CoordinatorLayout.Behavior自定義效果的實現

先看一張效果圖，要做什麼就比較清晰了：

實現思路：

1.首先自定義一個View包括頭部和列表

2.給自定義View添加注解，也就是默認使用自定義的BehaviorLayoutBehavior

 

@CoordinatorLayout.DefaultBehavior(BehaviorLayoutBehavior.class)

3.自定義BehaviorLayoutBehavior

 

BehaviorLayoutBehavior extends CoordinatorLayout.Behavior

4.關鍵的兩個方法是：

onMeasureChild, onLayoutChild

 

        public boolean onMeasureChild(CoordinatorLayout parent, V child,
                int parentWidthMeasureSpec, int widthUsed,
                int parentHeightMeasureSpec, int heightUsed) {
            return false;
        }

        public boolean onLayoutChild(CoordinatorLayout parent, V child, int layoutDirection) {
            return false;
        }

 

 

onMeasureChild用來測量子布局

onLayoutChild用來擺放子布局

 

    @Override
    public boolean onMeasureChild(CoordinatorLayout parent, BehaviorLayout child, int parentWidthMeasureSpec, int widthUsed, int parentHeightMeasureSpec, int heightUsed) {
        Log.i(TAG, "onMeasureChild: ");
        //測繪子控件
        //獲取子控件的偏移量
        int offset = getChildMeasureOffset(parent, child);
        //計算子控件的最大高度
        int measureHeight = View.MeasureSpec.getSize(parentHeightMeasureSpec) - offset - heightUsed;
        //生成MeasureSpec
        int heightMeasureSpec = View.MeasureSpec.makeMeasureSpec(measureHeight, View.MeasureSpec.EXACTLY);
        //測量
        child.measure(parentWidthMeasureSpec, heightMeasureSpec);
        return true;
    }

    //獲取子控件y方向偏移量
    private int getChildMeasureOffset(CoordinatorLayout parent, BehaviorLayout child) {
        int offset = 0;
        for(int i = 0; i < parent.getChildCount(); i++){
            View view = parent.getChildAt(i);
            if(view != child && view instanceof BehaviorLayout){
                offset += ((BehaviorLayout) view).getHeaderHeight();
            }
        }
        return offset;
    }

    @Override
    public boolean onLayoutChild(CoordinatorLayout parent, BehaviorLayout child, int layoutDirection) {
        Log.i(TAG, "onLayoutChild: ");
        //先按照默認擺放,然後自己控制
        parent.onLayoutChild(child, layoutDirection);
        BehaviorLayout preView = getPreViewChild(parent, child);
        int offset = 0;
        if(preView != null){
            offset = preView.getTop() + preView.getHeaderHeight();
        }
        //控制View距離頂部的距離
        child.offsetTopAndBottom(offset);
        //每個child都會離頂部有一個初始高度
        mInitialOffset = child.getTop();
        return true;
    }

    //獲取前面的view
    private BehaviorLayout getPreViewChild(CoordinatorLayout parent, BehaviorLayout child) {
        int childIndex = parent.indexOfChild(child);
        for(int i = childIndex - 1; i >= 0; i--){
            View view = parent.getChildAt(i);
            if(view instanceof BehaviorLayout){
                return (BehaviorLayout) view;
            }
        }
        return null;
    }


    //獲取後面的view
    private BehaviorLayout getNextChild(CoordinatorLayout parent, View child) {
        int cardIndex = parent.indexOfChild(child);
        for (int i = cardIndex + 1; i < parent.getChildCount(); i++) {
            View view = parent.getChildAt(i);
            if(view instanceof BehaviorLayout){
                return (BehaviorLayout) view;
            }
        }
        return null;
    }

5.測量擺放好了以後，接下來就是滑動事件的處理

 

滾動時執行順序是：onStartNestedScroll->onNestedPreScroll->onNestedScroll可以參考文章開始推薦的兩篇文章。

 

    @Override
    public boolean onStartNestedScroll(CoordinatorLayout coordinatorLayout, BehaviorLayout child, View directTargetChild, View target, int nestedScrollAxes) {
        Log.i(TAG, "onStartNestedScroll: ");
        //是否需要監聽滑動(水平,垂直)
        boolean isVertical = ((nestedScrollAxes & ViewCompat.SCROLL_AXIS_VERTICAL) != 0);
        return isVertical && child == directTargetChild;
    }

    @Override
    public void onNestedPreScroll(CoordinatorLayout coordinatorLayout, BehaviorLayout child, View target, int dx, int dy, int[] consumed) {
        Log.i(TAG, "onNestedPreScroll: " + dy);
        boolean show = dy < 0 && !ViewCompat.canScrollVertically(target, -1);
        boolean hide = dy > 0;
        if(child.getTop() >= mInitialOffset){
            if(hide || show) {//如果向上滾動,或者(向下滾動並且列表不能滑動)
                scroll(child, dy, mInitialOffset, mInitialOffset + child.getHeight() - child.getHeaderHeight());

                //下面獲取前面還是後面,為了保持聯動效果
                BehaviorLayout preView = getPreViewChild(coordinatorLayout, child);
                if (preView != null && preView.getTop() + child.getHeaderHeight() > child.getTop()) {
                    preView.offsetTopAndBottom(child.getTop() - preView.getHeaderHeight() - preView.getTop());
                }
                BehaviorLayout nextChild = getNextChild(coordinatorLayout, child);
                if (nextChild != null && nextChild.getTop() - child.getHeaderHeight() < child.getTop()) {
                    nextChild.offsetTopAndBottom(child.getTop() + child.getHeaderHeight() - nextChild.getTop());
                }
            }
        }
    }

    @Override
    public void onNestedScroll(CoordinatorLayout coordinatorLayout, BehaviorLayout child, View target, int dxConsumed, int dyConsumed, int dxUnconsumed, int dyUnconsumed) {
        Log.i(TAG, "onNestedScroll: ");
    }

    /**
     * 得到child滑動距離
     * @param child
     * @param dyConsumed
     * @param minOffset 最小偏移量
     * @param maxOffset 最大偏移量
     * @return
     */
    private int scroll(BehaviorLayout child, int dyConsumed, int minOffset, int maxOffset) {
        int initialOffset = child.getTop();
        //a在此范圍[minOffset, maxOffset], delta為移動距離
        int delta = clamp(initialOffset - dyConsumed, minOffset, maxOffset) - initialOffset;
        child.offsetTopAndBottom(delta);
        return delta;
    }

    //邊界檢查
    private int clamp(int i, int minOffset, int maxOffset) {
        if(i > maxOffset){
            return maxOffset;
        }

        if(i < minOffset){
            return minOffset;
        }

        return i;
    }

 

 

 

 

源碼：

1.layout布局：

 

2.BehaviorLayout

 

 

package com.test.git.coordinatorlayout.View;

import android.content.Context;
import android.support.design.widget.CoordinatorLayout;
import android.support.v7.widget.LinearLayoutManager;
import android.support.v7.widget.RecyclerView;
import android.util.AttributeSet;
import android.view.LayoutInflater;
import android.view.View;
import android.widget.FrameLayout;

import com.test.git.coordinatorlayout.Adapter.TestAdapter;
import com.test.git.coordinatorlayout.Behavior.BehaviorLayoutBehavior;
import com.test.git.coordinatorlayout.R;

import java.util.ArrayList;
import java.util.List;

/**
 * Created by lk on 16/9/7.
 */
@CoordinatorLayout.DefaultBehavior(BehaviorLayoutBehavior.class)
public class BehaviorLayout extends FrameLayout {
    private final View tv_header;
    private int mHeaderViewHeight;
    public BehaviorLayout(Context context) {
        this(context, null);
    }

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

    public BehaviorLayout(Context context, AttributeSet attrs, int defStyleAttr) {
        super(context, attrs, defStyleAttr);
        View view =  LayoutInflater.from(context).inflate(R.layout.item_header_recycler, null);
        tv_header = view.findViewById(R.id.tv_header);
        RecyclerView mRecyclerView = (RecyclerView) view.findViewById(R.id.mRecyclerView);
        //添加布局管理器
        LinearLayoutManager mLinearLayoutManager = new LinearLayoutManager(context);
        mRecyclerView.setLayoutManager(mLinearLayoutManager);
        //初始化數據
        List mMessages = new ArrayList<>();
        for(int i = 0; i < 20; i ++){
            mMessages.add("" + i);
        }
        TestAdapter mAdapter = new TestAdapter(context, mMessages, R.layout.item_text);
        mRecyclerView.setAdapter(mAdapter);
        addView(view);
    }

    @Override
    protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
        super.onMeasure(widthMeasureSpec, heightMeasureSpec);
    }

    @Override
    protected void onLayout(boolean changed, int left, int top, int right, int bottom) {
        super.onLayout(changed, left, top, right, bottom);
    }

    @Override
    protected void onSizeChanged(int w, int h, int oldw, int oldh) {
        super.onSizeChanged(w, h, oldw, oldh);
        if(h != oldh || w != oldw) {
            mHeaderViewHeight = tv_header.getMeasuredHeight();
        }
    }

    //獲取頭部高度
    public int getHeaderHeight(){
        return mHeaderViewHeight;
    }

}

3.BehaviorLayoutBehavior

 

 

package com.test.git.coordinatorlayout.Behavior;

import android.support.design.widget.CoordinatorLayout;
import android.support.v4.view.ViewCompat;
import android.util.Log;
import android.view.View;

import com.test.git.coordinatorlayout.View.BehaviorLayout;

/**
 * Created by lk on 16/9/7.
 */
public class BehaviorLayoutBehavior extends CoordinatorLayout.Behavior {

    private int mInitialOffset;
    private static final String TAG = "BehaviorLayoutBehavior";

    @Override
    public boolean onMeasureChild(CoordinatorLayout parent, BehaviorLayout child, int parentWidthMeasureSpec, int widthUsed, int parentHeightMeasureSpec, int heightUsed) {
        Log.i(TAG, "onMeasureChild: ");
        //測繪子控件
        //獲取子控件的偏移量
        int offset = getChildMeasureOffset(parent, child);
        //計算子控件的最大高度
        int measureHeight = View.MeasureSpec.getSize(parentHeightMeasureSpec) - offset - heightUsed;
        //生成MeasureSpec
        int heightMeasureSpec = View.MeasureSpec.makeMeasureSpec(measureHeight, View.MeasureSpec.EXACTLY);
        //測量
        child.measure(parentWidthMeasureSpec, heightMeasureSpec);
        return true;
    }

    //獲取子控件y方向偏移量
    private int getChildMeasureOffset(CoordinatorLayout parent, BehaviorLayout child) {
        int offset = 0;
        for(int i = 0; i < parent.getChildCount(); i++){
            View view = parent.getChildAt(i);
            if(view != child && view instanceof BehaviorLayout){
                offset += ((BehaviorLayout) view).getHeaderHeight();
            }
        }
        return offset;
    }

    @Override
    public boolean onLayoutChild(CoordinatorLayout parent, BehaviorLayout child, int layoutDirection) {
        Log.i(TAG, "onLayoutChild: ");
        //先按照默認擺放,然後自己控制
        parent.onLayoutChild(child, layoutDirection);
        BehaviorLayout preView = getPreViewChild(parent, child);
        int offset = 0;
        if(preView != null){
            offset = preView.getTop() + preView.getHeaderHeight();
        }
        //控制View距離頂部的距離
        child.offsetTopAndBottom(offset);
        //每個child都會離頂部有一個初始高度
        mInitialOffset = child.getTop();
        return true;
    }

    //獲取前面的view
    private BehaviorLayout getPreViewChild(CoordinatorLayout parent, BehaviorLayout child) {
        int childIndex = parent.indexOfChild(child);
        for(int i = childIndex - 1; i >= 0; i--){
            View view = parent.getChildAt(i);
            if(view instanceof BehaviorLayout){
                return (BehaviorLayout) view;
            }
        }
        return null;
    }


    //獲取後面的view
    private BehaviorLayout getNextChild(CoordinatorLayout parent, View child) {
        int cardIndex = parent.indexOfChild(child);
        for (int i = cardIndex + 1; i < parent.getChildCount(); i++) {
            View view = parent.getChildAt(i);
            if(view instanceof BehaviorLayout){
                return (BehaviorLayout) view;
            }
        }
        return null;
    }

    @Override
    public boolean onStartNestedScroll(CoordinatorLayout coordinatorLayout, BehaviorLayout child, View directTargetChild, View target, int nestedScrollAxes) {
        Log.i(TAG, "onStartNestedScroll: ");
        //是否需要監聽滑動(水平,垂直)
        boolean isVertical = ((nestedScrollAxes & ViewCompat.SCROLL_AXIS_VERTICAL) != 0);
        return isVertical && child == directTargetChild;
    }

    @Override
    public void onNestedPreScroll(CoordinatorLayout coordinatorLayout, BehaviorLayout child, View target, int dx, int dy, int[] consumed) {
        Log.i(TAG, "onNestedPreScroll: " + dy);
        boolean show = dy < 0 && !ViewCompat.canScrollVertically(target, -1);
        boolean hide = dy > 0;
        if(child.getTop() >= mInitialOffset){
            if(hide || show) {//如果向上滾動,或者(向下滾動並且列表不能滑動)
                scroll(child, dy, mInitialOffset, mInitialOffset + child.getHeight() - child.getHeaderHeight());

                //下面獲取前面還是後面,為了保持聯動效果
                BehaviorLayout preView = getPreViewChild(coordinatorLayout, child);
                if (preView != null && preView.getTop() + child.getHeaderHeight() > child.getTop()) {
                    preView.offsetTopAndBottom(child.getTop() - preView.getHeaderHeight() - preView.getTop());
                }
                BehaviorLayout nextChild = getNextChild(coordinatorLayout, child);
                if (nextChild != null && nextChild.getTop() - child.getHeaderHeight() < child.getTop()) {
                    nextChild.offsetTopAndBottom(child.getTop() + child.getHeaderHeight() - nextChild.getTop());
                }
            }
        }
    }

    @Override
    public void onNestedScroll(CoordinatorLayout coordinatorLayout, BehaviorLayout child, View target, int dxConsumed, int dyConsumed, int dxUnconsumed, int dyUnconsumed) {
        Log.i(TAG, "onNestedScroll: ");
    }

    /**
     * 得到child滑動距離
     * @param child
     * @param dyConsumed
     * @param minOffset 最小偏移量
     * @param maxOffset 最大偏移量
     * @return
     */
    private int scroll(BehaviorLayout child, int dyConsumed, int minOffset, int maxOffset) {
        int initialOffset = child.getTop();
        //a在此范圍[minOffset, maxOffset], delta為移動距離
        int delta = clamp(initialOffset - dyConsumed, minOffset, maxOffset) - initialOffset;
        child.offsetTopAndBottom(delta);
        return delta;
    }

    //邊界檢查
    private int clamp(int i, int minOffset, int maxOffset) {
        if(i > maxOffset){
            return maxOffset;
        }

        if(i < minOffset){
            return minOffset;
        }

        return i;
    }


    @Override
    public boolean onNestedPreFling(CoordinatorLayout coordinatorLayout, BehaviorLayout child, View target, float velocityX, float velocityY) {
        return super.onNestedPreFling(coordinatorLayout, child, target, velocityX, velocityY);
    }

    @Override
    public boolean onNestedFling(CoordinatorLayout coordinatorLayout, BehaviorLayout child, View target, float velocityX, float velocityY, boolean consumed) {
        return super.onNestedFling(coordinatorLayout, child, target, velocityX, velocityY, consumed);
    }
}

源碼地址：點擊打開鏈接