今天寫一個儲存在手機的文件

public class FileWriteActivity extends AppCompatActivity implements View.OnClickListener {

    private EditText et_name;
    private EditText et_age;
    private EditText et_height;
    private EditText et_weight;
    private CheckBox cb_marry;
    private String path;
    private TextView tv_read;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        EdgeToEdge.enable(this);
        setContentView(R.layout.activity_file_write);
        ViewCompat.setOnApplyWindowInsetsListener(findViewById(R.id.main), (v, insets) -> {
            Insets systemBars = insets.getInsets(WindowInsetsCompat.Type.systemBars());
            v.setPadding(systemBars.left, systemBars.top, systemBars.right, systemBars.bottom);
            return insets;
        });

        et_name = findViewById(R.id.et_name);
        et_age = findViewById(R.id.et_age);
        et_height = findViewById(R.id.et_height);
        et_weight = findViewById(R.id.et_weight);
        cb_marry = findViewById(R.id.cb_marry);
        tv_read = findViewById(R.id.tv_read);

        findViewById(R.id.btn_save).setOnClickListener(this);
        findViewById(R.id.btn_read).setOnClickListener(this);
    }

    @Override
    public void onClick(View view) {
        if(view.getId() == R.id.btn_save){
            String name = et_name.getText().toString();
            String age = et_age.getText().toString();
            String weight = et_weight.getText().toString();
            String height = et_height.getText().toString();
            StringBuilder sb = new StringBuilder();
            sb.append("姓名").append(name);
            sb.append("\n年齡").append(age);
            sb.append("\n身高").append(height);
            sb.append("\n體重").append(weight);
            sb.append("\n婚否").append(cb_marry.isChecked()?"是":"否");

            String fileName = System.currentTimeMillis() + ".txt";
            String direcyory = null;
            direcyory = getExternalFilesDir(Environment.DIRECTORY_DOWNLOADS).toString();
            path = direcyory+ File.separatorChar+ fileName;
            Log.d("ning",path);
            FileUtil.saveText(path, sb.toString());
            ToastUtil.show(this,"保存成功");
        } else if (view.getId() == R.id.btn_read) {
            tv_read.setText(FileUtil.openText(path));
        }
    }
}

public class FileUtil {

    public static void saveText(String path,String txt){
        BufferedWriter os = null;
        try {
            os = new BufferedWriter(new FileWriter(path));
            os.write(txt);
        }catch (Exception e){
            e.printStackTrace();
        }finally {
            if(os != null){
                try {
                    os.close();
                }catch (IOException e){
                    e.printStackTrace();
                }
            }
        }
    }


    public static String openText(String path){
        BufferedReader is = null;
        StringBuilder sb = new StringBuilder();
        try {
            is = new BufferedReader(new FileReader(path));
            String line = null;
            while ((line = is.readLine())!= null){
                sb.append(line);
            }
        }catch (Exception e){
            e.printStackTrace();
        }finally {
            if (is != null){
                try {
                    is.close();
                }catch(IOException e){
                    e.printStackTrace();
                }
            }
        }
        return sb.toString();
    }

}