src/com/android/launcher2/DragController.java

/*
 * Copyright (C) 2008 The Android Open Source Project
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package com.android.launcher2;

import android.content.Context;
import android.graphics.Bitmap;
import android.graphics.Rect;
import android.graphics.RectF;
import android.os.Handler;
import android.os.IBinder;
import android.os.Vibrator;
import android.util.DisplayMetrics;
import android.util.Log;
import android.view.KeyEvent;
import android.view.MotionEvent;
import android.view.View;
import android.view.ViewConfiguration;
import android.view.WindowManager;
import android.view.inputmethod.InputMethodManager;

import com.android.launcher.R;

import java.util.ArrayList;

/**
 * Class for initiating a drag within a view or across multiple views.
 */
public class DragController {
    @SuppressWarnings({"UnusedDeclaration"})
    private static final String TAG = "Launcher.DragController";

    /** Indicates the drag is a move.  */
    public static int DRAG_ACTION_MOVE = 0;

    /** Indicates the drag is a copy.  */
    public static int DRAG_ACTION_COPY = 1;

    private static final int SCROLL_DELAY = 600;
    private static final int VIBRATE_DURATION = 35;

    private static final boolean PROFILE_DRAWING_DURING_DRAG = false;

    private static final int SCROLL_OUTSIDE_ZONE = 0;
    private static final int SCROLL_WAITING_IN_ZONE = 1;

    static final int SCROLL_NONE = -1;
    static final int SCROLL_LEFT = 0;
    static final int SCROLL_RIGHT = 1;

    private Context mContext;
    private Handler mHandler;
    private final Vibrator mVibrator = new Vibrator();

    // temporaries to avoid gc thrash
    private Rect mRectTemp = new Rect();
    private final int[] mCoordinatesTemp = new int[2];

    /** Whether or not we're dragging. */
    private boolean mDragging;

    /** X coordinate of the down event. */
    private int mMotionDownX;

    /** Y coordinate of the down event. */
    private int mMotionDownY;

    /** Info about the screen for clamping. */
    private DisplayMetrics mDisplayMetrics = new DisplayMetrics();

    /** the area at the edge of the screen that makes the workspace go left
     *   or right while you're dragging.
     */
    private int mScrollZone;

    private DropTarget.DragObject mDragObject = new DropTarget.DragObject();

    /** Who can receive drop events */
    private ArrayList<DropTarget> mDropTargets = new ArrayList<DropTarget>();

    private ArrayList<DragListener> mListeners = new ArrayList<DragListener>();

    /** The window token used as the parent for the DragView. */
    private IBinder mWindowToken;

    /** The view that will be scrolled when dragging to the left and right edges of the screen. */
    private View mScrollView;

    private View mMoveTarget;

    private DragScroller mDragScroller;
    private int mScrollState = SCROLL_OUTSIDE_ZONE;
    private ScrollRunnable mScrollRunnable = new ScrollRunnable();

    private RectF mDeleteRegion;
    private DropTarget mLastDropTarget;

    private InputMethodManager mInputMethodManager;

    private int mLastTouch[] = new int[2];
    private int mDistanceSinceScroll = 0;

    /**
     * Interface to receive notifications when a drag starts or stops
     */
    interface DragListener {
        
        /**
         * A drag has begun
         * 
         * @param source An object representing where the drag originated
         * @param info The data associated with the object that is being dragged
         * @param dragAction The drag action: either {@link DragController#DRAG_ACTION_MOVE}
         *        or {@link DragController#DRAG_ACTION_COPY}
         */
        void onDragStart(DragSource source, Object info, int dragAction);
        
        /**
         * The drag has ended
         */
        void onDragEnd();
    }
    
    /**
     * Used to create a new DragLayer from XML.
     *
     * @param context The application's context.
     */
    public DragController(Context context) {
        mContext = context;
        mHandler = new Handler();
        mScrollZone = context.getResources().getDimensionPixelSize(R.dimen.scroll_zone);
    }

    public boolean dragging() {
        return mDragging;
    }

    /**
     * Starts a drag.
     *
     * @param v The view that is being dragged
     * @param source An object representing where the drag originated
     * @param dragInfo The data associated with the object that is being dragged
     * @param dragAction The drag action: either {@link #DRAG_ACTION_MOVE} or
     *        {@link #DRAG_ACTION_COPY}
     */
    public void startDrag(View v, DragSource source, Object dragInfo, int dragAction) {
        startDrag(v, source, dragInfo, dragAction, null);
    }

    /**
     * Starts a drag.
     *
     * @param v The view that is being dragged
     * @param source An object representing where the drag originated
     * @param dragInfo The data associated with the object that is being dragged
     * @param dragAction The drag action: either {@link #DRAG_ACTION_MOVE} or
     *        {@link #DRAG_ACTION_COPY}
     * @param dragRegion Coordinates within the bitmap b for the position of item being dragged.
     *          Makes dragging feel more precise, e.g. you can clip out a transparent border
     */
    public void startDrag(View v, DragSource source, Object dragInfo, int dragAction,
            Rect dragRegion) {
        Bitmap b = getViewBitmap(v);

        if (b == null) {
            // out of memory?
            return;
        }

        int[] loc = mCoordinatesTemp;
        v.getLocationOnScreen(loc);
        int screenX = loc[0];
        int screenY = loc[1];

        startDrag(b, screenX, screenY, source, dragInfo, dragAction, dragRegion);
        b.recycle();

        if (dragAction == DRAG_ACTION_MOVE) {
            v.setVisibility(View.GONE);
        }
    }

    /**
     * Starts a drag.
     *
     * @param v The view that is being dragged
     * @param bmp The bitmap that represents the view being dragged
     * @param source An object representing where the drag originated
     * @param dragInfo The data associated with the object that is being dragged
     * @param dragAction The drag action: either {@link #DRAG_ACTION_MOVE} or
     *        {@link #DRAG_ACTION_COPY}
     * @param dragRegion Coordinates within the bitmap b for the position of item being dragged.
     *          Makes dragging feel more precise, e.g. you can clip out a transparent border
     */
    public void startDrag(View v, Bitmap bmp, DragSource source, Object dragInfo, int dragAction,
            Rect dragRegion) {
        int[] loc = mCoordinatesTemp;
        v.getLocationOnScreen(loc);
        int screenX = loc[0];
        int screenY = loc[1];

        startDrag(bmp, screenX, screenY, source, dragInfo, dragAction, dragRegion);

        if (dragAction == DRAG_ACTION_MOVE) {
            v.setVisibility(View.GONE);
        }
    }

    /**
     * Starts a drag.
     *
     * @param b The bitmap to display as the drag image.  It will be re-scaled to the
     *          enlarged size.
     * @param screenX The x position on screen of the left-top of the bitmap.
     * @param screenY The y position on screen of the left-top of the bitmap.
     * @param source An object representing where the drag originated
     * @param dragInfo The data associated with the object that is being dragged
     * @param dragAction The drag action: either {@link #DRAG_ACTION_MOVE} or
     *        {@link #DRAG_ACTION_COPY}
     */
    public void startDrag(Bitmap b, int screenX, int screenY,
            DragSource source, Object dragInfo, int dragAction) {
        startDrag(b, screenX, screenY, source, dragInfo, dragAction, null);
    }

    /**
     * Starts a drag.
     *
     * @param b The bitmap to display as the drag image.  It will be re-scaled to the
     *          enlarged size.
     * @param screenX The x position on screen of the left-top of the bitmap.
     * @param screenY The y position on screen of the left-top of the bitmap.
     * @param source An object representing where the drag originated
     * @param dragInfo The data associated with the object that is being dragged
     * @param dragAction The drag action: either {@link #DRAG_ACTION_MOVE} or
     *        {@link #DRAG_ACTION_COPY}
     * @param dragRegion Coordinates within the bitmap b for the position of item being dragged.
     *          Makes dragging feel more precise, e.g. you can clip out a transparent border
     */
    public void startDrag(Bitmap b, int screenX, int screenY,
            DragSource source, Object dragInfo, int dragAction, Rect dragRegion) {
        if (PROFILE_DRAWING_DURING_DRAG) {
            android.os.Debug.startMethodTracing("Launcher");
        }

        // Hide soft keyboard, if visible
        if (mInputMethodManager == null) {
            mInputMethodManager = (InputMethodManager)
                    mContext.getSystemService(Context.INPUT_METHOD_SERVICE);
        }
        mInputMethodManager.hideSoftInputFromWindow(mWindowToken, 0);

        for (DragListener listener : mListeners) {
            listener.onDragStart(source, dragInfo, dragAction);
        }

        final int registrationX = ((int)mMotionDownX) - screenX;
        final int registrationY = ((int)mMotionDownY) - screenY;

        final int dragRegionLeft = dragRegion == null ? 0 : dragRegion.left;
        final int dragRegionTop = dragRegion == null ? 0 : dragRegion.top;

        mDragging = true;

        mDragObject.dragComplete = false;
        mDragObject.xOffset = mMotionDownX - (screenX + dragRegionLeft);
        mDragObject.yOffset = mMotionDownY - (screenY + dragRegionTop);
        mDragObject.dragSource = source;
        mDragObject.dragInfo = dragInfo;

        mVibrator.vibrate(VIBRATE_DURATION);

        final DragView dragView = mDragObject.dragView = new DragView(mContext, b, registrationX,
                registrationY, 0, 0, b.getWidth(), b.getHeight());

        final DragSource dragSource = source;
        dragView.setOnDrawRunnable(new Runnable() {
            public void run() {
                dragSource.onDragViewVisible();
            };
        });

        if (dragRegion != null) {
            dragView.setDragRegion(new Rect(dragRegion));
        }

        dragView.show(mWindowToken, (int)mMotionDownX, (int)mMotionDownY);

        handleMoveEvent((int) mMotionDownX, (int) mMotionDownY);
    }

    /**
     * Draw the view into a bitmap.
     */
    Bitmap getViewBitmap(View v) {
        v.clearFocus();
        v.setPressed(false);

        boolean willNotCache = v.willNotCacheDrawing();
        v.setWillNotCacheDrawing(false);

        // Reset the drawing cache background color to fully transparent
        // for the duration of this operation
        int color = v.getDrawingCacheBackgroundColor();
        v.setDrawingCacheBackgroundColor(0);
        float alpha = v.getAlpha();
        v.setAlpha(1.0f);

        if (color != 0) {
            v.destroyDrawingCache();
        }
        v.buildDrawingCache();
        Bitmap cacheBitmap = v.getDrawingCache();
        if (cacheBitmap == null) {
            Log.e(TAG, "failed getViewBitmap(" + v + ")", new RuntimeException());
            return null;
        }

        Bitmap bitmap = Bitmap.createBitmap(cacheBitmap);

        // Restore the view
        v.destroyDrawingCache();
        v.setAlpha(alpha);
        v.setWillNotCacheDrawing(willNotCache);
        v.setDrawingCacheBackgroundColor(color);

        return bitmap;
    }

    /**
     * Call this from a drag source view like this:
     *
     * <pre>
     *  @Override
     *  public boolean dispatchKeyEvent(KeyEvent event) {
     *      return mDragController.dispatchKeyEvent(this, event)
     *              || super.dispatchKeyEvent(event);
     * </pre>
     */
    @SuppressWarnings({"UnusedDeclaration"})
    public boolean dispatchKeyEvent(KeyEvent event) {
        return mDragging;
    }

    public boolean isDragging() {
        return mDragging;
    }

    /**
     * Stop dragging without dropping.
     */
    public void cancelDrag() {
        if (mDragging) {
            if (mLastDropTarget != null) {
                mLastDropTarget.onDragExit(mDragObject);
            }
            mDragObject.dragComplete = true;
            mDragObject.dragSource.onDropCompleted(null, mDragObject, false);
        }
        endDrag();
    }

    private void endDrag() {
        if (mDragging) {
            mDragging = false;
            for (DragListener listener : mListeners) {
                listener.onDragEnd();
            }
            if (mDragObject.dragView != null) {
                mDragObject.dragView.remove();
                mDragObject.dragView = null;
            }
        }
    }

    /**
     * Call this from a drag source view.
     */
    public boolean onInterceptTouchEvent(MotionEvent ev) {
        if (false) {
            Log.d(Launcher.TAG, "DragController.onInterceptTouchEvent " + ev + " mDragging="
                    + mDragging);
        }
        final int action = ev.getAction();

        if (action == MotionEvent.ACTION_DOWN) {
            recordScreenSize();
        }

        final int screenX = clamp((int)ev.getRawX(), 0, mDisplayMetrics.widthPixels);
        final int screenY = clamp((int)ev.getRawY(), 0, mDisplayMetrics.heightPixels);

        switch (action) {
            case MotionEvent.ACTION_MOVE:
                break;
            case MotionEvent.ACTION_DOWN:
                // Remember location of down touch
                mMotionDownX = screenX;
                mMotionDownY = screenY;
                mLastDropTarget = null;
                break;
            case MotionEvent.ACTION_UP:
                if (mDragging) {
                    drop(screenX, screenY);
                }
                endDrag();
                break;
            case MotionEvent.ACTION_CANCEL:
                cancelDrag();
                break;
        }

        return mDragging;
    }

    /**
     * Sets the view that should handle move events.
     */
    void setMoveTarget(View view) {
        mMoveTarget = view;
    }    

    public boolean dispatchUnhandledMove(View focused, int direction) {
        return mMoveTarget != null && mMoveTarget.dispatchUnhandledMove(focused, direction);
    }

    private void handleMoveEvent(int x, int y) {
        mDragObject.dragView.move(x, y);

        // Drop on someone?
        final int[] coordinates = mCoordinatesTemp;
        DropTarget dropTarget = findDropTarget(x, y, coordinates);
        mDragObject.x = coordinates[0];
        mDragObject.y = coordinates[1];
        if (dropTarget != null) {
            DropTarget delegate = dropTarget.getDropTargetDelegate(mDragObject);
            if (delegate != null) {
                dropTarget = delegate;
            }

            if (mLastDropTarget != dropTarget) {
                if (mLastDropTarget != null) {
                    mLastDropTarget.onDragExit(mDragObject);
                }
                dropTarget.onDragEnter(mDragObject);
            }
            dropTarget.onDragOver(mDragObject);
        } else {
            if (mLastDropTarget != null) {
                mLastDropTarget.onDragExit(mDragObject);
            }
        }
        mLastDropTarget = dropTarget;

        // Scroll, maybe, but not if we're in the delete region.
        boolean inDeleteRegion = false;
        if (mDeleteRegion != null) {
            inDeleteRegion = mDeleteRegion.contains(x, y);
        }

        // After a scroll, the touch point will still be in the scroll region.
        // Rather than scrolling immediately, require a bit of twiddling to scroll again
        final int slop = ViewConfiguration.get(mContext).getScaledWindowTouchSlop();
        mDistanceSinceScroll +=
            Math.sqrt(Math.pow(mLastTouch[0] - x, 2) + Math.pow(mLastTouch[1] - y, 2));
        mLastTouch[0] = x;
        mLastTouch[1] = y;

        if (!inDeleteRegion && x < mScrollZone) {
            if (mScrollState == SCROLL_OUTSIDE_ZONE && mDistanceSinceScroll > slop) {
                mScrollState = SCROLL_WAITING_IN_ZONE;
                mScrollRunnable.setDirection(SCROLL_LEFT);
                mHandler.postDelayed(mScrollRunnable, SCROLL_DELAY);
                mDragScroller.onEnterScrollArea(SCROLL_LEFT);
            }
        } else if (!inDeleteRegion && x > mScrollView.getWidth() - mScrollZone) {
            if (mScrollState == SCROLL_OUTSIDE_ZONE && mDistanceSinceScroll > slop) {
                mScrollState = SCROLL_WAITING_IN_ZONE;
                mScrollRunnable.setDirection(SCROLL_RIGHT);
                mHandler.postDelayed(mScrollRunnable, SCROLL_DELAY);
                mDragScroller.onEnterScrollArea(SCROLL_RIGHT);
            }
        } else {
            if (mScrollState == SCROLL_WAITING_IN_ZONE) {
                mScrollState = SCROLL_OUTSIDE_ZONE;
                mScrollRunnable.setDirection(SCROLL_RIGHT);
                mHandler.removeCallbacks(mScrollRunnable);
                mDragScroller.onExitScrollArea();
            }
        }
    }

    /**
     * Call this from a drag source view.
     */
    public boolean onTouchEvent(MotionEvent ev) {
        if (!mDragging) {
            return false;
        }

        final int action = ev.getAction();
        final int screenX = clamp((int)ev.getRawX(), 0, mDisplayMetrics.widthPixels);
        final int screenY = clamp((int)ev.getRawY(), 0, mDisplayMetrics.heightPixels);

        switch (action) {
        case MotionEvent.ACTION_DOWN:
            // Remember where the motion event started
            mMotionDownX = screenX;
            mMotionDownY = screenY;

            if ((screenX < mScrollZone) || (screenX > mScrollView.getWidth() - mScrollZone)) {
                mScrollState = SCROLL_WAITING_IN_ZONE;
                mHandler.postDelayed(mScrollRunnable, SCROLL_DELAY);
            } else {
                mScrollState = SCROLL_OUTSIDE_ZONE;
            }
            break;
        case MotionEvent.ACTION_MOVE:
            handleMoveEvent(screenX, screenY);
            break;
        case MotionEvent.ACTION_UP:
            // Ensure that we've processed a move event at the current pointer location.
            handleMoveEvent(screenX, screenY);

            mHandler.removeCallbacks(mScrollRunnable);
            if (mDragging) {
                drop(screenX, screenY);
            }
            endDrag();
            break;
        case MotionEvent.ACTION_CANCEL:
            cancelDrag();
            break;
        }

        return true;
    }

    private void drop(float x, float y) {
        final int[] coordinates = mCoordinatesTemp;
        final DropTarget dropTarget = findDropTarget((int) x, (int) y, coordinates);

        mDragObject.x = coordinates[0];
        mDragObject.y = coordinates[1];
        boolean accepted = false;
        if (dropTarget != null) {
            mDragObject.dragComplete = true;
            dropTarget.onDragExit(mDragObject);
            if (dropTarget.acceptDrop(mDragObject)) {
                dropTarget.onDrop(mDragObject);
                accepted = true;
            }
        }
        mDragObject.dragSource.onDropCompleted((View) dropTarget, mDragObject, accepted);
    }

    private DropTarget findDropTarget(int x, int y, int[] dropCoordinates) {
        final Rect r = mRectTemp;

        final ArrayList<DropTarget> dropTargets = mDropTargets;
        final int count = dropTargets.size();
        for (int i=count-1; i>=0; i--) {
            DropTarget target = dropTargets.get(i);
            if (!target.isDropEnabled())
                continue;

            target.getHitRect(r);

            // Convert the hit rect to screen coordinates
            target.getLocationOnScreen(dropCoordinates);
            r.offset(dropCoordinates[0] - target.getLeft(), dropCoordinates[1] - target.getTop());

            mDragObject.x = x;
            mDragObject.y = y;
            if (r.contains(x, y)) {
                DropTarget delegate = target.getDropTargetDelegate(mDragObject);
                if (delegate != null) {
                    target = delegate;
                    target.getLocationOnScreen(dropCoordinates);
                }

                // Make dropCoordinates relative to the DropTarget
                dropCoordinates[0] = x - dropCoordinates[0];
                dropCoordinates[1] = y - dropCoordinates[1];

                return target;
            }
        }
        return null;
    }

    /**
     * Get the screen size so we can clamp events to the screen size so even if
     * you drag off the edge of the screen, we find something.
     */
    private void recordScreenSize() {
        ((WindowManager)mContext.getSystemService(Context.WINDOW_SERVICE))
                .getDefaultDisplay().getMetrics(mDisplayMetrics);
    }

    /**
     * Clamp val to be &gt;= min and &lt; max.
     */
    private static int clamp(int val, int min, int max) {
        if (val < min) {
            return min;
        } else if (val >= max) {
            return max - 1;
        } else {
            return val;
        }
    }

    public void setDragScoller(DragScroller scroller) {
        mDragScroller = scroller;
    }

    public void setWindowToken(IBinder token) {
        mWindowToken = token;
    }

    /**
     * Sets the drag listner which will be notified when a drag starts or ends.
     */
    public void addDragListener(DragListener l) {
        mListeners.add(l);
    }

    /**
     * Remove a previously installed drag listener.
     */
    public void removeDragListener(DragListener l) {
        mListeners.remove(l);
    }

    /**
     * Add a DropTarget to the list of potential places to receive drop events.
     */
    public void addDropTarget(DropTarget target) {
        mDropTargets.add(target);
    }

    /**
     * Don't send drop events to <em>target</em> any more.
     */
    public void removeDropTarget(DropTarget target) {
        mDropTargets.remove(target);
    }

    /**
     * Set which view scrolls for touch events near the edge of the screen.
     */
    public void setScrollView(View v) {
        mScrollView = v;
    }

    /**
     * Specifies the delete region.  We won't scroll on touch events over the delete region.
     *
     * @param region The rectangle in screen coordinates of the delete region.
     */
    void setDeleteRegion(RectF region) {
        mDeleteRegion = region;
    }

    DragView getDragView() {
        return mDragObject.dragView;
    }

    private class ScrollRunnable implements Runnable {
        private int mDirection;

        ScrollRunnable() {
        }

        public void run() {
            if (mDragScroller != null) {
                if (mDirection == SCROLL_LEFT) {
                    mDragScroller.scrollLeft();
                } else {
                    mDragScroller.scrollRight();
                }
                mScrollState = SCROLL_OUTSIDE_ZONE;
                mDistanceSinceScroll = 0;
                mDragScroller.onExitScrollArea();
            }
        }

        void setDirection(int direction) {
            mDirection = direction;
        }
    }
}