf-8"? 
<resources 
  <declare-styleable name="SlideBottomLayout" 
    <attr name="handler_height" format="dimension" </attr 
  </declare-styleable 
</resources 

public class SlideBottomLayout extends LinearLayout {
public void setShortSlideListener(ShortSlideListener listener) {
this.shortSlideListener = listener;
}
private ShortSlideListener shortSlideListener;
/**
* The {@link MotionEvent#ACTION_DOWN} gesture location.
*/
private int downY;
/**
* The {@link MotionEvent#ACTION_MOVE} gesture location.
*/
private int moveY;
/**
* the value of moved distance by the gesture. When the value was modified and not exceed
* the {@link #movedMaxDis}, then make this ViewGroup move.
*/
private int movedDis;
/**
* The max distance that the {@link SlideBottomLayout} can scroll to, it used to compare with the
* {@link #downY}, determine whether it can slide by the gesture.
*/
private int movedMaxDis;
/**
* ChildView of the {@link SlideBottomLayout}, you can set a Layout such as the {@link LinearLayout}、
* {@link android.widget.RelativeLayout} ect.
* We set the rules that {@link SlideBottomLayout} just can have one child-view, or else get a
* {@link RuntimeException} at {@link #onFinishInflate()}
*/
private View childView;
/**
* The control {@link SlideBottomLayout} automatically switches the threshold of the state. if
* this ViewGroup moved distance more than {@link #movedMaxDis} * it, switch the state of
* {@link #arriveTop} right now.
* </p 
* See the {@link #touchActionUp(float)}.
*/
private float hideWeight = 0.25f;
//3.注意，这个接口用来设置「需要自定义自动到达顶部/隐藏的阈值」
public void setHideWeight(float hideWeight) {
if (hideWeight <= 0 || hideWeight   1)
throw new IllegalArgumentException("hideWeight should belong (0f,1f]");
this.hideWeight = hideWeight;
}
private Scroller mScroller;
/**
* It means the {@link #childView} is arriving the top of parent or else.
*/
private boolean arriveTop = false;
/**
* the {@link #childView} Initially visible height
*/
private float visibilityHeight;
//1.初始化Handle显示高度，建议您在xml中设置对应属性来实现该效果
public void setVisibilityHeight(float visibilityHeight) {
this.visibilityHeight = visibilityHeight;
}
public SlideBottomLayout(@NonNull Context context) {
super(context);
}
public SlideBottomLayout(@NonNull Context context, @Nullable AttributeSet attrs) {
super(context, attrs);
initAttrs(context, attrs);
}
public SlideBottomLayout(@NonNull Context context, @Nullable AttributeSet attrs, int defStyleAttr) {
super(context, attrs, defStyleAttr);
initAttrs(context, attrs);
}
/**
* Get the config from {@link R.styleable}, then init other configrations{@link #initConfig(Context)}.
*
* @param context the {@link Context}
* @param attrs  the configs in layout attrs.
*/
private void initAttrs(Context context, AttributeSet attrs) {
final TypedArray ta = context.obtainStyledAttributes(attrs, R.styleable.SlideBottomLayout);
visibilityHeight = ta.getDimension(R.styleable.SlideBottomLayout_handler_height, 0);
ta.recycle();
initConfig(context);
}
private void initConfig(Context context) {
if (mScroller == null)
mScroller = new Scroller(context);
this.setBackgroundColor(Color.TRANSPARENT);
}
/**
* It start a judgement for ensure the child-view be unique in this method，then assgin it
* to {{@link #childView}.
* this method will be called before the {@link #onMeasure(int, int)}
*/
@Override
protected void onFinishInflate() {
super.onFinishInflate();
if (getChildCount() == 0 || getChildAt(0) == null) {
throw new RuntimeException("there have no child-View in the SlideBottomLayout！");
}
if (getChildCount()   1) {
throw new RuntimeException("there just alow one child-View in the SlideBottomLayout!");
}
childView = getChildAt(0);
}
@Override
protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
super.onMeasure(widthMeasureSpec, heightMeasureSpec);
movedMaxDis = (int) (childView.getMeasuredHeight() - visibilityHeight);
}
@Override
protected void onLayout(boolean changed, int l, int t, int r, int b) {
super.onLayout(changed, l, t, r, b);
childView.layout(0, movedMaxDis, childView.getMeasuredWidth(), childView.getMeasuredHeight() + movedMaxDis);
}
@Override
public boolean onTouchEvent(MotionEvent event) {
final float dy = event.getY();
switch (event.getAction()) {
case MotionEvent.ACTION_DOWN:
if (touchActionDown(dy))
return true;
break;
case MotionEvent.ACTION_MOVE:
if (touchActionMove(dy))
return true;
break;
case MotionEvent.ACTION_UP:
if (touchActionUp(dy))
return true;
break;
}
return super.onTouchEvent(event);
}
@Override
public void computeScroll() {
super.computeScroll();
if (mScroller == null)
mScroller = new Scroller(getContext());
if (mScroller.computeScrollOffset()) {
scrollTo(0, mScroller.getCurrY());
postInvalidate();
}
}
/**
* When the touch event is {@link MotionEvent#ACTION_UP},
* then judge the state of view group and control the {@link Scroller} to scroll.
* <p 
* In this ViewGroup, we set the rules that is if this scroll gesture's move distance
* more than {@link #movedMaxDis} * {@link #hideWeight}(default hideWeight value is 1/4 heights
* of this ViewGroup), then call {@link #hide()} or {@link #show()} right now. which method will
* be call depends on {@link #arriveTop}.
* <p
* if the scroll gesture's move distance don't reach the goal value, then call the
* {@link ShortSlideListener#onShortSlide(float)} if you call {@link #setShortSlideListener(ShortSlideListener)}
* init this ViewGroup. else will call {@link #hide()}.
*
* @param eventY The location of trigger
* @return Be used to determine consume this event or else.
*/
public boolean touchActionUp(float eventY) {
if (movedDis   movedMaxDis * hideWeight) {
switchVisible();
} else {
if (shortSlideListener != null) {
shortSlideListener.onShortSlide(eventY);
} else {
hide();
}
}
return true;
}
/**
* When the touch event is {@link MotionEvent#ACTION_MOVE},
* then judge the state of view group and control the {@link Scroller} to scroll.
* <p 
* In this ViewGroup, we set the rules that is if this scroll gesture's move distance
* more than {@link #movedMaxDis} * {@link #hideWeight}(default hideWeight value is 1/4 heights of this ViewGroup),
* then call {@link #hide()} or {@link #show()} right now.
* <p 
*
* @param eventY The location of trigger
* @return Be used to determine consume this event or else.
*/
public boolean touchActionMove(float eventY) {
moveY = (int) eventY;
//the dy is sum of the move distance, the value   0 means scroll up, the value < 0 means scroll down.
final int dy = downY - moveY;
if (dy   0) {        //scroll up
movedDis += dy;
if (movedDis   movedMaxDis)
movedDis = movedMaxDis;
if (movedDis < movedMaxDis) {
scrollBy(0, dy);
downY = moveY;
return true;
}
} else {        //scroll down
movedDis += dy;
if (movedDis < 0) movedDis = 0;
if (movedDis   0) {
scrollBy(0, dy);
}
downY = moveY;
return true;
}
return false;
}
/**
* When the touch event is {@link MotionEvent#ACTION_DOWN},
* Record the location of this action.
*
* @param eventY The location of trigger
* @return Be used to determine consume this event or else.
*/
public boolean touchActionDown(float eventY) {
downY = (int) eventY;
//Whether custom this gesture.
if (!arriveTop && downY < movedMaxDis) {
return false;
} else
return true;
}
/**
* the extand method for showing {@link SlideBottomLayout}
*/
public void show() {
scroll2TopImmediate();
}
/**
* the extand method for hiding {@link SlideBottomLayout}
*/
public void hide() {
scroll2BottomImmediate();
}
/**
* @return The ViewGroup is arrive top or else.
*/
public boolean switchVisible() {
if (arriveTop())
hide();
else
show();
return arriveTop();
}
public boolean arriveTop() {
return this.arriveTop;
}
public void scroll2TopImmediate() {
mScroller.startScroll(0, getScrollY(), 0, (movedMaxDis - getScrollY()));
invalidate();
movedDis = movedMaxDis;
arriveTop = true;
}
public void scroll2BottomImmediate() {
mScroller.startScroll(0, getScrollY(), 0, -getScrollY());
postInvalidate();
movedDis = 0;
arriveTop = false;
}
}