在上一篇文章《Android自己定义组件系列【3】——自己定义ViewGroup实现側滑》中实现了仿Facebook和人人网的側滑效果，这一篇我们将接着上一篇来实现双面滑动的效果。
1、布局示意图：
2、核心代码
@Override
protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
super.onMeasure(widthMeasureSpec, heightMeasureSpec);
mWidth = MeasureSpec.getSize(widthMeasureSpec); //获取MyScrollView的宽度
mHeight = MeasureSpec.getSize(heightMeasureSpec); //获取MyScrollView的高度
if(!isLocked){
initX = getScrollX();
isLocked = true;
}
}在该方法中获取到初始的视图坐标偏移量getScrollX() @Override
public boolean onTouchEvent(MotionEvent event) {
float x = event.getX();
switch (event.getAction()) {
case MotionEvent.ACTION_DOWN:
System.out.println("ACTION_DOWN");
mDownX = x; //记录按下时的x坐标
break;
case MotionEvent.ACTION_UP:
System.out.println("ACTION_UP");
int dis = (int) (x - mDownX); //滑动的距离
if(Math.abs(dis) > (mWidth * mMenuWeight / 2)){
if(dis > 0){ //假设>0则是向右滑动
toRightMove();
}else{ //假设<0则是向左滑动
toLeftMove();
}
}
break;
default:
break;
}
return true;
}监听函数记录下按下和移动的屏幕坐标。求差计算出移动距离，假设这个距离大于阀值 （mWidth * mMenuWeight / 2)则滑动 public void toRightMove(){
System.out.println("maxRight = " + maxRight);
System.out.println("X = " + getScrollX());
if(getScrollX() >= initX){
int dx = (int)(mWidth * mMenuWeight);
mScroller.startScroll(getScrollX(), 0, -dx, 0, 500);
if(mListener != null){
mListener.onChanged();
}
invalidate();
}
}假设是向右滑动则。假设当前是初始位置（centerView在中间）则能够向右滑动（getScrollX == initX），或者当前左边View能够看见，则能够向右滑动将centerView移动到中间（getScrollX > initX).同理有向左滑动的方法。 public void toLeftMove(){
System.out.println("maxLeft = " + maxLeft);
System.out.println("X = " + getScrollX());
if(getScrollX() <= initX){
int dx = (int)(mWidth * mMenuWeight);
mScroller.startScroll(getScrollX(), 0, dx, 0, 500);
if(mListener != null){
mListener.onChanged();
}
invalidate();
}
}3、所有代码MyScrollView.java
package com.example.testscrollto;
import android.content.Context;
import android.util.AttributeSet;
import android.view.MotionEvent;
import android.view.View;
import android.view.ViewGroup;
import android.widget.LinearLayout;
import android.widget.Scroller;
public class MyScrollView extends LinearLayout{
private Context mContext;
private int mWidth;
private int mHeight;
private float mMenuWeight = 3.0f / 5; //菜单界面比例
private View mMenuView; //菜单界面
private View mPriView; //内容界面
private View mRightView; //右边界面
private int maxLeft;
private int maxRight;
private int initX;
private boolean isLocked = false;
private Scroller mScroller;
private OnMenuChangedListener mListener;
public MyScrollView(Context context, AttributeSet attrs) {
super(context, attrs);
mContext = context;
mScroller = new Scroller(mContext);
}
@Override
protected void onLayout(boolean changed, int l, int t, int r, int b) {
super.onLayout(changed, l, t, r, b);
mMenuView.layout(-(int)(mWidth * mMenuWeight), 0, 0, mHeight);
mPriView.layout(0, 0, mWidth, mHeight);
mRightView.layout(mWidth, 0, mWidth + (int)(mWidth * mMenuWeight), mHeight);
}
@Override
protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
super.onMeasure(widthMeasureSpec, heightMeasureSpec);
mWidth = MeasureSpec.getSize(widthMeasureSpec); //获取MyScrollView的宽度
mHeight = MeasureSpec.getSize(heightMeasureSpec); //获取MyScrollView的高度
if(!isLocked){
initX = getScrollX();
isLocked = true;
}
}
/**设置右滑的菜单View*/
public void setMenu(View menu){
mMenuView = menu;
addView(mMenuView);
}
/**
* 设置主界面View
*/
public void setPrimary(View primary){
mPriView = primary;
addView(mPriView);
}
public void setRightView(View rightview){
mRightView = rightview;
addView(mRightView);
}
private float mDownX;
@Override
public boolean onTouchEvent(MotionEvent event) {
float x = event.getX();
switch (event.getAction()) {
case MotionEvent.ACTION_DOWN:
System.out.println("ACTION_DOWN");
mDownX = x; //记录按下时的x坐标
break;
case MotionEvent.ACTION_UP:
System.out.println("ACTION_UP");
int dis = (int) (x - mDownX); //滑动的距离
if(Math.abs(dis) > (mWidth * mMenuWeight / 2)){
if(dis > 0){ //假设>0则是向右滑动
toRightMove();
}else{ //假设<0则是向左滑动
toLeftMove();
}
}
break;
default:
break;
}
return true;
}
@Override
public void computeScroll() {
super.computeScroll();
if(mScroller.computeScrollOffset()){
scrollTo(mScroller.getCurrX(), mScroller.getCurrY());
postInvalidate();
}
}
public void toRightMove(){
System.out.println("maxRight = " + maxRight);
System.out.println("X = " + getScrollX());
if(getScrollX() >= initX){
int dx = (int)(mWidth * mMenuWeight);
mScroller.startScroll(getScrollX(), 0, -dx, 0, 500);
if(mListener != null){
mListener.onChanged();
}
invalidate();
}
}
public void toLeftMove(){
System.out.println("maxLeft = " + maxLeft);
System.out.println("X = " + getScrollX());
if(getScrollX() <= initX){
int dx = (int)(mWidth * mMenuWeight);
mScroller.startScroll(getScrollX(), 0, dx, 0, 500);
if(mListener != null){
mListener.onChanged();
}
invalidate();
}
}
public interface OnMenuChangedListener{
public void onChanged();
}
public void setOnMenuChangedListener(OnMenuChangedListener listener){
mListener = listener;
}
}
MainActivity.javapackage com.example.testscrollto;
import android.app.Activity;
import android.os.Bundle;
import android.view.View;
import com.example.testscrollto.MyScrollView.OnMenuChangedListener;
public class MainActivity extends Activity {
private MyScrollView mScrollView;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
mScrollView = (MyScrollView)findViewById(R.id.rightscrollview);
final View menu = getLayoutInflater().inflate(R.layout.rightscrollview_menu, null);
final View primary = getLayoutInflater().inflate(R.layout.rightscrollview_primary, null);
final View rightview = getLayoutInflater().inflate(R.layout.rightscrollview_right_menu, null);
mScrollView.setMenu(menu);
mScrollView.setPrimary(primary);
mScrollView.setRightView(rightview);
mScrollView.setOnMenuChangedListener(new OnMenuChangedListener() {
@Override
public void onChanged() {
System.out.println("窗体切换了一次");
}
});
}
}activity_main.xml<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical" >
<com.example.testscrollto.MyScrollView
android:id="@+id/rightscrollview"
android:layout_width="match_parent"
android:layout_height="match_parent" />
</LinearLayout>其余三个视图界面无限制。能够自由定义，这里就不贴出来了。4、执行效果：
源码下载：http://download.csdn.net/detail/lxq_xsyu/7232701
这样就能够实现左右滑动了，没有不论什么bug吗？
事实上这样看似是没有什么问题了，上面用于推断界面位置的代码在逻辑上看似是对的，可是在实际的应用中偶尔会出现错乱。
以下我们用第二种方式解决：
package com.example.jaohangui.view;
import android.content.Context;
import android.util.AttributeSet;
import android.view.MotionEvent;
import android.view.View;
import android.widget.LinearLayout;
import android.widget.Scroller;
public class MyScrollLeftRightView extends LinearLayout{
private Scroller mScroller;
private View mLeftView; //坐标界面
private View mMainView; //中间主界面
private View mRightView; //右边界面
private float mMeasureWight = 3.0f / 5; //菜单界面比例
private int mWidth;
private int mHeight;
private boolean isLocked = false;
private boolean isToLeft = false;
private static int CENTER_PAGE = 1;
private static int LEFT_PAGE = 0;
private static int RIGHT_PAGE = 2;
private int currentPage = CENTER_PAGE;
public MyScrollLeftRightView(Context context, AttributeSet attrs) {
super(context, attrs);
mScroller = new Scroller(context);
}
@Override
protected void onLayout(boolean changed, int l, int t, int r, int b) {
super.onLayout(changed, l, t, r, b);
mLeftView.layout(-(int)(mWidth * mMeasureWight), 0, 0, mHeight);
mMainView.layout(0, 0, mWidth, mHeight);
mRightView.layout(mWidth, 0, mWidth + (int)(mWidth * mMeasureWight), mHeight);
}
@Override
protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
super.onMeasure(widthMeasureSpec, heightMeasureSpec);
mWidth = MeasureSpec.getSize(widthMeasureSpec);
mHeight = MeasureSpec.getSize(heightMeasureSpec);
}
/**
* 加入左边界面内容
* @param view
*/
public void setLeftView(View view){
mLeftView = view;
addView(mLeftView);
}
/**
* 加入主界面内容
* @param view
*/
public void setMainView(View view){
mMainView = view;
addView(mMainView);
}
/**
* 加入右边界面内容
* @param view
*/
public void setRightView(View view){
mRightView = view;
addView(mRightView);
}
private float mDownX;
@Override
public boolean onTouchEvent(MotionEvent event) {
float x = event.getX();
switch (event.getAction()) {
case MotionEvent.ACTION_DOWN:
mDownX = x;
break;
case MotionEvent.ACTION_UP:
int dis = (int)(x - mDownX); //滑动的距离
if(Math.abs(dis) > (mWidth * mMeasureWight / 3)){
if(dis > 0){
toRightMove();
}else{
toLeftMove();
}
}
break;
default:
break;
}
return true;
}
@Override
public void computeScroll() {
super.computeScroll();
if(mScroller.computeScrollOffset()){
isLocked = true;
scrollTo(mScroller.getCurrX(), mScroller.getCurrY());
postInvalidate();
}else{
if(currentPage == CENTER_PAGE){
if(isToLeft){
currentPage = RIGHT_PAGE;
}else{
currentPage = LEFT_PAGE;
}
}else{
currentPage = CENTER_PAGE;
}
isLocked = false;
}
}
public void toRightMove(){
if(currentPage == LEFT_PAGE || isLocked){
return;
}
int dx = (int)(mWidth * mMeasureWight);
mScroller.startScroll(getScrollX(), 0, -dx, 0, 500);
invalidate();
isToLeft = false;
}
public void toLeftMove(){
if(currentPage == RIGHT_PAGE || isLocked){
return;
}
System.out.println("ok");
int dx = (int)(mWidth * mMeasureWight);
mScroller.startScroll(getScrollX(), 0, dx, 0, 500);
invalidate();
isToLeft = true;
}
}上面使用了两个用来推断的变量和一个锁定状态（不让进入toLeftMove和toRightMove）的变量。1、在进入toLeftMove或者toRightMove方法的时候首先会推断是否isLocked为true，假设为true则说明当前是正在滑动状态，不能够执行这两个方法。假设不这样去控制。在界面正在滑动的时候上面的currentPage就会发生错乱。
2、将要滑动之前告诉computeScroll()方法，是从toLeftMove和toRightMove的那个方法中出来的（使用isToLeft）。
3、最后推断Scroller是否已经停止滑动（移动），假设停止则改变当前页面的状态（currentPage的值）
有的时候我们尽管实现了一个功能或者某个逻辑，而怎样才干使这段代码更加健壮和有效更值得我们去认真思考。
。。