PullToZoomListView改进+中文注释

PullToZoomListView.java

package com.matrixxun.pulltozoomlistsimple;

import android.content.Context;
import android.os.SystemClock;
import android.util.AttributeSet;
import android.util.DisplayMetrics;
import android.util.Log;
import android.view.MotionEvent;
import android.view.ViewGroup;
import android.view.WindowManager;
import android.view.animation.Interpolator;
import android.widget.AbsListView;
import android.widget.ImageView;
import android.widget.ImageView.ScaleType;
import android.widget.ListView;
import android.widget.RelativeLayout;

public class PullToZoomListView extends ListView implements
		AbsListView.OnScrollListener {
	private static final String TAG = PullToZoomListView.class.getSimpleName();
	/** 无效值 */
	private static final int INVALID_VALUE = -1;
	// 自定义的插值器
	private static final Interpolator sInterpolator = new Interpolator() {
		public float getInterpolation(float fraction) {
			float f = fraction - 1.0F;
			return 1.0F + f * (f * (f * (f * f)));
		}
	};
	private int mActivePointerId = INVALID_VALUE;
	/** 头部View容器 */
	private RelativeLayout mHeaderContainer;
	/** 头部View的高度 */
	private int mHeaderHeight;
	/** 头部View里的图片视图 */
	private ImageView mHeaderImage;
	private float mLastMotionY = INVALID_VALUE;
	private float mLastScale = INVALID_VALUE;
	private float mMaxScale = INVALID_VALUE;
	private float mHeaderScrollSpeed = 1f;
	private AbsListView.OnScrollListener mOnScrollListener;
	private ScalingRunnalable mScalingRunnalable;
	/** 屏幕高度 */
	private int mScreenHeight;
	private ImageView mShadow;

	public PullToZoomListView(Context context) {
		super(context);
		init(context);
	}

	public PullToZoomListView(Context context, AttributeSet paramAttributeSet) {
		super(context, paramAttributeSet);
		init(context);
	}

	public PullToZoomListView(Context context, AttributeSet paramAttributeSet,
			int paramInt) {
		super(context, paramAttributeSet, paramInt);
		init(context);
	}

	private void endScraling() {
		if (this.mHeaderContainer.getBottom() >= this.mHeaderHeight) {
			Log.d(TAG, "endScraling");
		}
		this.mScalingRunnalable.startAnimation(200L);
	}

	private void init(Context context) {
		// 获取屏幕高度
		DisplayMetrics localDisplayMetrics = new DisplayMetrics();
		((WindowManager) context.getSystemService(Context.WINDOW_SERVICE))
				.getDefaultDisplay().getMetrics(localDisplayMetrics);
		this.mScreenHeight = localDisplayMetrics.heightPixels;

		// 生成头部View
		this.mHeaderContainer = new RelativeLayout(context);
		this.mHeaderImage = new ImageView(context);

		// 获得屏幕宽度
		int i = localDisplayMetrics.widthPixels;
		// 设置头部View的宽高
		setHeaderViewSize(i, (int) (9.0F * (i / 16.0F)));

		// 生成阴影视图
		// this.mShadow = new ImageView(context);
		// FrameLayout.LayoutParams shadowLp = new FrameLayout.LayoutParams(
		// FrameLayout.LayoutParams.MATCH_PARENT,
		// FrameLayout.LayoutParams.WRAP_CONTENT);
		// shadowLp.gravity = 80;
		// this.mShadow.setLayoutParams(shadowLp);

		// 将图片和阴影视图添加到头部View容器
		RelativeLayout.LayoutParams params = new RelativeLayout.LayoutParams(
				RelativeLayout.LayoutParams.MATCH_PARENT,
				RelativeLayout.LayoutParams.MATCH_PARENT);
		params.topMargin = 0;
		this.mHeaderContainer.addView(this.mHeaderImage, params);
		// this.mHeaderContainer.addView(this.mShadow);

		// 将头部View添加到ListView里
		addHeaderView(this.mHeaderContainer);

		this.mScalingRunnalable = new ScalingRunnalable();

		// 设置滑动监听
		super.setOnScrollListener(this);
	}

	private void onSecondaryPointerUp(MotionEvent ev) {
		int i = ev.getActionIndex();
		if (ev.getPointerId(i) == this.mActivePointerId) {
			if (i != 0) {
				this.mLastMotionY = ev.getY(0);
				this.mActivePointerId = ev.getPointerId(0);
				return;
			}
		}
	}

	/**
	 * 重置头部View缩放相关的参数
	 */
	private void reset() {
		this.mActivePointerId = INVALID_VALUE;
		this.mLastMotionY = INVALID_VALUE;
		this.mMaxScale = INVALID_VALUE;
		this.mLastScale = INVALID_VALUE;
	}

	public ImageView getHeaderView() {
		return this.mHeaderImage;
	}

	@Override
	protected void onLayout(boolean changed, int l, int t, int r, int b) {
		super.onLayout(changed, l, t, r, b);
		if (this.mHeaderHeight == 0) {
			// 记录头部View正常大小时的高度
			this.mHeaderHeight = this.mHeaderContainer.getHeight();
		}
	}

	@Override
	public void onScroll(AbsListView view, int firstVisibleItem,
			int visibleItemCount, int totalItemCount) {
		Log.d("test", "onScroll()");
		float space = this.mHeaderHeight - this.mHeaderContainer.getBottom();
		Log.d(TAG, "onScroll()->Header scrolled space:" + space);
		if ((space > 0.0F) && (space < this.mHeaderHeight)) {
			int i = (int) (mHeaderScrollSpeed * space);
			this.mHeaderImage.scrollTo(0, -i);
		} else if (this.mHeaderImage.getScrollY() != 0) {
			this.mHeaderImage.scrollTo(0, 0);
		}
		if (this.mOnScrollListener != null) {
			this.mOnScrollListener.onScroll(view, firstVisibleItem,
					visibleItemCount, totalItemCount);
		}
	}

	public void onScrollStateChanged(AbsListView paramAbsListView, int paramInt) {
		if (this.mOnScrollListener != null) {
			this.mOnScrollListener.onScrollStateChanged(paramAbsListView,
					paramInt);
		}
	}

	@Override
	public boolean onTouchEvent(MotionEvent ev) {
		// 过滤掉多点触控的触控点信息(Action的高八位)，获取触摸事件类型(Action的低八位)
		int actionMasked = ev.getActionMasked();
		switch (actionMasked) {
		case MotionEvent.ACTION_OUTSIDE:
			// 用户触碰超出了正常的UI边界
		case MotionEvent.ACTION_DOWN:
			// 用户开始触摸
			Log.d(TAG, "onTouchEvent()->ACTION_DOWN or ACTION_OUTSIDE");
			if (!this.mScalingRunnalable.mIsFinished) {
				this.mScalingRunnalable.abortAnimation();
			}
			// 记录开始触摸时的y坐标
			this.mLastMotionY = ev.getY();
			// 记录第一个有效触摸的手指的id
			this.mActivePointerId = ev.getPointerId(0);
			// 记录头部View最大的放大比例
			this.mMaxScale = (this.mScreenHeight / this.mHeaderHeight);
			// 记录开始触摸时头部View已经缩放的比例
			this.mLastScale = (this.mHeaderContainer.getBottom() / this.mHeaderHeight);
			break;
		case MotionEvent.ACTION_MOVE:
			// 用户在移动(手指或者其他)
			Log.d(TAG, "onTouchEvent()->ACTION_MOVE");
			Log.d(TAG, "mActivePointerId" + mActivePointerId);
			// 记录第一个有效触摸手指的索引
			int pointerIndex = ev.findPointerIndex(this.mActivePointerId);
			// 检查手指索引的有效性
			if (pointerIndex == INVALID_VALUE) {
				// 无效的手指指针索引
				Log.e(TAG, "Invalid pointerId=" + this.mActivePointerId
						+ " in onTouchEvent");
			} else {// 有效的手指指针索引
				// 确保滑动时滑动前的y坐标记录正确
				if (this.mLastMotionY == INVALID_VALUE) {
					this.mLastMotionY = ev.getY(pointerIndex);
				}
				// 如果头部达到放大标准或者已经放大（头容器的底部坐标达到或者超出了正常大小的高度），就处理放大头部View逻辑
				// if (this.mHeaderContainer.getBottom() >= this.mHeaderHeight)
				// {
				// 获取头容器当前布局参数
				ViewGroup.LayoutParams hlp = this.mHeaderContainer
						.getLayoutParams();
				// 计算新的缩放比例
				float newScale = ((ev.getY(pointerIndex) - this.mLastMotionY + this.mHeaderContainer
						.getBottom()) / this.mHeaderHeight - this.mLastScale)
						/ 2.0F + this.mLastScale;
				// 如果上一次的缩放比正常比例要小，并且新的缩放比也小于上一次的缩放比
				// XXX 为什么新的缩放比也小于上一次的缩放比？
				if ((this.mLastScale <= 1.0f)) {
					mHeaderImage.setScaleType(ScaleType.FIT_CENTER);
					// // 那就恢复正常大小
					// hlp.height = this.mHeaderHeight;
					// this.mHeaderContainer.setLayoutParams(hlp);
					// // 调用父类方法处理onScroll事件
					// return super.onTouchEvent(ev);
					newScale = (mHeaderContainer.getBottom() + (ev
							.getY(pointerIndex) - this.mLastMotionY))
							/ this.mHeaderHeight;
					Log.d("test",
							"newScale:"
									+ newScale
									+ ",mHeaderContainer.getBottom():"
									+ mHeaderContainer.getBottom()
									+ ",deltaY:"
									+ (ev.getY(pointerIndex) - this.mLastMotionY)
									+ ",mHeaderHeight:" + mHeaderHeight);
				} else {
					mHeaderImage.setScaleType(ScaleType.CENTER_CROP);
				}
				// 记录最后一次的缩放比
				this.mLastScale = Math.min(Math.max(0, newScale),
						this.mMaxScale);

				// 计算头容器新的高度
				int newHeight = (int) (this.mHeaderHeight * this.mLastScale);
				Log.d("test", "hlp.height:" + hlp.height);
				if (newHeight <= 10) {
					Log.d("test", "newHeight" + newHeight);
					hlp.height = 1;
					this.mHeaderContainer.setLayoutParams(hlp);
					this.mLastScale = 0;
					return true;
				}
				// 新的高度不能超过整个屏幕的高度
				if (newHeight < this.mScreenHeight) {
					// 将新的高度参数应用到头容器上
					// 容器里的布局会自动伸缩
					hlp.height = newHeight;
					this.mHeaderContainer.setLayoutParams(hlp);
				}
				// 记录最后一次手指触摸的y坐标
				this.mLastMotionY = ev.getY(pointerIndex);
				// 消耗掉触摸事件
				Log.d("test", "this.mLastScale" + this.mLastScale);
				if (this.mLastScale <= 0.1) {
					return super.onTouchEvent(ev);
				}
				return true;
				// }
				// this.mLastMotionY = ev.getY(pointerIndex);
			}
			break;
		case MotionEvent.ACTION_UP:
			// 用户抬起了手指
			Log.d(TAG, "onTouchEvent()->ACTION_UP");
			reset();
			endScraling();
			break;
		case MotionEvent.ACTION_CANCEL:
			// 表示手势被取消了
			Log.d(TAG, "onTouchEvent()->ACTION_CANCEL");
			int i = ev.getActionIndex();
			this.mLastMotionY = ev.getY(i);
			this.mActivePointerId = ev.getPointerId(i);
			break;
		case MotionEvent.ACTION_POINTER_DOWN:
			// 有一个非主要的手指按下了.
			Log.d(TAG, "onTouchEvent()->ACTION_POINTER_DOWN");
			onSecondaryPointerUp(ev);
			this.mLastMotionY = ev.getY(ev
					.findPointerIndex(this.mActivePointerId));
			break;
		case MotionEvent.ACTION_POINTER_UP:
			// 一个非主要的手指抬起来了
			Log.d(TAG, "onTouchEvent()->ACTION_POINTER_UP");
			break;
		}
		return super.onTouchEvent(ev);
	}

	/**
	 * 设置头部View的宽、高
	 * 
	 * @param width
	 * @param height
	 */
	public void setHeaderViewSize(int width, int height) {
		Object lp = this.mHeaderContainer.getLayoutParams();
		if (lp == null) {
			lp = new AbsListView.LayoutParams(width, height);
		}
		((ViewGroup.LayoutParams) lp).width = width;
		((ViewGroup.LayoutParams) lp).height = height;
		this.mHeaderContainer.setLayoutParams((ViewGroup.LayoutParams) lp);
		this.mHeaderHeight = height;
	}

	public void setOnScrollListener(
			AbsListView.OnScrollListener paramOnScrollListener) {
		this.mOnScrollListener = paramOnScrollListener;
	}

	public void setShadow(int paramInt) {
		this.mShadow.setBackgroundResource(paramInt);
	}

	private class ScalingRunnalable implements Runnable {
		private long mDuration;
		private boolean mIsFinished = true;
		private float mScale;
		private long mStartTime;

		ScalingRunnalable() {
		}

		public void abortAnimation() {
			this.mIsFinished = true;
		}

		public boolean isFinished() {
			return this.mIsFinished;
		}

		public void run() {
			float scale = 0f;
			ViewGroup.LayoutParams lp = null;
			if ((!this.mIsFinished) && (this.mScale > 1.0D)) {
				// 头部View缩小动画播放开始，已经逝去的时间占总时间的百分比
				float animatedTimePercent = ((float) SystemClock
						.currentThreadTimeMillis() - (float) this.mStartTime)
						/ (float) this.mDuration;
				// 计算缩放量
				scale = this.mScale
						- (this.mScale - 1.0F)
						* PullToZoomListView.sInterpolator
								.getInterpolation(animatedTimePercent);
				lp = PullToZoomListView.this.mHeaderContainer.getLayoutParams();
				if (scale > 1.0F) {
					Log.d(TAG, "ScalingRunnalable->run()-> scale > 1.0");
					// 计算头容器的高度
					lp.height = ((int) (scale * PullToZoomListView.this.mHeaderHeight));
					// 参数应用到头部View上
					PullToZoomListView.this.mHeaderContainer
							.setLayoutParams(lp);
					// 播放动画，不停的更新参数和布局
					PullToZoomListView.this.post(this);
					return;
				}
				// 头部View缩小到原大小时停止缩小动画
				this.mIsFinished = true;
			}
		}

		/**
		 * 以一个动画的过程将头部View缩放到正常的大小
		 * 
		 * @param duration
		 *            动画时长
		 */
		public void startAnimation(long duration) {
			this.mStartTime = SystemClock.currentThreadTimeMillis();
			this.mDuration = duration;
			this.mScale = ((float) (PullToZoomListView.this.mHeaderContainer
					.getBottom()) / PullToZoomListView.this.mHeaderHeight);
			this.mIsFinished = false;
			PullToZoomListView.this.post(this);
		}
	}
}