Question

我在Android上部署Qt应用程序，需要阻止设备进入待机状态（否则，我的线程会中断，我的BLE连接也会丢失）。

我发现在SO：How do I prevent an Android device from going to sleep programmatically?

应执行此Java代码：

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应用程序中实现它？

Answer 1

QAndroidJniObject帮助从Qt执行Java代码。写它可能很难，当它不起作用时很难弄清楚它是错的......

以下是锁定PowerManager.WakeLock对象的解决方案（封装在辅助类中）：

LockHelper.h：

#pragma once
#include <QAndroidJniObject>

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

private:
    QAndroidJniObject m_wakeLock;
};

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：

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

注意：您需要确保在清单中设置了WAKE_LOCK权限才能使用此代码。

Answer 2

另一种解决方案：

QAndroidJniObject activity = QAndroidJniObject::callStaticObjectMethod("org/qtproject/qt5/android/QtNative", "activity", "()Landroid/app/Activity;");
if (activity.isValid()) {
    QAndroidJniObject window = activity.callObjectMethod("getWindow", "()Landroid/view/Window;");
    if (window.isValid()) {
        const int FLAG_KEEP_SCREEN_ON = 128;
        window.callMethod<void>("addFlags", "(I)V", FLAG_KEEP_SCREEN_ON);
    }
}

Source here

我建议你阅读this question用于教育目的。

如何防止Android设备从Qt应用程序进入休眠状态

2 个答案: