Android文件简单读写操作

作者: 时光磨棱角 | 来源:发表于2016-10-26 22:12 被阅读0次

android 读写文件
数据存储与访问之——文件存储读写
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flink之dataset的文件数据源
Python 学习笔记6 2018-04-13
java中的文件操作（干货）
android文件操作相关
Android 中的文件操作
Android中文件读写操作
python012-文件操作

MainActivity.java

import android.os.Bundle;
import android.support.v7.app.AppCompatActivity;
import android.util.Log;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.Toast;
import org.apache.commons.io.FileUtils;
import java.io.BufferedInputStream;
import java.io.BufferedOutputStream;
import java.io.BufferedReader;
import java.io.BufferedWriter;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.FileReader;
import java.io.FileWriter;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.OutputStreamWriter;
import java.io.UnsupportedEncodingException;
public class MainActivity extends AppCompatActivity {
    private Button bt1, bt2, bt3, bt4, bt5, bt6, bt7;
    private EditText save,write;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        bt1= (Button) findViewById(R.id.save);
        bt2= (Button) findViewById(R.id.write);
        bt3 = (Button) findViewById(R.id.copy);
        bt4 = (Button) findViewById(R.id.copy1);
        bt5 = (Button) findViewById(R.id.copy2);
        bt6 = (Button) findViewById(R.id.copy3);
        bt7 = (Button) findViewById(R.id.copy4);
        save= (EditText) findViewById(R.id.text1);
        write= (EditText) findViewById(R.id.text2);
        bt1.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
//              File sdcard= Environment.getExternalStorageDirectory();
//              File file=new File(sdcard,"1111.text");
                
                File directory = new File("/mnt/sdcard/Test/");
                File file = new File("/mnt/sdcard/Test/test.txt");
                if(!directory.exists()){
                    directory.mkdir();//没有目录先创建目录  
//                    Toast.makeText(getApplicationContext(), "创建目录成功", Toast.LENGTH_SHORT).show();
                }
                try {
                    if(!file.exists()){
                        file.createNewFile();
                    }
                    FileOutputStream fos=new FileOutputStream(file);
                    OutputStreamWriter osw = new OutputStreamWriter(fos, "utf-8");//读写文件要保持统一编码方式，否则读取为乱码
                    osw.write(save.getText().toString());
                    osw.flush();
                    osw.close();
                    fos.close();
                    Toast.makeText(MainActivity.this,"保存成功",Toast.LENGTH_LONG).show();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
        });
        //字节流读写数据
        bt2.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                try {
                    File directory = new File("/mnt/sdcard/Test/");
                    File file = new File("/mnt/sdcard/Test/test.txt");
                    if(!directory.exists()){
                        directory.mkdir();
                    }
//                  File sdcard= Environment.getExternalStorageDirectory();
//                  File file=new File(sdcard,"1111.text");
                    FileInputStream fis=new FileInputStream(file);
                    InputStreamReader isr = new InputStreamReader(fis, "utf-8");//读写文件要保持统一编码方式，否则读取为乱码
                    char input[] = new char[fis.available()];//获取fis长度
                    isr.read(input);
                    isr.close();
                    fis.close();
                    write.setText(new String(input));
                } catch (FileNotFoundException e) {
                    e.printStackTrace();
                } catch (UnsupportedEncodingException e) {
                    e.printStackTrace();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
        });
        //带缓冲的字节流读写数据
        bt3.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                try {
                    File ifile = new File("/mnt/sdcard/Download/3.gif");//目标文件
                    File wfile = new File("/mnt/sdcard/Test/3.gif");//复制文件
                    FileInputStream fis = new FileInputStream(ifile);
                    FileOutputStream fos = new FileOutputStream(wfile);
                    //使用缓存，复制文件效率更高
//                  BufferedInputStream bis=new BufferedInputStream(fis);
//                  BufferedOutputStream bos=new BufferedOutputStream(fos);
                    //添加上缓存大小，应该比byte数组in[]大一些，但也不需要过大，具体适合大小，根据测试消耗时长定
                    BufferedInputStream bis = new BufferedInputStream(fis, 1000);
                    BufferedOutputStream bos = new BufferedOutputStream(fos, 1000);
                    long before = System.currentTimeMillis();
                    //大型文件数组大小可以大一些，小文件对应数组小一些
                    byte in[] = new byte[100];
                    //通过循环，不使用缓存，边读边写
//                    while ((fis.read(in)) > 0) {
//                        fos.write(in);
//                    }
                    while ((bis.read(in)) != -1) {
                        bos.write(in);
                    }
                    bos.close();
                    bis.close();
                    fos.close();
                    fis.close();
                    Log.i("CopyTime", System.currentTimeMillis() - before + "ms");
                    if (wfile.length() > 0) {     //文件大小不为空
                        Toast.makeText(getApplicationContext(), "文件复制成功", Toast.LENGTH_SHORT).show();
                    }
                } catch (FileNotFoundException e) {
                    e.printStackTrace();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
        });
        //字符流读写文件
        bt4.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                try {
                    File ifile = new File("/mnt/sdcard/copy.txt");//目标文件
                    File wfile = new File("/mnt/sdcard/Test/copy1.txt");//复制文件
                    FileInputStream fis = new FileInputStream(ifile);
                    FileOutputStream fos = new FileOutputStream(wfile);
                    InputStreamReader isr = new InputStreamReader(fis, "UTF-8");
                    OutputStreamWriter osw = new OutputStreamWriter(fos, "UTF-8");
                    char input[] = new char[100];
                    int l = 0;//主要用来记录最后一次数组长短，写入文件；若不记录，char数组最后一次读取可能不足，将给文件写入多余或错误数据
                    while ((l = isr.read(input)) != -1) {
                        //String inputString = new String(input,0,l);
                        osw.write(input, 0, l);
                    }
                    isr.close();
                    fis.close();
                    osw.close();
                    fos.close();
                    if (wfile.length() > 0) {     //文件大小不为空
                        Toast.makeText(getApplicationContext(), "文件复制成功", Toast.LENGTH_SHORT).show();
                    }
                } catch (FileNotFoundException e) {
                    e.printStackTrace();
                } catch (UnsupportedEncodingException e) {
                    e.printStackTrace();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
        });
        //FileReader、FileWriter直接读写文件，包装缓冲流进行拷贝
        bt5.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                try {
                    File ifile = new File("/mnt/sdcard/copy.txt");//目标文件
                    File wfile = new File("/mnt/sdcard/Test/copy2.txt");//复制文件
                    FileReader fr = new FileReader(ifile);
                    BufferedReader br = new BufferedReader(fr);
                    FileWriter fw = new FileWriter(wfile);
                    BufferedWriter bw = new BufferedWriter(fw);
                    String line;
                    while ((line = br.readLine()) != null) {
                        bw.write(line + "\n");
                    }
                    bw.flush();//强制将缓冲流输出
                    bw.close();
                    fw.close();
                    br.close();
                    fr.close();
                    if (wfile.length() > 0) {     //文件大小不为空
                        Toast.makeText(getApplicationContext(), "文件复制成功", Toast.LENGTH_SHORT).show();
                    }
                } catch (FileNotFoundException e) {
                    e.printStackTrace();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
        });
        //RandomAccessFile随机读取,适用多线程下载等操作
        bt6.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                File file = new File("/mnt/sdcard/RandomAccessFile随机读取.txt");//目标文件
                //打乱线程順序不影响文件块写入
                new WriteFile(file, 5).start();
                new WriteFile(file, 3).start();
                new WriteFile(file, 1).start();
                new WriteFile(file, 4).start();
                new WriteFile(file, 2).start();
//                    RandomAccessFile raf = new RandomAccessFile(file, "r");//以只读方式打开文件
//                    raf.seek(300);
//                    byte[] str = new byte[20];
//                    raf.read(str);
//                    String in = new String(str);
//                    Log.i("RandomAccessFile随机读取",in);
                Toast.makeText(getApplicationContext(), "文件写入成功", Toast.LENGTH_SHORT).show();
            }
        });
        //通过调用Apache IO的jar包，快捷实现文件的操作
        bt7.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                try {
                    File file1 = new File("/mnt/sdcard/copy.txt");//目标文件
                    File file2 = new File("/mnt/sdcard/Apache IO Copy.txt");//目标文件
//                String input = FileUtils.readFileToString(file1, "UTF-8");//读取文件内容
                    FileUtils.copyFile(file1, file2);
                    Toast.makeText(getApplicationContext(), "文件复制成功", Toast.LENGTH_SHORT).show();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
        });
        
    }
}

WriteFile.java

import java.io.File;
import java.io.FileNotFoundException;
import java.io.IOException;
import java.io.RandomAccessFile;
public class WriteFile extends Thread {
    File file;
    int block;//块
    int L = 5;//块大小
    /**
     * File        数据插入文件
     *            |***        |+++
     * |-----------***---------+++--------------------------|
     *      |---
     */
    /**
     * 文件块示意图
     * 1            2            3            4            5
     * |------------|------------|------------|------------|------------|
     * 0xL          1xL
     *
     * @param f
     * @param b
     */
    public WriteFile(File f, int b) {
        this.file = f;
        this.block = b;
    }
    @Override
    public void run() {
        try {
            RandomAccessFile raf = new RandomAccessFile(file, "rw");//rw代表可读可写，参数还有r、rws、rwd
            raf.seek((block - 1) * L);//定位指针
            raf.writeBytes("abcde" + block);
            /**
             * 注：如果写入数据小于块大小，未填满数据块，多余字节位置大小依然存在（虽然不一定可见）
             * 若数据大于块大小，将占用后面块的位置，后写入的块数据从块指定位置开始，又会重叠在后方块之上
             */
//            for (int i = 0; i < 20; i++) {
//                raf.writeBytes("-");
//            }
            raf.writeBytes("\n");//会占用一个字节的位置大小
        } catch (FileNotFoundException e) {
            e.printStackTrace();
        } catch (IOException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
    }
}

activity.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:id="@+id/activity_main"
    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.example.administrator.filetestapplacation.MainActivity">
    <EditText
        android:id="@+id/text1"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:gravity="center"
        android:hint="请输入文本信息"/>
    <Button
        android:id="@+id/save"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="保存文本"/>
    <Button
        android:id="@+id/write"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="输出文本"/>
    <EditText
        android:id="@+id/text2"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:gravity="center"
        android:hint="输出文本信息"/>
    <Button
        android:id="@+id/copy"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="Copy by 缓冲字节流" />
    <Button
        android:id="@+id/copy1"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="Copy by 字符流" />
    <Button
        android:id="@+id/copy2"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="Copy by File字符流" />
    <Button
        android:id="@+id/copy3"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="RandomAccessFile随机读取" />
    <Button
        android:id="@+id/copy4"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="Apache IO Copy" />
</LinearLayout>