2源码的角度分析View

同为纵向滑动冲突（核心代码）

• 思路:根据业务逻辑处理,使用外部拦截
• 首先有个父容器StickyLayout继承LinearLayout，内部放header和一个Listview;
• 滑动规则：拦截：Header显示；listview滑动到顶部；Header隐藏，并且listview滑动手势为向下滑动；其他情况不拦截。
• 先看下布局：

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context="com.example.ceshiactivity.viewdemo.DemoCoreActivity">

    <com.example.ceshiactivity.viewdemo.StickyLayout
        android:id="@+id/sticky_layout"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:background="#ffffff"
        android:orientation="vertical">

        <LinearLayout
            android:id="@+id/sticky_header"
            android:layout_width="match_parent"
            android:layout_height="100dp"
            android:background="#78A524"
            android:gravity="center"
            android:orientation="vertical">

            <ImageView
                android:id="@+id/imageView1"
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                android:src="@mipmap/ic_launcher" />

        </LinearLayout>

        <LinearLayout
            android:id="@+id/sticky_content"
            android:layout_width="match_parent"
            android:layout_height="match_parent"
            android:orientation="vertical">

            <ListView
                android:id="@+id/list"
                android:layout_width="match_parent"
                android:layout_height="match_parent"
                android:background="#fff4f7f9"
                android:cacheColorHint="#00000000"
                android:divider="#dddbdb"
                android:dividerHeight="1.0px"
                android:listSelector="@android:color/transparent" />
        </LinearLayout>
    </com.example.ceshiactivity.viewdemo.StickyLayout>
</RelativeLayout>

DemoCoreActivity
这里主要调用一个接口，以获得listview的item0位置

public class DemoCoreActivity extends AppCompatActivity implements StickyLayout.OnGiveUpTouchEventListener {
    private StickyLayout stickyLayout;
    ListView listView;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_demo_core);
        initView();
        LinearLayout ll= (LinearLayout) findViewById(R.id.sticky_header);
        stickyLayout= (StickyLayout) findViewById(R.id.sticky_layout);
        stickyLayout.setOnGiveUpTouchEventListener(this);

    }

    private void initView() {
        listView = (ListView)findViewById(R.id.list);
        ArrayList<String> datas = new ArrayList<String>();
        for (int i = 0; i < 50; i++) {
            datas.add("name " + i);
        }

        ArrayAdapter<String> adapter = new ArrayAdapter<String>(this,
                R.layout.content_list_item, R.id.name, datas);
        listView.setAdapter(adapter);
        listView.setOnItemClickListener(new AdapterView.OnItemClickListener() {
            @Override
            public void onItemClick(AdapterView<?> parent, View view,
                                    int position, long id) {
                Toast.makeText(DemoCoreActivity.this, "click item",
                        Toast.LENGTH_SHORT).show();

            }
        });
    }

    @Override
    public boolean giveUpTouchEvent(MotionEvent event) {
        //如果位置为0，获取0位置的view
        if (listView.getFirstVisiblePosition() == 0) {
            View view = listView.getChildAt(0);
            //view在顶部位置单位像素
            if (view != null && view.getTop() >= 0) {
                return true;
            }
        }
        return false;
    }

然后是核心代码StickyLayout

public class StickyLayout extends LinearLayout {
    private static final String TAG = "StickyLayout";
    private static final boolean DEBUG = true;
    //用来判断listview是否滑动到顶端
    public interface OnGiveUpTouchEventListener {
        public boolean giveUpTouchEvent(MotionEvent event);
    }

    private View mHeader;//上半部分布局
    private View mContent;//下半部分布局
    private OnGiveUpTouchEventListener mGiveUpTouchEventListener;

    // header的高度  单位：px
    private int mOriginalHeaderHeight;
    private int mHeaderHeight;
    //滑动方向
    private int mStatus = STATUS_EXPANDED;
    public static final int STATUS_EXPANDED = 1;
    public static final int STATUS_COLLAPSED = 2;
    //滚动的像素值
    private int mTouchSlop;

    // 分别记录上次滑动的坐标
    private int mLastX = 0;
    private int mLastY = 0;

    // 分别记录上次滑动的坐标(onInterceptTouchEvent)
    private int mLastXIntercept = 0;
    private int mLastYIntercept = 0;

    // 用来控制滑动角度，仅当角度a满足如下条件才进行滑动：tan a = deltaX / deltaY > 2
    private static final int TAN = 2;

    private boolean mIsSticky = true;
    private boolean mInitDataSucceed = false;
    private boolean mDisallowInterceptTouchEventOnHeader = true;

    public StickyLayout(Context context) {
        super(context);
    }

    public StickyLayout(Context context, AttributeSet attrs) {
        super(context, attrs);
    }

    @TargetApi(Build.VERSION_CODES.HONEYCOMB)
    public StickyLayout(Context context, AttributeSet attrs, int defStyle) {
        super(context, attrs, defStyle);
    }

    @Override
    public void onWindowFocusChanged(boolean hasWindowFocus) {
        super.onWindowFocusChanged(hasWindowFocus);
        if (hasWindowFocus && (mHeader == null || mContent == null)) {
            initData();
        }
    }

    private void initData() {
        int headerId= getResources().getIdentifier("sticky_header", "id", getContext().getPackageName());
        int contentId = getResources().getIdentifier("sticky_content", "id", getContext().getPackageName());
        if (headerId != 0 && contentId != 0) {
            mHeader = findViewById(headerId);
            mContent = findViewById(contentId);
            mOriginalHeaderHeight = mHeader.getMeasuredHeight();
            mHeaderHeight = mOriginalHeaderHeight;
            mTouchSlop = ViewConfiguration.get(getContext()).getScaledTouchSlop();
            if (mHeaderHeight > 0) {
                mInitDataSucceed = true;
            }
            if (DEBUG) {
                Log.d(TAG, "mTouchSlop = " + mTouchSlop + "mHeaderHeight = " + mHeaderHeight);
            }
        } else {
            throw new NoSuchElementException("Did your view with id \"sticky_header\" or \"sticky_content\" exists?");
        }
    }

    /**
     * 传递跟布局
     * @param l this
     */
    public void setOnGiveUpTouchEventListener(OnGiveUpTouchEventListener l) {
        mGiveUpTouchEventListener = l;
    }

    /**
     * 片段
     */
    @Override
    public boolean onInterceptTouchEvent(MotionEvent event) {
        int intercepted = 0;
        int x = (int) event.getX();
        int y = (int) event.getY();

        switch (event.getAction()) {
            case MotionEvent.ACTION_DOWN: {
                mLastXIntercept = x;
                mLastYIntercept = y;
                mLastX = x;
                mLastY = y;
                intercepted = 0;
                break;
            }
            case MotionEvent.ACTION_MOVE: {
                int deltaX = x - mLastXIntercept;
                int deltaY = y - mLastYIntercept;
                if (mDisallowInterceptTouchEventOnHeader && y <= getHeaderHeight()) {
                    //竖直滑动距离小于header高度，不拦截
                    intercepted = 0;
                } else if (Math.abs(deltaY) <= Math.abs(deltaX)) {
                    //竖直距离差小于等于水平距离不拦截
                    intercepted = 0;
                } else if (mStatus == STATUS_EXPANDED && deltaY <= -mTouchSlop) {
                    //header展开状态，向上滑动，拦截
                    intercepted = 1;
                } else if (mGiveUpTouchEventListener != null) {
                    //布局不为空
                    if (mGiveUpTouchEventListener.giveUpTouchEvent(event) && deltaY >= mTouchSlop) {
                        //listview滑动到顶部并向下滑动，拦截
                        intercepted = 1;
                    }
                }
                break;
            }
            case MotionEvent.ACTION_UP: {
                intercepted = 0;
                mLastXIntercept = mLastYIntercept = 0;
                break;
            }
            default:
                break;
        }

        if (DEBUG) {
            Log.d(TAG, "intercepted=" + intercepted);
        }
        return intercepted != 0 && mIsSticky;
    }
    /**
     * 片段
     */
    @Override
    public boolean onTouchEvent(MotionEvent event) {
        if (!mIsSticky) {
            return true;
        }
        int x = (int) event.getX();
        int y = (int) event.getY();
        switch (event.getAction()) {
            case MotionEvent.ACTION_DOWN: {
                break;
            }
            case MotionEvent.ACTION_MOVE: {
                int deltaX = x - mLastX;
                int deltaY = y - mLastY;
                if (DEBUG) {
                    Log.d(TAG, "mHeaderHeight=" + mHeaderHeight + "  deltaY=" + deltaY + "  mlastY=" + mLastY);
                }
                mHeaderHeight += deltaY;
                setHeaderHeight(mHeaderHeight);
                break;
            }
            case MotionEvent.ACTION_UP: {
                // 这里做了下判断，当松开手的时候，会自动向两边滑动，具体向哪边滑，要看当前所处的位置
                int destHeight = 0;
                if (mHeaderHeight <= mOriginalHeaderHeight * 0.5) {
                    destHeight = 0;
                    mStatus = STATUS_COLLAPSED;
                } else {
                    destHeight = mOriginalHeaderHeight;
                    mStatus = STATUS_EXPANDED;
                }
                // 慢慢滑向终点
                this.smoothSetHeaderHeight(mHeaderHeight, destHeight, 500);
                break;
            }
            default:
                break;
        }
        mLastX = x;
        mLastY = y;
        return true;
    }

    public void smoothSetHeaderHeight(final int from, final int to, long duration) {
        smoothSetHeaderHeight(from, to, duration, false);
    }

    /**
     * 线程设置高度变化
     * @param from head初始高度
     * @param to  移动到的高度
     * @param duration  时间
     * @param modifyOriginalHeaderHeight
     */
    public void smoothSetHeaderHeight(final int from, final int to, long duration, final boolean modifyOriginalHeaderHeight) {
        final int frameCount = (int) (duration / 1000f * 30) + 1;
        //速度公式
        final float partation = (to - from) / (float) frameCount;
        new Thread("Thread#smoothSetHeaderHeight") {

            @Override
            public void run() {
                for (int i = 0; i < frameCount; i++) {
                    //动态变化
                    final int height;
                    if (i == frameCount - 1) {
                        height = to;
                    } else {
                        height = (int) (from + partation * i);
                    }
                    post(new Runnable() {
                        public void run() {
                            setHeaderHeight(height);
                        }
                    });
                    try {
                        sleep(10);
                    } catch (InterruptedException e) {
                        e.printStackTrace();
                    }
                }

                if (modifyOriginalHeaderHeight) {
                    setOriginalHeaderHeight(to);
                }
            };

        }.start();
    }

    public void setOriginalHeaderHeight(int originalHeaderHeight) {
        mOriginalHeaderHeight = originalHeaderHeight;
    }

    public void setHeaderHeight(int height, boolean modifyOriginalHeaderHeight) {
        if (modifyOriginalHeaderHeight) {
            setOriginalHeaderHeight(height);
        }
        setHeaderHeight(height);
    }

    /**
     * 赋值 并设置高度到Header中
     * @param height
     */
    public void setHeaderHeight(int height) {
        if (!mInitDataSucceed) {
            initData();
        }

        if (DEBUG) {
            Log.d(TAG, "setHeaderHeight height=" + height);
        }
        if (height <= 0) {
            height = 0;
        } else if (height > mOriginalHeaderHeight) {
            //这行注释掉可实现下拉到任意位置后弹回
            height = mOriginalHeaderHeight;
        }

        if (height == 0) {
            mStatus = STATUS_COLLAPSED;
        } else {
            mStatus = STATUS_EXPANDED;
        }

        if (mHeader != null && mHeader.getLayoutParams() != null) {
            mHeader.getLayoutParams().height = height;
            mHeader.requestLayout();
            mHeaderHeight = height;
        } else {
            if (DEBUG) {
                Log.e(TAG, "null LayoutParams when setHeaderHeight");
            }
        }
    }

    public int getHeaderHeight() {
        return mHeaderHeight;
    }

    public void setSticky(boolean isSticky) {
        mIsSticky = isSticky;
    }

    public void requestDisallowInterceptTouchEventOnHeader(boolean disallowIntercept) {
        mDisallowInterceptTouchEventOnHeader = disallowIntercept;
    }
}

效果图：

纵向与纵向滑动冲突.jpg

遗留问题手指向上滑动不离开屏幕则listview无法滑动（待解决）