Android开发--滑动侧边栏的实现

        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();
	}

}

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();
			}
		});
	}

}