自定义ScrollView显示和隐藏header

效果

实现MyScrollView

  1 package test2.example.com.scrollviewdemo.view;
  2 
  3 import android.content.Context;
  4 import android.graphics.Canvas;
  5 import android.util.AttributeSet;
  6 import android.util.DisplayMetrics;
  7 import android.util.Log;
  8 import android.view.MotionEvent;
  9 import android.view.WindowManager;
 10 import android.view.animation.DecelerateInterpolator;
 11 import android.widget.LinearLayout;
 12 import android.widget.ScrollView;
 13 import android.widget.Scroller;
 14 
 15 
 16 public class MyScrollView extends ScrollView {
 17     private ScrollHeader mHeader;
 18     private float mLastY = -1;
 19     private Context mContext;
 20     private int MAX_VISI_HEIGHT;
 21     private Scroller mScroller;
 22 
 23     public MyScrollView(Context context, AttributeSet attrs) {
 24         super(context, attrs);
 25         mContext = context;
 26         MAX_VISI_HEIGHT = getScreenHeight() / 3;
 27         mScroller = new Scroller(context, new DecelerateInterpolator());
 28 
 29     }
 30 
 31     @Override
 32     protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
 33         super.onMeasure(widthMeasureSpec, heightMeasureSpec);
 34         //获取Scroller的第一个孩子,就是包裹所有孩子的View
 35         LinearLayout firstLL = (LinearLayout) getChildAt(0);
 36         mHeader = (ScrollHeader) firstLL.getChildAt(0);
 37     }
 38 
 39     @Override
 40     protected void onDraw(Canvas canvas) {
 41         super.onDraw(canvas);
 42 
 43     }
 44 
 45     @Override
 46     public boolean onTouchEvent(MotionEvent ev) {
 47         if (mLastY == -1) {
 48             mLastY = ev.getRawY();
 49         }
 50         switch (ev.getAction()) {
 51             case MotionEvent.ACTION_DOWN:
 52                 mLastY = ev.getRawY();
 53                 break;
 54             case MotionEvent.ACTION_MOVE:
 55                 final float deltaY = ev.getRawY() - mLastY;
 56                 mLastY = ev.getRawY();
 57                 if (deltaY > 0) {
 58                     int height = mHeader.getVisiableHeight();
 59                     if (MAX_VISI_HEIGHT > height) {
 60                         //更新header高度
 61                         mHeader.setVisiableHeight((int) deltaY + height);
 62                     }
 63 
 64                 }
 65 
 66                 break;
 67             case MotionEvent.ACTION_UP:
 68                 Log.d("MyScrollerView", "MOVE_UP");
 69                 if (mHeader.getVisiableHeight() > 0) {
 70                     resetHeaderHeight();
 71                 }
 72 
 73 
 74                 break;
 75         }
 76         return super.onTouchEvent(ev);
 77     }
 78 
 79     /**
 80      * 获取屏幕的高度
 81      *
 82      * @return
 83      */
 84     private int getScreenHeight() {
 85         WindowManager windowManager = (WindowManager) mContext.getSystemService(Context.WINDOW_SERVICE);
 86         DisplayMetrics displayMetrics = new DisplayMetrics();
 87         windowManager.getDefaultDisplay().getMetrics(displayMetrics);
 88         return displayMetrics.heightPixels;
 89     }
 90 
 91     private void resetHeaderHeight() {
 92         int height = mHeader.getVisiableHeight();
 93         Log.d("MyScrollerView", "移动的高度:" + (0 - height));
 94         mScroller.startScroll(0, height, 0, 0 - height,
 95                 400);
 96         invalidate();
 97     }
 98 
 99     @Override
100     public void computeScroll() {
101         if (mScroller.computeScrollOffset()) {
102             mHeader.setVisiableHeight(mScroller.getCurrY());
103             postInvalidate();
104         }
105         super.computeScroll();
106     }
107 }

ScrollHeader

  1 package test2.example.com.scrollviewdemo.view;
  2 
  3 import android.content.Context;
  4 import android.util.AttributeSet;
  5 import android.view.Gravity;
  6 import android.view.LayoutInflater;
  7 import android.widget.LinearLayout;
  8 
  9 import test2.example.com.scrollviewdemo.R;
 10 
 11 
 12 public class ScrollHeader extends LinearLayout {
 13     private LinearLayout mContainer;
 14     private Context mContext;
 15 
 16     public ScrollHeader(Context context, AttributeSet attrs) {
 17         super(context, attrs);
 18         mContext = context;
 19         initView();
 20     }
 21 
 22     private void initView() {
 23         // 初始情况
 24         LayoutParams lp = new LayoutParams(
 25                 android.view.ViewGroup.LayoutParams.FILL_PARENT, 0);
 26         mContainer = (LinearLayout) LayoutInflater.from(mContext).inflate(
 27                 R.layout.scroller_header, null);
 28 
 29         addView(mContainer, lp);
 30         setGravity(Gravity.BOTTOM);
 31     }
 32 
 33 
 34     /**
 35      * 设置显示的高度
 36      *
 37      * @param height
 38      */
 39     public void setVisiableHeight(int height) {
 40         if (height < 0)
 41             height = 0;
 42         LayoutParams lp = (LayoutParams) mContainer
 43                 .getLayoutParams();
 44         lp.height = height;
 45         mContainer.setLayoutParams(lp);
 46     }
 47 
 48     /**
 49      * 获取显示的高度
 50      *
 51      * @return
 52      */
 53     public int getVisiableHeight() {
 54         return mContainer.getHeight();
 55     }
 56 }