[Lesson4] SharedPreferences

• SharedPreferences用来存取简单类型的数据资料，储存key与value的对应资料(只限基本型态的资料)
• 资料的储存格式是XML档，储存在手机中每个APP都会有的一个专用目录下

新增一个Drawable Resource File

输入完档名後，按下OK

shapetextview:

<?xml version="1.0" encoding="utf-8"?>
<selector xmlns:android="http://schemas.android.com/apk/res/android">
    <item>
        <shape android:shape="rectangle"> //使用的外型为矩形
            <stroke android:width="3dp" android:color="#000000"/>//边线宽度为3dp，边线颜色黑色
            <solid android:color="#2FF" /> //边线内部的颜色为浅蓝色
            
            //设定左上和左下的圆角
            <corners android:topLeftRadius="10dp" android:bottomLeftRadius="10dp" />
        </shape>
    </item>
</selector>

activity_main:
以LinearLayout为主的排版

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout
    xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical"
    tools:context=".MainActivity">

    <TextView
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="登入画面"
        android:textSize="30dp"
        android:gravity="center"/>

    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content">
        <TextView
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:background="@drawable/shapetextview"
            android:text="帐号"
            android:textSize="30dp"/>
        <EditText
            android:id="@+id/username"
            android:layout_width="200dp"
            android:layout_height="wrap_content"
            android:inputType="textPassword"/>
    </LinearLayout>

    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content">
        <TextView
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:background="@drawable/shapetextview"
            android:text="密码"
            android:textSize="30dp"/>
        <EditText
            android:id="@+id/password"
            android:layout_width="200dp"
            android:layout_height="wrap_content"
            android:inputType="textPassword"/>
    </LinearLayout>

    <Button
        android:id="@+id/submit"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="注册"
        android:textSize="30dp"
        android:onClick="submit"/>
    <Button
        android:id="@+id/login"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="登入"
        android:textSize="30dp"
        android:onClick="login"/>
</LinearLayout>

activity_submit:
除了以LinearLayout为主的排版，也用RelativeLayout帮Button对齐

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout
    xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical"
    tools:context=".submit">
    <TextView
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="注册画面"
        android:textSize="30dp"
        android:gravity="center"/>
    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content">
        <TextView
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:background="@drawable/shapetextview"
            android:text="帐号"
            android:textSize="30dp"/>
        <EditText
            android:id="@+id/newUsername"
            android:layout_width="200dp"
            android:layout_height="wrap_content"/>
    </LinearLayout>
    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content">
        <TextView
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:background="@drawable/shapetextview"
            android:text="密码"
            android:textSize="30dp"/>
        <EditText
            android:id="@+id/newPassword"
            android:layout_width="200dp"
            android:layout_height="wrap_content"/>
    </LinearLayout>
    <RelativeLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content">
        <Button
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="清除"
            android:onClick="clear"/>
        <Button
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="返回"
            android:layout_centerHorizontal="true"
            android:onClick="back"/>
        <Button
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="确定"
            android:layout_alignParentRight="true"
            android:onClick="ok"/>
    </RelativeLayout>
</LinearLayout>

submit:
储存注册的帐号、密码

public class submit extends AppCompatActivity {
    private EditText newUsername,newPassword;
    private String user,pass;
    
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_submit);
        findID();
    }
    
    private void findID() {
        newUsername = findViewById(R.id.newUsername);
        newPassword = findViewById(R.id.newPassword);
    }
    
    public void back(View view){
        Intent it = new Intent(this,MainActivity.class);
        startActivity(it);
        finish();
    }
    
    public void clear(View view){
        newUsername.setText("");
        newPassword.setText("");
    }
    
    public void ok(View view){
        user = newUsername.getText().toString().trim();
        pass = newPassword.getText().toString().trim();
        if (TextUtils.isEmpty(user) || TextUtils.isEmpty(pass)) {
            Toast.makeText(this, "请输入帐号/密码", Toast.LENGTH_SHORT).show();
        }else {
            SharedPreferences sp = getSharedPreferences("data", MODE_PRIVATE);
            SharedPreferences.Editor editor = sp.edit();
            editor.putString("id",user);
            editor.putString("val",pass);
            editor.commit();
            Toast.makeText(this, "注册成功", Toast.LENGTH_SHORT).show();
            Intent it = new Intent(this,MainActivity.class);
            startActivity(it);
            finish();
        }
    }
}

MainActivity:
比对注册完的帐号、密码是否一致

public class MainActivity extends AppCompatActivity {
    public EditText username,password;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        findID();
    }
    
    public void findID() {
        username = findViewById(R.id.username);
        password = findViewById(R.id.password);
    }
    
    public void submit(View view){
        Intent it = new Intent(this,submit.class);
        startActivity(it);
        finish();
    }
    
    public void login(View view){
        String loginUser = username.getText().toString();
        String loginPass = password.getText().toString();
        SharedPreferences sp = getSharedPreferences("data",MODE_PRIVATE);
        if (loginUser.equals(sp.getString("id","")) && loginPass.equals(sp.getString("val",""))){
            SharedPreferences.Editor edit = sp.edit();
            edit.apply();
            Intent it = new Intent(this,login.class);
            startActivity(it);
            finish();
        }else {
            Toast.makeText(this, "输入错误", Toast.LENGTH_SHORT).show();
        }
    }
}

activity_login:
将元件放入只以RelativeLayout为主的排版

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".login">

    <TextView
        android:id="@+id/textView"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="登入成功"
        android:textSize="30dp"
        android:layout_centerHorizontal="true"/>

    <Button
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="返回"
        android:textSize="30dp"
        android:layout_centerHorizontal="true"
        android:layout_centerVertical="true"
        android:onClick="back"/>
</RelativeLayout>

login:
登入之後，做个可以返回的按钮

public class login extends AppCompatActivity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_login);
    }
    
    public void back(View view){
        Intent it = new Intent(this,MainActivity.class);
        startActivity(it);
        finish();
    }
}

谢谢大家愿意花时间阅读，小弟弟我在此鞠躬