Android example source code file (VersionedGestureDetector.java)

This example Android source code file (VersionedGestureDetector.java) is included in the DevDaily.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Android by Example" ^TM.

Java - Android tags/keywords

android, content, created, cupcakedetector, eclairdetector, froyodetector, invalid_pointer_id, ongesturelistener, os, override, scalegesturedetector, string, tag, ui, utilities, versionedgesturedetector, view

The VersionedGestureDetector.java Android example source code

/*
 * Copyright (C) 2010 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.example.android.touchexample;

import android.content.Context;
import android.os.Build;
import android.util.Log;
import android.view.MotionEvent;
import android.view.ScaleGestureDetector;

public abstract class VersionedGestureDetector {
    private static final String TAG = "VersionedGestureDetector";

    OnGestureListener mListener;

    public static VersionedGestureDetector newInstance(Context context,
            OnGestureListener listener) {
        final int sdkVersion = Integer.parseInt(Build.VERSION.SDK);
        VersionedGestureDetector detector = null;
        if (sdkVersion < Build.VERSION_CODES.ECLAIR) {
            detector = new CupcakeDetector();
        } else if (sdkVersion < Build.VERSION_CODES.FROYO) {
            detector = new EclairDetector();
        } else {
            detector = new FroyoDetector(context);
        }

        Log.d(TAG, "Created new " + detector.getClass());
        detector.mListener = listener;

        return detector;
    }

    public abstract boolean onTouchEvent(MotionEvent ev);

    public interface OnGestureListener {
        public void onDrag(float dx, float dy);
        public void onScale(float scaleFactor);
    }

    private static class CupcakeDetector extends VersionedGestureDetector {
        float mLastTouchX;
        float mLastTouchY;

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

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

        boolean shouldDrag() {
            return true;
        }

        @Override
        public boolean onTouchEvent(MotionEvent ev) {
            switch (ev.getAction()) {
            case MotionEvent.ACTION_DOWN: {
                mLastTouchX = getActiveX(ev);
                mLastTouchY = getActiveY(ev);
                break;
            }
            case MotionEvent.ACTION_MOVE: {
                final float x = getActiveX(ev);
                final float y = getActiveY(ev);

                if (shouldDrag()) {
                    mListener.onDrag(x - mLastTouchX, y - mLastTouchY);
                }

                mLastTouchX = x;
                mLastTouchY = y;
                break;
            }
            }
            return true;
        }
    }

    private static class EclairDetector extends CupcakeDetector {
        private static final int INVALID_POINTER_ID = -1;
        private int mActivePointerId = INVALID_POINTER_ID;
        private int mActivePointerIndex = 0;

        @Override
        float getActiveX(MotionEvent ev) {
            return ev.getX(mActivePointerIndex);
        }

        @Override
        float getActiveY(MotionEvent ev) {
            return ev.getY(mActivePointerIndex);
        }

        @Override
        public boolean onTouchEvent(MotionEvent ev) {
            final int action = ev.getAction();
            switch (action & MotionEvent.ACTION_MASK) {
            case MotionEvent.ACTION_DOWN:
                mActivePointerId = ev.getPointerId(0);
                break;
            case MotionEvent.ACTION_CANCEL:
            case MotionEvent.ACTION_UP:
                mActivePointerId = INVALID_POINTER_ID;
                break;
            case MotionEvent.ACTION_POINTER_UP:
                final int pointerIndex = (ev.getAction() & MotionEvent.ACTION_POINTER_INDEX_MASK)
                        >> MotionEvent.ACTION_POINTER_INDEX_SHIFT;
                final int pointerId = ev.getPointerId(pointerIndex);
                if (pointerId == mActivePointerId) {
                    // This was our active pointer going up. Choose a new
                    // active pointer and adjust accordingly.
                    final int newPointerIndex = pointerIndex == 0 ? 1 : 0;
                    mActivePointerId = ev.getPointerId(newPointerIndex);
                    mLastTouchX = ev.getX(newPointerIndex);
                    mLastTouchY = ev.getY(newPointerIndex);
                }
                break;
            }

            mActivePointerIndex = ev.findPointerIndex(mActivePointerId);
            return super.onTouchEvent(ev);
        }
    }

    private static class FroyoDetector extends EclairDetector {
        private ScaleGestureDetector mDetector;

        public FroyoDetector(Context context) {
            mDetector = new ScaleGestureDetector(context,
                    new ScaleGestureDetector.SimpleOnScaleGestureListener() {
                @Override public boolean onScale(ScaleGestureDetector detector) {
                    mListener.onScale(detector.getScaleFactor());
                    return true;
                }
            });
        }

        @Override
        boolean shouldDrag() {
            return !mDetector.isInProgress();
        }

        @Override
        public boolean onTouchEvent(MotionEvent ev) {
            mDetector.onTouchEvent(ev);
            return super.onTouchEvent(ev);
        }
    }
}