（1）说明:操作SD卡上的文件须要增加下面权限

 在SD卡上创建和删除文件权限

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

在SD卡上写入数据的权限
<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE"/>

在sd卡上的文件操作和我上一篇文章几乎相同，假设有不懂的能够看我的上一篇文章

 

android 读写文件演示样例

http://blog.csdn.net/liuzuyi200/article/details/25049183

仅仅只是多加了推断SD卡是否存在的方法

Environment.getExternalStorageState().equals(Environment.MEDIA_MOUNTED)

（2）布局文件

<?

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

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

    android:layout_width="fill_parent"

    android:layout_height="fill_parent"

    android:orientation="vertical" >

    <RelativeLayout

        android:layout_width="fill_parent"

        android:layout_height="wrap_content"

        android:orientation="vertical" >

        <TextView

            android:id="@+id/label_01"

            android:layout_width="wrap_content"

            android:layout_height="wrap_content"

            android:text="@string/name"

            android:textSize="20dp" />

        <EditText

            android:id="@+id/filename"

            android:layout_width="160dp"

            android:layout_height="wrap_content"

            android:layout_alignTop="@id/label_01"

            android:layout_toRightOf="@id/label_01" />

    </RelativeLayout>

    <TextView

        android:id="@+id/label_02"

        android:layout_width="wrap_content"

        android:layout_height="wrap_content"

        android:text="@string/neirong" />

    <EditText

        android:id="@+id/content"

        android:layout_width="fill_parent"

        android:layout_height="120px"

        android:ems="10" >

        <requestFocus />

    </EditText>

    <LinearLayout

        android:layout_width="fill_parent"

        android:layout_height="wrap_content"

        android:orientation="horizontal" >

        <Button

            android:id="@+id/savebutton"

            android:layout_width="wrap_content"

            android:layout_height="wrap_content"

            android:gravity="right"

            android:text="@string/save" />

        <Button

            android:id="@+id/readbutton"

            android:layout_width="wrap_content"

            android:layout_height="wrap_content"

            android:gravity="right"

            android:text="@string/read" />

    </LinearLayout>

    <TextView

        android:id="@+id/textcontent"

        android:layout_width="match_parent"

        android:layout_height="wrap_content"

        android:layout_weight="0.10" />

</LinearLayout>

（3）代码

package com.liuzuyi.file;

import java.io.ByteArrayOutputStream;

import java.io.File;

import java.io.FileInputStream;

import java.io.FileOutputStream;

import java.io.InputStream;

import java.io.OutputStream;

import android.support.v7.app.ActionBarActivity;

import android.support.v7.app.ActionBar;

import android.support.v4.app.Fragment;

import android.app.Activity;

import android.content.Context;

import android.os.Bundle;

import android.os.Environment;

import android.util.Log;

import android.view.LayoutInflater;

import android.view.Menu;

import android.view.MenuItem;

import android.view.View;

import android.view.View.OnClickListener;

import android.view.ViewGroup;

import android.widget.Button;

import android.widget.EditText;

import android.widget.TextView;

import android.widget.Toast;

import android.os.Build;

public class MainActivity extends Activity {

	private  EditText filename;

	private  EditText context;

	private TextView textcontent;

	private static final String TAG="simplefile";

	protected void onCreate(Bundle savedInstanceState) {

		super.onCreate(savedInstanceState);

		setContentView(R.layout.activity_main);

		filename=(EditText)this.findViewById(R.id.filename);

		context=(EditText)this.findViewById(R.id.content);

		textcontent=(TextView)this.findViewById(R.id.textcontent);

		Button savebtn=(Button)this.findViewById(R.id.savebutton);

		Button viewbtn=(Button)this.findViewById(R.id.readbutton);

		savebtn.setOnClickListener(l);

		viewbtn.setOnClickListener(l);

	}

   private View.OnClickListener l =new OnClickListener() {

	public void onClick(View v) {

		 Button button =(Button)v;

		 //过滤掉开头结尾的空格

		 String namestr = filename.getText().toString().trim();

		 String contentstr =context.getText().toString();

		 switch ( button.getId() ) {

		case R.id.savebutton:

			String resid_s ="success";

			OutputStream fileos = null;

			try {

				if(Environment.getExternalStorageState().equals(Environment.MEDIA_MOUNTED))

				  {

					FileOutputStream outstream = new FileOutputStream("/sdcard/"+namestr+".txt");

					outstream.write(contentstr.getBytes() );

					outstream.close();

				  }

				else

					return ;

			} catch (Exception e) {

				 resid_s = "faile";

				 e.printStackTrace();

			}

			Toast.makeText(MainActivity.this,  resid_s,Toast.LENGTH_LONG).show();

			Log.i(TAG, namestr);

			Log.i(TAG, contentstr);

			break;

		case R.id.readbutton:

			String resid_v ="success";

			InputStream filsIs= null;

			String contentst = null;

			try {

				if(Environment.getExternalStorageState().equals(Environment.MEDIA_MOUNTED))

				  {

					File SDCardDir=Environment.getExternalStorageDirectory();

					File saveFile = new File(SDCardDir,namestr+".txt");

					FileInputStream instream = new FileInputStream(saveFile);

					ByteArrayOutputStream Ostream = new ByteArrayOutputStream();

					byte[] buffer = new byte[1024];

					int len = -1;

					  while( (len = instream.read(buffer)) != -1 )

					    {

						  Ostream.write(buffer,0,len);

						  }

					  contentst = Ostream.toString();

					  Ostream.close();

					  instream.close();

				  }

				else

				{

					Toast.makeText(MainActivity.this, "SD卡不存在", Toast.LENGTH_LONG).show();

				}

			} catch (Exception e) {

				 resid_v ="faile";

				 e.printStackTrace();

			}

			textcontent.setText( contentst);

			Log.i(TAG, contentst);

			Toast.makeText(MainActivity.this, resid_v,Toast.LENGTH_LONG).show();

			Log.i(TAG,namestr);

			break;

		}

	  }

    };

}