android 操作SD卡上的文件

（1）说明:操作SD卡上的文件需要加入以下权限

 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差不多，如果有不懂的可以看我的上一篇文章

 

android 读写文件示例

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

只不过多加了判断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;
}
}
};
}