Android 根据按Power键的次数来实现自定义的动能

通过查看 PhoneWindowManager 中 power 相关流程，发现Android 原生code中已经添加了对Power键连按的接口，目前可以定义按一次、按两次及按三次时对应的响应操作。

Android中对Power键连按次数的定义如下：
frameworks\base\core\res\res\values\config.xml

短按一次power键系统定义：

 <!-- Control the behavior when the user short presses the power button.
            0 - Nothing
            1 - Go to sleep (doze)
            2 - Really go to sleep (don't doze)
            3 - Really go to sleep and go home (don't doze)
            4 - Go to home
            5 - Dismiss IME if shown. Otherwise go to home
    -->
    <integer name="config_shortPressOnPowerBehavior">1</integer>

连续短按两次power键系统定义：

<!-- Control the behavior when the user double presses the power button.
            0 - Nothing
            1 - Toggle theater mode setting
            2 - Brightness boost
    -->
    <integer name="config_doublePressOnPowerBehavior">0</integer>

连续短按三次power键系统定义：

<!-- Control the behavior when the user triple presses the power button.
            0 - Nothing
            1 - Toggle theater mode setting
            2 - Brightness boost
    -->
    <integer name="config_triplePressOnPowerBehavior">0</integer>

可以看到短按两次和短按三次都是定义的 0，对应为 nothing，即不做任何操作。

power键在config中的定义，最终是在PhoneWindowManager.java 的 powerPress()方法中判断和实现。
frameworks\base\services\core\java\com\android\server\policy\PhoneWindowManager.java

 private void powerPress(long eventTime, boolean interactive, int count) {
        if (mScreenOnEarly && !mScreenOnFully) {
            Slog.i(TAG, "Suppressed redundant power key press while "
                    + "already in the process of turning the screen on.");
            return;
        }

        if (count == 2) {//短按两次power键的实现
            powerMultiPressAction(eventTime, interactive, mDoublePressOnPowerBehavior);
        } else if (count == 3) {{//短按三次power键的实现
            powerMultiPressAction(eventTime, interactive, mTriplePressOnPowerBehavior);
        } else if (interactive && !mBeganFromNonInteractive) {
            switch (mShortPressOnPowerBehavior) {
                case SHORT_PRESS_POWER_NOTHING:
                    break;
                case SHORT_PRESS_POWER_GO_TO_SLEEP:
                    goToSleep(eventTime, PowerManager.GO_TO_SLEEP_REASON_POWER_BUTTON, 0);
                    break;
                case SHORT_PRESS_POWER_REALLY_GO_TO_SLEEP:
                    goToSleep(eventTime, PowerManager.GO_TO_SLEEP_REASON_POWER_BUTTON,
                            PowerManager.GO_TO_SLEEP_FLAG_NO_DOZE);
                    break;
                case SHORT_PRESS_POWER_REALLY_GO_TO_SLEEP_AND_GO_HOME:
                    goToSleep(eventTime, PowerManager.GO_TO_SLEEP_REASON_POWER_BUTTON,
                            PowerManager.GO_TO_SLEEP_FLAG_NO_DOZE);
                    launchHomeFromHotKey();
                    break;
                case SHORT_PRESS_POWER_GO_HOME:
                    shortPressPowerGoHome();
                    break;
                case SHORT_PRESS_POWER_CLOSE_IME_OR_GO_HOME: {
                    if (mDismissImeOnBackKeyPressed) {
                        if (mInputMethodManagerInternal == null) {
                            mInputMethodManagerInternal =
                                    LocalServices.getService(InputMethodManagerInternal.class);
                        }
                        if (mInputMethodManagerInternal != null) {
                            mInputMethodManagerInternal.hideCurrentInputMethod();
                        }
                    } else {
                        shortPressPowerGoHome();
                    }
                    break;
                }
            }
        }
    }

由code中发现，短按两次，三次都是在powerMultiPressAction()中实现

 private void powerMultiPressAction(long eventTime, boolean interactive, int behavior) {
        switch (behavior) {
            case MULTI_PRESS_POWER_NOTHING:
                break;
            case MULTI_PRESS_POWER_THEATER_MODE:
                if (!isUserSetupComplete()) {
                    Slog.i(TAG, "Ignoring toggling theater mode - device not setup.");
                    break;
                }

                if (isTheaterModeEnabled()) {
                    Slog.i(TAG, "Toggling theater mode off.");
                    Settings.Global.putInt(mContext.getContentResolver(),
                            Settings.Global.THEATER_MODE_ON, 0);
                    if (!interactive) {
                        wakeUpFromPowerKey(eventTime);
                    }
                } else {
                    Slog.i(TAG, "Toggling theater mode on.");
                    Settings.Global.putInt(mContext.getContentResolver(),
                            Settings.Global.THEATER_MODE_ON, 1);

                    if (mGoToSleepOnButtonPressTheaterMode && interactive) {
                        goToSleep(eventTime, PowerManager.GO_TO_SLEEP_REASON_POWER_BUTTON, 0);
                    }
                }
                break;
            case MULTI_PRESS_POWER_BRIGHTNESS_BOOST:
                Slog.i(TAG, "Starting brightness boost.");
                if (!interactive) {
                    wakeUpFromPowerKey(eventTime);
                }
                mPowerManager.boostScreenBrightness(eventTime);
                break;
        }
    }

正好就是config_doublePressOnPowerBehavior和config_triplePressOnPowerBehavior对应的三种状态，因此，可以以此为入口，通过自定义第四种状态，来实现自定义功能，比如：紧急呼叫功能。

附上同事所实现的连续短按三次power键实现紧急呼叫功能：

1)  自定义状态值
Config.xml
<integer name="config_triplePressOnPowerBehavior">3</integer>

PhoneWindowManager.java
static final int MULTI_PRESS_POWER_EMERGENCY_CALL = 3;

2)  实现对应功能
PhoneWindowManager.java 的 powerMultiPressAction()方法添加 case：

case MULTI_PRESS_POWER_EMERGENCY_CALL:
Intent callIntent = new Intent(Intent.ACTION_CALL_EMERGENCY);
callIntent.setFlags(Intent.FLAG_ACTIVITY_NEW_TASK);
callIntent.setData(Uri.parse("tel:112"));
mContext.startActivity(callIntent);
break;

Android 根据按Power键的次数来实现自定义的动能

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