java - 使用 AsyncTask 作为内部类

Question

我创建了一个计步器应用程序，它作为独立应用程序运行良好。我认为我可以在我拥有的另一个应用程序中使用它，因此了解 AsyncTask 类来执行相同的操作。我阅读了 AsyncTask 的语法，并相应地将计步器代码粘贴到其中，但它给了我无法修复的错误。所以我刚刚创建了一个新项目，并将 AsyncTask 代码粘贴到那里，以找出我到底错在哪里，但我没有得到任何结果。请帮忙。

这是我的代码:

package com.example.momo.background;

import android.hardware.Sensor;
import android.hardware.SensorEvent;
import android.hardware.SensorEventListener;
import android.hardware.SensorManager;
import android.os.AsyncTask;
import android.os.Bundle;
import android.support.design.widget.FloatingActionButton;
import android.support.design.widget.Snackbar;
import android.support.v7.app.AppCompatActivity;
import android.support.v7.widget.Toolbar;
import android.view.View;
import android.view.Menu;
import android.view.MenuItem;
import android.widget.TextView;
import android.widget.Toast;

public class MainActivity extends AppCompatActivity implements SensorEventListener {

public TextView count;
public TextView mod;
public TextView cTime;
public TextView pTime;
public TextView timeDiff;
public TextView stepSpeed;
public SensorManager sensorManager;

public float speed;
float fin, initial, tdiff, sSpeed;
public SensorEvent event;


@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    new backgroundtask().execute();


}

@Override
public void onSensorChanged(SensorEvent event) {
    Sensor countSensor = sensorManager.getDefaultSensor(Sensor.TYPE_STEP_COUNTER);
    if (countSensor != null) {

        sensorManager.registerListener(this, countSensor, SensorManager.SENSOR_DELAY_UI); // original
        new backgroundtask().execute();

    } else {
        Toast.makeText(this, "count sensor not available!", Toast.LENGTH_LONG).show(); //toast prints the message
    }
}

@Override
public void onAccuracyChanged(Sensor sensor, int accuracy) {

}

class backgroundtask extends AsyncTask<Void, Float, Float> {

    protected void onPreExecute() {
    }

    protected Float doInBackground(Void... params) {


        fin = initial / 1000000000;
        initial = event.timestamp;
        tdiff = initial / 1000000000 - fin;
        sSpeed = 1 /tdiff;
        speed = sSpeed;
        publishProgress(speed);
        return speed;

    }

    @Override
    protected void onProgressUpdate(Float... values) {
        pTime.setText(String.valueOf(fin));
        cTime.setText(String.valueOf(initial / 1000000000));
        count.setText(String.valueOf(event.values[0])); // normal pedometer
        mod.setText(String.valueOf((initial / 1000000000) % 5));
        timeDiff.setText(String.valueOf(tdiff));
        stepSpeed.setText(String.valueOf(values));
    }

    protected void onPostExecute(Void unused)
    {

    }
}

}

Answer 1

据我了解，您对异步类的实现不正确。您向我们展示了堆栈跟踪或解释了错误，这也可能会有所帮助将代码从

移出

@Override
protected void onProgressUpdate(Float... values) {

}

至

protected void onPostExecute(Float speed)
{
    pTime.setText(String.valueOf(fin));
    cTime.setText(String.valueOf(initial / 1000000000));
    count.setText(String.valueOf(event.values[0])); // normal pedometer
    mod.setText(String.valueOf((initial / 1000000000) % 5));
    timeDiff.setText(String.valueOf(tdiff));
    stepSpeed.setText(String.valueOf(speed));
}

每次调用 onSensorChanged(SensorEvent event) 方法时，它都会创建一个新的 AsyncTask。