123.gif

要實現如上圖的效果，紅色區域是篩選條件的區域，隨著想向上滾動并且停留在頂部。

第一感覺是想用CoordinatorLayout.Behavior 來實現，將Toolbar+圖片區域+紅色篩選區域作為折疊的頭部。但是這樣SwipeRefreshLayout的下拉圈圈就不是從Toolbar下面下拉出來的。

我嘗試過自己用CoordinatorLayout.Behavior來實現這這個效果，而且上下滾動的效果已經實現了，但是寫到下拉刷新處的時候，我暫時放棄了，我想到了另外一個方法，就是仿CoordinatorLayout.Behavior 來攔截SwipeRefreshLayout 的nestedscroll事件，因為SwipeRefreshLayout也繼承了NestedScrollingParent。

public class MySwipeRefreshLayout extends SwipeRefreshLayout {
    private static final String TAG = "MySwipeRefreshLayout";
    private static  int HEADER_EXPEND_HEIGTH =0;
    private  View rootScrollLayout;
    private View mScrollUpChild;
    private int curentTranslationY;

    public MySwipeRefreshLayout(Context context) {
        this(context, null);
    }

    public MySwipeRefreshLayout(Context context, AttributeSet attrs) {
        super(context, attrs);
        HEADER_EXPEND_HEIGTH = (int) TypedValue.applyDimension(TypedValue.COMPLEX_UNIT_DIP, 200, context.getResources().getDisplayMetrics());
        curentTranslationY = HEADER_EXPEND_HEIGTH;
    }

    @Override
    protected void onLayout(boolean changed, int left, int top, int right, int bottom) {
        super.onLayout(changed, left, top, right, bottom);
        rootScrollLayout = findViewById(R.id.rootScrollLayout);
        Log.i(TAG, "MySwipeRefreshLayout: rootScrollLayout=" + rootScrollLayout);
        rootScrollLayout.setTranslationY(curentTranslationY);

    }

    @Override
    public boolean canChildScrollUp() {
        if (mScrollUpChild != null) {
            return ViewCompat.canScrollVertically(mScrollUpChild, -1);
        }
        return super.canChildScrollUp();
    }

    public void setScrollUpChild(View view) {
        mScrollUpChild = view;
    }


    @Override
    public boolean onStartNestedScroll(View child, View target, int nestedScrollAxes) {
        Log.i(TAG, "onStartNestedScroll: child="+child);
        //接收垂直方向的滾動事件，SwipeRefreshLayout默認是，只要正在刷新，父控件就不接受嵌套事件，由scrollview自己內部消耗
        return isEnabled() &&  (nestedScrollAxes & ViewCompat.SCROLL_AXIS_VERTICAL) != 0;
//        return super.onStartNestedScroll(child, target, nestedScrollAxes);
    }

    @Override
    public void onNestedPreScroll(View target, int dx, int dy, int[] consumed) {
        if (dy > 0) {//向上滾動
            if (curentTranslationY>=0) {//可以整體先向上滾動
                int min = (int) Math.min(rootScrollLayout.getTranslationY(), dy);
                curentTranslationY = (int) (rootScrollLayout.getTranslationY() - min);
                rootScrollLayout.setTranslationY(curentTranslationY);
                consumed[1] = min;
            }
        }
        super.onNestedPreScroll(target, dx, dy, consumed);
        Log.i(TAG, "onNestedPreScroll: ");
    }

    @Override
    public void onNestedScroll(View target, int dxConsumed, int dyConsumed, int dxUnconsumed, int dyUnconsumed) {

        int max = 0;
        if (dyConsumed <= 0 && dyUnconsumed < 0) {//向下滾動
            if (curentTranslationY<HEADER_EXPEND_HEIGTH) {//可以整體先向下滾動
                 max = (int) Math.max(rootScrollLayout.getTranslationY()-HEADER_EXPEND_HEIGTH, dyUnconsumed);
                curentTranslationY = (int) (rootScrollLayout.getTranslationY() - max);
                rootScrollLayout.setTranslationY(curentTranslationY);
            }
            if (isRefreshing()) {//如果正在更新，則不顯示讓SwipeRefreshLayout處理，否則會二度下拉正在更新
                return;
            }
        }
        //如果還有多余的需要SwipeRefreshLayout 處理，比如再下拉顯示正在更新
        super.onNestedScroll(target, dxConsumed, dyConsumed, dxUnconsumed, dyUnconsumed-max);
        Log.i(TAG, "onNestedScroll: ");
    }

    @Override
    protected boolean drawChild(Canvas canvas, View child, long drawingTime) {
        Log.i(TAG, "drawChild: child=" + child);
        return super.drawChild(canvas, child, drawingTime);
    }
}

onlayout

主要處理紅色篩選區與scrollview所在區域的setTranslationY偏移，以露出imageView，實現滑動遮蓋的效果

由于滾動后系統有可能會調用onlayout方法，所以要記錄當前的curentTranslationY，在onlayout的時候設置他的偏移

onStartNestedScroll

只要是垂直方向的滾動就都要處理，SwipeRefreshLayout默認的是在Refreshing狀態就不接收子view的nested事件。而這里正在刷新的時候，整體還要能向上滾動，所以重寫了此處。

onNestedPreScroll

當開始向上滾動的時候，先整體向上移動SwipeRefreshLayout的內部控件，剩余的再給子view去內部消耗
向下滾動的時候，先由子view內部消耗。

onNestedScroll
當子view 滾動完畢后，如果是向下滾動，先整體向下移動SwipeRefreshLayout的內部控件，還有多余的就給SwipeRefreshLayout自己處理，比如顯示下拉進度條。而如果正在刷新的時候，是不應該二次顯示下拉進度條的，這也是為啥isRefreshing 為true的時候，直接return的原因，否則你會看到下拉進度條再次被下拉下來。

布局文件如下：

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools" android:id="@+id/activity_main"
    android:layout_width="match_parent" android:layout_height="match_parent"

    android:orientation="vertical"
    tools:context="com.tospur.exmind.testswiperefresh.MainActivity">

    <android.support.v7.widget.Toolbar
        android:id="@+id/toolBar"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"></android.support.v7.widget.Toolbar>

    <com.tospur.exmind.testswiperefresh.MySwipeRefreshLayout
        android:id="@+id/mySwipeRefreshLayout"
        android:layout_width="match_parent"
        android:layout_height="match_parent">

        <FrameLayout
            android:layout_width="match_parent"
            android:layout_height="match_parent">

            <ImageView
                android:id="@+id/mImgView"
                android:layout_width="match_parent"
                android:layout_height="200dp"
                android:src="@mipmap/test"
                />
            <LinearLayout
                android:id="@+id/rootScrollLayout"
                android:orientation="vertical"
                android:layout_width="match_parent"
                android:layout_height="match_parent">
                <LinearLayout
                    android:id="@+id/mFilterView"
                    android:orientation="vertical"
                    android:layout_width="match_parent"
                    android:background="#f0f"
                    android:layout_height="72dp"></LinearLayout>
                <android.support.v7.widget.RecyclerView
                    android:id="@+id/recyclerView"
                    android:background="#ff0"
                    android:layout_width="match_parent"
                    android:layout_height="match_parent"></android.support.v7.widget.RecyclerView>
            </LinearLayout>

        </FrameLayout>
    </com.tospur.exmind.testswiperefresh.MySwipeRefreshLayout>

</LinearLayout>

public class MainActivity extends AppCompatActivity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        setSupportActionBar((Toolbar) findViewById(R.id.toolBar));
        MySwipeRefreshLayout mySwipeRefreshLayout = (MySwipeRefreshLayout) findViewById(R.id.mySwipeRefreshLayout);
        RecyclerView recyclerView = (RecyclerView) findViewById(R.id.recyclerView);
        recyclerView.setLayoutManager(new LinearLayoutManager(this));
        recyclerView.setAdapter(new MAdapter());
        mySwipeRefreshLayout.setScrollUpChild(recyclerView);


    }

    private class MAdapter extends RecyclerView.Adapter<MHolder> {
        @Override
        public MHolder onCreateViewHolder(ViewGroup parent, int viewType) {
            TextView textView = new TextView(parent.getContext());
            return new MHolder(textView);
        }

        @Override
        public void onBindViewHolder(MHolder holder, int position) {
            holder.textView.setText("A "+position);
        }

        @Override
        public int getItemCount() {
            return 50;
        }
    }

    private class MHolder extends RecyclerView.ViewHolder {
        TextView textView;
        public MHolder(View itemView) {
            super(itemView);
            textView = (TextView) itemView;
        }
    }
}

如果要實現平滑滾動，就是imageview隨著一起向上滾動，只需要做個簡單的調整

123.gif

public class MySwipeRefreshLayout2 extends SwipeRefreshLayout {
    private static final String TAG = "MySwipeRefreshLayout";
    private static  int HEADER_MAX_TOP_OFFSET =0;
    private  View rootScrollLayout;
    private View mScrollUpChild;
    private int curentTranslationY;

    public MySwipeRefreshLayout2(Context context) {
        this(context, null);
    }

    public MySwipeRefreshLayout2(Context context, AttributeSet attrs) {
        super(context, attrs);
        HEADER_MAX_TOP_OFFSET = (int) TypedValue.applyDimension(TypedValue.COMPLEX_UNIT_DIP, 200, context.getResources().getDisplayMetrics());
        curentTranslationY = 0;
    }

    @Override
    protected void onLayout(boolean changed, int left, int top, int right, int bottom) {
        super.onLayout(changed, left, top, right, bottom);
        rootScrollLayout = findViewById(R.id.rootScrollLayout);
        Log.i(TAG, "onMeasure: getMeasuredHeight="+rootScrollLayout.getMeasuredHeight()+" getMeasuredWidth="+rootScrollLayout.getMeasuredWidth());
        Log.i(TAG, "onMeasure: parent.getMeasuredHeight="+getMeasuredHeight());
        int w = View.MeasureSpec.makeMeasureSpec(rootScrollLayout.getMeasuredWidth(),View.MeasureSpec.EXACTLY);
        int h = View.MeasureSpec.makeMeasureSpec(getMeasuredHeight()+HEADER_MAX_TOP_OFFSET,View.MeasureSpec.EXACTLY);
        rootScrollLayout.measure(w,h);//讓rootScrollLayout的子view知道，重新測量讓子view鋪滿rootScrollLayout
        //擴大rootScrollLayout在SwipeRefreshLayout中的顯示區域
        rootScrollLayout.layout(rootScrollLayout.getLeft(), rootScrollLayout.getTop(), rootScrollLayout.getRight(), rootScrollLayout.getBottom() + HEADER_MAX_TOP_OFFSET);
        rootScrollLayout.setTranslationY(curentTranslationY);
    }

    @Override
    public void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
        super.onMeasure(widthMeasureSpec, heightMeasureSpec);
        //這里的measure沒有效果
        /*rootScrollLayout = findViewById(R.id.rootScrollLayout);
        Log.i(TAG, "onMeasure: getMeasuredHeight="+rootScrollLayout.getMeasuredHeight()+" getMeasuredWidth="+rootScrollLayout.getMeasuredWidth());
        Log.i(TAG, "onMeasure: parent.getMeasuredHeight="+getMeasuredHeight());
        int w = View.MeasureSpec.makeMeasureSpec(rootScrollLayout.getMeasuredWidth(),View.MeasureSpec.EXACTLY);
        int h = View.MeasureSpec.makeMeasureSpec(getMeasuredHeight()+HEADER_MAX_TOP_OFFSET,View.MeasureSpec.EXACTLY);
        rootScrollLayout.measure(w,h);*/
    }

    @Override
    public boolean canChildScrollUp() {
        if (mScrollUpChild != null) {
            return ViewCompat.canScrollVertically(mScrollUpChild, -1);
        }
        return super.canChildScrollUp();
    }

    public void setScrollUpChild(View view) {
        mScrollUpChild = view;
    }


    @Override
    public boolean onStartNestedScroll(View child, View target, int nestedScrollAxes) {
        Log.i(TAG, "onStartNestedScroll: child="+child);
        //接收垂直方向的滾動事件，SwipeRefreshLayout默認是，只要正在刷新，父控件就不接受嵌套事件，由scrollview自己內部消耗
        return isEnabled() &&  (nestedScrollAxes & ViewCompat.SCROLL_AXIS_VERTICAL) != 0;
//        return super.onStartNestedScroll(child, target, nestedScrollAxes);
    }

    @Override
    public void onNestedPreScroll(View target, int dx, int dy, int[] consumed) {
        if (dy > 0) {//向上滾動
            if (curentTranslationY<=0) {//可以整體先向上滾動
                int min = (int) Math.min(rootScrollLayout.getTranslationY()+ HEADER_MAX_TOP_OFFSET, dy);
                curentTranslationY = (int) (rootScrollLayout.getTranslationY() - min);
                rootScrollLayout.setTranslationY(curentTranslationY);
                consumed[1] = min;
            }
        }
        super.onNestedPreScroll(target, dx, dy, consumed);
        Log.i(TAG, "onNestedPreScroll: ");
    }

    @Override
    public void onNestedScroll(View target, int dxConsumed, int dyConsumed, int dxUnconsumed, int dyUnconsumed) {

        int max = 0;
        if (dyConsumed <= 0 && dyUnconsumed < 0) {//向下滾動
            if (curentTranslationY<0) {//可以整體先向下滾動
                max = (int) Math.max(rootScrollLayout.getTranslationY(), dyUnconsumed);
                curentTranslationY = (int) (rootScrollLayout.getTranslationY() - max);
                rootScrollLayout.setTranslationY(curentTranslationY);
            }
            if (isRefreshing()) {//如果正在更新，則不顯示讓SwipeRefreshLayout處理，否則會二度下拉正在更新
                return;
            }
        }
        //如果還有多余的需要SwipeRefreshLayout 處理，比如再下拉顯示正在更新
        super.onNestedScroll(target, dxConsumed, dyConsumed, dxUnconsumed, dyUnconsumed-max);
    }

    @Override
    protected boolean drawChild(Canvas canvas, View child, long drawingTime) {
        Log.i(TAG, "drawChild: child=" + child);
        return super.drawChild(canvas, child, drawingTime);
    }
}

這里要注意onlayout方法中的代碼，需要調整rootScrollLayout 的高度，防止向上整體滾動時，底部空白問題

device-2017-03-02-112321.png

如上圖底部。

剛開始在onMeasure中重新測量，死活出不來，然后想起CoordinatorLayout.Behavior 中也有調整位置大小的代碼，于是在onLayout中重新layout，擴大顯示區域，但是必須也要measure一下，否則里面的子view無法完全填充。

附布局代碼

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools" android:id="@+id/activity_main"
    android:layout_width="match_parent" android:layout_height="match_parent"

    android:orientation="vertical"
    tools:context="com.tospur.exmind.testswiperefresh.MainActivity">

    <android.support.v7.widget.Toolbar
        android:id="@+id/toolBar"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"></android.support.v7.widget.Toolbar>

    <com.tospur.exmind.testswiperefresh.MySwipeRefreshLayout2
        android:id="@+id/mySwipeRefreshLayout"
        android:layout_width="match_parent"
        android:layout_height="match_parent">

            <LinearLayout
                android:background="#00f"
                android:id="@+id/rootScrollLayout"
                android:orientation="vertical"
                android:layout_width="match_parent"
                android:layout_height="match_parent">
                <ImageView
                    android:id="@+id/mImgView"
                    android:layout_width="match_parent"
                    android:layout_height="200dp"
                    android:src="@mipmap/test"
                    />
                <LinearLayout
                    android:id="@+id/mFilterView"
                    android:orientation="vertical"
                    android:layout_width="match_parent"
                    android:background="#f0f"
                    android:layout_height="72dp"></LinearLayout>
                <android.support.v7.widget.RecyclerView
                    android:id="@+id/recyclerView"
                    android:background="#ff0"
                    android:layout_width="match_parent"
                    android:layout_height="match_parent"></android.support.v7.widget.RecyclerView>
            </LinearLayout>
    </com.tospur.exmind.testswiperefresh.MySwipeRefreshLayout2>

</LinearLayout>