Question

所以开发用于将传感器值存储在一个文件中的android应用程序。我的主要问题是app只是在文件中写入最后一个值。基本上我正在尝试编写将每个传感器值存储到文件的代码。开始编写Android应用程序时...有人可以帮忙吗？这是代码：

package com.example.hello;

import java.io.File;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.OutputStreamWriter;

import android.app.Activity;
import android.content.Context;
import android.hardware.Sensor;
import android.hardware.SensorEvent;
import android.hardware.SensorEventListener;
import android.hardware.SensorManager;
import android.os.Bundle;
import android.os.Environment;
import android.view.Menu;
import android.widget.TextView;

public class MainActivity extends Activity {

private TextView xAxis, yAxis, zAxis;
private SensorManager sm;
private Sensor mSensor;
final File file = new File(Environment.getExternalStorageDirectory(),
        "results.txt");
static FileOutputStream fos;
static OutputStreamWriter myOutWriter;
private String writeString;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    xAxis = (TextView) findViewById(R.id.xAxis);
    yAxis = (TextView) findViewById(R.id.yAxis);
    zAxis = (TextView) findViewById(R.id.zAxis);

    sm = (SensorManager) getSystemService(Context.SENSOR_SERVICE);
    mSensor = sm.getDefaultSensor(Sensor.TYPE_MAGNETIC_FIELD);
    try {
        fos = new FileOutputStream(file);
        myOutWriter = new OutputStreamWriter(fos);
    } catch (FileNotFoundException e1) {
        // TODO Auto-generated catch block
        e1.printStackTrace();
    }

    SensorEventListener sensor = new SensorEventListener() {

        @Override
        public void onSensorChanged(SensorEvent event) {
            xAxis.setText("xAxis: " + event.values[0]);
            yAxis.setText("yAxis: " + event.values[1]);
            zAxis.setText("zAxis: " + event.values[2]);
            String test = new String(" " + event.values[0] + " "
                    + event.values[1] + " " + event.values[2]);
            writeData(test);
        }

        @Override
        public void onAccuracyChanged(Sensor sensor, int accuracy) {
            // TODO Auto-generated method stub
        }
    };

    sm.registerListener(sensor,
            sm.getDefaultSensor(Sensor.TYPE_MAGNETIC_FIELD),
            SensorManager.SENSOR_DELAY_UI);
}

@Override
public boolean onCreateOptionsMenu(Menu menu) {
    // Inflate the menu; this adds items to the action bar if it is present.
    getMenuInflater().inflate(R.menu.main, menu);
    return true;
}

public static void writeData(String test) {
    try {

        myOutWriter.append(test);
        myOutWriter.flush();
        myOutWriter.close();
    } catch (FileNotFoundException e) {
        // handle exception
    } catch (IOException e) {
        // handle exception
    }
}

}

Answer 1

每次写作时你都会关闭作者而不再打开它。将记录添加到异常而不是将它们留空，你应该看到一些堆栈跟踪。

以下内容： Log.e（标签，消息，异常），所以： Log.e（“MainActivity”，“无法将值写入文件”，e）;

Answer 2

尝试使用其他构造函数，将true作为布尔附加值。 http://bit.ly/16lxbld

fos = new FileOutputStream(file,true);

Answer 3

还请考虑FileOutputStream的以下构造函数

fos = new FileOutputStream(file,true);

Android在文件中写入最后一个值

3 个答案: