存取手机中的文件数据。

写入和读取的操作格式均为UTF-8。

import java.io.File;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.OutputStreamWriter;
import java.io.UnsupportedEncodingException;

import android.app.Activity;
import android.content.Context;
import android.os.Bundle;
import android.os.Environment;
import android.view.View;
import android.widget.EditText;
import android.widget.TextView;
import android.widget.Toast;

public class MainActivity extends Activity {
	
	private String filename = "test";
	private TextView show;
	private EditText et;
	File sdcard = Environment.getExternalStorageDirectory();
	@Override
	protected void onCreate(Bundle savedInstanceState) {
		super.onCreate(savedInstanceState);
		setContentView(R.layout.activity_main);
		et = (EditText) findViewById(R.id.et);
		show = (TextView) findViewById(R.id.show);
		
		findViewById(R.id.writeBtn).setOnClickListener(new View.OnClickListener() {
			
			@Override
			public void onClick(View v) {
				try {
					FileOutputStream fos = openFileOutput(filename, Context.MODE_PRIVATE);
					OutputStreamWriter osw = new OutputStreamWriter(fos,"UTF-8");
					osw.write(et.getText().toString());
					osw.flush();
					fos.flush();
					osw.close();
					fos.close();
					Toast.makeText(getApplicationContext(), "写入完成", Toast.LENGTH_SHORT).show();
				} catch (FileNotFoundException e) {
					// TODO Auto-generated catch block
					e.printStackTrace();
				} catch (UnsupportedEncodingException e) {
					// TODO Auto-generated catch block
					e.printStackTrace();
				} catch (IOException e) {
					// TODO Auto-generated catch block
					e.printStackTrace();
				}
				
			}
		});
		
		findViewById(R.id.readBtn).setOnClickListener(new View.OnClickListener() {
			
			@Override
			public void onClick(View v) {
				try {
					FileInputStream fis = openFileInput(filename);
					InputStreamReader isr = new InputStreamReader(fis,"UTF-8");
					char input[] = new char[fis.available()];
					isr.read(input);
					isr.close();
					fis.close();
					String readed = new String(input);
					show.setText(readed);
				} catch (FileNotFoundException e) {
					// TODO Auto-generated catch block
					e.printStackTrace();
				} catch (UnsupportedEncodingException e) {
					// TODO Auto-generated catch block
					e.printStackTrace();
				} catch (IOException e) {
					// TODO Auto-generated catch block
					e.printStackTrace();
				}
				
			}
		});
		
		findViewById(R.id.writeBtn1).setOnClickListener(new View.OnClickListener() {
			
			@Override
			public void onClick(View v) {
				//首先要获得当前sd卡的工作目录
				File myfile = new File(sdcard,"This is my file.txt");
				if(!sdcard.exists()){
					Toast.makeText(getApplicationContext(), "there is no sdcard", Toast.LENGTH_SHORT).show();
					return;
				}
				try {
					myfile.createNewFile();
					FileOutputStream fos = new FileOutputStream(myfile);
					OutputStreamWriter osw = new OutputStreamWriter(fos,"UTF-8");
					osw.write(et.getText().toString());
					osw.flush();
					osw.close();
					fos.close();
					Toast.makeText(getApplicationContext(), "文件已创建完成", Toast.LENGTH_SHORT).show();
				} catch (IOException e) {
					// TODO Auto-generated catch block
					e.printStackTrace();
				}
				
			}
		});
		findViewById(R.id.readBtn1).setOnClickListener(new View.OnClickListener() {
			
			@Override
			public void onClick(View v) {
				File myfile = new File(sdcard,"This is my file.txt");
				if(myfile.exists()){
					try {
						FileInputStream fis = new FileInputStream(myfile);
						InputStreamReader isr = new InputStreamReader(fis, "UTF-8");
						char[] input = new char[fis.available()];
						isr.read(input);
						isr.close();
						fis.close();
						String inString = new String(input);
						show.setText(inString);
					} catch (UnsupportedEncodingException e) {
						// TODO Auto-generated catch block
						e.printStackTrace();
					} catch (FileNotFoundException e) {
						// TODO Auto-generated catch block
						e.printStackTrace();
					} catch (IOException e) {
						// TODO Auto-generated catch block
						e.printStackTrace();
					}
				}
			}
		});
	}

}

布局文件：

放入1个EditText，4个button，1个textview

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical"
    android:paddingBottom="@dimen/activity_vertical_margin"
    android:paddingLeft="@dimen/activity_horizontal_margin"
    android:paddingRight="@dimen/activity_horizontal_margin"
    android:paddingTop="@dimen/activity_vertical_margin"
    tools:context="com.rust.readfiletest.MainActivity" >

    <EditText
        android:id="@+id/et"
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        
        android:hint="enter" />

    <Button
        android:id="@+id/writeBtn"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_below="@id/et"
        android:text="save" />

    <Button
        android:id="@+id/readBtn"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_below="@id/et"
        android:layout_toRightOf="@id/writeBtn"
        android:text="read" />

    <Button
        android:id="@+id/writeBtn1"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_below="@id/et"
        android:layout_toRightOf="@id/readBtn"
        android:text="write e" />

    <Button
        android:id="@+id/readBtn1"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_below="@id/et"
        android:layout_toRightOf="@id/writeBtn1"
        android:text="read e" />

    <TextView
        android:id="@+id/show"
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:layout_below="@id/writeBtn"
        />

</RelativeLayout>