实现Activity滑动退出

三好码农

发布于 2018-09-11 10:55:10

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发布于 2018-09-11 10:55:10

实现Activity滑动退出

很多应用在二级详情页面加入了滑动退出activity的效果，很方便，心血来潮，想着自己也来实现这个效果，就当做练手吧。

实现View的滑动有很多种方法，如自己在onTouchEvent中处理触摸事件，然后滚动View到相应位置，也可以用google V4包为我们提供的ViewDragHelper来处理触摸事件，我们这里选择后者，因为滑动退出操作都是在屏幕的边缘时触发，而ViewDragHelper刚好提供了想要的实现，可以说利用ViewDragHelper来实现我们的需求非常简单。

先定义一个ViewGroup，并做一些必要的变量声明 BaseSwipeLayout

  public class BaseSwipeLayout extends FrameLayout{

    private View mDragView;

    private ViewDragHelper mViewDragHelper;

    private Point mAutoBackOrignalPoint = new Point();

    private Point mCurArrivePoint = new Point();

    private int mCurEdgeFlag = ViewDragHelper.EDGE_LEFT;
    private int mSwipeEdge = ViewDragHelper.EDGE_LEFT;

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

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

    public BaseSwipeLayout(Context context, AttributeSet attrs, int defStyleAttr) {
        super(context, attrs, defStyleAttr);
        init();
    }
 }

既然使用ViewDragHelper，我们把触摸事件交给ViewDragHelper处理，ViewDragHelper不熟悉的同学，相关知识，网上一大堆，自行查看

    @Override
    public boolean onInterceptTouchEvent(MotionEvent ev) {
        return mViewDragHelper.shouldInterceptTouchEvent(ev);
    }

    @Override
    public boolean onTouchEvent(MotionEvent event) {
        mViewDragHelper.processTouchEvent(event);
        return true;
    }

下面对ViewDragHelper的配置，比较简单，大家看代码吧。

private void init() {
        mViewDragHelper = ViewDragHelper.create(this, 1.0f, new ViewDragHelper.Callback() {
            @Override
            public boolean tryCaptureView(View child, int pointerId) {
                return false;
            }

            @Override
            public int clampViewPositionHorizontal(View child, int left, int dx) {
                mCurArrivePoint.x = left;
                //允许左右触发滑动，否则return 0
                if (mCurEdgeFlag != ViewDragHelper.EDGE_BOTTOM) {
                    return left;
                }else return 0;
            }

            @Override
            public int clampViewPositionVertical(View child, int top, int dy) {
                mCurArrivePoint.y = top;
                //允许底部触发滑动，否则return 0
                if (mCurEdgeFlag == ViewDragHelper.EDGE_BOTTOM) {
                    return top;
                }else return 0;
            }

            @Override
            public void onViewReleased(View releasedChild, float xvel, float yvel) {
                super.onViewReleased(releasedChild, xvel, yvel);
                switch (mCurEdgeFlag) {
                    case ViewDragHelper.EDGE_LEFT:
                        //水平滑动超过一半，触发结束
                        if (mCurArrivePoint.x > getWidth()/2) {
                            mViewDragHelper.settleCapturedViewAt(getWidth(), mAutoBackOrignalPoint.y);
                        }else {
                            mViewDragHelper.settleCapturedViewAt(mAutoBackOrignalPoint.x, mAutoBackOrignalPoint.y);
                        }
                        break;
                    case ViewDragHelper.EDGE_RIGHT:
                        //水平滑动超过一半，触发结束
                        if (mCurArrivePoint.x < -getWidth()/2) {
                            mViewDragHelper.settleCapturedViewAt(-getWidth(), mAutoBackOrignalPoint.y);
                        }else {
                            mViewDragHelper.settleCapturedViewAt(mAutoBackOrignalPoint.x, mAutoBackOrignalPoint.y);
                        }
                        break;
                    case ViewDragHelper.EDGE_BOTTOM:
                        //垂直滑动超过一半，触发结束
                        if (mCurArrivePoint.y < -getHeight()/2) {
                            mViewDragHelper.settleCapturedViewAt(mAutoBackOrignalPoint.x, -getHeight());
                        }else {
                            mViewDragHelper.settleCapturedViewAt(mAutoBackOrignalPoint.x, mAutoBackOrignalPoint.y);
                        }
                        break;
                }

                mCurArrivePoint.x = 0;
                mCurArrivePoint.y = 0;
                invalidate();
            }

            @Override
            public void onViewPositionChanged(View changedView, int left, int top, int dx, int dy) {
                super.onViewPositionChanged(changedView, left, top, dx, dy);
                switch (mCurEdgeFlag) {
                    case ViewDragHelper.EDGE_LEFT:
                        if (left >= getWidth()) {
                            if (mFinishScroll != null) {
                                mFinishScroll.complete();
                            }
                        }
                        break;
                    case ViewDragHelper.EDGE_RIGHT:
                        if (left <= -getWidth()) {
                            if (mFinishScroll != null) {
                                mFinishScroll.complete();
                            }
                        }
                        break;
                    case ViewDragHelper.EDGE_BOTTOM:
                        if (top <= -getHeight()) {
                            if (mFinishScroll != null) {
                                mFinishScroll.complete();
                            }
                        }
                        break;
                }
            }

            @Override
            public void onEdgeDragStarted(int edgeFlags, int pointerId) {
                mCurEdgeFlag = edgeFlags;
                if (mDragView == null) mDragView = getChildAt(0);
                mViewDragHelper.captureChildView(mDragView, pointerId);
            }
        });

        mViewDragHelper.setEdgeTrackingEnabled(ViewDragHelper.EDGE_LEFT);
    }

这里还有个步骤不要忘了，手指离开屏幕或者滑动超过屏幕的时候，我们触发了ViewGroup自行完全滚动出屏幕的调用，所以我们需要在computeScroll中做检查，如果滚动没有结束，刷新View，继续滚动。

    @Override
    public void computeScroll() {
        if (mViewDragHelper.continueSettling(true)) {
            invalidate();
        }
    }

这样我们自定义的BaseSwipeLayout打造完毕，我们把它设为activity的根布局测试一下

<?xml version="1.0" encoding="utf-8"?>
<com.aliouswang.swipeback.widget.BaseSwipeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:orientation="vertical" android:layout_width="match_parent"
    android:id="@+id/swipe_layout"
    android:layout_height="match_parent">

    <ScrollView
        android:layout_width="match_parent"
        android:layout_height="match_parent">
        <LinearLayout
            android:orientation="vertical"
            android:layout_width="match_parent"
            android:layout_height="wrap_content">
            <TextView
                android:text="Swipe Back Demo"
                android:gravity="center"
                android:textColor="@android:color/white"
                android:background="@android:color/holo_red_light"
                android:layout_width="match_parent"
                android:layout_height="100dp" />

            <TextView
                android:text="Swipe Back Demo"
                android:gravity="center"
                android:textColor="@android:color/white"
                android:background="@android:color/holo_blue_light"
                android:layout_width="match_parent"
                android:layout_height="100dp" />

            <TextView
                android:text="Swipe Back Demo"
                android:gravity="center"
                android:textColor="@android:color/white"
                android:background="@android:color/holo_green_light"
                android:layout_width="match_parent"
                android:layout_height="100dp" />

            <TextView
                android:text="Swipe Back Demo"
                android:gravity="center"
                android:textColor="@android:color/white"
                android:background="@android:color/holo_purple"
                android:layout_width="match_parent"
                android:layout_height="100dp" />

            <TextView
                android:text="Swipe Back Demo"
                android:gravity="center"
                android:textColor="@android:color/white"
                android:background="@android:color/holo_green_dark"
                android:layout_width="match_parent"
                android:layout_height="100dp" />

            <TextView
                android:text="Swipe Back Demo"
                android:gravity="center"
                android:textColor="@android:color/white"
                android:background="@android:color/holo_red_dark"
                android:layout_width="match_parent"
                android:layout_height="100dp" />

            <TextView
                android:text="Swipe Back Demo"
                android:gravity="center"
                android:textColor="@android:color/white"
                android:background="@android:color/holo_blue_dark"
                android:layout_width="match_parent"
                android:layout_height="100dp" />

            <TextView
                android:text="Swipe Back Demo"
                android:gravity="center"
                android:textColor="@android:color/white"
                android:background="@android:color/holo_orange_dark"
                android:layout_width="match_parent"
                android:layout_height="100dp" />
        </LinearLayout>
    </ScrollView>

</com.aliouswang.swipeback.widget.BaseSwipeLayout>

当然，我们已经实现了整个功能，但是有一点很不爽的是，我们必须将BaseSwipeLayout作为布局的根，这样实现还不够优雅，我们能不能不改变我们原有的布局文件，却依然能加入滑动退出功能。这里我们要介绍一个DecorView，它是Window的最顶层View，它含有一个子LinearLayout，代表整个Window，包括通知栏，状态栏，内容显示区域，所以我们activity页面是DecorView的子View的子View，那么我们能不能直接给DecorView的子View添加到我们的BaseSwipeLayout，再将BaseSwipeLayout添加到DecorView，当然是可以的，而且这种方式，我们不需要改变原来的布局文件，更加优雅。

我们定义一个SwipeHelper类，辅助我们进行BaseSwipeLayout插入操作。

public class SwipeHelper {

    private Activity mActivity;
    private BaseSwipeLayout mBaseSwipeLayout;

    public SwipeHelper(Activity activity) {
        this.mActivity = activity;
    }

    public void onActivityCreate() {
        mBaseSwipeLayout = (BaseSwipeLayout) LayoutInflater.from(mActivity)
                .inflate(R.layout.swipe_layout, null);
        mBaseSwipeLayout.setOnFinishScroll(new BaseSwipeLayout.OnFinishScroll() {
            @Override
            public void complete() {
                mActivity.finish();
            }
        });
    }

    public void onPostCreate() {
        mBaseSwipeLayout.attachToActivity(mActivity);
    }

    public void setSwipeEdge(int edgeFlag) {
        mBaseSwipeLayout.setSwipeEdge(edgeFlag);
    }
}

BaseSwipeLayout

//核心代码，绑定到相应activity
    public void attachToActivity(Activity activity) {
        this.mActivity = activity;
        TypedArray a = activity.getTheme().obtainStyledAttributes(new int[]{
                android.R.attr.windowBackground
        });
        int background = a.getResourceId(0, 0);
        a.recycle();
        ViewGroup decorView = (ViewGroup) activity.getWindow().getDecorView();
        ViewGroup decorChild = (ViewGroup) decorView.getChildAt(0);
        decorChild.setBackgroundResource(background);
        decorView.removeView(decorChild);
        addView(decorChild);
        decorView.addView(this);
    }

需要添加滑动退出的activity，添加想要代码

    private SwipeHelper mSwipeHelper;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.view_drag_helper_act_layout);
        mSwipeHelper = new SwipeHelper(this);
        mSwipeHelper.onActivityCreate();
        mSwipeHelper.setSwipeEdge(ViewDragHelper.EDGE_RIGHT);
    }

    @Override
    protected void onPostCreate(Bundle savedInstanceState) {
        super.onPostCreate(savedInstanceState);
        mSwipeHelper.onPostCreate();
    }