Android 跌倒检测问题

Posted 2023-02-24

【中文标题】Android 跌倒检测问题

【英文标题】：Android Fall Detection Issue

【发布时间】：2018-06-29 22:27:36

【问题描述】：

我正在尝试使用 android 的accelerometer 实现一个简单的跌倒检测算法。

手机当前的加速度存储在mAccel中，如果检测到突然抖动Timer t开始。 Timer 内部有两个 CountDownTimers。

firstTimer 用于在用户在过去 5 秒内没有移动时注册“跌倒”，secondTimer 用于在用户未按下按钮时确认跌倒（尚未实现） .

public void onSensorChanged(SensorEvent event) 

    if (event.sensor.getType() == Sensor.TYPE_ACCELEROMETER) 
        mGravity = event.values.clone();

        float x = mGravity[0];
        float y = mGravity[1];
        float z = mGravity[2];
        mAccelLast = mAccelCurrent;
        mAccelCurrent = (float) Math.sqrt(x * x + y * y + z * z);
        float delta = mAccelCurrent - mAccelLast;
        mAccel = mAccel * 0.9f + delta;
        mAccel = abs(mAccel);
        textView.setText("a:"+mAccel);
        if (abs(mAccel) > 5.0f)  // Shake detection
            t();
        
    

public void t () 

    firstTimer = new CountDownTimer(5000, 1000)   //fall registration timer

        @Override
        public void onTick(long millisUntilFinished) 
            //if there is movement before 5 seconds pass cancel the timer
            if (abs(mAccel) > 2.0f) 
                firstTimer.cancel();
                firstTimer = null;
            
        

        @Override
        public void onFinish() 
            toast.show();

            secondTimer = new CountDownTimer(30*1000, 1000)  //fall confirmation timer

                @Override
                public void onTick(long millisUntilFinished) 
                    textView2.setText("" + millisUntilFinished / 1000);
                

                @Override
                public void onFinish() 
                    Toast toast = Toast.makeText(getApplicationContext(),
                                  "Fall Registered!", Toast.LENGTH_LONG);
                        toast.show();
                    
                .start();
            
        .start();
    

主要问题是大多数时候firstTimer被访问，由于mAccel超过2.0阈值而被取消，同时它正在减速。

我尝试使用Timer.schedule() 将firstTimer 的激活延迟到加速度值“休息”之后，但它无法使用它。

【参考方案1】：

我创建了一个新的 Timer 对象 mTimer，这似乎适用于所有情况。

CountDownTimer firstTimer = new CountDownTimer(5000, 1000)   //fall registration timer

        @Override
        public void onTick(long millisUntilFinished) 
            //if there is movement before 5 seconds pass cancel the timer
            if (abs(mAccel) > 2.0f) 
                Toast toast = Toast.makeText(getApplicationContext(),
                              "Fall not Detected", Toast.LENGTH_SHORT);
                toast.show();
                firstTimer.cancel();
            
        

        @Override
        public void onFinish() 
            Toast toast = Toast.makeText(getApplicationContext(),
                          "Fall Detected!", Toast.LENGTH_SHORT);
            toast.show();
            secondTimer.start();
        
    ;

    CountDownTimer secondTimer = new CountDownTimer(30*1000, 1000) 
    //fall confirmation timer

        @Override
        public void onTick(long millisUntilFinished) 
            textView2.setText("" + millisUntilFinished / 1000);
        

        @Override
        public void onFinish() 
            Toast toast = Toast.makeText(getApplicationContext(),
            "Fall Registered!", Toast.LENGTH_LONG);
            toast.show();
        
    ;


@Override
public void onSensorChanged(SensorEvent event) 

    if (event.sensor.getType() == Sensor.TYPE_ACCELEROMETER) 
        mGravity = event.values.clone();
        float x = mGravity[0];
        float y = mGravity[1];
        float z = mGravity[2];
        mAccelLast = mAccelCurrent;
        mAccelCurrent = (float) Math.sqrt(x * x + y * y + z * z);
        float delta = mAccelCurrent - mAccelLast;
        mAccel = mAccel * 0.9f + delta;
        mAccel = abs(mAccel);
        textView.setText("a:"+mAccel);
        if (abs(mAccel) > 5.0f)  // Shake detection
            mTimer.schedule(new TimerTask()  
            //start after 2 second delay to make acceleration values "rest"

                @Override
                public void run() 
                    firstTimer.start();
                

            , 2000);