ScrollView中浮动条的实现

简单的浮窗
http://www.open-open.com/lib/view/open1467185415741.html


ScrollView中如果内容比较长，往下拉的时候有一部分（通常是菜单）View就一直固定在屏幕顶端，像个浮动条一样，该效果Web页面使用比较多。
实现这种效果需要重写ScrollView的onScrollChanged(),具体如下：

import android.content.Context;
import android.util.AttributeSet;
import android.view.View;
import android.widget.ScrollView;

/**
 * 带浮动条的ScrollView
 * 
 * 
 */
public class ObservableScrollView extends ScrollView {
	private OnScrollListener onScrollListener = null;

	private View viewInScroll,viewOutScroll;
	public ObservableScrollView(Context context, AttributeSet attrs,
			int defStyle) {
		super(context, attrs, defStyle);
	}

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

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

	public void setOnScrollListener(OnScrollListener onScrollListener) {
		this.onScrollListener = onScrollListener;
	}

	@Override
	protected void onScrollChanged(int x, int y, int oldx, int oldy) {
		super.onScrollChanged(x, y, oldx, oldy);
		if (onScrollListener != null) {
			onScrollListener.onScrollChanged(this, x, y, oldx, oldy);
		}
		computeFloatIfNecessary();
	}

	/**
	 * 监听ScrollView滚动接口
	 * @author reyo
	 *
	 */
	public interface OnScrollListener {

		public void onScrollChanged(ObservableScrollView scrollView, int x,
				int y, int oldx, int oldy);

	}
	
	/**
	 * 设置需要浮动的View
	 * @param viewInScroll ScollView内的view
	 * @param viewFloat ScollView外的view，真正需要浮动的view
	 */
	public void setFloatView(View viewInScroll,View viewOutScroll){
		this.viewInScroll=viewInScroll;
		this.viewOutScroll=viewOutScroll;
	}
	
	private void computeFloatIfNecessary(){
		if(viewInScroll==null&&viewOutScroll==null){
			return;
		}
		// 获取ScrollView的x,y坐标
		int[] location = new int[2];
		this.getLocationInWindow(location);
		// 获取浮动View的x,y坐标
		int[] loc = new int[2];
		viewInScroll.getLocationOnScreen(loc);
		// 当浮动view的y <= ScrollView的y坐标时，把固定的view显示出来
		if (loc[1] <= location[1]) {
			// 处理一下把原有view设置INVISIBLE，这样显示效果会好点
			viewOutScroll.setVisibility(View.VISIBLE);
			viewInScroll.setVisibility(View.INVISIBLE);
		} else {
			// 记得还原回来
			viewOutScroll.setVisibility(View.GONE);
			viewInScroll.setVisibility(View.VISIBLE);
		}
	}
}

用法：

import android.app.Activity;
import android.os.Bundle;
import android.util.Log;

import com.reyo.view.ObservableScrollView;
public class FloatActivity extends Activity{

	private ObservableScrollView scrollView;

	@Override
	public void onCreate(Bundle savedInstanceState) {
		super.onCreate(savedInstanceState);
		setContentView(R.layout.activity_float);
		scrollView = (ObservableScrollView) findViewById(R.id.scrollView);
		scrollView.setFloatView(findViewById(R.id.viewInScroll), findViewById(R.id.viewOutScroll));
		scrollView.setOnScrollListener(new com.reyo.view.ObservableScrollView.OnScrollListener() {

			@Override
			public void onScrollChanged(ObservableScrollView scrollView, int x,
					int y, int oldx, int oldy) {
				Log.i("tag", "y="+y+";oldy="+oldy);
			}
		});

	}

}

界面：

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent" >
    <com.reyo.view.ObservableScrollView
        android:id="@+id/scrollView"
        android:layout_width="match_parent"
        android:layout_height="match_parent" >

        <LinearLayout
            android:layout_width="match_parent"
            android:layout_height="wrap_content" 
            android:orientation="vertical"
            >

            <ImageView
                android:id="@+id/img"
                android:layout_width="match_parent"
                android:layout_height="wrap_content"
                android:src="@drawable/pic" />

            <LinearLayout
                android:id="@+id/viewInScroll"
                android:layout_width="match_parent"
                android:layout_height="wrap_content"
                android:orientation="horizontal" >

                <Button
                    android:id="@+id/button0"
                    android:layout_width="0dp"
                    android:layout_height="wrap_content"
                    android:layout_weight="1"
                    android:text="排队叫号" />

                <Button
                    android:id="@+id/button1"
                    android:layout_width="0dp"
                    android:layout_height="wrap_content"
                    android:layout_weight="1"
                    android:text="预定桌位" />

            </LinearLayout>

            <TextView
                android:layout_width="match_parent"
                android:layout_height="wrap_content"
                android:layout_marginTop="20dp"
                android:padding="5dp"
                android:text="@string/test1"
                android:textColor="#555555"
                android:textSize="20dip" />

            <TextView
                android:layout_width="match_parent"
                android:layout_height="wrap_content"
                android:layout_marginTop="20dp"
                android:padding="5dp"
                android:text="@string/test2"
                android:textColor="#555555"
                android:textSize="20dip" />

            <TextView
                android:layout_width="match_parent"
                android:layout_height="wrap_content"
                android:layout_marginTop="20dp"
                android:padding="5dp"
                android:text="@string/test3"
                android:textColor="#555555"
                android:textSize="20dip" />

            <TextView
                android:layout_width="match_parent"
                android:layout_height="wrap_content"
                android:layout_marginTop="20dp"
                android:padding="5dp"
                android:text="@string/test4"
                android:textColor="#555555"
                android:textSize="20dip" />
        </LinearLayout>
    </com.reyo.view.ObservableScrollView>

    <FrameLayout
        android:id="@+id/viewOutScroll"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_alignParentTop="true"
        android:visibility="gone" >

        <LinearLayout
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:orientation="horizontal" >

            <Button
                android:id="@+id/button0"
                android:layout_width="0dp"
                android:layout_height="wrap_content"
                android:layout_weight="1"
                android:text="排队叫号" />

            <Button
                android:id="@+id/button1"
                android:layout_width="0dp"
                android:layout_height="wrap_content"
                android:layout_weight="1"
                android:text="预定桌位" />

        </LinearLayout>
    </FrameLayout>
</RelativeLayout>

测试时尽量让ScrollView超过一屏，好让其滑动，这样才能看出效果。


Android 仿美团网,大众点评购买框悬浮效果之修改版
http://blog.csdn.net/xiaanming/article/details/17761431


一个可以滚动监听的类，这下可以根据自己的需求任意扩展了

import android.content.Context;
import android.util.AttributeSet;
import android.view.MotionEvent;
import android.widget.ScrollView;

/**
 * A custom ScrollView that can accept a scroll listener.
 */
public class ObservableScrollView extends ScrollView {
    private Callbacks mCallbacks;

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

    @Override
    protected void onScrollChanged(int l, int t, int oldl, int oldt) {
        super.onScrollChanged(l, t, oldl, oldt);
        if (mCallbacks != null) {
            mCallbacks.onScrollChanged(t);
        }
    }

    @Override
    public boolean onTouchEvent(MotionEvent ev) {
        if (mCallbacks != null) {
            switch (ev.getActionMasked()) {
                case MotionEvent.ACTION_DOWN:
                    mCallbacks.onDownMotionEvent();
                    break;
                case MotionEvent.ACTION_UP:
                case MotionEvent.ACTION_CANCEL:
                    mCallbacks.onUpOrCancelMotionEvent();
                    break;
            }
        }
        return super.onTouchEvent(ev);
    }

    @Override
    public int computeVerticalScrollRange() {
        return super.computeVerticalScrollRange();
    }

    public void setCallbacks(Callbacks listener) {
        mCallbacks = listener;
    }

    public static interface Callbacks {
        public void onScrollChanged(int scrollY);
        public void onDownMotionEvent();
        public void onUpOrCancelMotionEvent();
    }
}

如何解决ViewPager在ScrollView中滑动经常失效、无法正常滑动问题？
解决方法只需要在接近水平滚动时ScrollView不处理事件而交由其子View(即这里的ViewPager)处理即可，重写ScrollView的onInterceptTouchEvent函数，如下：

package cc.newnews.view;

import android.content.Context;
import android.util.AttributeSet;
import android.view.GestureDetector;
import android.view.GestureDetector.SimpleOnGestureListener;
import android.view.MotionEvent;
import android.widget.ScrollView;

public class VerticalScrollView extends ScrollView {

	private GestureDetector mGestureDetector;

	public VerticalScrollView(Context context, AttributeSet attrs) {
		super(context, attrs);
		mGestureDetector = new GestureDetector(context, new YScrollDetector());
	}

	@Override
	public boolean onInterceptTouchEvent(MotionEvent ev) {
		return super.onInterceptTouchEvent(ev)
				&& mGestureDetector.onTouchEvent(ev);
	}

	class YScrollDetector extends SimpleOnGestureListener {

		@Override
		public boolean onScroll(MotionEvent e1, MotionEvent e2,
				float distanceX, float distanceY) {
			/**
			 * 如果我们滚动更接近水平方向,返回false,让子视图来处理它
			 */
			return (Math.abs(distanceY) > Math.abs(distanceX));
		}
	}
}

再将xml中的ScrollView改为<xxx.xxx.xxx.VerticalScrollView>即包名.重写的ScrollView的类名)即可。
本方法同样适用于ScrollView中ListView等其他View无法滚动。

Android UI开发第四十篇——ScrollTricks介绍
http://blog.csdn.net/xyz_lmn/article/details/20557925

Android-ObservableScrollView
https://github.com/ksoichiro/Android-ObservableScrollView