SharedPreferences和SD存储

内容存储：
data/data/项目包名
特点：随着App卸载而消失
shared_prefs文件夹
getsharedprefereces（文件名，Mo——private/Moide_apped）
file path=getFileDir()返回文件夹
外部存储
mnt/shell/emulated/0
分类：
android 私有路径 随着App卸载而消失
其余公共路径，永久存在

private SharedPreferences sharedPreferences;
private EditText username;
private EditText password;
private CheckBox cb;
private Button login;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
username = (EditText) findViewById(R.id.username);
password = (EditText) findViewById(R.id.password);
cb=(CheckBox)findViewById(R.id.cb);
login=(Button)findViewById(R.id.login);

    sharedPreferences=getSharedPreferences("1702A",MODE_PRIVATE);
    boolean ischeck= sharedPreferences.getBoolean("ischeck",false);
    if(ischeck){
        //读到用户名和密码展现在页面中,复选框被勾选
        String username1=sharedPreferences.getString("username","");
        String password1=sharedPreferences.getString("password","");
        username.setText(username1);
        password.setText(password1);
        cb.setChecked(true);
    }
    //TODO 写数据
    login.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            String username2=username.getText().toString().trim();
            String password2=password.getText().toString().trim();

            if("zhangsan".equals(username2)&&"123456".equals(password2)){

                if(cb.isChecked()){
                    SharedPreferences.Editor edit = sharedPreferences.edit();
                    edit.putBoolean("ischeck",true);
                    edit.putString("username",username2);
                    edit.putString("password",password2);
                    Intent intent=new Intent(MainActivity.this,Main2Activity.class);
                    startActivity(intent);
                    edit.commit();

                }else{
                    SharedPreferences.Editor edit = sharedPreferences.edit();
                    edit.putBoolean("ischeck",false);
                    edit.commit();
                }
            }
        }
    });
}

}