如何防止Android设备从Qt应用程序进入睡眠 [英] How do I prevent an Android device from going to sleep from Qt application

问题描述

我在Android上部署一个Qt应用程序，需要防止设备进入待机状态（否则，我的线程被中断，并且我的BLE连接丢失）。

I'm deploying a Qt application on Android and need to prevent the device from going to standby (else, my threads are interrupted and also my BLE connection gets lost).

我发现在SO：

I found that on SO: How do I prevent an Android device from going to sleep programmatically?

这个Java代码应该执行：

This Java code should be executed:

PowerManager pm = (PowerManager) getSystemService(Context.POWER_SERVICE);
PowerManager.WakeLock wl = pm.newWakeLock(PowerManager.SCREEN_DIM_WAKE_LOCK, "My Tag");
wl.acquire();

// screen and CPU will stay awake during this section

wl.release();

但是如何在我的Qt应用程序中实现呢？

But how to implement that in my Qt application?

推荐答案

QAndroidJniObject 有助于执行来自Qt的Java代码。写入它可能很难，很难弄清楚什么问题，当它不工作....

QAndroidJniObject helps executing Java code from Qt. Writting it could be hard and it's hard to figure out what's wrong when it does not work....

这里是解决方案（封装在一个帮助类）来锁定 PowerManager.WakeLock 物件：

Here is the solution (encapsulated in a helper class) to lock a PowerManager.WakeLock object:

LockHelper.h：

LockHelper.h:

#pragma once
#include <QAndroidJniObject>

class KeepAwakeHelper
{
public:
    KeepAwakeHelper();
    virtual ~KeepAwakeHelper();

private:
    QAndroidJniObject m_wakeLock;
};

LockHelper.cpp：

LockHelper.cpp:

#include "LockHelper.h"
#include <QAndroidJniObject>
#include <QDebug>
#include "jni.h"

KeepAwakeHelper::KeepAwakeHelper()
{
    QAndroidJniObject activity = QAndroidJniObject::callStaticObjectMethod("org/qtproject/qt5/android/QtNative", "activity", "()Landroid/app/Activity;");
    if ( activity.isValid() )
    {
        QAndroidJniObject serviceName = QAndroidJniObject::getStaticObjectField<jstring>("android/content/Context","POWER_SERVICE");
        if ( serviceName.isValid() )
        {
            QAndroidJniObject powerMgr = activity.callObjectMethod("getSystemService", "(Ljava/lang/String;)Ljava/lang/Object;",serviceName.object<jobject>());
            if ( powerMgr.isValid() )
            {
                jint levelAndFlags = QAndroidJniObject::getStaticField<jint>("android/os/PowerManager","SCREEN_DIM_WAKE_LOCK");

                QAndroidJniObject tag = QAndroidJniObject::fromString( "My Tag" );

                m_wakeLock = powerMgr.callObjectMethod("newWakeLock", "(ILjava/lang/String;)Landroid/os/PowerManager$WakeLock;", levelAndFlags,tag.object<jstring>());
            }
        }
    }

    if ( m_wakeLock.isValid() )
    {
        m_wakeLock.callMethod<void>("acquire", "()V");
        qDebug() << "Locked device, can't go to standby anymore";
    }
    else
    {
        assert( false );
    }
}

KeepAwakeHelper::~KeepAwakeHelper()
{
    if ( m_wakeLock.isValid() )
    {
        m_wakeLock.callMethod<void>("release", "()V");
        qDebug() << "Unlocked device, can now go to standby";
    }
}

然后，只需执行：

{
    KeepAwakeHelper helper;
    // screen and CPU will stay awake during this section
    // lock will be released when helper object goes out of scope
}

注意：您需要确保您拥有 WAKE_LOCK 您的清单中设置的权限，以便使用此代码。

Note: You need to be sure you have the WAKE_LOCK permission set in your manifest in order to use this code.

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