VolumeButtonPatternDetector.java

/*
 * Copyright 2015 Google Inc.
 *
 * 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.talkback.volumebutton;

import android.os.Handler;
import android.os.Looper;
import android.os.Message;
import android.view.KeyEvent;
import android.view.ViewConfiguration;

import java.util.ArrayList;
import java.util.List;

public class VolumeButtonPatternDetector {

    public static final int SHORT_PRESS_PATTERN = 1;
    public static final int TWO_BUTTONS_LONG_PRESS_PATTERN = 2;
    public static final int TWO_BUTTONS_THREE_PRESS_PATTERN = 3;

    public static final int VOLUME_UP = KeyEvent.KEYCODE_VOLUME_UP;
    public static final int VOLUME_DOWN = KeyEvent.KEYCODE_VOLUME_DOWN;
    public static final int TWO_BUTTONS = 1;

    private static final long LONG_PRESS_TIMEOUT = ViewConfiguration.getLongPressTimeout();
    private static final int CHECK_MATCHERS_MESSAGE = 1;

    private OnPatternMatchListener mListener;
    private List<VolumeButtonPatternMatcher> mPatternMatchers;

    private Handler mHandler = new Handler(Looper.getMainLooper()) {
        @Override
        public void handleMessage(Message message) {
            if (message.what == CHECK_MATCHERS_MESSAGE) {
                checkMatchers();
            }
        }
    };

    public VolumeButtonPatternDetector() {
        mPatternMatchers = new ArrayList<>();
        mPatternMatchers.add(new SingleVolumeButtonShortPressPatternMatcher(VOLUME_UP));
        mPatternMatchers.add(new SingleVolumeButtonShortPressPatternMatcher(VOLUME_DOWN));
        mPatternMatchers.add(new DoubleVolumeButtonLongPressPatternMatcher());
        mPatternMatchers.add(new DoubleVolumeButtonTreeShortPressPatternMatcher());
    }

    public boolean onKeyEvent(KeyEvent keyEvent) {
        if (!isFromVolumeKey(keyEvent.getKeyCode())) {
            return false;
        }

        processKeyEvent(keyEvent);
        checkMatchers();

        mHandler.removeMessages(CHECK_MATCHERS_MESSAGE);
        mHandler.sendEmptyMessageDelayed(CHECK_MATCHERS_MESSAGE, LONG_PRESS_TIMEOUT);
        return true;
    }

    private boolean isFromVolumeKey(int keyCode) {
        switch (keyCode) {
            case KeyEvent.KEYCODE_VOLUME_DOWN:
            case KeyEvent.KEYCODE_VOLUME_UP:
                return true;
        }

        return false;
    }

    private void processKeyEvent(KeyEvent event) {
        for (VolumeButtonPatternMatcher matcher : mPatternMatchers) {
            matcher.onKeyEvent(event);
        }
    }

    private void checkMatchers() {
        for (VolumeButtonPatternMatcher matcher : mPatternMatchers) {
            if (matcher.checkMatch()) {
                notifyPatternMatched(matcher.getPatternCode(), matcher.getButtonCombination());
                matcher.clear();
            }
        }
    }

    public void clearState() {
        for (VolumeButtonPatternMatcher matcher : mPatternMatchers) {
            matcher.clear();
        }
    }

    public void setOnPatternMatchListener(OnPatternMatchListener listener) {
        mListener = listener;
    }

    private void notifyPatternMatched(int patternCode, int buttonCombination) {
        if (mListener != null) {
            mListener.onPatternMatched(patternCode, buttonCombination);
        }
    }

    public interface OnPatternMatchListener {
        public void onPatternMatched(int patternCode, int buttonCombination);
    }
}