Android实现滑动侧边栏

在Android应用开发中，滑动侧边栏经常使用，今天我也试着自己进行了一个简单的实践，虽然功能还不是很强大，但是可以保留下来为以后的开发使用，有需要时在进行简单的修改。实现一个滑动侧边栏思路也很简单：

1.重写一个SlidingMenu类继承ViewGroup，病危该ViewGroup添加两个子布局，分别为菜单和主界面显示；

2.为了得到一个滑动的效果，选择Scroller帮助我们实现，配合ViewGroup下的computeScroll方法实现界面的更新；

3.利用一个boolean来记录菜单是否打开，在菜单打开的状态下向右滑动不会响应，在菜单关闭的情况向左滑动不会响应；

4.为了得到一个良好的交互，我们可以为界面滑动与手指移动的距离定义一个比例，如每次触摸事件发生，界面移动的距离仅为手指移动距离的一半；

下面是两张效果图，界面没怎么布局，大家凑合看

SlidingMenu实现代码：

package com.example.test; 

import android.content.Context;
import android.view.MotionEvent;
import android.view.View;
import android.view.ViewGroup;
import android.widget.Scroller; 

public class SlidingMenu extends ViewGroup { 

 private static final String TAG = SlidingMenu.class.getName(); 

 private enum Scroll_State {
  Scroll_to_Open, Scroll_to_Close;
 } 

 private Scroll_State state;
 private int mMostRecentX;
 private int downX;
 private boolean isOpen = false; 

 private View menu;
 private View mainView; 

 private Scroller mScroller; 

 private OnSlidingMenuListener onSlidingMenuListener; 

 public SlidingMenu(Context context, View main, View menu) {
  super(context);
  // TODO Auto-generated constructor stub
  setMainView(main);
  setMenu(menu);
  init(context);
 } 

 private void init(Context context) {
  mScroller = new Scroller(context);
 } 

 @Override
 protected void onLayout(boolean arg0, int l, int t, int r, int b) {
  // TODO Auto-generated method stub
  mainView.layout(l, t, r, b);
  menu.layout(-menu.getMeasuredWidth(), t, 0, b);
 } 

 public void setMainView(View view) {
  mainView = view;
  addView(mainView);
 } 

 public void setMenu(View view) {
  menu = view;
  addView(menu);
 } 

 @Override
 protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
  // TODO Auto-generated method stub
  super.onMeasure(widthMeasureSpec, heightMeasureSpec);
  mainView.measure(widthMeasureSpec, heightMeasureSpec);
  menu.measure(widthMeasureSpec - 150, heightMeasureSpec);
 } 

 @Override
 public boolean onTouchEvent(MotionEvent event) {
  switch (event.getAction()) {
  case MotionEvent.ACTION_DOWN:
   mMostRecentX = (int) event.getX();
   downX = (int) event.getX();
   break;
  case MotionEvent.ACTION_MOVE:
   int moveX = (int) event.getX();
   int deltaX = mMostRecentX - moveX;
   // 如果在菜单打开时向右滑动及菜单关闭时向左滑动不会触发Scroll事件
   if ((!isOpen && (downX - moveX) < 0)
     || (isOpen && (downX - moveX) > 0)) {
    scrollBy(deltaX / 2, 0);
   }
   mMostRecentX = moveX;
   break;
  case MotionEvent.ACTION_UP:
   int upX = (int) event.getX();
   int dx = upX - downX;
   if (!isOpen) {// 菜单关闭时
    // 向右滑动超过menu一半宽度才会打开菜单
    if (dx > menu.getMeasuredWidth() / 3) {
     state = Scroll_State.Scroll_to_Open;
    } else {
     state = Scroll_State.Scroll_to_Close;
    }
   } else {// 菜单打开时
    // 当按下时的触摸点在menu区域时，只有向左滑动超过menu的一半，才会关闭
    // 当按下时的触摸点在main区域时，会立即关闭
    if (downX < menu.getMeasuredWidth()) {
     if (dx < -menu.getMeasuredWidth() / 3) {
      state = Scroll_State.Scroll_to_Close;
     } else {
      state = Scroll_State.Scroll_to_Open;
     }
    } else {
     state = Scroll_State.Scroll_to_Close;
    }
   }
   smoothScrollto();
   break;
  default:
   break;
  }
  return true;
 } 

 private void smoothScrollto() {
  int scrollx = getScrollX();
  switch (state) {
  case Scroll_to_Close:
   mScroller.startScroll(scrollx, 0, -scrollx, 0, 500);
   if (onSlidingMenuListener != null && isOpen) {
    onSlidingMenuListener.close();
   }
   isOpen = false;
   break;
  case Scroll_to_Open:
   mScroller.startScroll(scrollx, 0,
     -scrollx - menu.getMeasuredWidth(), 0, 500);
   if (onSlidingMenuListener != null && !isOpen) {
    onSlidingMenuListener.close();
   }
   isOpen = true;
   break;
  default:
   break;
  }
 } 

 @Override
 public void computeScroll() {
  if (mScroller.computeScrollOffset()) {
   scrollTo(mScroller.getCurrX(), 0);
  }
  invalidate();
 } 

 public void open() {
  state = Scroll_State.Scroll_to_Open;
  smoothScrollto();
 } 

 public void close() {
  state = Scroll_State.Scroll_to_Close;
  smoothScrollto();
 } 

 public boolean isOpen() {
  return isOpen;
 } 

 public void setOnSlidingMenuListener(
   OnSlidingMenuListener onSlidingMenuListener) {
  this.onSlidingMenuListener = onSlidingMenuListener;
 } 

 public interface OnSlidingMenuListener {
  public void open(); 

  public void close();
 } 

} 

在MainActivity中进行调用

package com.example.test; 

import android.os.Bundle;
import android.support.v4.app.FragmentActivity;
import android.view.LayoutInflater;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button; 

public class MainActivity extends Activity { 

 private Button openButton;
 private Button closeButton;
 private SlidingMenu mSlidingMenu; 

 @Override
 protected void onCreate(Bundle savedInstanceState) {
  super.onCreate(savedInstanceState);
  mSlidingMenu = new SlidingMenu(this, LayoutInflater
    .from(this).inflate(R.layout.fragment1, null), LayoutInflater
    .from(this).inflate(R.layout.fragment2, null));
  setContentView(mSlidingMenu);//注意setContentView需要换为我们的SlidingMenu
  openButton = (Button) findViewById(R.id.button1);
  closeButton = (Button) findViewById(R.id.button_close);
  openButton.setOnClickListener(new OnClickListener() { 

   @Override
   public void onClick(View arg0) {
    // TODO Auto-generated method stub
    mSlidingMenu.open();
   }
  });
  closeButton.setOnClickListener(new OnClickListener() { 

   @Override
   public void onClick(View arg0) {
    // TODO Auto-generated method stub
    mSlidingMenu.close();
   }
  });
 } 

}

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