public class Login extends AppCompatActivity {

    private SharedPreferences spf;
    private SharedPreferences.Editor spfe;

    private int num = 0;
    private EditText account = null;
    private EditText passWord = null;
    private CheckBox saveSelect = null;
    private Button login = null ;

    @Override
    protected void onCreate(Bundle saveInstanceState){

        //加载布局
        super.onCreate(saveInstanceState);
        setContentView(R.layout.login);

        //初始化控件
        account = (EditText)findViewById(R.id.account);
        passWord = (EditText)findViewById(R.id.passWord);
        saveSelect = (CheckBox)findViewById(R.id.saveSelect);
        login = (Button)findViewById(R.id.login);

        //使用Context的getSharedPreferences(String name,int mode)方法得到SharedPreferences对象;
        spf = getSharedPreferences("data", Context.MODE_PRIVATE);
        //使用SharedPreferences对象的edit()方法得到 SharedPreferences.Editor 的对象;
        spfe = spf.edit();

        //复选框是否被选中,若为选中状态，则保存过账户，要恢复数据
        if(spf.getBoolean("isSelect",false)){//选中标志,默认值为false
            String acc = spf.getString("account","");
            String pas = spf.getString("passWord","");
            account.setText(acc);
            passWord.setText(pas);
            saveSelect.setChecked(true);
        }

        //设置登录按钮监听事件
        login.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                //确认帐号密码
                if(account.getText().toString().equals("visen") && passWord.getText().toString().equals("dsy402645063!")){

                    //复选框是否被勾选，若被勾选，则需要保存账户后登录；否则直接登录且不保存账户
                    if(saveSelect.isChecked()){
                        saveDate();
                    }else {
                        spfe.clear();
                        spfe.commit();
                    }
                    
                    //页面跳转
                    Intent intent = new Intent(Login.this,MainActivity.class);
                    startActivity(intent);
                    finish();
                }else {//账户或密码错误
                    Toast.makeText(Login.this, "account or password is invalid", Toast.LENGTH_SHORT).show();
                }
            }
        });

    }

    public voi