Android文件简单读写操作

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"?>

注：需导入Apache IO包

前两个按钮效果图（未完整版）：

incomplete photo.gif

注：需导入Apache IO包

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