[Context方法本应用数据文件夹]

    public FileInputStream openFileInput(String name)
        throws FileNotFoundException 

     public FileOutputStream openFileOutput(String name, int mode)
        throws FileNotFoundException 

package org.crazyit.io;

import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.PrintStream;

import android.app.Activity;
import android.os.Bundle;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.EditText;


public class FileTest extends Activity
{
	final String FILE_NAME = "crazyit.bin";

	@Override
	public void onCreate(Bundle savedInstanceState)
	{
		super.onCreate(savedInstanceState);
		setContentView(R.layout.main);
		System.out.println(new StringBuilder("a").append("b").append("c")
			.toString());
		// 获取两个按钮
		Button read = (Button) findViewById(R.id.read);
		Button write = (Button) findViewById(R.id.write);
		// 获取两个文本框
		final EditText edit1 = (EditText) findViewById(R.id.edit1);
		final EditText edit2 = (EditText) findViewById(R.id.edit2);
		// 为write按钮绑定事件监听器
		write.setOnClickListener(new OnClickListener()
		{
			@Override
			public void onClick(View source)
			{
				// 将edit1中的内容写入文件中
				write(edit1.getText().toString());
				edit1.setText("");
			}
		});

		read.setOnClickListener(new OnClickListener()
		{
			@Override
			public void onClick(View v)
			{
				// 读取指定文件中的内容，并显示出来
				edit2.setText(read());
			}
		});
	}

	private String read()
	{
		try
		{
			// 打开文件输入流
			FileInputStream fis = openFileInput(FILE_NAME);
			byte[] buff = new byte[1024];
			int hasRead = 0;
			StringBuilder sb = new StringBuilder("");
			// 读取文件内容
			while ((hasRead = fis.read(buff)) > 0)
			{
				sb.append(new String(buff, 0, hasRead));
			}
			// 关闭文件输入流
			fis.close();
			return sb.toString();
		}
		catch (Exception e)
		{
			e.printStackTrace();
		}
		return null;
	}

	private void write(String content)
	{
		try
		{
			// 以追加模式打开文件输出流
			FileOutputStream fos = openFileOutput(FILE_NAME, MODE_APPEND);
			// 将FileOutputStream包装成PrintStream
			PrintStream ps = new PrintStream(fos);
			// 输出文件内容
			ps.println(content);
			// 关闭文件输出流
			ps.close();
		}
		catch (Exception e)
		{
			e.printStackTrace();
		}
	}
}

[读写SD卡上文件]

	private String read()
	{
		try
		{
			// 如果手机插入了SD卡，而且应用程序具有访问SD的权限
			if (Environment.getExternalStorageState().equals(
					Environment.MEDIA_MOUNTED))
			{
				// 获取SD卡对应的存储目录
				File sdCardDir = Environment.getExternalStorageDirectory();
				// 获取指定文件对应的输入流
				FileInputStream fis = new FileInputStream(
					sdCardDir.getCanonicalPath() + FILE_NAME);
				// 将指定输入流包装成BufferedReader
				BufferedReader br = new BufferedReader(new 
					InputStreamReader(fis));
				StringBuilder sb = new StringBuilder("");
				String line = null;
				// 循环读取文件内容				
				while ((line = br.readLine()) != null)
				{
					sb.append(line);
				}
				// 关闭资源
				br.close();
				return sb.toString();
			}
		}
		catch (Exception e)
		{
			e.printStackTrace();
		}
		return null;
	}

	private void write(String content)
	{
		try
		{
			// 如果手机插入了SD卡，而且应用程序具有访问SD的权限
			if (Environment.getExternalStorageState().equals(
				Environment.MEDIA_MOUNTED))
			{
				// 获取SD卡的目录
				File sdCardDir = Environment.getExternalStorageDirectory();
				File targetFile = new File(sdCardDir
					.getCanonicalPath() + FILE_NAME);
				// 以指定文件创建 RandomAccessFile对象
				RandomAccessFile raf = new RandomAccessFile(
					targetFile, "rw");
				// 将文件记录指针移动到最后
				raf.seek(targetFile.length());
				// 输出文件内容
				raf.write(content.getBytes());
				// 关闭RandomAccessFile				
				raf.close();
			}
		}
		catch (Exception e)
		{
			e.printStackTrace();
		}
	}

android之 文件IO,,5-wow.com