Android_Scroller滑动动画

转载请注明出处：http://blog.csdn.net/y22222ly/article/details/51842218

当我们在使用view的scrollTo()或scrollBy()时，会发现这个滑动很生硬，没有动画效果，一下就过去了，就像我前篇文章提到的那样。如果能平滑的滑动回去的话，最好不过了，刚好安卓提供一个Scroller类，专门来处理view在scrollTo()或scrollBy()时没有滑动效果的问题。

Scroller基本使用

下例源码引用自：http://ipjmc.iteye.com/blog/1615828

该大神详细说明了各个方法的用法。

import android.content.Context;
import android.util.AttributeSet;
import android.util.Log;
import android.view.View;
import android.widget.LinearLayout;
import android.widget.Scroller;

public class CustomView extends LinearLayout {

private static final String TAG = "Scroller";

private Scroller mScroller;

public CustomView(Context context, AttributeSet attrs) {
super(context, attrs);
mScroller = new Scroller(context);
}

//调用此方法滚动到目标位置
public void smoothScrollTo(int fx, int fy) {
int dx = fx - mScroller.getFinalX();
int dy = fy - mScroller.getFinalY();
smoothScrollBy(dx, dy);
}

//调用此方法设置滚动的相对偏移
public void smoothScrollBy(int dx, int dy) {

//设置mScroller的滚动偏移量
mScroller.startScroll(mScroller.getFinalX(), mScroller.getFinalY(), dx, dy);
invalidate();//这里必须调用invalidate()才能保证computeScroll()会被调用，否则不一定会刷新界面，看不到滚动效果
}

@Override
public void computeScroll() {

//先判断mScroller滚动是否完成
if (mScroller.computeScrollOffset()) {

//这里调用View的scrollTo()完成实际的滚动
scrollTo(mScroller.getCurrX(), mScroller.getCurrY());

//必须调用该方法，否则不一定能看到滚动效果
postInvalidate();
}
super.computeScroll();
}
}

使用Scroller分三步：

1. 声明与初始化

2. 调用startScroll()一定要注意4个参数，前2个为当前滑动偏移量，后2个为需要滑动的偏移量

3. 重写view的computeScroll()方法，调用mScroller.computeScrollOffset()计算滑动值

4. 使用计算后的Scroller实例，调用view的scrollTo()进行滑动

Scroller实战

根据上述代码后自己学习后，对前一篇文章提到的滑动处理scrollTo()问题做了实现。

效果图：



源码：

package com.example.y2222.myview;

import android.content.Context;
import android.util.AttributeSet;
import android.util.Log;
import android.view.GestureDetector;
import android.view.LayoutInflater;
import android.view.MotionEvent;
import android.view.animation.LinearInterpolator;
import android.widget.LinearLayout;
import android.widget.Scroller;

import com.example.y2222.myapplication.R;

/**
* Created by raise.yang on 2016/06/29.
*/
public class GestureDemoView extends LinearLayout {
//1,定义GestureDetector类
private GestureDetector m_gestureDetector;
//1,定义Scroller类
private Scroller m_scroller;
private int m_max_scrollX;

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

public GestureDemoView(Context context, AttributeSet attrs, int defStyleAttr) {
super(context, attrs, defStyleAttr);
//设置为可点击
setClickable(true);
//2,初始化手势类，同时设置手势监听
m_gestureDetector = new GestureDetector(context, onGestureListener);

LayoutInflater.from(context).inflate(R.layout.view_gesture, this);
// 2,初始化Scroller类，可自定义插值器
m_scroller = new Scroller(getContext(), new LinearInterpolator());
}

@Override
public boolean onTouchEvent(MotionEvent event) {
//3,将touch事件交给gesture处理
m_gestureDetector.onTouchEvent(event);
if (event.getAction() == MotionEvent.ACTION_UP) {
// GestureDetector没有处理up事件的方法，只能在这里处理了。
int scrollX = getScrollX();
if (scrollX > m_max_scrollX / 2) {
show_right_view();
} else {
hide_right_view();
}
}
return super.onTouchEvent(event);
}

@Override
protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
super.onMeasure(widthMeasureSpec, heightMeasureSpec);
int childCount = getChildCount();
for (int i = 0; i < childCount; i++) {
//测量子view的宽高，？不测量，右侧布局会不显示，这里有点疑问
measureChild(getChildAt(i), widthMeasureSpec, heightMeasureSpec);
if (i == 1) {
m_max_scrollX = getChildAt(i).getMeasuredWidth();
}
}
}

//初始化手势监听对象，使用GestureDetector.OnGestureListener的实现抽象类，因为实际开发中好多方法用不上
private final GestureDetector.OnGestureListener onGestureListener = new GestureDetector.SimpleOnGestureListener() {

@Override
public boolean onScroll(MotionEvent e1, MotionEvent e2, float distanceX, float distanceY) {
Log.d("GestureDemoView", "onScroll() distanceX = " + distanceX + " getScrollX = " + getScrollX() + " max_scrollX = " + m_max_scrollX);
int scrollX = getScrollX();
int minScrollX = -scrollX;
int maxScrollY = m_max_scrollX - scrollX;
// 对滑动的距离边界控制
if (distanceX > maxScrollY) {
distanceX = maxScrollY;
} else if (distanceX < minScrollX) {
distanceX = minScrollX;
}
//            m_scroller.startScroll(m_scroller.getFinalX(), m_scroller.getFinalY(), m_scroller.getFinalX() + (int) distanceX, 0);
scrollBy((int) distanceX, 0);
return true;
}

@Override
public boolean onFling(MotionEvent e1, MotionEvent e2, float velocityX, float velocityY) {
Log.d("GestureDemoView", "onFling() velocityX = " + velocityX);
if (velocityX < 0) {
//快速向左滑动
show_right_view();
} else {
hide_right_view();
}
return super.onFling(e1, e2, velocityX, velocityY);
}
};

private void show_right_view() {
//3,开启滑动条
// 注意：前两个参数为起始滑动点，后2个参数为滑动距离
m_scroller.startScroll(getScrollX(), 0, m_max_scrollX-getScrollX(), 0);
//这里必须调用invalidate()才能保证computeScroll()会被调用，否则不一定会刷新界面，看不到滚动效果
invalidate();
//        scrollTo(m_max_scrollX, 0);
}

private void hide_right_view() {
// 注意：前两个参数为起始滑动点，后2个参数为滑动距离
m_scroller.startScroll(getScrollX(), 0, 0 - getScrollX(), 0);
invalidate();
//        scrollTo(0, 0);
}

@Override
public void computeScroll() {
//4,调用view自身的scrollTo()滑动
if (m_scroller.computeScrollOffset()) {//计算滑动值，并判断是否结束false表示结束
// 两个参数为相对父布局的绝对坐标，这里去Scroller计算出来的当前滑动值
scrollTo(m_scroller.getCurrX(), m_scroller.getCurrY());
postInvalidate();
}
}
}

Scroller就像属性动画中的ValueAnimator，他只产生一段连续的值，而不做处理，需要view根据自身的情况去处理这些值，目前看好像只用在scrollTo()或scrollBy()中。

还可以控制动画时间，调用5个参数的startScroll()即可：

/**
* Start scrolling by providing a starting point, the distance to travel,
* and the duration of the scroll.
*
* @param startX Starting horizontal scroll offset in pixels. Positive
*        numbers will scroll the content to the left.
* @param startY Starting vertical scroll offset in pixels. Positive numbers
*        will scroll the content up.
* @param dx Horizontal distance to travel. Positive numbers will scroll the
*        content to the left.
* @param dy Vertical distance to travel. Positive numbers will scroll the
*        content up.
* @param duration Duration of the scroll in milliseconds.
*/
public void startScroll(int startX, int startY, int dx, int dy, int duration) {
}

ListView滑动删除

单个item的滑动效果已经出来了，那么顺便将其集成在ListView中，做成滑动删除效果也不错，效果图如下：



实现起来并不难，主要解决的问题就是：如何处理滑动冲突：左右滑动时，若上下滑动父控件（ListView）会拦截滑动事件，去做上下滑动。这时，子view(ViewGroup)就只接收到一个

MotionEvent.ACTION_CANCEL

事件。

如何让子view在滑动时，提醒父控件不要拦截事件，将事件传递下去呢？我之前在子View中，设置一个flag用来标识view在滑动状态，然后ListView去根据这个值判断是否拦截滑动事件，这样做起来有些bug，在偶然看listview源码时，看到一个方法可以请求父控件不要拦截touch事件,这个事件就是requestDisallowInterceptTouchEvent(true)，在AbsListView.startScrollIfNeeded()方法中。

有了这个方法，实现起来简单很多，只要在左右开始滑动时，请求父类不要拦截，我们自己讲touch事件消耗即可。记住要在ACTION_UP时，将其还原为false.直接上代码：

GestureDemoView：

package com.example.y2222.myview;

import android.content.Context;
import android.util.AttributeSet;
import android.util.Log;
import android.view.GestureDetector;
import android.view.LayoutInflater;
import android.view.MotionEvent;
import android.view.animation.LinearInterpolator;
import android.widget.LinearLayout;
import android.widget.Scroller;
import android.widget.TextView;

import com.example.y2222.myapplication.R;

/**
* Created by raise.yang on 2016/06/29.
*/
public class GestureDemoView extends LinearLayout {
private GestureDetector m_gestureDetector;
private Scroller m_scroller;
private int m_max_scrollX;
private TextView m_primary;

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

public GestureDemoView(Context context, AttributeSet attrs, int defStyleAttr) {
super(context, attrs, defStyleAttr);
//设置为可点击
setClickable(true);
m_gestureDetector = new GestureDetector(context, onGestureListener);
m_gestureDetector.setIsLongpressEnabled(false);
LayoutInflater.from(context).inflate(R.layout.view_gesture, this);
m_scroller = new Scroller(getContext(), new LinearInterpolator());
}

@Override
protected void onFinishInflate() {
super.onFinishInflate();
m_primary = (TextView) findViewById(R.id.primary_text);
}

public void setPrimaryText(String text) {
m_primary.setText(text);
}

@Override
public boolean onTouchEvent(MotionEvent event) {
Log.d("GestureDemoView", "onTouchEvent() ");
m_gestureDetector.onTouchEvent(event);
if (event.getAction() == MotionEvent.ACTION_UP) {

// 抬起手指，请求父类可以拦截touch事件
requestDisallowInterceptTouchEvent(false);

int scrollX = getScrollX();
if (scrollX > m_max_scrollX / 2) {
show_right_view();
} else {
hide_right_view();
}
}
// 返回true，将此事件消耗，父类就不会处理onTouchEvent事件
return true;
}

@Override
protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
super.onMeasure(widthMeasureSpec, heightMeasureSpec);
int childCount = getChildCount();
for (int i = 0; i < childCount; i++) {
measureChild(getChildAt(i), widthMeasureSpec, heightMeasureSpec);
if (i == 1) {
m_max_scrollX = getChildAt(i).getMeasuredWidth();
}
}
}

private final GestureDetector.OnGestureListener onGestureListener = new GestureDetector.SimpleOnGestureListener() {

@Override
public boolean onScroll(MotionEvent e1, MotionEvent e2, float distanceX, float distanceY) {
Log.d("GestureDemoView", "onScroll() distanceX = " + distanceX + " getScrollX = " + getScrollX() + " max_scrollX = " + m_max_scrollX);
int scrollX = getScrollX();
int minScrollX = -scrollX;
int maxScrollY = m_max_scrollX - scrollX;
// 对滑动的距离边界控制
if (distanceX > maxScrollY) {
distanceX = maxScrollY;
} else if (distanceX < minScrollX) {
distanceX = minScrollX;
}
scrollBy((int) distanceX, 0);
//当前view开始滑动，请求父类不要拦截move事件
requestDisallowInterceptTouchEvent(true);
return true;
}

@Override
public boolean onFling(MotionEvent e1, MotionEvent e2, float velocityX, float velocityY) {
Log.d("GestureDemoView", "onFling() velocityX = " + velocityX);
if (velocityX < 0) {
//快速向左滑动
show_right_view();
} else {
hide_right_view();
}
return super.onFling(e1, e2, velocityX, velocityY);
}
};

private void show_right_view() {
m_scroller.startScroll(getScrollX(), 0, m_max_scrollX - getScrollX(), 0, 100);
invalidate();
}

private void hide_right_view() {
m_scroller.startScroll(getScrollX(), 0, 0 - getScrollX(), 0, 100);
invalidate();
}

@Override
public void computeScroll() {
if (m_scroller.computeScrollOffset()) {//计算滑动值，并判断是否结束false表示结束
scrollTo(m_scroller.getCurrX(), m_scroller.getCurrY());
postInvalidate();
}
}

public void initViewPosition() {
scrollTo(0, 0);
}

}

GestureActivity：

package com.example.y2222.myapplication;

import android.app.Activity;
import android.os.Bundle;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.BaseAdapter;
import android.widget.ListView;

import com.example.y2222.myview.GestureDemoView;

public class GestureActivity extends Activity {

private ListView m_listView;
private String[] m_datas = new String[]{
"1", "2", "3", "4", "5",
"6", "7", "8", "9", "10",
};

@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_gesture);

m_listView = (ListView) findViewById(R.id.listview);
m_listView.setAdapter(new Adapter());
}

class Adapter extends BaseAdapter {

@Override
public View getView(int position, View convertView, ViewGroup parent) {
if (convertView == null) {
convertView = LayoutInflater.from(GestureActivity.this).inflate(R.layout.item_slide_listview, parent, false);
}
GestureDemoView root = (GestureDemoView) convertView;
root.setPrimaryText(getItem(position));
root.initViewPosition();
return convertView;
}

@Override
public int getCount() {
return m_datas.length;
}

@Override
public String getItem(int position) {
return m_datas[position];
}

@Override
public long getItemId(int position) {
return position;
}
}

}

item的布局文件：

<?xml version="1.0" encoding="utf-8"?>
<com.example.y2222.myview.GestureDemoView xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="80dp">

</com.example.y2222.myview.GestureDemoView>

Activity的布局文件：

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout
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:background="@android:color/holo_blue_light"
tools:context="com.example.y2222.myapplication.GestureActivity">

<ListView
android:id="@+id/listview"
android:layout_width="match_parent"
android:layout_height="match_parent"/>
</RelativeLayout>