CupcakeScaleDragGestureDetector.java

/*******************************************************************************
 * Copyright 2011, 2012 Chris Banes.
 * <p/>
 * 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
 * <p/>
 * http://www.apache.org/licenses/LICENSE-2.0
 * <p/>
 * 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 me.xiaopan.sketch.feature.zoom.gestures;

import android.content.Context;
import android.view.MotionEvent;
import android.view.VelocityTracker;
import android.view.ViewConfiguration;

import me.xiaopan.sketch.SLogType;
import me.xiaopan.sketch.SLog;

public class CupcakeScaleDragGestureDetector implements ScaleDragGestureDetector {
    private static final String NAME = "CupcakeGestureDetector";
    protected final float mTouchSlop;
    protected final float mMinimumVelocity;
    protected OnScaleDragGestureListener mListener;
    protected ActionListener actionListener;
    protected float mLastTouchX;
    protected float mLastTouchY;
    private VelocityTracker mVelocityTracker;
    private boolean mIsDragging;

    public CupcakeScaleDragGestureDetector(Context context) {
        final ViewConfiguration configuration = ViewConfiguration.get(context);
        mMinimumVelocity = configuration.getScaledMinimumFlingVelocity();
        mTouchSlop = configuration.getScaledTouchSlop();
    }

    @Override
    public void setOnGestureListener(OnScaleDragGestureListener listener) {
        this.mListener = listener;
    }

    @Override
    public void setActionListener(ActionListener actionListener) {
        this.actionListener = actionListener;
    }

    protected float getActiveX(MotionEvent ev) {
        return ev.getX();
    }

    protected float getActiveY(MotionEvent ev) {
        return ev.getY();
    }

    @Override
    public boolean isScaling() {
        return false;
    }

    @Override
    public boolean isDragging() {
        return mIsDragging;
    }

    @Override
    public boolean onTouchEvent(MotionEvent ev) {
        switch (ev.getAction()) {
            case MotionEvent.ACTION_DOWN: {
                mVelocityTracker = VelocityTracker.obtain();
                if (null != mVelocityTracker) {
                    mVelocityTracker.addMovement(ev);
                } else {
                    SLog.w(SLogType.ZOOM, NAME, "Velocity tracker is null");
                }

                mLastTouchX = getActiveX(ev);
                mLastTouchY = getActiveY(ev);
                mIsDragging = false;

                if (actionListener != null) {
                    actionListener.onActionDown(ev);
                }
                break;
            }

            case MotionEvent.ACTION_MOVE: {
                final float x = getActiveX(ev);
                final float y = getActiveY(ev);
                final float dx = x - mLastTouchX, dy = y - mLastTouchY;

                if (!mIsDragging) {
                    // Use Pythagoras to see if drag length is larger than
                    // touch slop
                    mIsDragging = Math.sqrt((dx * dx) + (dy * dy)) >= mTouchSlop;
                }

                if (mIsDragging) {
                    mListener.onDrag(dx, dy);
                    mLastTouchX = x;
                    mLastTouchY = y;

                    if (null != mVelocityTracker) {
                        mVelocityTracker.addMovement(ev);
                    }
                }
                break;
            }

            case MotionEvent.ACTION_CANCEL: {
                // Recycle Velocity Tracker
                if (null != mVelocityTracker) {
                    mVelocityTracker.recycle();
                    mVelocityTracker = null;
                }

                if (actionListener != null) {
                    actionListener.onActionCancel(ev);
                }
                break;
            }

            case MotionEvent.ACTION_UP: {
                if (mIsDragging) {
                    if (null != mVelocityTracker) {
                        mLastTouchX = getActiveX(ev);
                        mLastTouchY = getActiveY(ev);

                        // Compute velocity within the last 1000ms
                        mVelocityTracker.addMovement(ev);
                        mVelocityTracker.computeCurrentVelocity(1000);

                        final float vX = mVelocityTracker.getXVelocity(), vY = mVelocityTracker
                                .getYVelocity();

                        // If the velocity is greater than minVelocity, call
                        // listener
                        if (Math.max(Math.abs(vX), Math.abs(vY)) >= mMinimumVelocity) {
                            mListener.onFling(mLastTouchX, mLastTouchY, -vX,
                                    -vY);
                        }
                    }
                }

                // Recycle Velocity Tracker
                if (null != mVelocityTracker) {
                    mVelocityTracker.recycle();
                    mVelocityTracker = null;
                }

                if (actionListener != null) {
                    actionListener.onActionUp(ev);
                }
                break;
            }
        }

        return true;
    }
}