gecko-dev/mobile/android/base/OuterLayout.java

/* This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this file,
 * You can obtain one at http://mozilla.org/MPL/2.0/. */
package org.mozilla.gecko;

import android.content.Context;
import android.support.v4.view.ViewCompat;
import android.support.v4.widget.ViewDragHelper;
import android.util.AttributeSet;
import android.view.MotionEvent;
import android.view.View;
import android.widget.RelativeLayout;

/* Outerlayout is the container layout of all the main views. It allows mainlayout to be dragged while targeting
   the toolbar and it's responsible for handling the dragprocess. It relies on ViewDragHelper to ease the drag process.
 */
public class OuterLayout extends RelativeLayout {
    private final double AUTO_OPEN_SPEED_LIMIT = 800.0;
    private ViewDragHelper mDragHelper;
    private int mDraggingBorder;
    private int mDragRange;
    private boolean mIsOpen = false;
    private int mDraggingState = ViewDragHelper.STATE_IDLE;
    private DragCallback mDragCallback;

    public static interface DragCallback {
        public void startDrag(boolean wasOpen);
        public void stopDrag(boolean stoppingToOpen);
        public int getDragRange();
        public int getOrderedChildIndex(int index);
        public boolean canDrag(MotionEvent event);
        public boolean canInterceptEventWhileOpen(MotionEvent event);
        public void onDragProgress(float progress);
        public View getViewToDrag();
        public int getLowerLimit();
    }

    private class DragHelperCallback extends ViewDragHelper.Callback {
        @Override
        public void onViewDragStateChanged(int newState) {
            if (newState == mDraggingState) { // no change
                return;
            }

            // if the view stopped moving.
            if ((mDraggingState == ViewDragHelper.STATE_DRAGGING || mDraggingState == ViewDragHelper.STATE_SETTLING) &&
                 newState == ViewDragHelper.STATE_IDLE) {

                final float rangeToCheck = mDragRange;
                final float lowerLimit = mDragCallback.getLowerLimit();
                if (mDraggingBorder == lowerLimit) {
                    mIsOpen = false;
                    mDragCallback.onDragProgress(0);
                } else if (mDraggingBorder == rangeToCheck) {
                    mIsOpen = true;
                    mDragCallback.onDragProgress(1);
                }
                mDragCallback.stopDrag(mIsOpen);
            }

            // The view was previuosly moving.
            if (newState == ViewDragHelper.STATE_DRAGGING && !isMoving()) {
                mDragCallback.startDrag(mIsOpen);
                updateRanges();
            }

            mDraggingState = newState;
        }

        @Override
        public void onViewPositionChanged(View changedView, int left, int top, int dx, int dy) {
            mDraggingBorder = top;
            final float progress = Math.min(1, ((float) top) / mDragRange);
            mDragCallback.onDragProgress(progress);
        }

        @Override
        public int getViewVerticalDragRange(View child) {
            return mDragRange;
        }

        @Override
        public int getOrderedChildIndex(int index) {
            return mDragCallback.getOrderedChildIndex(index);
        }

        @Override
        public boolean tryCaptureView(View view, int i) {
            return (view.getId() == mDragCallback.getViewToDrag().getId());
        }

        @Override
        public int clampViewPositionVertical(View child, int top, int dy) {
            return top;
        }

        @Override
        public void onViewReleased(View releasedChild, float xvel, float yvel) {
            final float rangeToCheck = mDragRange;
            final float speedToCheck = yvel;

            if (mDraggingBorder == mDragCallback.getLowerLimit()) {
                return;
            }

            if (mDraggingBorder == rangeToCheck) {
                return;
            }

            boolean settleToOpen = false;
            // Speed has priority over position.
            if (speedToCheck > AUTO_OPEN_SPEED_LIMIT) {
                settleToOpen = true;
            } else if (speedToCheck < -AUTO_OPEN_SPEED_LIMIT) {
                settleToOpen = false;
            } else if (mDraggingBorder > rangeToCheck / 2) {
                settleToOpen = true;
            } else if (mDraggingBorder < rangeToCheck / 2) {
                settleToOpen = false;
            }

            final int settleDestX;
            final int settleDestY;
            if (settleToOpen) {
                settleDestX = 0;
                settleDestY = mDragRange;
            } else {
                settleDestX = 0;
                settleDestY = mDragCallback.getLowerLimit();
            }

            if(mDragHelper.settleCapturedViewAt(settleDestX, settleDestY)) {
                ViewCompat.postInvalidateOnAnimation(OuterLayout.this);
            }
        }
    }

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

    private void updateRanges() {
        // Need to wait for the tabs to show in order to fetch the right sizes.
        mDragRange = mDragCallback.getDragRange() + mDragCallback.getLowerLimit();
    }

    private void updateOrientation() {
        mDragHelper.setEdgeTrackingEnabled(0);
    }

    @Override
    protected void onFinishInflate() {
        mDragHelper = ViewDragHelper.create(this, 1.0f, new DragHelperCallback());
        mIsOpen = false;
        super.onFinishInflate();
    }

    @Override
    public boolean onInterceptTouchEvent(MotionEvent event) {
        if (mDragCallback.canDrag(event)) {
            if (mDragHelper.shouldInterceptTouchEvent(event)) {
                return true;
            }
        }

        // Because while open the target layout is translated and draghelper does not catch it.
        if (mIsOpen && mDragCallback.canInterceptEventWhileOpen(event)) {
            return true;
        }
        return false;
    }

    @Override
    public boolean onTouchEvent(MotionEvent event) {
        // touch events can be passed to the helper if we target the toolbar or we are already dragging.
        if (mDragCallback.canDrag(event) || mDraggingState == ViewDragHelper.STATE_DRAGGING) {
            mDragHelper.processTouchEvent(event);
        }
        return true;
    }

    @Override
    protected void onSizeChanged(int w, int h, int oldw, int oldh) {
        // The first time fennec is started, tabs might not have been created while we drag. In that case we need
        // an arbitrary range to start dragging that will be updated as soon as the tabs are created.

        if (mDragRange == 0) {
            mDragRange = h / 2;
        }
        super.onSizeChanged(w, h, oldw, oldh);
    }

    @Override
    public void computeScroll() { // needed for automatic settling.
        if (mDragHelper.continueSettling(true)) {
            ViewCompat.postInvalidateOnAnimation(this);
        }
    }

    /**
     * To be called when closing the tabs from outside (i.e. when touching the main layout).
     */
    public void setClosed() {
        mIsOpen = false;
        mDragHelper.abort();
    }

    /**
     * To be called when opening the tabs from outside (i.e. when clicking on the tabs button).
     */
    public void setOpen() {
        mIsOpen = true;
        mDragHelper.abort();
    }

    public void setDraggableCallback(DragCallback dragCallback) {
        mDragCallback = dragCallback;
        updateOrientation();
    }

    // If a change happens while we are dragging, we abort the dragging and set to open state.
    public void reset() {
        updateOrientation();
        if (isMoving()) {
            mDragHelper.abort();
            if (mDragCallback != null) {
                mDragCallback.stopDrag(false);
                mDragCallback.onDragProgress(0f);
            }
        }
    }

    public void updateDragHelperParameters() {
        mDragRange = mDragCallback.getDragRange() + mDragCallback.getLowerLimit();
        updateOrientation();
    }

    public boolean isMoving() {
        return (mDraggingState == ViewDragHelper.STATE_DRAGGING ||
                mDraggingState == ViewDragHelper.STATE_SETTLING);
    }

    public boolean isOpen() {
        return mIsOpen;
    }

    public View findTopChildUnder(MotionEvent event) {
        return mDragHelper.findTopChildUnder((int) event.getX(), (int) event.getY());
    }

    public void restoreTargetViewPosition() {
        mDragCallback.getViewToDrag().offsetTopAndBottom(mDraggingBorder);
    }
}