使用ViewDragHelper实现的DragLayout开门效果

先看一下图，有个直观的了解，向下拖动handle就“开门了”：



此DragLayout继承自LinearLayout，这样使得布局变的简单。
我把最顶部的View叫做HeadView，中间的叫“把手”HandleView，底部的叫ContentView，姑且这样叫着。
只有把手可以拖动，下面的ContentView不可以！
只要给DragLayout设置一个background,就会产生一个渐变显示背后布局的效果。
由于DragLayout继承自LinearLayout，所以背后的布局不属于DragLayout的范畴，
DragLayout只有三部分组成（HeadView，HandleView，ContentView）。
这样就造成了背后的布局不能响应手势事件（点击，拖动等），为什么？（该问题已经解决，见帖子最后部分）
因为使用ViewDragHelper需要重写onTouchEvent方法：

@Override
	public boolean onTouchEvent(MotionEvent ev) {
		mDragHelper.processTouchEvent(ev);
		return true;
	}

此方法必须返回true，消费掉了手势事件，所以背后的View就不会响应事件啦。
有无好办法让背后的View也响应事件？？？
我初步的构想：把背后的View也纳入到DragLayout布局中去，这样DragLayout就不应该继承LinearLayout，最好继承ViewGroup，这样布局的灵活度更高，当然也更繁碎，需要重写onLayout和onMeasure等方法。但至少可以解决背后View不能响应点击事件的问题！（我想应该是这样）

目前只能将就一下，给个初步的DragLayout实现源码：

import android.content.Context;
import android.support.v4.view.MotionEventCompat;
import android.support.v4.view.ViewCompat;
import android.support.v4.widget.ViewDragHelper;
import android.util.AttributeSet;
import android.util.Log;
import android.view.MotionEvent;
import android.view.View;
import android.widget.LinearLayout;

/**
 * 
 * @author pythoner
 * @since 2015-10-23
 *
 */
public class DragLayout extends LinearLayout {

	private ViewDragHelper mDragHelper;
	private View headView,handleView,contentView;//三个控件
	private int headViewHeight,handleViewHeight,contentViewHeight;//三个控件高度
	private boolean isOpen=false;
	public DragLayout(Context context) {
		this(context, null);
	}

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

	public DragLayout(Context context, AttributeSet attrs, int defStyle) {
		super(context, attrs, defStyle);
		mDragHelper = ViewDragHelper.create(this, 1.0f, new DragHelperCallback());
		setOrientation(LinearLayout.VERTICAL);
	}

	@Override
	protected void onFinishInflate() {
		super.onFinishInflate();
		headView = findViewById(R.id.headView);
		handleView = findViewById(R.id.handleView);
		contentView = findViewById(R.id.contentView);
	}
	
	@Override
	protected void onLayout(boolean changed, int l, int t, int r, int b) {
		super.onLayout(changed, l, t, r, b);
	}

	@Override
	protected void onSizeChanged(int w, int h, int oldw, int oldh) {
		super.onSizeChanged(w, h, oldw, oldh);
		headViewHeight = headView.getMeasuredHeight();
		handleViewHeight = handleView.getMeasuredHeight();
		contentViewHeight = contentView.getMeasuredHeight();
	}

	@Override
	public boolean onInterceptTouchEvent(MotionEvent ev) {
		final int action = MotionEventCompat.getActionMasked(ev);
		if (action == MotionEvent.ACTION_CANCEL || action == MotionEvent.ACTION_UP) {
			mDragHelper.cancel();
			return false;
		}
		return mDragHelper.shouldInterceptTouchEvent(ev);
	}

	@Override
	public boolean onTouchEvent(MotionEvent ev) {
		mDragHelper.processTouchEvent(ev);
		return true;
	}

	@Override
	public void computeScroll() {
		super.computeScroll();
		if (mDragHelper.continueSettling(true)) {
			ViewCompat.postInvalidateOnAnimation(this);
		}
	}

	class DragHelperCallback extends ViewDragHelper.Callback {

		@Override
		public boolean tryCaptureView(View child, int pointerId) {
			return child == handleView;//只有把手可以拖拽
		}

		@Override
		public int clampViewPositionVertical(View child, int top, int dy) {
			// final int topBound = getPaddingTop();
			//只在Y方向上可以拖动，且拖动范围介于HeadView之下
			final int topBound = getPaddingTop() + headViewHeight;
			final int bottomBound = getHeight() - handleViewHeight;
			final int newTop = Math.min(Math.max(top, topBound), bottomBound);
			return newTop;
		}

		@Override
		public void onViewReleased(View releasedChild, float xvel, float yvel) {
			super.onViewReleased(releasedChild, xvel, yvel);
			//向下快速滑动或者向下滑动超过一半的ContentView时（慢速拖动的情况）
			if(yvel>0||releasedChild.getY()>headViewHeight+contentViewHeight/2){
				mDragHelper.settleCapturedViewAt((int) handleView.getX(), getHeight() - handleViewHeight);
				if(onScrollListener!=null){
					onScrollListener.onOpen(releasedChild);
				}
				isOpen=true;
			}else{
				mDragHelper.settleCapturedViewAt((int) handleView.getX(), headViewHeight);
				if(onScrollListener!=null){
					onScrollListener.onClose(releasedChild);
				}
				isOpen=false;
			}
			// 需要invalidate()以及结合computeScroll方法一起
			invalidate();
		}

		@Override
		public void onViewPositionChanged(View changedView, int left, int top, int dx, int dy) {
			super.onViewPositionChanged(changedView, left, top, dx, dy);
			headView.setY(headView.getY() - dy);
//			 contentView.setY(contentView.getY()+dy);//此处不能使用setY()，否则拖动不上去了，why?所以采用了变通的layout()改变位置
			contentView.layout(contentView.getLeft(), (int) (contentView.getY() + dy), contentView.getRight(),
					contentView.getBottom());
			float fraction=(top-headViewHeight)*1.00f/contentViewHeight;//滑动位移比率
			getBackground().setAlpha((int)(255*(1-fraction)));//背景根据滑动比率产生渐变效果
			if(onScrollListener!=null){
				onScrollListener.onScroll(changedView,fraction);
			}
		}
		
	}

	public boolean isOpen(){
		return isOpen;
	}
	
	private OnScrollListener onScrollListener;
	
	public void setOnScrollListener(OnScrollListener onScrollListener) {
		this.onScrollListener = onScrollListener;
	}

	interface OnScrollListener{
		void onScroll(View view,float fraction);
		void onOpen(View view);
		void onClose(View view);
	}
}

测试代码：

import android.app.Activity;
import android.os.Bundle;
import android.util.Log;
import android.view.View;
import android.widget.TextView;
import android.widget.Toast;

public class MainActivity extends Activity {

	@Override
	protected void onCreate(Bundle savedInstanceState) {
		super.onCreate(savedInstanceState);
		setContentView(R.layout.activity_main);
		
		DragLayout dragLayout=(DragLayout)findViewById(R.id.dragLayout);
		dragLayout.setOnScrollListener(new DragLayout.OnScrollListener() {
			
			@Override
			public void onScroll(View view, float fraction) {
				// TODO Auto-generated method stub
				
			}
			
			@Override
			public void onOpen(View view) {
				// TODO Auto-generated method stub
				Log.i("tag", "============onOpen============");
			}
			
			@Override
			public void onClose(View view) {
				// TODO Auto-generated method stub
				Log.i("tag", "============onClose============");
			}
		});
		
		TextView tv_head=(TextView)findViewById(R.id.tv_head);
		TextView tv_content=(TextView)findViewById(R.id.tv_content);
		tv_head.setOnClickListener(new View.OnClickListener() {
			
			@Override
			public void onClick(View v) {
				// TODO Auto-generated method stub
				Toast.makeText(MainActivity.this, "tv_head clicked", Toast.LENGTH_SHORT).show();
			}
		});
		tv_content.setOnClickListener(new View.OnClickListener() {
			
			@Override
			public void onClick(View v) {
				// TODO Auto-generated method stub
				Toast.makeText(MainActivity.this, "tv_content clicked", Toast.LENGTH_SHORT).show();
			}
		});
		
	}
}

测试布局：

<FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent" 
    android:background="@android:color/holo_orange_dark"
    >

    <com.example.viewdraghelper.DragLayout
        android:id="@+id/dragLayout"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:background="@android:color/background_dark" >

        <FrameLayout
            android:id="@+id/headView"
            android:layout_width="match_parent"
            android:layout_height="200dp"
            android:background="@android:color/holo_blue_bright" >

            <TextView
                android:id="@+id/tv_head"
                android:layout_width="match_parent"
                android:layout_height="match_parent"
                android:gravity="center"
                android:text="head"
                android:textSize="48sp" />
        </FrameLayout>

        <TextView
            android:id="@+id/handleView"
            android:layout_width="match_parent"
            android:layout_height="64dp"
            android:background="@android:color/holo_blue_dark"
            android:gravity="center"
            android:text="handle" />

        <FrameLayout
            android:id="@+id/contentView"
            android:layout_width="match_parent"
            android:layout_height="match_parent"
            android:background="@android:color/holo_blue_bright"
            android:focusable="false"
            android:focusableInTouchMode="false" >

            <TextView
                android:id="@+id/tv_content"
                android:layout_width="match_parent"
                android:layout_height="match_parent"
                android:gravity="center"
                android:text="content"
                android:textSize="48sp" />
        </FrameLayout>
    </com.example.viewdraghelper.DragLayout>

</FrameLayout>

整体的项目代码我不提供，有这三个就够了我想。


突然发现
解决背后的布局不能响应手势事件的问题很容易解决
只需要使用boolean isViewUnder = mDragHelper.isViewUnder(handleView, (int) x, (int) y);
判断一下就可以了
修改onTouchEvent（）如下：

@Override
	public boolean onTouchEvent(MotionEvent ev) {
		try {
			mDragHelper.processTouchEvent(ev);
		} catch (Exception e) {
			// TODO: handle exception
		}
		final float x = ev.getX();  
	    final float y = ev.getY();
		boolean isViewUnder = mDragHelper.isViewUnder(handleView, (int) x, (int) y); 
		return isViewUnder;
	}

原来很简单的，之前还不知道此方法。

ViewDragHelper.CallBack中每个方法的用法
http://m.blog.csdn.net/blog/coder_nice/44678153


一个可以下滑显示出一个面板的Toolbar。这个library受Drawerlayout的启发，但有别于Drawerlayout显示左右抽屉，这个library会提供下拉toolbar显示一个面板的功能
http://www.jcodecraeer.com/a/opensource/2015/1204/3750.html