1、main.xml

<?xml version="1.0" encoding="utf-8"?>

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"

    android:layout_width="match_parent"

    android:layout_height="match_parent"

    android:orientation="vertical" >

    <EditText

        android:id="@+id/numET"

        android:layout_width="fill_parent"

        android:layout_height="wrap_content"

        android:hint="请输入文件名" />

    <EditText

        android:id="@+id/contentET"

        android:layout_width="fill_parent"

        android:layout_height="wrap_content"

        android:hint="请输入文件内容"//提示文本

        android:inputType="textMultiLine"

        android:minLines="3" />//最小为3行，多了自动变大

    <LinearLayout

        android:layout_width="match_parent"

        android:layout_height="match_parent"

        android:orientation="horizontal" >

        <Button android:id="@+id/sdcBT"

            android:layout_width="wrap_content"

            android:layout_height="wrap_content"

            android:text="保存到sd卡"

            android:onClick="onClick"

            />

        <Button android:id="@+id/romBT"

            android:layout_width="wrap_content"

            android:layout_height="wrap_content"

            android:text="保存到手机"

            android:onClick="onClick"

            />

    </LinearLayout>

</LinearLayout>

2、MainActivity

package com.njupt.file1;

import android.os.Bundle;

import android.os.Environment;

import android.app.Activity;

import android.view.Menu;

import android.view.View;

import android.widget.EditText;

import android.widget.Toast;

public class MainActivity extends Activity {

	private EditText numET;

	private EditText contentET;

	@Override

	protected void onCreate(Bundle savedInstanceState) {

		super.onCreate(savedInstanceState);

		setContentView(R.layout.main);

		numET = (EditText) findViewById(R.id.numET);

	    contentET = (EditText) findViewById(R.id.contentET);

	}

	@Override

	protected void onResume() {

		super.onResume();

		//Environment.getExternalStorageState().获取sd卡的状态，判断是安装，还是移除

		findViewById(R.id.sdcBT).setEnabled(Environment.getExternalStorageState().equals(Environment.MEDIA_MOUNTED));

	}

	@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 void onClick(View v){

		try{

		String name = numET.getText().toString();

		String content = contentET.getText().toString();

		FileService service = new FileService();

		switch(v.getId()){

		case R.id.sdcBT:

			service.saveToSDCard(name,content);

			break;

		case R.id.romBT:

			service.saveToRom(name,content);

			break;

		}

		Toast.makeText(getApplicationContext(), "保存成功", Toast.LENGTH_SHORT).show();

		}catch(Exception e){

			e.printStackTrace();

			Toast.makeText(getApplication(), "dacard出异常", Toast.LENGTH_SHORT).show();

		}

	}

}

3、FileService

package com.njupt.file1;

import java.io.File;

import java.io.FileOutputStream;

import java.io.IOException;

import android.os.Environment;

public class FileService {

	public void saveToSDCard(String name, String content) {

		 FileOutputStream fos = null;

		try{

			//Environment.getExternalStorageDirectory()。获取sd卡的路径

		File file = new File(Environment.getExternalStorageDirectory(),name);

	    fos = new FileOutputStream(file);

	    fos.write(content.getBytes());

		}catch(Exception e){

			e.printStackTrace();

		}finally{

			try {

				fos.close();

			} catch (IOException e) {

				e.printStackTrace();

			}

		}

	}

	public void saveToRom(String name, String content) {

		// TODO Auto-generated method stub

	}

}

4、AndroidManifest.xml

最后在AndroidManifest.xml配上

<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE"/>