Android 自定义底部上拉控件的实现方法

前言

又到了新的一月，今天提供一个Android自定义底部上拉布局的实现，起因是自己在项目中需要实现这样一个控件，干脆自己写一个练练手。

写完了觉得能想到的需求都基本有了（可能会有其它需求，不过基本上改吧改吧就行了），又花了一点时间直接放到了Github上托管，希望能给您一些参考价值：

SlideBottomLayout-Android 简单易上手的Android底部上拉控件

先看一下实现效果：

分析一下这种控件的基本需求有以下几种：

1.有一个部分是能够作为把手（就是图中的handle，）进行拖拽的，这部分高度是暴露在界面中的 -> 需要实现：Handle按钮

* 特殊需求特殊分析，比如让这个Handle透明实现无Handle的效果

2.底部上啦布局是有一定高度限制的，不一定覆盖设备的整个屏幕 -> 需要自定义最大高度

3.当从底部上拉一点点时抬手，布局缩回，若超过一定高度，自动弹到最高，隐藏同理 -> 需要自定义自动到达顶部/隐藏的阈值

直接使用

直接使用也很简单，笔者进行了简单的封装，以供参考：

1. 在Project的build.gradle文件中添加：

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

2.在Module的build.gradle文件中添加：

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

3.Add view in your layout:

需要注意的是：为了简单实现，笔者偷了个懒，设定为该布局下只能有一个直接的子View(类似ScrollView)

因此如果您添加需要一个布局，请在外面嵌套一个ViewGroup：

<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>

实现步骤

具体代码如下，其中上述需求的设置方式都已经在代码中声明：

先看下属性声明：

<?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},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(),(movedMaxdis - getScrollY()));
    invalidate();
    moveddis = movedMaxdis;
    arrivetop = true;
  }
  public void scroll2BottomImmediate() {
    mScroller.startScroll(0,-getScrollY());
    postInvalidate();
    moveddis = 0;
    arrivetop = false;
  }
}

注释也比较明了，如果有疑问，详细请参照SlideBottomLayout-Android 简单易上手的Android底部上拉控件

里面有相对详细的使用说明，此外，如果还有一些需求，您可以在issue中提出，提前感谢！

以上这篇Android 自定义底部上拉控件的实现方法就是小编分享给大家的全部内容了，希望能给大家一个参考，也希望大家多多支持编程小技巧。

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