Android 数据持久化

1. 文件存储
   Context类提供了一个方法：openFileOutput(),默认存储位置在/data/data/packagename/files/目录下
   第一个参数是文件名，不包含路径，第二个参数是模式：MODE_PRIVATE和MODE_APPEND

  private void saveData() {
        String data = mEditText.getText().toString();
        BufferedWriter bufferedWriter = null;
        try {
            FileOutputStream fileOutputStream = openFileOutput("hello", MODE_APPEND);
            bufferedWriter = new BufferedWriter(new OutputStreamWriter(fileOutputStream));
            bufferedWriter.write(data);
        } catch (FileNotFoundException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        } finally {

            try {
                if (bufferedWriter != null) {
                    bufferedWriter.close();
                }
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
    }

读取文件数据:openFileInput()

private void load() {
        FileInputStream fileInputStream = null;
        BufferedReader bufferedReader = null;
        StringBuilder stringBuilder = new StringBuilder();
        try {
            fileInputStream = openFileInput("hello");
            bufferedReader = new BufferedReader(new InputStreamReader(fileInputStream));
            String line = "";
            while ((line = bufferedReader.readLine()) != null) {
                stringBuilder.append(line);
            }
        } catch (IOException e) {
            e.printStackTrace();
            Toast.makeText(MainActivity.this,e.getMessage(),Toast.LENGTH_SHORT).show();
        } finally {
            {
                try {
                    if (bufferedReader != null) {
                        bufferedReader.close();
                    }
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
        }
        Toast.makeText(MainActivity.this,stringBuilder,Toast.LENGTH_SHORT).show();
    }

2. SharedPreferences存储
   存储位置：/data/data/包名/shared_prefs/目录下，以xml格式存储
   参数1：文件名，参数2：模式

SharedPreferences sp = getSharedPreferences("data", MODE_PRIVATE);
        SharedPreferences.Editor edit = sp.edit();
        edit.putString("key","value");
        edit.apply();// edit.commit();

3. SQLite存储