Android ScrollView的顶部下拉和底部上拉回弹效果

/** * A Simple Rebound ScrollView * @author Denluoyia */public class ReboundScrollView extends ScrollView{  private boolean mEnableTopRebound = true;  private boolean mEnableBottomRebound = true;  private OnReboundEndListener mOnReboundEndListener;  private View mContentView;  private Rect mRect = new Rect();  public ReboundScrollView(Context context) {    super(context);  }  public ReboundScrollView(Context context, AttributeSet attrs) {    super(context, attrs);  }  public ReboundScrollView(Context context, AttributeSet attrs, int defStyleAttr) {    super(context, attrs, defStyleAttr);  }  /** after inflating view, we can get the width and height of view */  @Override  protected void onFinishInflate() {    super.onFinishInflate();    mContentView = getChildAt(0);  }  @Override  protected void onLayout(boolean changed, int l, int t, int r, int b) {    super.onLayout(changed, l, t, r, b);    if (mContentView == null) return;    // to remember the location of mContentView    mRect.set(mContentView.getLeft(), mContentView.getTop(), mContentView.getRight(), mContentView.getBottom());  }  public ReboundScrollView setOnReboundEndListener(OnReboundEndListener onReboundEndListener){    this.mOnReboundEndListener = onReboundEndListener;    return this;  }  public ReboundScrollView setEnableTopRebound(boolean enableTopRebound){    this.mEnableTopRebound = enableTopRebound;    return this;  }  public ReboundScrollView setEnableBottomRebound(boolean mEnableBottomRebound){    this.mEnableBottomRebound = mEnableBottomRebound;    return this;  }  private int lastY;  private boolean rebound = false;  private int reboundDirection = 0; //<0 表示下部回弹 >0 表示上部回弹 0表示不回弹  @Override  public boolean dispatchTouchEvent(MotionEvent ev) {    if (mContentView == null){      return super.dispatchTouchEvent(ev);    }    switch (ev.getAction()){      case MotionEvent.ACTION_DOWN:        lastY = (int) ev.getY();        break;      case MotionEvent.ACTION_MOVE:        if (!isScrollToTop() && !isScrollToBottom()){          lastY = (int) ev.getY();          break;        }        //处于顶部或者底部        int deltaY = (int) (ev.getY() - lastY);        //deltaY > 0 下拉 deltaY < 0 上拉        //disable top or bottom rebound        if ((!mEnableTopRebound && deltaY > 0) || (!mEnableBottomRebound && deltaY < 0)){          break;        }        int offset = (int) (deltaY * 0.48);        mContentView.layout(mRect.left, mRect.top + offset, mRect.right, mRect.bottom + offset);        rebound = true;        break;      case MotionEvent.ACTION_UP:        if (!rebound) break;        reboundDirection = mContentView.getTop() - mRect.top;        TranslateAnimation animation = new TranslateAnimation(0, 0, mContentView.getTop(), mRect.top);        animation.setDuration(300);        animation.setAnimationListener(new Animation.AnimationListener() {          @Override          public void onAnimationStart(Animation animation) {          }          @Override          public void onAnimationEnd(Animation animation) {            if (mOnReboundEndListener != null){              if (reboundDirection > 0){                mOnReboundEndListener.onReboundTopComplete();              }              if (reboundDirection < 0){                mOnReboundEndListener.onReboundBottomComplete();              }              reboundDirection = 0;            }          }          @Override          public void onAnimationRepeat(Animation animation) {          }        });        mContentView.startAnimation(animation);        mContentView.layout(mRect.left, mRect.top, mRect.right, mRect.bottom);        rebound = false;        break;    }    return super.dispatchTouchEvent(ev);  }  @Override  public void setFillViewport(boolean fillViewport) {    super.setFillViewport(true); //默认是填充ScrollView 或者再XML布局文件中设置fillViewport属性  }  /**   * 判断当前ScrollView是否处于顶部   */  private boolean isScrollToTop(){    return getScrollY() == 0;  }  /**   * 判断当前ScrollView是否已滑到底部   */  private boolean isScrollToBottom(){    return mContentView.getHeight() <= getHeight() + getScrollY();  }  /**   * listener for top and bottom rebound   * do your implement in the following methods   */  public interface OnReboundEndListener{    void onReboundTopComplete();    void onReboundBottomComplete();  }}

<?xml version="1.0" encoding="utf-8"?><LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"  xmlns:tools="http://schemas.android.com/tools"  android:layout_width="match_parent"  android:layout_height="match_parent"  android:orientation="vertical"  tools:context=".TestActivity">  <com.denluoyia.dtils.widget.ReboundScrollView    android:id="@+id/reboundScrollView"    android:layout_width="match_parent"    android:layout_height="match_parent">    <LinearLayout      android:layout_width="match_parent"      android:layout_height="match_parent"      android:background="#eefade"      android:padding="16dp">      <TextView        android:layout_width="match_parent"        android:layout_height="match_parent"        android:textSize="15sp"        android:lineSpacingExtra="5dp"        android:text="@string/content"/>    </LinearLayout>  </com.denluoyia.dtils.widget.ReboundScrollView></LinearLayout>

 public class TestActivity extends AppCompatActivity {  private ReboundScrollView reboundScrollView;  @Override  protected void onCreate(Bundle savedInstanceState) {    super.onCreate(savedInstanceState);    setContentView(R.layout.activity_test);    reboundScrollView = findViewById(R.id.reboundScrollView);    //reboundScrollView.setEnableTopRebound(false);    //reboundScrollView.setEnableBottomRebound(false);    reboundScrollView.setOnReboundEndListener(new ReboundScrollView.OnReboundEndListener() {      @Override      public void onReboundTopComplete() {        Toast.makeText(TestActivity.this, "顶部回弹", Toast.LENGTH_SHORT).show();      }      @Override      public void onReboundBottomComplete() {        Toast.makeText(TestActivity.this, "底部回弹", Toast.LENGTH_SHORT).show();      }    });  }}