文件内部写入及读取（参考疯狂安卓讲义）

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:orientation="vertical"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent">
<EditText android:id="@+id/edit1"
    android:layout_width="fill_parent"
    android:layout_height="wrap_content"
    android:lines="4"/>
<Button android:id="@+id/write"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content" 
    android:text="@string/write"/>
<EditText android:id="@+id/edit2"
    android:layout_width="fill_parent"
    android:layout_height="wrap_content"
    android:editable="false"
    android:cursorVisible="false"
    android:lines="4"/>        
<Button android:id="@+id/read"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content" 
    android:text="@string/read"/>
</LinearLayout>

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

   <string name="hello">Hello World, FileTest!</string>
    <string name="app_name">文件读写入门</string>
    <string name="read">读取</string>
    <string name="write">写入</string>        
    
    <string name="action_settings">hello</string>
</resources>

package com.swust.filetest;

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

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

public class MainActivity extends Activity {
    
    final String FILE_NAME = "1.txt";

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_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MODE_APPEND
            //该文件只能被当前程序读写,也就是每次重新写模式
            FileOutputStream fos = openFileOutput(FILE_NAME,MODE_PRIVATE );
            // 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();
        }
    }
    
}