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/*
* Copyright (C) 2015 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.server.accessibility;
import android.os.Handler;
import android.os.Message;
import android.os.SystemClock;
import android.util.Pools;
import android.util.Slog;
import android.view.KeyEvent;
import android.view.WindowManagerPolicy;
/**
* Intercepts key events and forwards them to accessibility manager service.
*/
public class KeyboardInterceptor extends BaseEventStreamTransformation implements Handler.Callback {
private static final int MESSAGE_PROCESS_QUEUED_EVENTS = 1;
private static final String LOG_TAG = "KeyboardInterceptor";
private final AccessibilityManagerService mAms;
private final WindowManagerPolicy mPolicy;
private final Handler mHandler;
private KeyEventHolder mEventQueueStart;
private KeyEventHolder mEventQueueEnd;
/**
* @param service The service to notify of key events
* @param policy The policy to check for keys that may affect a11y
*/
public KeyboardInterceptor(AccessibilityManagerService service, WindowManagerPolicy policy) {
mAms = service;
mPolicy = policy;
mHandler = new Handler(this);
}
/**
* @param service The service to notify of key events
* @param policy The policy to check for keys that may affect a11y
* @param handler The handler to use. Only used for testing.
*/
public KeyboardInterceptor(AccessibilityManagerService service, WindowManagerPolicy policy,
Handler handler) {
// Can't combine the constructors without making at least mHandler non-final.
mAms = service;
mPolicy = policy;
mHandler = handler;
}
@Override
public void onKeyEvent(KeyEvent event, int policyFlags) {
/*
* Certain keys have system-level behavior that affects accessibility services.
* Let that behavior settle before handling the keys
*/
long eventDelay = getEventDelay(event, policyFlags);
if (eventDelay < 0) {
return;
}
if ((eventDelay > 0) || (mEventQueueStart != null)) {
addEventToQueue(event, policyFlags, eventDelay);
return;
}
mAms.notifyKeyEvent(event, policyFlags);
}
@Override
public boolean handleMessage(Message msg) {
if (msg.what != MESSAGE_PROCESS_QUEUED_EVENTS) {
Slog.e(LOG_TAG, "Unexpected message type");
return false;
}
processQueuedEvents();
if (mEventQueueStart != null) {
scheduleProcessQueuedEvents();
}
return true;
}
private void addEventToQueue(KeyEvent event, int policyFlags, long delay) {
long dispatchTime = SystemClock.uptimeMillis() + delay;
if (mEventQueueStart == null) {
mEventQueueEnd = mEventQueueStart =
KeyEventHolder.obtain(event, policyFlags, dispatchTime);
scheduleProcessQueuedEvents();
return;
}
final KeyEventHolder holder = KeyEventHolder.obtain(event, policyFlags, dispatchTime);
holder.next = mEventQueueStart;
mEventQueueStart.previous = holder;
mEventQueueStart = holder;
}
private void scheduleProcessQueuedEvents() {
if (!mHandler.sendEmptyMessageAtTime(
MESSAGE_PROCESS_QUEUED_EVENTS, mEventQueueEnd.dispatchTime)) {
Slog.e(LOG_TAG, "Failed to schedule key event");
};
}
private void processQueuedEvents() {
final long currentTime = SystemClock.uptimeMillis();
while ((mEventQueueEnd != null) && (mEventQueueEnd.dispatchTime <= currentTime)) {
final long eventDelay = getEventDelay(mEventQueueEnd.event, mEventQueueEnd.policyFlags);
if (eventDelay > 0) {
// Reschedule the event
mEventQueueEnd.dispatchTime = currentTime + eventDelay;
return;
}
// We'll either send or drop the event
if (eventDelay == 0) {
mAms.notifyKeyEvent(mEventQueueEnd.event, mEventQueueEnd.policyFlags);
}
final KeyEventHolder eventToBeRecycled = mEventQueueEnd;
mEventQueueEnd = mEventQueueEnd.previous;
if (mEventQueueEnd != null) {
mEventQueueEnd.next = null;
}
eventToBeRecycled.recycle();
if (mEventQueueEnd == null) {
mEventQueueStart = null;
}
}
}
private long getEventDelay(KeyEvent event, int policyFlags) {
int keyCode = event.getKeyCode();
if ((keyCode == KeyEvent.KEYCODE_VOLUME_DOWN) || (keyCode == KeyEvent.KEYCODE_VOLUME_UP)) {
return mPolicy.interceptKeyBeforeDispatching(null, event, policyFlags);
}
return 0;
}
private static class KeyEventHolder {
private static final int MAX_POOL_SIZE = 32;
private static final Pools.SimplePool<KeyEventHolder> sPool =
new Pools.SimplePool<>(MAX_POOL_SIZE);
public int policyFlags;
public long dispatchTime;
public KeyEvent event;
public KeyEventHolder next;
public KeyEventHolder previous;
public static KeyEventHolder obtain(KeyEvent event, int policyFlags, long dispatchTime) {
KeyEventHolder holder = sPool.acquire();
if (holder == null) {
holder = new KeyEventHolder();
}
holder.event = KeyEvent.obtain(event);
holder.policyFlags = policyFlags;
holder.dispatchTime = dispatchTime;
return holder;
}
public void recycle() {
event.recycle();
event = null;
policyFlags = 0;
dispatchTime = 0;
next = null;
previous = null;
sPool.release(this);
}
}
}
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