Android内部存储与外部存储的示例讲解

				// 存
 				FileOutputStream fos = null;
                try {
                    //第一个参数：文件名
                    //第二个参数：表示文件输出的类型 这里选择Context.MODE_PRIVATE每次生成相同的文件名,则覆盖原有的文件
                    fos = openFileOutput('test', Context.MODE_PRIVATE);
                    String nameAndPassWord = username + "." + password;
                    byte[] bytes = nameAndPassword.getBytes();
                    fos.write(bytes);
                } catch (Exception e) {
                    e.printStackTrace();
                } finally {
                    if (fos != null) {
                        try {
                            fos.close();
                        } catch (IOException e) {
                            e.printStackTrace();
                        }
                    }
                }
				// 取
				FileInputStream fis = null;
                try {
                    fis = openFileInput(fileName);
                    //fis.available() 判断文件有多少个字节
                    byte[] bytes = new byte[fis.available()];
                    while (fis.read(bytes) != -1) {
                        String message = new String(bytes);
                        String[] split = message.split("\\.");
                        tv_message.setText("用户名：" + split[0] + "\n" + "密码：" + split[1]);
                    }
                } catch (Exception e) {
                    e.printStackTrace();
                }

// 获取外部存储地址的位置并创建文件：
new File(getExternalFilesDir(Environment.DIRECTORY_DOWNLOADS)
				// 存
				OutputStream outputStream = null;
                try {
                        outputStream = new FileOutputStream(new File(getExternalFilesDir(Environment.DIRECTORY_DOWNLOADS), 'test2'));
                        String nameAndPassword = username + "." + password;
                        byte[] bytes = nameAndPassword.getBytes();
                        outputStream.write(bytes);
                } catch (Exception e) {
                    e.printStackTrace();
                } finally {
                    if (outputStream != null) {
                        try {
                            outputStream.close();
                        } catch (IOException e) {
                            e.printStackTrace();
                        }
                    }
                }
				// 取
				 FileInputStream fis = null;
                try {
                    //第一个参数：文件目录 第二个参数：文件名
                    //getExternalFilesDir(Environment.DIRECTORY_DOWNLOADS)对应的路径为：
                    // /storage/emulated/0/Android/data/com.example.customviewproject/files/Download
                    File file = new File(getExternalFilesDir(Environment.DIRECTORY_DOWNLOADS), fileName);
                        fis = new FileInputStream(file);
                        //判断当前文件的字节个数
                        byte[] bytes = new byte[fis.available()];
                        while (fis.read(bytes) != -1) {
                            String message = new String(bytes);
                            String[] split = message.split("\\.");
                            tv_message.setText("用户名：" + split[0] + "\n" + "密码：" + split[1]);
                        }
                } catch (Exception e) {
                    e.printStackTrace();
                } finally {
                    if (fis != null) {
                        try {
                            fis.close();
                        } catch (IOException e) {
                            e.printStackTrace();
                        }
                    }
                }