之前都一直是看郭大神的博客，也就看到了那个仿人人网的侧滑菜单，但是感觉太冗杂，权当理解原理最好不过。后来实际开发过程中也要用到，我就想可不可以自己写一个，自制侧滑侧单，既可以左侧滑出，也可以从右侧滑出，或者是双向滑动的，那该多好啊，于是，我就上路了。。。
在此我得知android本身就有一个类Scroller，用于处理布局内容的滑动，然后就一探究竟（这里面尤其值得注意滑动的偏移量与屏幕坐标系是相反的，详情可自行科普），用这个类的确省了好多事，那我也废话不多说，先上源码：
package com.cjt_pc.myslidingmenu;
import android.content.Context;
import android.graphics.Color;
import android.graphics.Point;
import android.support.annotation.NonNull;
import android.util.AttributeSet;
import android.view.MotionEvent;
import android.view.VelocityTracker;
import android.view.View;
import android.view.animation.DecelerateInterpolator;
import android.widget.FrameLayout;
import android.widget.RelativeLayout;
import android.widget.Scroller;
/**
* Created by cjt-pc on 2015/7/27.
* Email:879309896@qq.com
*/
public class SlidingLayout extends FrameLayout {
// 滚动显示和隐藏menu时，手指滑动需要达到的速度
public static final int SNAP_VELOCITY = 400;
// 手指横向滑动临界距离，判断滑动类型
public static final int SCROLL_DIS = 20;
// 上下文
private Context mContext;
// 左中右三个layout
private BaseSlideLayout leftSlideLayout, middleSlideLayout, rightSlideLayout;
// 中间内容的“面罩”
private BaseSlideLayout maskLayout;
// 是否开启滑动渐变效果，默认为true
private boolean isOnAlpha = true;
// 渐变程度，1代表满足条件时完全不透明
private float alphaRate = 0.5f;
// 手指按下的坐标
private int downX, downY;
// 当前手指触摸屏幕的点
private Point point;
// 用于计算手指滑动的速度
private VelocityTracker mVelocityTracker;
// 滚动控制器
private Scroller mScroller;
// 手指移动类型是否为横向滑动
private boolean isLeftRight = false;
// 是否计算了滑动类型
private boolean isCalTyped = false;
// 是否屏蔽所有事件
private boolean isIntercept = false;
// 手指是否抬起
private boolean fingerUp = true;
// 视图移动的距离范围，注意这是偏移量，正负与坐标相反
private int minX = 0, maxX = 0;
// 侧边菜单的宽度比例，默认为主界面的0.8
private double widthRate = 0.8;
// 侧边菜单的宽度
private int menuWidth = 0;
public SlidingLayout(Context context) {
super(context);
mContext = context;
mScroller = new Scroller(context, new DecelerateInterpolator());
point = new Point();
// 设置clickable可以使dispatchTouchEvent恒为true
this.setClickable(true);
}
public SlidingLayout(Context context, AttributeSet attrs) {
super(context, attrs);
}
@Override
protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
super.onMeasure(widthMeasureSpec, heightMeasureSpec);
int finalX = 0;
// 分别给存在的layout设置大小
if (middleSlideLayout != null) {
middleSlideLayout.measure(widthMeasureSpec, heightMeasureSpec);
maskLayout.measure(widthMeasureSpec, heightMeasureSpec);
menuWidth = (int) (middleSlideLayout.getMeasuredWidth() * widthRate);
finalX = (MeasureSpec.makeMeasureSpec(menuWidth, MeasureSpec.EXACTLY));
}
if (leftSlideLayout != null) {
leftSlideLayout.measure(finalX, heightMeasureSpec);
}
if (rightSlideLayout != null) {
rightSlideLayout.measure(finalX, heightMeasureSpec);
}
}
@Override
protected void onLayout(boolean changed, int l, int t, int r, int b) {
super.onLayout(changed, l, t, r, b);
if (middleSlideLayout != null) {
middleSlideLayout.layout(l, t, r, b);
maskLayout.layout(l, t, r, b);
}
if (leftSlideLayout != null) {
leftSlideLayout.layout(l - leftSlideLayout.getMeasuredWidth(), t, l, b);
minX = -leftSlideLayout.getMeasuredWidth();
}
if (rightSlideLayout != null) {
rightSlideLayout.layout(r, t, r + rightSlideLayout.getMeasuredWidth(), b);
maxX = rightSlideLayout.getMeasuredWidth();
}
}
@Override
public boolean dispatchTouchEvent(@NonNull MotionEvent ev) {
createVelocityTracker(ev);
switch (ev.getAction()) {
case MotionEvent.ACTION_DOWN:
fingerUp = false;
downX = (int) ev.getX();
downY = (int) ev.getY();
break;
case MotionEvent.ACTION_MOVE:
int dX = (int) (ev.getX() - point.x);
// 当滑动距离超过了计算滑动类型最小值，判断是否为左右滑动，只计算一次
if (!isCalTyped && ((Math.abs((int) ev.getX() - downX) >= SCROLL_DIS) ||
Math.abs((int) ev.getY() - downY) >= SCROLL_DIS)) {
if (Math.abs(ev.getX() - downX) > Math.abs(ev.getY() - downY)) {
isLeftRight = true;
}
isCalTyped = true;
}
if (isLeftRight) {
isIntercept = true;
int expectX = getScrollX() - dX;
// 左右滑动的最小和最大值
if (expectX >= minX && expectX <= maxX) {
// 只有视图在滑动的时候让当前视图屏蔽掉所有控件事件
// 滚动视图到指定点
scrollBy(-dX, 0);
}
}
break;
case MotionEvent.ACTION_UP:
case MotionEvent.ACTION_CANCEL:
fingerUp = true;
isLeftRight = false;
isCalTyped = false;
beginStart();
invalidate();
recycleVelocityTracker();
break;
default:
break;
}
point.x = (int) ev.getX();
point.y = (int) ev.getY();
return super.dispatchTouchEvent(ev);
}
@Override
public void scrollTo(int x, int y) {
super.scrollTo(x, y);
if (isOnAlpha) {
int curScroX = Math.abs(getScrollX());
float scale = curScroX / (float) menuWidth;
if (middleSlideLayout != null) {
maskLayout.setAlpha(scale * alphaRate);
}
}
}
// 手指抬起时判断情况滚动视图到指定点
private void beginStart() {
int curScroX = getScrollX();
int cpX = menuWidth >> 1;
int moveSp = getScrollVelocity();
// 当手指移动速度满足要求时换一种判断方式
if (Math.abs(moveSp) < SNAP_VELOCITY) {
if (curScroX >= -cpX && curScroX < 0) {//左侧菜单缩进
mScroller.startScroll(curScroX, 0, -curScroX, 0);
} else if (curScroX < -cpX) {//左侧菜单展出
mScroller.startScroll(curScroX, 0, -menuWidth - curScroX, 0);
} else if (curScroX > 0 && curScroX <= cpX) {//右侧菜单缩进
mScroller.startScroll(curScroX, 0, -curScroX, 0);
} else if (curScroX > cpX) {//右侧菜单展出
mScroller.startScroll(curScroX, 0, menuWidth - curScroX, 0);
}
} else {
if (moveSp < 0 && getScrollX() < 0 && getScrollX() > -menuWidth) {
mScroller.startScroll(curScroX, 0, -curScroX, 0);
} else if (moveSp > 0 && getScrollX() < 0 && getScrollX() > -menuWidth) {
mScroller.startScroll(curScroX, 0, -menuWidth - curScroX, 0);
} else if (moveSp > 0 && getScrollX() > 0 && getScrollX() < menuWidth) {
mScroller.startScroll(curScroX, 0, -curScroX, 0);
} else if (moveSp < 0 && getScrollX() > 0 && getScrollX() < menuWidth) {
mScroller.startScroll(curScroX, 0, menuWidth - curScroX, 0);
}
}
}
/**
* 初始化VelocityTracker对象，并将触摸滑动事件加入到VelocityTracker当中
*
* @param event 触摸滑动事件
*/
private void createVelocityTracker(MotionEvent event) {
if (mVelocityTracker == null) {
mVelocityTracker = VelocityTracker.obtain();
}
mVelocityTracker.addMovement(event);
}
/**
* 获取手指在content界面滑动的速度
*
* @return 滑动速度，以每秒钟移动了多少像素值为单位
*/
private int getScrollVelocity() {
mVelocityTracker.computeCurrentVelocity(1000);
return (int) mVelocityTracker.getXVelocity();
}
/**
* 回收VelocityTracker对象。
*/
private void recycleVelocityTracker() {
mVelocityTracker.recycle();
mVelocityTracker = null;
}
@Override
public boolean onInterceptTouchEvent(MotionEvent ev) {
return isIntercept;
}
// scrollTo就会触发该事件，scrollBy为scrollTo的重写方法
@Override
public void computeScroll() {// 动画绘制方法
super.computeScroll();
if (fingerUp) {
if (!mScroller.computeScrollOffset()) {// 滑动完成
isIntercept = false;
// 滑动结束如若在两端就屏蔽掉中间layout事件
middleSlideLayout.isIntercept =
(Math.abs(mScroller.getFinalX()) == menuWidth);
return;
}
int tempX = mScroller.getCurrX();
scrollTo(tempX, 0);
postInvalidate();
}
}
public void setLeftSlideLayout(View view) {
if (leftSlideLayout == null) {
leftSlideLayout = new BaseSlideLayout(mContext);
leftSlideLayout.addView(view);
this.addView(leftSlideLayout);
}
}
public void setMiddleSlideLayout(View view) {
if (middleSlideLayout == null) {
middleSlideLayout = new BaseSlideLayout(mContext);
middleSlideLayout.addView(view);
middleSlideLayout.setOnClickListener(new OnClickListener() {
@Override
public void onClick(View v) {
int curScroX = getScrollX();
mScroller.startScroll(curScroX, 0, -curScroX, 0);
}
});
this.addView(middleSlideLayout);
maskLayout = new BaseSlideLayout(mContext);
maskLayout.setBackgroundColor(Color.GRAY);
// float类型，0-1，完全透明-完全不透明
maskLayout.setAlpha(0.0f);
this.addView(maskLayout);
}
}
public void setRightSlideLayout(View view) {
if (rightSlideLayout == null) {
rightSlideLayout = new BaseSlideLayout(mContext);
rightSlideLayout.addView(view);
this.addView(rightSlideLayout);
}
}
public void setOnAlpha(boolean onAlpha) {
this.isOnAlpha = onAlpha;
}
public void setAlphaRate(float rate) {
this.alphaRate = rate;
}
public void setWidthRate(double rate) {
this.widthRate = rate;
}
private class BaseSlideLayout extends RelativeLayout {
private boolean isIntercept = false;
public BaseSlideLayout(Context context) {
super(context);
}
public BaseSlideLayout(Context context, AttributeSet attrs) {
super(context, attrs);
}
@Override
public boolean onInterceptTouchEvent(MotionEvent ev) {
return isIntercept;
}
}
}很清楚这是一个FrameLayout类，这里就是一个可自定义功能的布局。里面注释已经写的很清楚了，我还是先介绍一下这个里面提供的公共方法：
- setLeftSlideLayout(View view)：设置左侧菜单
- setMiddleSlideLayout(View view)：设置中间内容
- setRightSlideLayout(View view)：设置右侧菜单
- setOnAlpha(boolean onAlpha)：是否开启滑动时中间模糊处理
- setAlphaRate(float rate)：设置模糊处理程度
- setWidthRate(double rate)：设置菜单布局宽度系数
具体使用方法呢，也非常的简单，首先将这个类添加到你的工程中，然后在要展示的Activity中的onCreate方法中：
SlidingLayout slidingLayout = new SlidingLayout(this);
slidingLayout.setLeftSlideLayout(new LinearLayout(this));
slidingLayout.setMiddleSlideLayout(new LinearLayout(this));
slidingLayout.setRightSlideLayout(new LinearLayout(this));
slidingLayout.setOnAlpha(true);
slidingLayout.setAlphaRate(0.6f);
slidingLayout.setWidthRate(0.6);
setContentView(slidingLayout);当然，你也可以有自己的想法，仿qq侧滑？完全可以，源码都给你了，自己去慢慢研究吧，^_^
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