我想开发一个应用程序
- 在外部存储中创建文件
2.点击开始按钮时将加速度计读数写入文件
3.单击停止按钮时停止写入
4.点击读取按钮读取文件内容
我不知道如何在外部存储中创建文件并将加速度计的读数存储在其中，然后从文件中读取值。
我在 MainACtivity.java 中尝试了以下代码
package com.example.startstopbuttonaccelerometerreading;
import java.io.File;
import java.io.FileOutputStream;
import java.io.FileWriter;
import java.io.IOException;
import java.io.OutputStreamWriter;
import android.hardware.Sensor;
import android.hardware.SensorEvent;
import android.hardware.SensorEventListener;
import android.hardware.SensorManager;
import android.os.Bundle;
import android.app.Activity;
import android.content.Context;
import android.view.Menu;
import android.view.View;
import android.widget.Button;
import android.widget.RelativeLayout;
import android.widget.TextView;
import android.widget.Toast;
public class MainActivity extends Activity implements SensorEventListener {
private SensorManager mSensorManager;
private Sensor mAccelerometer;
TextView title,tv,tv1,tv2;
RelativeLayout layout;
/** Called when the activity is first created. */
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
mSensorManager = (SensorManager) getSystemService(Context.SENSOR_SERVICE);
mAccelerometer = mSensorManager.getDefaultSensor(Sensor.TYPE_ACCELEROMETER);
//get layout
layout = (RelativeLayout) findViewById(R.id.relative);
//get textviews
title=(TextView)findViewById(R.id.name);
tv=(TextView)findViewById(R.id.xval);
tv1=(TextView)findViewById(R.id.yval);
tv2=(TextView)findViewById(R.id.zval);
}
public void onStartClick(View view) {
final SensorEventListener mySensorEventListener = new SensorEventListener() {
public void onSensorChanged(SensorEvent sensorEvent) {
if (sensorEvent.sensor.getType() == Sensor.TYPE_ACCELEROMETER) {
float x = sensorEvent.values[0];
float y = sensorEvent.values[1];
float z = sensorEvent.values[2]; // TODO apply the acceleration changes to your application.
textView.append("\nACC_x = "+ x + ", ACC_y = "+y+ ", ACC_z = " + z);
acc+="\n"+x+ ", "+ y+","+z;
try {
File myFile = new File("/sdcard/acc.txt");
myFile.createNewFile();
FileOutputStream fOut = new FileOutputStream(myFile);
OutputStreamWriter myOutWriter =
new OutputStreamWriter(fOut);
myOutWriter.append(acc);
myOutWriter.close();
fOut.close();
Toast.makeText(getBaseContext(),
"Done writing SD 'acc.txt'",
Toast.LENGTH_SHORT).show();
} catch (Exception e) {
Toast.makeText(getBaseContext(), e.getMessage(),
Toast.LENGTH_SHORT).show();
}
}
}
@Override
public void onAccuracyChanged(Sensor sensor, int accuracy) {
// TODO Auto-generated method stub
}
};
// write on SD card file data in the text box
int sensorType = Sensor.TYPE_ACCELEROMETER;
mSensorManager.registerListener(this, mAccelerometer, SensorManager.SENSOR_DELAY_NORMAL);
}// onClick
;
public void onStopClick(View view) {
mSensorManager.unregisterListener(this);
}
@Override
public void onAccuracyChanged(Sensor sensor, int accuracy) {
}
}
这是 activity_main.xml 代码：
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:paddingBottom="@dimen/activity_vertical_margin"
android:paddingLeft="@dimen/activity_horizontal_margin"
android:paddingRight="@dimen/activity_horizontal_margin"
android:paddingTop="@dimen/activity_vertical_margin"
tools:context=".MainActivity"
android:id="@+id/relative" >
<Button
android:id="@+id/button1"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_marginLeft="40dp"
android:layout_marginTop="124dp"
android:text="Start"
android:onClick="onStartClick" />
<Button
android:id="@+id/button2"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignBottom="@+id/button1"
android:layout_marginLeft="37dp"
android:layout_toRightOf="@+id/button1"
android:text="Stop"
android:onClick="onStopClick" />
<TextView
android:textSize="30dp"
android:id="@+id/name"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
/>
<TextView
android:textSize="20dp"
android:layout_below="@+id/name"
android:id="@+id/xval"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
/>
<TextView
android:textSize="20dp"
android:id="@+id/yval"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:layout_below="@+id/xval"
/>
<TextView
android:textSize="20dp"
android:id="@+id/zval"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:layout_below="@+id/yval"
/>
</RelativeLayout>
我在 androidmanifest.xml 中写了权限
<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE"/>
MainActivity 没有被编译。错误是 acc 和 textview 无法解决。我想知道在外部存储中创建文件并向其中写入加速度计读数并从文件中读取数据的代码。