一、作用

    文件存取读写

二、使用

//覆盖写入
boolean isSuccess = IOUtil.writeTxtFile(file, array + "\n");

三、注意

    1.文件的读写要开线程

    2.需要相应的权限

    3.Android6.0以上需要动态权限获取，参考动态权限获取的工具类和帮助类

四、代码

import android.content.Context;
import android.os.Environment;
import android.widget.Toast;
import java.io.BufferedReader;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.FileReader;
import java.io.FileWriter;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.RandomAccessFile;
import java.util.LinkedList;
import java.util.List;
/**
 * author : GodH
 * date   : 2019/8/20 10:13
 * desc   : 输出输入流工具类
 * version: 1.0
 */
public class IOUtil extends IOException {
    /**
     * 创建文件,但是路径不对时会报错
     *
     * @param fileName
     * @return
     */
    public static boolean createFile(File fileName) throws Exception {
        try {
            if (!fileName.exists()) {
                fileName.createNewFile();
            }
        } catch (Exception e) {
            e.printStackTrace();
        }
        return true;
    }
    /**
     * 创建文件,但是路径不对时会自动创建
     *
     * @param file
     * @return
     */
    public static boolean createDirFile(File file) throws Exception {
        File fileParent = file.getParentFile();
        try {
            if (!fileParent.exists()) {
                fileParent.mkdirs();
            }
            if (!file.exists()) {
                file.createNewFile();
            }
            return true;
        } catch (Exception e) {
            e.printStackTrace();
        }
        return false;
    }
    /**
     * 读取TXT内容
     *
     * @param file
     * @return
     */
    public static String readTxtFile(File file) {
        String result = "";
        try {
            InputStreamReader reader = new InputStreamReader(new FileInputStream(file), "utf-8");
            BufferedReader br = new BufferedReader(reader);
            String s = null;
            while ((s = br.readLine()) != null) {
                result = result + s;
                System.out.println(s);
            }
        } catch (Exception e) {
            e.printStackTrace();
        }
        return result;
    }
    /**
     * 写入TXT，覆盖原内容
     *
     * @param content
     * @param fileName
     * @return
     * @throws IOException
     */
    public static boolean writeTxtFile(File fileName, String content) throws IOException {
        RandomAccessFile mm = null;
        boolean flag = false;
        FileOutputStream fileOutputStream = null;
        try {
            fileOutputStream = new FileOutputStream(fileName);
            fileOutputStream.write(content.getBytes("utf-8"));
            fileOutputStream.close();
            flag = true;
        } catch (IOException e) {
            e.printStackTrace();
        }
        return flag;
    }
    /**
     * 写入TXT，追加写入
     *
     * @param filePath
     * @param content
     */
    public static void fileChaseFW(String filePath, String content) {
        try {
            //构造函数中的第二个参数true表示以追加形式写文件
            FileWriter fw = new FileWriter(filePath, true);
            fw.write(content);
            fw.close();
        } catch (IOException e) {
            System.out.println("文件写入失败！" + e);
        }
    }
    /**
     * @param  filePath 文件路径
     * @param  context 查找的字符串
     * @return 包含搜索的字符串的行
     * @throws IOException
     * @return List<String>
     * @Title: findLines
     * @Description: TODO
     */
    public static List<String> findLines(String filePath, String context) throws IOException {
        List<String> list = new LinkedList<String>();
        BufferedReader read = new BufferedReader(new FileReader(filePath));
        String str = null;
        while ((str = read.readLine()) != null) {
            if (str.indexOf(context) != -1) {
                list.add(str);
            }
        }
        read.close();
        return list;
    }
    /**
     * 将内容写入内存卡卡中
     *
     * @param context
     * @param filename 要写入的文件名
     * @param content  待写入的内容
     * @throws IOException
     *//*
    public void outputJSON(Context context, String filename, String content) throws IOException {
        File file = context.getFilesDir();
        filename =  Environment.getExternalStorageDirectory().getAbsolutePath() + File.separator + filename;
        //打开文件输出流
//        FileOutputStream outputStream = new FileOutputStream(filename);
//
//        //写数据到文件中
//        outputStream.write(content.getBytes());
//        outputStream.flush();
//        outputStream.close();
        FileWriter fileWriter = new FileWriter(filename);
        fileWriter.write(content);
        fileWriter.flush();
        fileWriter.close();
        Toast.makeText(context, "生成jjs.json文件成功,位置：" + filename, Toast.LENGTH_SHORT).show();
    }*/
}