prefs

一：界面（用的是之前建的一个界面 省了很多时间<TextView

        android:layout_width="match_parent"        android:layout_height="50dp"        android:background="@android:color/transparent"        android:gravity="center"

android:textSize="22sp"/>    <EditText        android:id="@+id/ev_userName"        android:layout_width="match_parent"        android:layout_height="wrap_content"        android:digits="1234567890.+-*/%\n()"        android:hint="请输入用户名" />

<EditText        android:id="@+id/ev_password"        android:layout_width="match_parent"        android:layout_height="wrap_content"        android:hint="请输入年龄"/>

<CheckBox        android:id="@+id/chb"        android:layout_width="wrap_content"        android:layout_height="wrap_content"        android:text="记住用户名"/>        <LinearLayout            android:orientation="horizontal"            android:layout_height="0dp"            android:layout_width="wrap_content"            android:layout_weight="1">

<Button            android:id="@+id/btn_write"            android:layout_height="wrap_content"            android:layout_width="wrap_content"            android:layout_marginTop="10dp"            android:text="写入"/>

<Button        android:id="@+id/btn_login"        android:layout_marginTop="10dp"        android:layout_width="wrap_content"        android:layout_height="wrap_content"        android:text="读取"        android:textSize="20sp"/>二：对其功能的实现（第一步永远是定义相关组件）

public class MainActivity extends AppCompatActivity {    private EditText evuserName;    private EditText evpassword;    private Button btnLogin;    private CheckBox chkRemenber;    @Override    protected void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        setContentView(R.layout.activity_main);

evuserName = (EditText) findViewById(R.id.ev_userName);        evpassword = (EditText) findViewById(R.id.ev_password);        btnLogin = (Button) findViewById(R.id.btn_login);        chkRemenber = (CheckBox) findViewById(R.id.chb);        String userName=readFromFile("data.txt");        if (!TextUtils.isEmpty(userName))            btnLogin.setOnClickListener(new View.OnClickListener() {            @Override            public void onClick(View arg0) {                String userName = evuserName.getText().toString();                String password = evpassword.getText().toString();                Toast.makeText(MainActivity.this, "用户名:" + userName +                        "年龄:" + password, Toast.LENGTH_LONG).show();

if (chkRemenber.isChecked()) {                  if (saveToFile(userName)) {                      Toast.makeText(MainActivity.this,"保存成功",Toast.LENGTH_SHORT).show();                      Intent intent=new Intent(MainActivity.this,MainActivity.class);

}                }

}        });    }    private String readFromFile(String filename) {        //1.打开输入流文件        //2.读取        try {            FileInputStream in=openFileInput(filename);            int length=in.available();            byte[]data=new byte[length];            in.read(data);            return new String(data,"utf8");        } catch (java.io.IOException e) {            e.printStackTrace();            return null;        }

}

private boolean saveToFile(String userName) {        //1.打开文件            try {

FileOutputStream out=openFileOutput("data.txt",MODE_PRIVATE);                //2.写入                out.write(userName.getBytes());            //3.关闭文件输出流                out.close();                return true;            } catch (java.io.IOException e) {                e.printStackTrace();                return false;            }}        private boolean saveToPrefs(String userName){

SharedPreferences.Editor editor=getSharedPreferences("data.txt",MODE_PRIVATE).edit();            editor.putString("username",userName);            editor.putString("password",userName);            editor.putInt("age",18);           return true;    }    private void readFromPrefs(){        SharedPreferences preferences=getPreferences("data",MODE_PRIVATE);        String userName=preferences.getString("userName","");        if (!TextUtils.isEmpty(userName)){            evuserName.setText(userName);        }        int age=preferences.getInt("age",0);        evpassword.setText(age);}

private SharedPreferences getPreferences(String data, int modePrivate) {        return null;    }