add refresh bg view

Author: ToDou

nestrefresh/src/main/java/com/todou/nestrefresh/RefreshBarLayout.kt

@@ -98,6 +98,10 @@ class RefreshBarLayout @JvmOverloads constructor(
         return lastInsets?.systemWindowInsetTop ?: 0
     }
 
+    fun getTopBottomOffset(): Int {
+        return refreshBarBehavior?.getTopAndBottomOffset() ?: 0
+    }
+
     private fun updateAllChildList() {
         childScrollAbleList = getScrollableChild(this)
     }

nestrefresh/src/main/java/com/todou/nestrefresh/RefreshBgView.java

@@ -0,0 +1,138 @@
+package com.todou.nestrefresh;
+
+import android.content.Context;
+import android.content.res.TypedArray;
+import android.graphics.Canvas;
+import android.graphics.Color;
+import android.graphics.drawable.ColorDrawable;
+import android.support.annotation.NonNull;
+import android.support.annotation.Nullable;
+import android.support.design.widget.CoordinatorLayout;
+import android.util.AttributeSet;
+import android.view.View;
+
+public class RefreshBgView extends View implements CoordinatorLayout.AttachedBehavior{
+    private int mDrawBgHeight = 0;
+    private int mBgColor;
+    private BgDrawable mBgDrawable;
+
+    public RefreshBgView(Context context) {
+        this(context, null);
+    }
+
+    public RefreshBgView(Context context, @Nullable AttributeSet attrs) {
+        this(context, attrs, 0);
+    }
+
+
+    public RefreshBgView(Context context, @Nullable AttributeSet attrs, int defStyleAttr) {
+        super(context, attrs, defStyleAttr);
+
+        TypedArray a = context.obtainStyledAttributes(attrs, R.styleable.RefreshBgView);
+        this.mBgColor = a.getColor(R.styleable.RefreshBgView_refresh_bg_color, Color.WHITE);
+        a.recycle();
+
+        mBgDrawable = new BgDrawable(mBgColor);
+        mBgDrawable.setMaxBottom(getBottom());
+        setBackground(mBgDrawable);
+    }
+
+    @Override
+    protected void onLayout(boolean changed, int left, int top, int right, int bottom) {
+        super.onLayout(changed, left, top, right, bottom);
+        mBgDrawable.setMaxBottom(bottom);
+    }
+
+    @NonNull
+    @Override
+    public CoordinatorLayout.Behavior getBehavior() {
+        return new Behavior();
+    }
+
+    protected static class BaseBehavior<T extends RefreshBgView> extends CoordinatorLayout.Behavior<T>{
+        public BaseBehavior() {
+        }
+
+        public BaseBehavior(Context context, AttributeSet attrs) {
+            super(context, attrs);
+        }
+
+        @Override
+        public boolean layoutDependsOn(CoordinatorLayout parent, T child, View dependency) {
+            if (dependency instanceof RefreshBarLayout) {
+                return true;
+            }
+            return super.layoutDependsOn(parent, child, dependency);
+        }
+
+        @Override
+        public boolean onDependentViewChanged(CoordinatorLayout parent, T child, View dependency) {
+            if (dependency instanceof RefreshBarLayout) {
+                RefreshBarLayout refreshBarLayout = (RefreshBarLayout) dependency;
+                int refreshHeaderHeight = refreshBarLayout.getRefreshHeaderOffset();
+                int offset = refreshBarLayout.getTopBottomOffset();
+                int preHeight = child.getLayoutParams().height;
+                int newHeight;
+                if (offset > refreshHeaderHeight) {
+                    newHeight = offset;
+                } else {
+                    newHeight = 0;
+                }
+                if (preHeight != newHeight) {
+                    child.updateBgHeight(newHeight);
+                }
+            }
+            return false;
+        }
+    }
+
+    @Override
+    public void draw(Canvas canvas) {
+        updateBgDrawable();
+        super.draw(canvas);
+    }
+
+    private void updateBgDrawable() {
+        int height = mDrawBgHeight;
+        int width = getWidth();
+        if (getBackground() != null) {
+            getBackground().setBounds(0, 0, width, height);
+        }
+    }
+
+    public void updateBgHeight(int height) {
+        mDrawBgHeight = height;
+        invalidate();
+    }
+
+    public static class BgDrawable extends ColorDrawable {
+        private int mMaxBottom = 0;
+
+        public BgDrawable(int color) {
+            super(color);
+        }
+
+        public void setMaxBottom(int maxBottom) {
+            mMaxBottom = maxBottom;
+        }
+
+        @Override
+        public void setBounds(int left, int top, int right, int bottom) {
+            if (bottom >= mMaxBottom) {
+                bottom = getBounds().bottom;
+            }
+            super.setBounds(left, top, right, bottom);
+        }
+    }
+
+    public static class Behavior extends BaseBehavior<RefreshBgView> {
+        public Behavior() {
+        }
+
+        public Behavior(Context context, AttributeSet attrs) {
+            super(context, attrs);
+        }
+    }
+
+
+}

nestrefresh/src/main/res/values/attrs.xml

@@ -17,6 +17,10 @@
         <attr name="behavior_maxRange" format="dimension"/>
     </declare-styleable>
 
+    <declare-styleable name="RefreshBgView">
+        <attr name="refresh_bg_color" format="color"/>
+    </declare-styleable>
+
     <declare-styleable name="NRCollapsingToolbarLayout">
         <!--  Specifies extra space on the start, top, end and bottom
               sides of the the expanded title text. Margin values should be positive. -->