写文件

package com.example.duang;

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

import android.app.Activity;
import android.os.Bundle;
import android.os.Environment;
import android.util.Log;
import android.view.Menu;
import android.view.MenuItem;

public class MainActivity extends Activity {

@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
boolean isMounted =Environment.getExternalStorageState().equals(android.os.Environment.MEDIA_MOUNTED);
if(isMounted){
try {
createFile();
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
}
private void createFile() throws IOException{
File parent_path = Environment.getExternalStorageDirectory();

// 可以建立一个子目录专门存放自己专属文件
File dir = new File(parent_path.getAbsoluteFile(), "lyx");
dir.mkdir();

File file = new File(dir.getAbsoluteFile(), "myfile.txt");

Log.d("文件路径", file.getAbsolutePath());

// 创建这个文件，如果不存在
file.createNewFile();

FileOutputStream fos = new FileOutputStream(file);

String data = "hello,world!";
byte[] buffer = data.getBytes();

// 开始写入数据到这个文件。
fos.write(buffer, 0, buffer.length);
fos.flush();
fos.close();

Log.d("文件写入", "成功");

}
}

<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="com.example.duang.MainActivity" >

<TextView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="@string/hello_world" />

</RelativeLayout>