Android 类似launcher左右滑动(实例二)

原文地址：http://iaiai.iteye.com/blog/1193466

运行效果:

main.xml

<?xml version="1.0" encoding="utf-8"?>
<com.cn.ScrollLayout xmlns:android="http://schemas.android.com/apk/res/android"
	android:id="@+id/ScrollLayoutTest" android:layout_width="fill_parent"
	android:layout_height="fill_parent">
	<LinearLayout android:background="#FF00"
		android:layout_width="fill_parent" android:layout_height="fill_parent"></LinearLayout>

	<FrameLayout android:background="#F00F"
		android:layout_width="fill_parent" android:layout_height="fill_parent">
	</FrameLayout>

	<LinearLayout android:layout_width="wrap_content"
		android:layout_height="wrap_content">
		<Button android:layout_width="wrap_content"
			android:layout_height="wrap_content" android:text="Button2" />
	</LinearLayout>
</com.cn.ScrollLayout>

MainActivity.java

package com.cn;

import android.app.Activity;
import android.os.Bundle;

/**
 * 
 * <p>
 * Title: MainActivity.java
 * </p>
 * <p>
 * E-Mail: [e-mail]
 * </p>
 * <p>
 * QQ: 176291935
 * </p>
 * <p>
 * Http: iaiai.iteye.com
 * </p>
 * <p>
 * Create time: 2011-10-13
 * </p>
 * 
 * @author 丸子
 * @version 0.0.1
 */
public class MainActivity extends Activity {
	/** Called when the activity is first created. */
	@Override
	public void onCreate(Bundle savedInstanceState) {
		super.onCreate(savedInstanceState);
		setContentView(R.layout.main);
	}
}

ScrollLayout.java

package com.cn;

import android.content.Context;
import android.util.AttributeSet;
import android.util.Log;
import android.view.MotionEvent;
import android.view.VelocityTracker;
import android.view.View;
import android.view.ViewConfiguration;
import android.view.ViewGroup;
import android.widget.Scroller;

/**
 * 
 * <p>
 * Title: ScrollLayout.java
 * </p>
 * <p>
 * E-Mail: [e-mail]
 * </p>
 * <p>
 * QQ: 176291935
 * </p>
 * <p>
 * Http: iaiai.iteye.com
 * </p>
 * <p>
 * Create time: 2011-10-13
 * </p>
 * 
 * @author 丸子
 * @version 0.0.1
 */
public class ScrollLayout extends ViewGroup {

	private static final String TAG = "ScrollLayout";

	private Scroller mScroller;

	private VelocityTracker mVelocityTracker;

	private int mCurScreen;

	private int mDefaultScreen = 0;

	private static final int TOUCH_STATE_REST = 0;

	private static final int TOUCH_STATE_SCROLLING = 1;

	private static final int SNAP_VELOCITY = 600;

	private int mTouchState = TOUCH_STATE_REST;

	private int mTouchSlop;

	private float mLastMotionX;

	private float mLastMotionY;

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

	public ScrollLayout(Context context, AttributeSet attrs, int defStyle) {
		super(context, attrs, defStyle);

		mScroller = new Scroller(context);
		mCurScreen = mDefaultScreen;
		mTouchSlop = ViewConfiguration.get(getContext()).getScaledTouchSlop();
	}

	@Override
	protected void onLayout(boolean changed, int l, int t, int r, int b) {
		if (changed) {
			int childLeft = 0;
			final int childCount = getChildCount();

			for (int i = 0; i < childCount; i++) {
				final View childView = getChildAt(i);

				if (childView.getVisibility() != View.GONE) {
					final int childWidth = childView.getMeasuredWidth();
					childView.layout(childLeft, 0, childLeft + childWidth,
							childView.getMeasuredHeight());
					childLeft += childWidth;
				}
			}
		}
	}

	@Override
	protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
		Log.e(TAG, "onMeasure");
		super.onMeasure(widthMeasureSpec, heightMeasureSpec);

		final int width = MeasureSpec.getSize(widthMeasureSpec);
		final int widthMode = MeasureSpec.getMode(widthMeasureSpec);

		if (widthMode != MeasureSpec.EXACTLY) {
			throw new IllegalStateException(
					"ScrollLayout only canmCurScreen run at EXACTLY mode!");
		}

		final int heightMode = MeasureSpec.getMode(heightMeasureSpec);

		if (heightMode != MeasureSpec.EXACTLY) {
			throw new IllegalStateException(
					"ScrollLayout only can run at EXACTLY mode!");
		}

		// The children are given the same width and height as the scrollLayout
		final int count = getChildCount();
		for (int i = 0; i < count; i++) {
			getChildAt(i).measure(widthMeasureSpec, heightMeasureSpec);
		}

		// Log.e(TAG, "moving to screen "+mCurScreen);
		scrollTo(mCurScreen * width, 0);
	}

	/**
	 * 
	 * According to the position of current layout
	 * 
	 * scroll to the destination page.
	 */
	public void snapToDestination() {
		final int screenWidth = getWidth();
		final int destScreen = (getScrollX() + screenWidth / 2) / screenWidth;
		snapToScreen(destScreen);
	}

	public void snapToScreen(int whichScreen) {
		// get the valid layout page
		whichScreen = Math.max(0, Math.min(whichScreen, getChildCount() - 1));

		if (getScrollX() != (whichScreen * getWidth())) {
			final int delta = whichScreen * getWidth() - getScrollX();
			mScroller.startScroll(getScrollX(), 0, delta, 0,
					Math.abs(delta) * 2);
			mCurScreen = whichScreen;
			invalidate(); // Redraw the layout
		}
	}

	public void setToScreen(int whichScreen) {
		whichScreen = Math.max(0, Math.min(whichScreen, getChildCount() - 1));
		mCurScreen = whichScreen;
		scrollTo(whichScreen * getWidth(), 0);
	}

	public int getCurScreen() {
		return mCurScreen;
	}

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

	@Override
	public boolean onTouchEvent(MotionEvent event) {
		if (mVelocityTracker == null) {
			mVelocityTracker = VelocityTracker.obtain();
		}

		mVelocityTracker.addMovement(event);

		final int action = event.getAction();
		final float x = event.getX();
		final float y = event.getY();

		switch (action) {
		case MotionEvent.ACTION_DOWN:
			Log.e(TAG, "event down!");
			if (!mScroller.isFinished()) {
				mScroller.abortAnimation();
			}
			mLastMotionX = x;
			break;
		case MotionEvent.ACTION_MOVE:
			int deltaX = (int) (mLastMotionX - x);
			mLastMotionX = x;
			scrollBy(deltaX, 0);
			break;
		case MotionEvent.ACTION_UP:
			Log.e(TAG, "event : up");
			// if (mTouchState == TOUCH_STATE_SCROLLING) {
			final VelocityTracker velocityTracker = mVelocityTracker;
			velocityTracker.computeCurrentVelocity(1000);
			int velocityX = (int) velocityTracker.getXVelocity();
			Log.e(TAG, "velocityX:" + velocityX);

			if (velocityX > SNAP_VELOCITY && mCurScreen > 0) {
				// Fling enough to move left
				Log.e(TAG, "snap left");
				snapToScreen(mCurScreen - 1);
			} else if (velocityX < -SNAP_VELOCITY
					&& mCurScreen < getChildCount() - 1) {
				// Fling enough to move right
				Log.e(TAG, "snap right");
				snapToScreen(mCurScreen + 1);
			} else {
				snapToDestination();
			}
			// if (velocityX > SNAP_VELOCITY && mCurScreen > 0) {
			//
			// // Fling enough to move left
			//
			// Log.e(TAG, "snap left");
			// if (mCurScreen > getChildCount() - 1) {
			// View v1 = getChildAt(0);
			// View v2 = getChildAt(1);
			// View v3 = getChildAt(2);
			//
			// }
			// snapToScreen(mCurScreen - 1);
			//
			// } else if (velocityX < -SNAP_VELOCITY
			//
			// && mCurScreen < getChildCount() - 1) {
			//
			// // Fling enough to move right
			//
			// Log.e(TAG, "snap right");
			//
			// snapToScreen(mCurScreen + 1);
			//
			// } else {
			//
			// snapToDestination();
			//
			// }
			//
			// if (mVelocityTracker != null) {
			//
			// mVelocityTracker.recycle();
			//
			// mVelocityTracker = null;
			//
			// }
			// }
			mTouchState = TOUCH_STATE_REST;
			break;
		case MotionEvent.ACTION_CANCEL:
			mTouchState = TOUCH_STATE_REST;
			break;
		}
		return true;
	}

	@Override
	public boolean onInterceptTouchEvent(MotionEvent ev) {
		Log.e(TAG, "onInterceptTouchEvent-slop:" + mTouchSlop + "; action = "
				+ ev.getAction());
		final int action = ev.getAction();

		if ((action == MotionEvent.ACTION_MOVE)
				&& (mTouchState != TOUCH_STATE_REST)) {
			Log.e(TAG, "onInterceptTouchEvent-action:" + action);
			return true;
		}

		final float x = ev.getX();
		final float y = ev.getY();

		switch (action) {
		case MotionEvent.ACTION_MOVE:
			final int xDiff = (int) Math.abs(mLastMotionX - x);
			Log.e(TAG, "onInterceptTouchEvent-move: xDiff = " + xDiff
					+ "; mLastMotionX = " + mLastMotionX);
			if (xDiff > mTouchSlop) {
				mTouchState = TOUCH_STATE_SCROLLING;
			}
			break;
		case MotionEvent.ACTION_DOWN:
			mLastMotionX = x;
			mLastMotionY = y;
			Log.e(TAG, "onInterceptTouchEvent-down: x = " + x + "; y = " + y);
			mTouchState = mScroller.isFinished() ? TOUCH_STATE_REST
					: TOUCH_STATE_SCROLLING;
			break;
		case MotionEvent.ACTION_CANCEL:
		case MotionEvent.ACTION_UP:
			Log.e(TAG, "onInterceptTouchEvent-up: mLastMotionX = "
					+ mLastMotionX);
			mTouchState = TOUCH_STATE_REST;
			break;
		}
		return mTouchState != TOUCH_STATE_REST;
	}

}