文件操作需要手机权限,需要在AndroidManifest.xml添加

--------------------------------第一种方式------------------------------------------

1、获取文件路径

/**

* 获取文件路径

* filePath=/storage/emulated/0/Android/data/com.example.wifiapplication/files/20120101_100216_log.txt

* */

public String getFilesPath(Context context) {

// 20120101_100216_log.txt 用时间格式创建文件名

Calendar c = Calendar.getInstance();

SimpleDateFormat fdate = new SimpleDateFormat("yyyyMMdd_HHmmss");

String fname = fdate.format(c.getTime()) + "_log.txt";

String filePath ;

if (Environment.MEDIA_MOUNTED.equals(Environment.getExternalStorageState()) || !Environment.isExternalStorageRemovable()) {

//外部存储可用

filePath = context.getExternalFilesDir(null).getPath() + "/" + fname;

} else {

//外部存储不可用

filePath = context.getFilesDir().getPath() + "/" + fname;

}

return filePath;

}

2、写入数据

try {

FileOutputStream outputStream = new FileOutputStream(filePath, true);// true 为 追加写入，false 为删除写入(把之前的数据清除掉，再写入)

outputStream.write("88888".getBytes());

outputStream.write("99999999".getBytes());

outputStream.close();

} catch (FileNotFoundException e) {

e.printStackTrace();

} catch (IOException e) {

e.printStackTrace();

}

3、读取数据

try {

FileInputStream inputStream = new FileInputStream(filePath);

byte[] buffer = new byte[1024];

int hasRead = inputStream.read(buffer);

StringBuilder sb = new StringBuilder();

sb.append(new String(buffer, 0, hasRead));

Log.e("wyy", "读取数据=" + sb.toString());

inputStream.close();

} catch (FileNotFoundException e) {

e.printStackTrace();

} catch (IOException e) {

e.printStackTrace();

}

--------------------------------第二种方式------------------------------------------

1、获取名称

/**

* 获取文件名称

* */

private String getFileName(){

Calendar c = Calendar.getInstance();

SimpleDateFormat fdate = new SimpleDateFormat("yyyyMMdd_HHmmss");

return fdate.format(c.getTime()) + "_log.txt";

}

2、写入数据

try {

FileOutputStream outputStream = FileHandleActivity.this.openFileOutput(getFileName(),Context.MODE_APPEND);

outputStream.write("需要写入的数据".getBytes());

outputStream.close();// 关闭文件

} catch (FileNotFoundException e) {

e.printStackTrace();

} catch (IOException e) {

e.printStackTrace();

}

3、读取数据

try {

FileInputStream inputStream = this.openFileInput(fname);

byte[] buffer = new byte[1024];

int hasRead = inputStream.read(buffer);

StringBuilder sb = new StringBuilder();

sb.append(new String(buffer, 0, hasRead));

Log.e("wyy", "读取数据=" + sb.toString());

inputStream.close();

} catch (FileNotFoundException e) {

e.printStackTrace();

} catch (IOException e) {

e.printStackTrace();

}

【注意】第一种方法和第二种方法的区别：

1.文件路径不一样

2.第一种方法可能对API要求比较高，亲测在minSdkVersion 19 / targetSdkVersion 29上是没有问题。但是不保证在你的手机上没有问题。具体情况具体分析。