学步园

1.在AndroidManifest文件下添加SDCard的读写权限

<!-- 在SDCard中创建与删除文件权限 --><br /> <uses-permission android:name="android.permission.MOUNT_UNMOUNT_FILESYSTEMS"/><br /> <!-- 往SDCard写入数据权限 --><br /> <uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE"/>

2.文件操作的各种模式如下代码：（注意通过getExternalStorageDirectory方法获取SDCard的文件路径）

package com.hoo.file;<br /> import java.io.ByteArrayOutputStream;<br /> import java.io.File;<br /> import java.io.FileInputStream;<br /> import java.io.FileOutputStream;<br /> import android.content.Context;<br /> import android.os.Environment;<br /> public class FileService<br /> {<br /> private Context context;<br /> public FileService(Context context)<br /> {<br /> this.context = context;<br /> }</p> <p> /**<br /> * 读取文件的内容<br /> * @param filename 文件名称<br /> * @return<br /> * @throws Exception<br /> */<br /> public String readFile(String filename) throws Exception<br /> {<br /> //获得输入流<br /> FileInputStream inStream = context.openFileInput(filename);<br /> //new一个缓冲区<br /> byte[] buffer = new byte[1024];<br /> int len = 0;<br /> //使用ByteArrayOutputStream类来处理输出流<br /> ByteArrayOutputStream outStream = new ByteArrayOutputStream();<br /> while( (len = inStream.read(buffer))!= -1)<br /> {<br /> //写入数据<br /> outStream.write(buffer, 0, len);<br /> }<br /> //得到文件的二进制数据<br /> byte[] data = outStream.toByteArray();<br /> //关闭流<br /> outStream.close();<br /> inStream.close();<br /> return new String(data);<br /> }<br /> /**<br /> * 以默认私有方式保存文件内容至SDCard中<br /> * @param filename<br /> * @param content<br /> * @throws Exception<br /> */<br /> public void saveToSDCard(String filename, String content) throws Exception<br /> {<br /> //通过getExternalStorageDirectory方法获取SDCard的文件路径<br /> File file = new File(Environment.getExternalStorageDirectory(), filename);<br /> //获取输出流<br /> FileOutputStream outStream = new FileOutputStream(file);<br /> outStream.write(content.getBytes());<br /> outStream.close();<br /> }</p> <p> /**<br /> * 以默认私有方式保存文件内容，存放在手机存储空间中<br /> * @param filename<br /> * @param content<br /> * @throws Exception<br /> */<br /> public void save(String filename, String content) throws Exception<br /> {<br /> //<br /> FileOutputStream outStream = context.openFileOutput(filename, Context.MODE_PRIVATE);<br /> outStream.write(content.getBytes());<br /> outStream.close();<br /> }</p> <p> /**<br /> * 以追加的方式保存文件内容<br /> * @param filename 文件名称<br /> * @param content 文件内容<br /> * @throws Exception<br /> */<br /> public void saveAppend(String filename, String content) throws Exception<br /> {<br /> FileOutputStream outStream = context.openFileOutput(filename, Context.MODE_APPEND);<br /> outStream.write(content.getBytes());<br /> outStream.close();<br /> }</p> <p> /**<br /> * 以允许其他应用从该文件中读取内容的方式保存文件(Context.MODE_WORLD_READABLE)<br /> * @param filename 文件名称<br /> * @param content 文件内容<br /> * @throws Exception<br /> */<br /> public void saveReadable(String filename, String content) throws Exception<br /> {<br /> FileOutputStream outStream = context.openFileOutput(filename, Context.MODE_WORLD_READABLE);<br /> outStream.write(content.getBytes());<br /> outStream.close();<br /> }</p> <p> /**<br /> * 以允许其他应用往该文件写入内容的方式保存文件<br /> * @param filename 文件名称<br /> * @param content 文件内容<br /> * @throws Exception<br /> */<br /> public void saveWriteable(String filename, String content) throws Exception<br /> {<br /> FileOutputStream outStream = context.openFileOutput(filename, Context.MODE_WORLD_WRITEABLE);<br /> outStream.write(content.getBytes());<br /> outStream.close();<br /> }</p> <p> /**<br /> * 以允许其他应用对该文件读和写的方式保存文件(MODE_WORLD_READABLE与MODE_WORLD_WRITEABLE)<br /> * @param filename 文件名称<br /> * @param content 文件内容<br /> * @throws Exception<br /> */<br /> public void saveRW(String filename, String content) throws Exception<br /> {<br /> FileOutputStream outStream = context.openFileOutput(filename,<br /> Context.MODE_WORLD_READABLE + Context.MODE_WORLD_WRITEABLE);<br /> //Context.MODE_WORLD_READABLE(1) + Context.MODE_WORLD_WRITEABLE(2),其实可用3替代<br /> outStream.write(content.getBytes());<br /> outStream.close();<br /> }<br /> }<br />

3.写入数据前判断sdcard是否存在于手机上，是否有写保护

package com.hoo.file;<br /> import android.app.Activity;<br /> import android.os.Bundle;<br /> import android.os.Environment;<br /> import android.util.Log;<br /> import android.view.View;<br /> import android.widget.Button;<br /> import android.widget.EditText;<br /> import android.widget.Toast;<br /> public class MainActivity extends Activity<br /> {<br /> private static final String TAG = "MainActivity";<br /> private FileService fileService;</p> <p> @Override<br /> public void onCreate(Bundle savedInstanceState)<br /> {<br /> super.onCreate(savedInstanceState);<br /> setContentView(R.layout.main);</p> <p> fileService = new FileService(this);<br /> //使用下面的方法可以快速获取当前文件夹的位置，<br /> //这样可以在后面追加路径从而避免使用绝对路径<br /> //File filedir = this.getFilesDir();<br /> Button button = (Button) this.findViewById(R.id.button);<br /> button.setOnClickListener(new View.OnClickListener()<br /> {<br /> @Override<br /> public void onClick(View v)<br /> {<br /> //获取EditText中的内容<br /> EditText filenameText = (EditText) findViewById(R.id.filename);<br /> EditText contentText = (EditText) findViewById(R.id.filecontent);<br /> String filename = filenameText.getText().toString();<br /> String content = contentText.getText().toString();<br /> try<br /> {<br /> //使用通常文件保存方式,默认保存在data/data/包名/file/XXX里面<br /> //fileService.save(filename, content);</p> <p> //判断sdcard是否存在于手机上而且没有写保护<br /> //Android2.2版本以后sdcard的路径在mnt/sdcard，2.2之前在/sdcard<br /> if(Environment.getExternalStorageState().equals(Environment.MEDIA_MOUNTED))<br /> {<br /> //保存到SDCard中<br /> fileService.saveToSDCard(filename, content);<br /> //提示保存成功<br /> Toast.makeText(MainActivity.this, R.string.success, 1).show();<br /> }<br /> else<br /> {<br /> //提示保存失败<br /> Toast.makeText(MainActivity.this, R.string.sdcarderror, 1).show();<br /> }<br /> }<br /> catch (Exception e)<br /> {<br /> Log.e(TAG, e.toString());<br /> Toast.makeText(MainActivity.this, R.string.error, 1).show();<br /> }<br /> }<br /> });<br /> }<br /> }