ViewDragHelper实现QQ侧滑效果

前言

侧滑的实现方式有很多方式来实现，这次总结的ViewDragHelper就是其中一种方式，ViewDragHelper是2013年谷歌I/O大会发布的新的控件，为了解决界面控件拖拽问题。下面就是自己学习写的一个实现类似于QQ侧滑效果的实现。
activity_main.xml:

<com.yctc.drag.DragLayout xmlns:android="http://schemas.android.com/apk/res/android"
 xmlns:tools="http://schemas.android.com/tools"
 android:id="@+id/dl"
 android:layout_width="match_parent"
 android:layout_height="match_parent"
 android:background="@drawable/bg"
 tools:context=".MainActivity" >

 <LinearLayout
  android:layout_width="match_parent"
  android:layout_height="match_parent"
  android:orientation="vertical"
  android:paddingBottom="50dp"
  android:paddingLeft="10dp"
  android:paddingRight="50dp"
  android:paddingTop="50dp" >

  <ImageView
   android:layout_width="50dp"
   android:layout_height="50dp"
   android:src="@drawable/head" />

  <ListView
   android:id="@+id/lv_left"
   android:layout_width="match_parent"
   android:layout_height="match_parent" >
  </ListView>
 </LinearLayout>

 <com.yctc.drag.MyLinearLayout
  android:id="@+id/mll"
  android:layout_width="match_parent"
  android:layout_height="match_parent"
  android:background="#ffffff"
  android:orientation="vertical" >

  <RelativeLayout
   android:layout_width="match_parent"
   android:layout_height="50dp"
   android:background="#18B6EF"
   android:gravity="center_vertical" >

   <ImageView
    android:id="@+id/iv_header"
    android:layout_width="30dp"
    android:layout_height="30dp"
    android:layout_marginLeft="15dp"
    android:src="@drawable/head" />

   <TextView
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_centerHorizontal="true"
    android:text="Header" />
  </RelativeLayout>

  <ListView
   android:id="@+id/lv_main"
   android:layout_width="match_parent"
   android:layout_height="match_parent" >
  </ListView>
 </com.yctc.drag.MyLinearLayout>
</com.yctc.drag.DragLayout>

DragLayout.Java:

public class DragLayout extends FrameLayout {

 private static final String TAG = "TAG";
 private ViewDragHelper mDragHelper;
 private ViewGroup mLeftContent;
 private ViewGroup mMainContent;
 private OnDragStatusChangeListener mListener;
 private Status mStatus = Status.Close;

 /**
  * 状态枚举
  */
 public static enum Status {
  Close, Open, Draging;
 }
 public interface OnDragStatusChangeListener{
  void onClose();
  void onOpen();
  void onDraging(float percent);
 }

 public Status getStatus() {
  return mStatus;
 }

 public void setStatus(Status mStatus) {
  this.mStatus = mStatus;
 }

 public void setDragStatusListener(OnDragStatusChangeListener mListener){
  this.mListener = mListener;
 }

 public DragLayout(Context context) {
  this(context, null);
 }

 public DragLayout(Context context, AttributeSet attrs) {
  this(context, attrs, 0);
 }

 public DragLayout(Context context, AttributeSet attrs, int defStyle) {
  super(context, attrs, defStyle);

  // a.初始化 (通过静态方法)
  mDragHelper = ViewDragHelper.create(this , mCallback);

 }

 ViewDragHelper.Callback mCallback = new ViewDragHelper.Callback() {
  // c. 重写事件

  // 1. 根据返回结果决定当前child是否可以拖拽
  // child 当前被拖拽的View
  // pointerId 区分多点触摸的id
  @Override
  public boolean tryCaptureView(View child, int pointerId) {
   Log.d(TAG, "tryCaptureView: " + child);
   return true;
  };

  @Override
  public void onViewCaptured(View capturedChild, int activePointerId) {
   Log.d(TAG, "onViewCaptured: " + capturedChild);
   // 当capturedChild被捕获时,调用.
   super.onViewCaptured(capturedChild, activePointerId);
  }

  @Override
  public int getViewHorizontalDragRange(View child) {
   // 返回拖拽的范围, 不对拖拽进行真正的限制. 仅仅决定了动画执行速度
   return mRange;
  }

  // 2. 根据建议值 修正将要移动到的(横向)位置 (重要)
  // 此时没有发生真正的移动
  public int clampViewPositionHorizontal(View child, int left, int dx) {
   // child: 当前拖拽的View
   // left 新的位置的建议值, dx 位置变化量
   // left = oldLeft + dx;
   Log.d(TAG, "clampViewPositionHorizontal: "
     + "oldLeft: " + child.getLeft() + " dx: " + dx + " left: " +left);

   if(child == mMainContent){
    left = fixLeft(left);
   }
   return left;
  }

  // 3. 当View位置改变的时候, 处理要做的事情 (更新状态, 伴随动画, 重绘界面)
  // 此时,View已经发生了位置的改变
  @Override
  public void onViewPositionChanged(View changedView, int left, int top,
    int dx, int dy) {
   // changedView 改变位置的View
   // left 新的左边值
   // dx 水平方向变化量
   super.onViewPositionChanged(changedView, left, top, dx, dy);
   Log.d(TAG, "onViewPositionChanged: " + "left: " + left + " dx: " + dx);

   int newLeft = left;
   if(changedView == mLeftContent){
    // 把当前变化量传递给mMainContent
    newLeft = mMainContent.getLeft() + dx;
   }

   // 进行修正
   newLeft = fixLeft(newLeft);

   if(changedView == mLeftContent) {
    // 当左面板移动之后, 再强制放回去.
    mLeftContent.layout(0, 0, 0 + mWidth, 0 + mHeight);
    mMainContent.layout(newLeft, 0, newLeft + mWidth, 0 + mHeight);
   }
   // 更新状态,执行动画
   dispatchDragEvent(newLeft);

   // 为了兼容低版本, 每次修改值之后, 进行重绘
   invalidate();
  }

  // 4. 当View被释放的时候, 处理的事情(执行动画)
  @Override
  public void onViewReleased(View releasedChild, float xvel, float yvel) {
   // View releasedChild 被释放的子View
   // float xvel 水平方向的速度, 向右为+
   // float yvel 竖直方向的速度, 向下为+
   Log.d(TAG, "onViewReleased: " + "xvel: " + xvel + " yvel: " + yvel);
   super.onViewReleased(releasedChild, xvel, yvel);

   // 判断执行 关闭/开启
   // 先考虑所有开启的情况,剩下的就都是关闭的情况
   if(xvel == 0 && mMainContent.getLeft() > mRange / 2.0f){
    open();
   }else if (xvel > 0) {
    open();
   }else {
    close();
   }

  }

  @Override
  public void onViewDragStateChanged(int state) {
   // TODO Auto-generated method stub
   super.onViewDragStateChanged(state);
  }

 };

 /**
  * 根据范围修正左边值
  * @param left
  * @return
  */
 private int fixLeft(int left) {
  if(left < 0){
   return 0;
  }else if (left > mRange) {
   return mRange;
  }
  return left;
 }

 protected void dispatchDragEvent(int newLeft) {
  float percent = newLeft * 1.0f/ mRange;
  //0.0f -> 1.0f
  Log.d(TAG, "percent: " + percent);

  if(mListener != null){
   mListener.onDraging(percent);
  }

  // 更新状态, 执行回调
  Status preStatus = mStatus;
  mStatus = updateStatus(percent);
  if(mStatus != preStatus){
   // 状态发生变化
   if(mStatus == Status.Close){
    // 当前变为关闭状态
    if(mListener != null){
     mListener.onClose();
    }
   }else if (mStatus == Status.Open) {
    if(mListener != null){
     mListener.onOpen();
    }
   }
  }

//  * 伴随动画:
  animViews(percent);

 }

 private Status updateStatus(float percent) {
  if(percent == 0f){
   return Status.Close;
  }else if (percent == 1.0f) {
   return Status.Open;
  }
  return Status.Draging;
 }

 private void animViews(float percent) {
  //  > 1. 左面板: 缩放动画, 平移动画, 透明度动画
     // 缩放动画 0.0 -> 1.0 >>> 0.5f -> 1.0f >>> 0.5f * percent + 0.5f
   //  mLeftContent.setScaleX(0.5f + 0.5f * percent);
   //  mLeftContent.setScaleY(0.5f + 0.5f * percent);
     ViewHelper.setScaleX(mLeftContent, evaluate(percent, 0.5f, 1.0f));
     ViewHelper.setScaleY(mLeftContent, 0.5f + 0.5f * percent);
     // 平移动画: -mWidth / 2.0f -> 0.0f
     ViewHelper.setTranslationX(mLeftContent, evaluate(percent, -mWidth / 2.0f, 0));
     // 透明度: 0.5 -> 1.0f
     ViewHelper.setAlpha(mLeftContent, evaluate(percent, 0.5f, 1.0f));

  //  > 2. 主面板: 缩放动画
     // 1.0f -> 0.8f
     ViewHelper.setScaleX(mMainContent, evaluate(percent, 1.0f, 0.8f));
     ViewHelper.setScaleY(mMainContent, evaluate(percent, 1.0f, 0.8f));

  //  > 3. 背景动画: 亮度变化 (颜色变化)
     getBackground().setColorFilter((Integer)evaluateColor(percent, Color.BLACK, Color.TRANSPARENT), Mode.SRC_OVER);
 }

 /**
  * 估值器
  * @param fraction
  * @param startValue
  * @param endValue
  * @return
  */
 public Float evaluate(float fraction, Number startValue, Number endValue) {
  float startFloat = startValue.floatValue();
  return startFloat + fraction * (endValue.floatValue() - startFloat);
 }
 /**
  * 颜色变化过度
  * @param fraction
  * @param startValue
  * @param endValue
  * @return
  */
 public Object evaluateColor(float fraction, Object startValue, Object endValue) {
  int startInt = (Integer) startValue;
  int startA = (startInt >> 24) & 0xff;
  int startR = (startInt >> 16) & 0xff;
  int startG = (startInt >> 8) & 0xff;
  int startB = startInt & 0xff;

  int endInt = (Integer) endValue;
  int endA = (endInt >> 24) & 0xff;
  int endR = (endInt >> 16) & 0xff;
  int endG = (endInt >> 8) & 0xff;
  int endB = endInt & 0xff;

  return (int)((startA + (int)(fraction * (endA - startA))) << 24) |
    (int)((startR + (int)(fraction * (endR - startR))) << 16) |
    (int)((startG + (int)(fraction * (endG - startG))) << 8) |
    (int)((startB + (int)(fraction * (endB - startB))));
 }

 @Override
 public void computeScroll() {
  super.computeScroll();

  // 2. 持续平滑动画 (高频率调用)
  if(mDragHelper.continueSettling(true)){
   // 如果返回true, 动画还需要继续执行
   ViewCompat.postInvalidateOnAnimation(this);
  }
 }

 public void close(){
  close(true);
 }
 /**
  * 关闭
  */
 public void close(boolean isSmooth) {
  int finalLeft = 0;
  if(isSmooth){
   // 1. 触发一个平滑动画
   if(mDragHelper.smoothSlideViewTo(mMainContent, finalLeft, 0)){
    // 返回true代表还没有移动到指定位置, 需要刷新界面.
    // 参数传this(child所在的ViewGroup)
    ViewCompat.postInvalidateOnAnimation(this);
   }
  }else {
   mMainContent.layout(finalLeft, 0, finalLeft + mWidth, 0 + mHeight);
  }
 }

 public void open(){
  open(true);
 }
 /**
  * 开启
  */
 public void open(boolean isSmooth) {
  int finalLeft = mRange;
  if(isSmooth){
   // 1. 触发一个平滑动画
   if(mDragHelper.smoothSlideViewTo(mMainContent, finalLeft, 0)){
    // 返回true代表还没有移动到指定位置, 需要刷新界面.
    // 参数传this(child所在的ViewGroup)
    ViewCompat.postInvalidateOnAnimation(this);
   }
  }else {
   mMainContent.layout(finalLeft, 0, finalLeft + mWidth, 0 + mHeight);
  }
 }

 private int mHeight;
 private int mWidth;
 private int mRange;

 // b.传递触摸事件
 @Override
 public boolean onInterceptTouchEvent(MotionEvent ev) {
  // 传递给mDragHelper
  return mDragHelper.shouldInterceptTouchEvent(ev);
 }
 @Override
 public boolean onTouchEvent(MotionEvent event) {
  try {
   mDragHelper.processTouchEvent(event);
  } catch (Exception e) {
   e.printStackTrace();
  }
  // 返回true, 持续接受事件
  return true;
 }

 @Override
 protected void onFinishInflate() {
  super.onFinishInflate();
  // Github
  // 写注释
  // 容错性检查 (至少有俩子View, 子View必须是ViewGroup的子类)

  if(getChildCount() < 2){
   throw new IllegalStateException("布局至少有俩孩子. Your ViewGroup must have 2 children at least.");
  }
  if(!(getChildAt(0) instanceof ViewGroup && getChildAt(1) instanceof ViewGroup)){
   throw new IllegalArgumentException("子View必须是ViewGroup的子类. Your children must be an instance of ViewGroup");
  }

  mLeftContent = (ViewGroup) getChildAt(0);
  mMainContent = (ViewGroup) getChildAt(1);
 }

 @Override
 protected void onSizeChanged(int w, int h, int oldw, int oldh) {
  super.onSizeChanged(w, h, oldw, oldh);
  // 当尺寸有变化的时候调用

  mHeight = getMeasuredHeight();
  mWidth = getMeasuredWidth();

  // 移动的范围
  mRange = (int) (mWidth * 0.6f);

 }

}

MyLineatLayout.java:

public class MyLinearLayout extends LinearLayout {

 private DragLayout mDragLayout;

 public MyLinearLayout(Context context) {
  super(context);
 }

 public MyLinearLayout(Context context, AttributeSet attrs) {
  super(context, attrs);
 }

 public void setDraglayout(DragLayout mDragLayout){
  this.mDragLayout = mDragLayout;
 }

 @Override
 public boolean onInterceptTouchEvent(MotionEvent ev) {
  // 如果当前是关闭状态, 按之前方法判断
  if(mDragLayout.getStatus() == Status.Close){
   return super.onInterceptTouchEvent(ev);
  }else {
   return true;
  }
 }

 @Override
 public boolean onTouchEvent(MotionEvent event) {
  // 如果当前是关闭状态, 按之前方法处理
  if(mDragLayout.getStatus() == Status.Close){
   return super.onTouchEvent(event);
  }else {
   // 手指抬起, 执行关闭操作
   if(event.getAction() == MotionEvent.ACTION_UP){
    mDragLayout.close();
   }

   return true;
  }
 }

}

MainActivity.java:

public class MainActivity extends Activity {

 private static final String TAG = "TAG";

 @Override
 protected void onCreate(Bundle savedInstanceState) {
  super.onCreate(savedInstanceState);
  requestWindowFeature(Window.FEATURE_NO_TITLE);
  setContentView(R.layout.activity_main);

  final ListView mLeftList = (ListView) findViewById(R.id.lv_left);
  final ListView mMainList = (ListView) findViewById(R.id.lv_main);
  final ImageView mHeaderImage = (ImageView) findViewById(R.id.iv_header);
  MyLinearLayout mLinearLayout = (MyLinearLayout) findViewById(R.id.mll);

  // 查找Draglayout, 设置监听
  DragLayout mDragLayout = (DragLayout) findViewById(R.id.dl);

  // 设置引用
  mLinearLayout.setDraglayout(mDragLayout);

  mDragLayout.setDragStatusListener(new OnDragStatusChangeListener() {

   @Override
   public void onOpen() {
    Utils.showToast(MainActivity.this, "onOpen");
    // 左面板ListView随机设置一个条目
    Random random = new Random();

    int nextInt = random.nextInt(50);
    mLeftList.smoothScrollToPosition(nextInt);

   }

   @Override
   public void onDraging(float percent) {
    Log.d(TAG, "onDraging: " + percent);// 0 -> 1
    // 更新图标的透明度
    // 1.0 -> 0.0
    ViewHelper.setAlpha(mHeaderImage, 1 - percent);
   }

   @Override
   public void onClose() {
    Utils.showToast(MainActivity.this, "onClose");
    // 让图标晃动
//    mHeaderImage.setTranslationX(translationX)
    ObjectAnimator mAnim = ObjectAnimator.ofFloat(mHeaderImage, "translationX", 15.0f);
    mAnim.setInterpolator(new CycleInterpolator(4));
    mAnim.setDuration(500);
    mAnim.start();
   }
  });

  mLeftList.setAdapter(new ArrayAdapter<String>(this, android.R.layout.simple_list_item_1, Cheeses.sCheeseStrings){
   @Override
   public View getView(int position, View convertView, ViewGroup parent) {
    View view = super.getView(position, convertView, parent);
    TextView mText = ((TextView)view);
    mText.setTextColor(Color.WHITE);
    return view;
   }
  });

  mMainList.setAdapter(new ArrayAdapter<String>(this, android.R.layout.simple_list_item_1, Cheeses.NAMES))
 }
}

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