自定義ViewGroup 實現拖動跟快速滾動的效果

之前做到個項目要類似listView或者GridView中的控件移動的效果（主屏上所有程序列表上的效果）：
1：子控件跟着手指移動
2：快速撥動一下，根據撥動的速度 滑動過去
3：拖過頭，放手後彈回去

但是用listView或者GridView又不好實現項目要求的其他效果..於是繼承viewGroup實現以上效果。

既然要獲取撥動速度，並以此滑動。首先想到了OnGestureListener 這個接口，實現這個接口並實現其onFling方法.

還要控制拖動。重寫onTouchEvent方法，並在其中控制內容控件的拖動，反彈等效果

這時候基本已經完成了。。。。測試了一下了，發現了一個問題，當手指點在viewGroup上

進行 拖動是沒問題的，但是在子控件上就不行了，這是事件響應的問題 那麼還要做如面的處

理:實現onInterceptTouchEvent方法，判斷是拖動事件時 ，將事件傳遞下去。

package com.android.moveViewGroup;

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

public class MoveViewGroupActivity extends Activity {
    /** Called when the activity is first created. */
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(new Workspace(this));
    }
}

package com.android.moveViewGroup;

import android.content.Context;
import android.view.View;
import android.view.ViewGroup;

public class Workspace extends ViewGroup {

	public Workspace(Context context) {
		super(context);
		// TODO Auto-generated constructor stub
		addView(new MyViewGroup(context));
	}

	@Override
	protected void onLayout(boolean changed, int l, int t, int r, int b) {
		// TODO Auto-generated method stub
		final int count = getChildCount();
		for (int i = 0; i < count; i++) {
			final View child = getChildAt(i);
			child.measure(r - l, b - t);
			child.layout(0, 0, 320, 480);
		}
	}

}

package com.android.moveViewGroup;


import java.util.List;
import android.content.Context;
import android.graphics.Color;
import android.util.Log;
import android.view.GestureDetector;
import android.view.MotionEvent;
import android.view.View;
import android.view.ViewConfiguration;
import android.view.ViewGroup;
import android.view.GestureDetector.OnGestureListener;
import android.widget.Button;
import android.widget.Scroller;
import android.widget.Toast;


public class MyViewGroup extends ViewGroup implements OnGestureListener {

	private float mLastMotionY;// 最後點擊的點
	private GestureDetector detector;
	int move = 0;// 移動距離
	int MAXMOVE = 850;// 最大允許的移動距離
	private Scroller mScroller;
	int up_excess_move = 0;// 往上多移的距離
	int down_excess_move = 0;// 往下多移的距離
	private final static int TOUCH_STATE_REST = 0;
	private final static int TOUCH_STATE_SCROLLING = 1;
	private int mTouchSlop;
	private int mTouchState = TOUCH_STATE_REST;
	Context mContext;
	

	public MyViewGroup(Context context) {
		super(context);
		mContext = context;
		// TODO Auto-generated constructor stub
		//setBackgroundResource(R.drawable.pic);
		mScroller = new Scroller(context);
		detector = new GestureDetector(this);

		final ViewConfiguration configuration = ViewConfiguration.get(context);
		// 獲得可以認爲是滾動的距離
		mTouchSlop = configuration.getScaledTouchSlop();

		// 添加子View
		for (int i = 0; i < 48; i++) {
			final Button MButton = new Button(context);
			MButton.setText("" + (i + 1));
			MButton.setOnClickListener(new OnClickListener() {
				
				public void onClick(View v) {
					// TODO Auto-generated method stub
					Toast.makeText(mContext, MButton.getText(), Toast.LENGTH_SHORT).show(); 
				}
			});
			addView(MButton);
		}
	}

	@Override
	public void computeScroll() {
		if (mScroller.computeScrollOffset()) {
			// 返回當前滾動X方向的偏移
			scrollTo(0, mScroller.getCurrY());
			postInvalidate();
		}
	}

	@Override
	public boolean onInterceptTouchEvent(MotionEvent ev) {
		final int action = ev.getAction();

		final float y = ev.getY();
		switch (ev.getAction())
		{
		case MotionEvent.ACTION_DOWN:

			mLastMotionY = y;
			mTouchState = mScroller.isFinished() ? TOUCH_STATE_REST
					: TOUCH_STATE_SCROLLING;
			break;
		case MotionEvent.ACTION_MOVE:
			final int yDiff = (int) Math.abs(y - mLastMotionY);
			boolean yMoved = yDiff > mTouchSlop;
			// 判斷是否是移動
			if (yMoved) {
				mTouchState = TOUCH_STATE_SCROLLING;
			}
			break;
		case MotionEvent.ACTION_UP:
			mTouchState = TOUCH_STATE_REST;
			break;
		}
		return mTouchState != TOUCH_STATE_REST;
	}

	@Override
	public boolean onTouchEvent(MotionEvent ev) {

		// final int action = ev.getAction();

		final float y = ev.getY();
		switch (ev.getAction())
		{
		case MotionEvent.ACTION_DOWN:
			if (!mScroller.isFinished()) {
				mScroller.forceFinished(true);
				move = mScroller.getFinalY();
			}
			mLastMotionY = y;
			break;
		case MotionEvent.ACTION_MOVE:
			if (ev.getPointerCount() == 1) {
				
				// 隨手指 拖動的代碼
				int deltaY = 0;
				deltaY = (int) (mLastMotionY - y);
				mLastMotionY = y;
				Log.d("move", "" + move);
				if (deltaY < 0) {
					// 下移
					// 判斷上移 是否滑過頭
					if (up_excess_move == 0) {
						if (move > 0) {
							int move_this = Math.max(-move, deltaY);
							move = move + move_this;
							scrollBy(0, move_this);
						} else if (move == 0) {// 如果已經是最頂端 繼續往下拉
							Log.d("down_excess_move", "" + down_excess_move);
							down_excess_move = down_excess_move - deltaY / 2;// 記錄下多往下拉的值
							scrollBy(0, deltaY / 2);
						}
					} else if (up_excess_move > 0)// 之前有上移過頭
					{					
						if (up_excess_move >= (-deltaY)) {
							up_excess_move = up_excess_move + deltaY;
							scrollBy(0, deltaY);
						} else {						
							up_excess_move = 0;
							scrollBy(0, -up_excess_move);				
						}
					}
				} else if (deltaY > 0) {
					// 上移
					if (down_excess_move == 0) {
						if (MAXMOVE - move > 0) {
							int move_this = Math.min(MAXMOVE - move, deltaY);
							move = move + move_this;
							scrollBy(0, move_this);
						} else if (MAXMOVE - move == 0) {
							if (up_excess_move <= 100) {
								up_excess_move = up_excess_move + deltaY / 2;
								scrollBy(0, deltaY / 2);
							}
						}
					} else if (down_excess_move > 0) {
						if (down_excess_move >= deltaY) {
							down_excess_move = down_excess_move - deltaY;
							scrollBy(0, deltaY);
						} else {
							down_excess_move = 0;
							scrollBy(0, down_excess_move);
						}
					}
				}		
			} 
			break;
		case MotionEvent.ACTION_UP:			
			// 多滾是負數 記錄到move裏
			if (up_excess_move > 0) {
				// 多滾了 要彈回去
				scrollBy(0, -up_excess_move);
				invalidate();
				up_excess_move = 0;
			}
			if (down_excess_move > 0) {
				// 多滾了 要彈回去
				scrollBy(0, down_excess_move);
				invalidate();
				down_excess_move = 0;
			}
			mTouchState = TOUCH_STATE_REST;
			break;
		}
		return this.detector.onTouchEvent(ev);
	}

	int Fling_move = 0;

	public boolean onFling(MotionEvent e1, MotionEvent e2, float velocityX,
			float velocityY) {
		 //隨手指 快速撥動的代碼
		Log.d("onFling", "onFling");
		if (up_excess_move == 0 && down_excess_move == 0) {

			int slow = -(int) velocityY * 3 / 4;
			mScroller.fling(0, move, 0, slow, 0, 0, 0, MAXMOVE);
			move = mScroller.getFinalY();
			computeScroll();
		}
		return false;
	}

	public boolean onDown(MotionEvent e) {
		// TODO Auto-generated method stub
		return true;
	}

	public boolean onScroll(MotionEvent e1, MotionEvent e2, float distanceX,
			float distanceY) {
		return false;
	}

	public void onShowPress(MotionEvent e) {
		// // TODO Auto-generated method stub
	}

	public boolean onSingleTapUp(MotionEvent e) {
		// TODO Auto-generated method stub
		return false;
	}

	public void onLongPress(MotionEvent e) {
		// TODO Auto-generated method stub
	}

	@Override
	protected void onLayout(boolean changed, int l, int t, int r, int b) {
		// TODO Auto-generated method stub
		int childTop = 0;
		int childLeft = 0;
		final int count = getChildCount();
		for (int i = 0; i < count; i++) {
			final View child = getChildAt(i);
			if (child.getVisibility() != View.GONE) {
				child.setVisibility(View.VISIBLE);
				child.measure(r - l, b - t);
				child.layout(childLeft, childTop, childLeft + 80,
								childTop + 80);
				if (childLeft < 160) {
					childLeft += 80;
				} else {
					childLeft = 0;
					childTop += 80;
				}
			}
		}
	}

}