如何提高 BufferedWriter 在 Android 中的性能？答案

【问题标题】：How to improve the performance of the BufferedWriter in Android?如何提高 BufferedWriter 在 Android 中的性能？
【发布时间】：2018-10-14 11:09:49
【问题描述】：

我在Android开发，我尝试通过BufferedWriter将Android手机的Sensor值记录到.csv文件中。

代码如下：

//recordData
private float ACCELEROMETER_Gx = 0 , ACCELEROMETER_Gy = 0 , ACCELEROMETER_Gz = 0;
private float GRAVITY_X = 0 , GRAVITY_Y = 0 , GRAVITY_Z = 0;
private float GYROSCOPE_X = 0 , GYROSCOPE_Y = 0 , GYROSCOPE_Z = 0;
private float ACCELERATION_X = 0 , ACCELERATION_Y = 0 , ACCELERATION_Z = 0;
private float MAGNETIC_FIELD_X = 0 , MAGNETIC_FIELD_Y = 0 , MAGNETIC_FIELD_Z = 0;
private float PRESSURE = 0;
private float ROTATION_VECTOR_X = 0 , ROTATION_VECTOR_Y = 0 , ROTATION_VECTOR_Z = 0;

当 Sensor 发生变化时，会写入.csv 文件。

    @Override
        public void onSensorChanged(SensorEvent event) {
            if (event.sensor.getType() == Sensor.TYPE_ACCELEROMETER) {

                ACCELEROMETER_Gx = event.values[0];
                ACCELEROMETER_Gy = event.values[1];
                ACCELEROMETER_Gz = event.values[2];

            }else if (event.sensor.getType() == Sensor.TYPE_GRAVITY) {
                GRAVITY_X = event.values[0];
                GRAVITY_Y = event.values[1];
                GRAVITY_Z = event.values[2];


            }else if (event.sensor.getType() == Sensor.TYPE_GYROSCOPE) {
                GYROSCOPE_X = event.values[0];
                GYROSCOPE_Y = event.values[1];
                GYROSCOPE_Z = event.values[2];


            }else if (event.sensor.getType() == Sensor.TYPE_LINEAR_ACCELERATION) {
                ACCELERATION_X = event.values[0];
                ACCELERATION_Y = event.values[1];
                ACCELERATION_Z = event.values[2];


            }else if (event.sensor.getType() == Sensor.TYPE_MAGNETIC_FIELD) {

                MAGNETIC_FIELD_X = event.values[0];
                MAGNETIC_FIELD_Y = event.values[1];
                MAGNETIC_FIELD_Z = event.values[2];

            }else if (event.sensor.getType() == Sensor.TYPE_PRESSURE) {
                PRESSURE = event.values[0];

            }else if (event.sensor.getType() == Sensor.TYPE_ROTATION_VECTOR) {

                ROTATION_VECTOR_X = event.values[0];
                ROTATION_VECTOR_Y = event.values[1];
                ROTATION_VECTOR_Z = event.values[2];
            }


            SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd hh:mm:ss.SSS");
            String SensorChangeTime = sdf.format(new Date(System.currentTimeMillis()));

            String SensorValue =
                    SensorChangeTime + "," +
                    appendcomma(ACCELEROMETER_Gx) + appendcomma(ACCELEROMETER_Gy) + appendcomma(ACCELEROMETER_Gz) +
                    appendcomma(GRAVITY_X) + appendcomma(GRAVITY_Y) + appendcomma(GRAVITY_Z) +
                    appendcomma(GYROSCOPE_X) + appendcomma(GYROSCOPE_Y) + appendcomma(GYROSCOPE_Z) +
                    appendcomma(ACCELERATION_X) + appendcomma(ACCELERATION_Y) + appendcomma(ACCELERATION_Z) +
                    appendcomma(MAGNETIC_FIELD_X) + appendcomma(MAGNETIC_FIELD_Y) + appendcomma(MAGNETIC_FIELD_Z) +
                    appendcomma(PRESSURE) +
                    appendcomma(ROTATION_VECTOR_X) + appendcomma(ROTATION_VECTOR_Y) + appendcomma(ROTATION_VECTOR_Z) + '\n';

            writeData(SensorValue);
        }

        private String appendcomma(float value){
            return String.valueOf(value) + ",";
        }

        private void writeData(String Data){
            try {

                fw = new FileWriter(path+"/" + FileRecordName, true);
                BufferedWriter bw = new BufferedWriter(fw);
                bw.write(Data);
                bw.close();

            }catch (IOException e){
                Log.d(TAG,"writeData---e = " + e.toString());
            }
        }

当传感器值发生变化时，每次都会通过以下代码写入.csv文件：

            fw = new FileWriter(path+"/" + FileRecordName, true);
            BufferedWriter bw = new BufferedWriter(fw);
            bw.write(Data);
            bw.close();

每次创建new FileWriter 和coles 是否正确？

如何提高BufferedWriter在Android中的性能？

【问题讨论】：

检查this。它解释得很好。

标签： android filewriter bufferedwriter

【解决方案1】：

是的，这是正确的行为，对于每个写入操作，您都必须创建一个新的FileWriter 并关闭它。但是，从 API 19 开始，您可以使用 try-with-resources 来简单起见：

try (BufferedWriter bw = new BufferedWriter(new FileWriter(FILENAME))) {

    bw.write(data);

    // no need to close it.
    //bw.close();

} catch (IOException e) {
    e.printStackTrace();
}

【讨论】：