取消双击按键启动相机
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在项目开发过程中，测试报了一个有关相机的bug，在双击按键时会去打开相机，但是板子上没有摄像头，所以打开时就会报错，于是乎我拿着板子抓了一个双击power键的日志：
04-03 00:46:44.252 615 615 D KeyguardViewMediator: handleNotifyStartedGoingToSleep
04-03 00:46:44.285 453 523 I GestureLauncherService: Power button double tap gesture detected, launching camera. Interval=210ms
04-03 00:46:44.286 453 523 I PowerManagerService: Waking up from Asleep (uid=1000, reason=WAKE_REASON_POWER_BUTTON, details=android.policy:POWER)...
04-03 00:46:44.288 239 983 D gralloc4: [File] : hardware/rockchip/libgralloc/bifrost/src/hidl_common/Allocator.cpp; [Line] : 149; [Func] : allocate;
04-03 00:46:44.288 239 983 D gralloc4: got new private_handle_t instance @0xb4000075c08cafd0 for buffer 'ColorFade#0'. share_fd : 8, share_attr_fd : 9, flags : 0x4, width : 800, height : 1280, req_format : 0x1, producer_usage : 0x40000000000b00, consumer_usage : 0x40000000000b00, internal_format : 0x0, stride : 0, byte_stride : 0, internalWidth : 0, internalHeight : 0, alloc_format : 0x100000001, size : 4160512, layer_count : 1, backing_store_size : 4160512, backing_store_id : 1026497183873, allocating_pid : 239, ref_count : 1, yuv_info : 0
04-03 00:46:44.288 239 983 D gralloc4: plane_info[0]: offset : 0, byte_stride : 3200, alloc_width : 800, alloc_height : 1280
04-03 00:46:44.288 239 983 D gralloc4: plane_info[1]: offset : 0, byte_stride : 0, alloc_width : 0, alloc_height : 0
04-03 00:46:44.292 615 634 D KeyguardViewMediator: onFinishedGoingToSleep(2)
04-03 00:46:44.292 615 634 D KeyguardViewMediator: notifyFinishedGoingToSleep
04-03 00:46:44.292 615 634 I KeyguardViewMediator: Camera gesture was triggered, preventing Keyguard locking.
04-03 00:46:44.294 615 634 D KeyguardViewMediator: onStartedWakingUp, seq = 3
04-03 00:46:44.294 615 634 D KeyguardViewMediator: notifyStartedWakingUp
04-03 00:46:44.295 615 615 D KeyguardViewMediator: handleNotifyFinishedGoingToSleep
04-03 00:46:44.298 239 983 D gralloc4: [File] : hardware/rockchip/libgralloc/bifrost/src/hidl_common/Allocator.cpp; [Line] : 149; [Func] : allocate;
04-03 00:46:44.298 239 983 D gralloc4: got new private_handle_t instance @0xb4000075c08caa30 for buffer 'ColorFade#0'. share_fd : 8, share_attr_fd : 9, flags : 0x4, width : 800, height : 1280, req_format : 0x1, producer_usage : 0x40000000000b00, consumer_usage : 0x40000000000b00, internal_format : 0x0, stride : 0, byte_stride : 0, internalWidth : 0, internalHeight : 0, alloc_format : 0x100000001, size : 4160512, layer_count : 1, backing_store_size : 4160512, backing_store_id : 1026497183874, allocating_pid : 239, ref_count : 1, yuv_info : 0
04-03 00:46:44.298 239 983 D gralloc4: plane_info[0]: offset : 0, byte_stride : 3200, alloc_width : 800, alloc_height : 1280
04-03 00:46:44.298 239 983 D gralloc4: plane_info[1]: offset : 0, byte_stride : 0, alloc_width : 0, alloc_height : 0
04-03 00:46:44.301 453 453 D WifiSleepController: onReceive, action=android.intent.action.SCREEN_OFF
04-03 00:46:44.302 453 453 D WifiSleepController: isScanAlwaysAvailable = false
04-03 00:46:44.302 453 453 D WifiSleepController: shouldStartWifiSleep: isWifiOpen = true
04-03 00:46:44.302 453 453 D WifiSleepController: shouldStartBtSleep: isBtOpen = true
04-03 00:46:44.307 239 983 D gralloc4: [File] : hardware/rockchip/libgralloc/bifrost/src/hidl_common/Allocator.cpp; [Line] : 149; [Func] : allocate;
04-03 00:46:44.307 239 983 D gralloc4: got new private_handle_t instance @0xb4000075c08cafd0 for buffer 'ColorFade#0'. share_fd : 8, share_attr_fd : 9, flags : 0x4, width : 800, height : 1280, req_format : 0x1, producer_usage : 0x40000000000b00, consumer_usage : 0x40000000000b00, internal_format : 0x0, stride : 0, byte_stride : 0, internalWidth : 0, internalHeight : 0, alloc_format : 0x100000001, size : 4160512, layer_count : 1, backing_store_size : 4160512, backing_store_id : 1026497183875, allocating_pid : 239, ref_count : 1, yuv_info : 0
04-03 00:46:44.307 268 1055 D AudioHardwareTiny: adev_set_parameters: kvpairs = screen_state=off
04-03 00:46:44.307 239 983 D gralloc4: plane_info[0]: offset : 0, byte_stride : 3200, alloc_width : 800, alloc_height : 1280
04-03 00:46:44.307 239 983 D gralloc4: plane_info[1]: offset : 0, byte_stride : 0, alloc_width : 0, alloc_height : 0
04-03 00:46:44.325 615 615 D KeyguardViewMediator: handleNotifyWakingUp
04-03 00:46:44.329 0 0 W dhd_set_suspend: force extra suspend setting
04-03 00:46:44.329 0 0 W dhd_enable_packet_filter: enter, value = 1
04-03 00:46:44.341 453 826 E VibratorService: vibratorOff command failed (1).
04-03 00:46:44.342 615 615 V StatusBar: Camera launch
从日志中我们可以提取到"GestureLauncherService: Power button double tap gesture detected, launching camera. Interval=210ms"这样一条信息，然后我们可以去framework中找到这个"Power button double tap"打印的位置，
public boolean interceptPowerKeyDown(KeyEvent event, boolean interactive,
MutableBoolean outLaunched) {
if (event.isLongPress()) {
// Long presses are sent as a second key down. If the long press threshold is set lower
// than the double tap of sequence interval thresholds, this could cause false double
// taps or consecutive taps, so we want to ignore the long press event.
return false;
}
boolean launched = false;
boolean intercept = false;
long powerTapInterval;
synchronized (this) {
powerTapInterval = event.getEventTime() - mLastPowerDown;
if (mCameraDoubleTapPowerEnabled
&& powerTapInterval < CAMERA_POWER_DOUBLE_TAP_MAX_TIME_MS) {
launched = true;
intercept = interactive;
mPowerButtonConsecutiveTaps++;
} else if (powerTapInterval < POWER_SHORT_TAP_SEQUENCE_MAX_INTERVAL_MS) {
mPowerButtonConsecutiveTaps++;
} else {
mPowerButtonConsecutiveTaps = 1;
}
mLastPowerDown = event.getEventTime();
}
if (DBG && mPowerButtonConsecutiveTaps > 1) {
Slog.i(TAG, Long.valueOf(mPowerButtonConsecutiveTaps) +
" consecutive power button taps detected");
}
/*
if (launched) {
Slog.i(TAG, "Power button double tap gesture detected, launching camera. Interval="
+ powerTapInterval + "ms");
launched = handleCameraGesture(false // useWakelock,
StatusBarManager.CAMERA_LAUNCH_SOURCE_POWER_DOUBLE_TAP);
if (launched) {
mMetricsLogger.action(MetricsEvent.ACTION_DOUBLE_TAP_POWER_CAMERA_GESTURE,
(int) powerTapInterval);
mUiEventLogger.log(GestureLauncherEvent.GESTURE_CAMERA_DOUBLE_TAP_POWER);
}
}
*/
mMetricsLogger.histogram("power_consecutive_short_tap_count", mPowerButtonConsecutiveTaps);
mMetricsLogger.histogram("power_double_tap_interval", (int) powerTapInterval);
outLaunched.value = launched;
return intercept && launched;
}