自定义ScrollView实现可拖出边界的效果

来源：互联网发布：java线程与进程的区别编辑：程序博客网时间：2024/05/21 05:23

我们经常看到这样的效果,一个ListView和GridView亦或者是RecycleView,再上拉或下拉到顶部的时候,还能再拖拽一段距离,这种效果是是非常常见的,因为用的比较多,所以记录一下.
就是如下效果图
实现思路是自定义一个ScrollView:
具体代码如下

package fenganoschina.fenganoschina;import android.annotation.SuppressLint;import android.content.Context;import android.graphics.Rect;import android.util.AttributeSet;import android.view.MotionEvent;import android.view.View;import android.view.animation.TranslateAnimation;import android.widget.ListView;import android.widget.ScrollView;/** * 可以拖动的ScrollView */public class CustomerScrollView extends ScrollView {    private static final int size = 4;//拖动的距离为屏幕的高度的1/4    private View inner;    private float y;    private Rect normal = new Rect();;    public CustomerScrollView(Context context) {        super(context);    }    public CustomerScrollView(Context context, AttributeSet attrs) {        super(context, attrs);        setOverScrollMode(ListView.OVER_SCROLL_NEVER);    }    @Override    protected void onFinishInflate() {        if (getChildCount() > 0) {            inner = getChildAt(0);        }    }    @SuppressLint("ClickableViewAccessibility")    @Override    public boolean onTouchEvent(MotionEvent ev) {        if (inner == null) {            return super.onTouchEvent(ev);        } else {            commOnTouchEvent(ev);        }        return super.onTouchEvent(ev);    }    public void commOnTouchEvent(MotionEvent ev) {        int action = ev.getAction();        switch (action) {        case MotionEvent.ACTION_DOWN:            y = ev.getY();            break;        case MotionEvent.ACTION_UP:            if (isNeedAnimation()) {                // Log.v("mlguitar", "will up and animation");                animation();            }            break;        case MotionEvent.ACTION_MOVE:            final float preY = y;            float nowY = ev.getY();            /**             * size=4 表示 拖动的距离为屏幕的高度的1/4             */            int deltaY = (int) (preY - nowY) / size;            // 滚动            // scrollBy(0, deltaY);            y = nowY;            if (isNeedMove()) {                if (normal.isEmpty()) {                    normal.set(inner.getLeft(), inner.getTop(),                            inner.getRight(), inner.getBottom());                    return;                }                int yy = inner.getTop() - deltaY;                // 移动布局                inner.layout(inner.getLeft(), yy, inner.getRight(),                        inner.getBottom() - deltaY);            }            break;        default:            break;        }    }    public void animation() {        TranslateAnimation ta = new TranslateAnimation(0, 0, inner.getTop(),                normal.top);        ta.setDuration(200);        inner.startAnimation(ta);        inner.layout(normal.left, normal.top, normal.right, normal.bottom);        normal.setEmpty();    }    public boolean isNeedAnimation() {        return !normal.isEmpty();    }    public boolean isNeedMove() {        int offset = inner.getMeasuredHeight() - getHeight();        int scrollY = getScrollY();        if (scrollY == 0 || scrollY == offset) {            return true;        }        return false;    }}1
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布局文件

<?xml version="1.0" encoding="utf-8"?><RelativeLayout    xmlns:android="http://schemas.android.com/apk/res/android"    android:layout_width="match_parent"    android:layout_height="match_parent">    <com.fengan.CustomerScrollView        android:layout_width="match_parent"        android:layout_height="match_parent">        <com.fengan.ListViewForSc            android:id="@+id/lv"            android:layout_width="match_parent"            android:layout_height="wrap_content">        </com.fengan.ListViewForSc>    </com.fengan.CustomerScrollView></RelativeLayout>1
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需要注意的是:因为涉及到ScrollView和ListView的嵌套,会导致ListView上显示数据不完全
可以简单的自定义ListView代码:
(具体见上篇http://blog.csdn.net/fenganit/article/details/53732479)
代码如下:

import android.content.Context;import android.util.AttributeSet;import android.widget.ListView;/** * Created by fengan on 2016/12/19. */public class ListViewForSc extends ListView{    public ListViewForSc(Context context) {        super(context);    }    public ListViewForSc(Context context, AttributeSet attrs, int defStyleAttr) {        super(context, attrs, defStyleAttr);    }    public ListViewForSc(Context context, AttributeSet attrs) {        super(context, attrs);    }    @Override    protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {        heightMeasureSpec = MeasureSpec.makeMeasureSpec(Integer.MAX_VALUE>>2, MeasureSpec.AT_MOST);        super.onMeasure(widthMeasureSpec, heightMeasureSpec);    }}

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