Java 如何修复SharedReference以保存数据并跳过活动？

我想使用“共享首选项”保存我的用户名和密码，它已保存，但在我第二次打开应用程序时不起作用

 import android.content.Intent;
 import android.content.SharedPreferences;
 import android.graphics.Typeface;
 import android.icu.text.IDNA;
 import android.support.v4.media.RatingCompat;
 import android.support.v7.app.AppCompatActivity;
 import android.os.Bundle;
 import android.util.Log;
 import android.view.View;
 import android.view.animation.Animation;
 import android.view.animation.AnimationUtils;
 import android.widget.Button;
 import android.widget.EditText;
 import android.widget.ImageView;
 import android.widget.TextView;
 import android.widget.Toast;

public class Login_page extends AppCompatActivity {

TextView tv_user, tv_pass;
EditText tx_user, tx_pass;
Button btn_login;
ImageView img_ghorme;

SharedPreferences save;

public void findall()
{
    tv_user = (TextView)findViewById(R.id.tv_user);
    tv_pass = (TextView)findViewById(R.id.tv_pass);
    tx_user = (EditText)findViewById(R.id.tx_user);
    tx_pass = (EditText)findViewById(R.id.tx_pass);
    btn_login = (Button)findViewById(R.id.btn_login);
    img_ghorme = (ImageView)findViewById(R.id.img_ghorme);
}



public String save_user = "";
public String save_pass = "";

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_login_page2);

    findall();



    if(save_user.equals("admin") && save_pass.equals("admin"))
    {

        Intent skip = new Intent(Login_page.this, food_page.class);
        startActivity(skip);
    }


    btn_login.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            String user = tx_user.getText()+"";
            String pass = tx_pass.getText()+"";

            save_user = save.getString("username", "");
            save_pass = save.getString("password", "");

            SharedPreferences.Editor e = save.edit();
            e.putString("username", user);
            e.putString("password", pass);
            e.apply();



            if(user.equals("admin") && pass.equals("admin"))
            {

                Intent food = new Intent(Login_page.this, food_page.class);
                startActivity(food);

            }

            if (!user.equals("admin") || !pass.equals("admin"))
            {

                e.putString("username", "");
                e.putString("password", "");
                e.apply();

                tx_user.setText("");
                tx_pass.setText("");
            }
        }
    });



    save = getSharedPreferences("user", MODE_PRIVATE);
    save = getSharedPreferences("pass", MODE_PRIVATE);

    Typeface font_shabnam = Typeface.createFromAsset(getAssets(),"fonts/Shabnam.ttf");
    Typeface font_shabnam_light = Typeface.createFromAsset(getAssets(),"fonts/Shabnam_Light.ttf");
    Typeface font_shabnam_bold = Typeface.createFromAsset(getAssets(),"fonts/Shabnam.ttf");

    tv_user.setTypeface(font_shabnam_bold);
    tv_pass.setTypeface(font_shabnam_bold);
    tx_user.setTypeface(font_shabnam_light);
    tx_pass.setTypeface(font_shabnam_light);
    btn_login.setTypeface(font_shabnam_bold);


    Animation ani_rtl = AnimationUtils.loadAnimation(Login_page.this, R.anim.animation_ltr);
    Animation ani_ltr = AnimationUtils.loadAnimation(Login_page.this, R.anim.animation_rtl);
    Animation ani_fade = AnimationUtils.loadAnimation(Login_page.this, R.anim.fade);
    Animation ani_dtu = AnimationUtils.loadAnimation(Login_page.this, R.anim.animation_dtu);

    tv_user.setVisibility(View.VISIBLE);
    tv_user.startAnimation(ani_rtl);

    tv_pass.setVisibility(View.VISIBLE);
    tv_pass.startAnimation(ani_rtl);

    tx_user.setVisibility(View.VISIBLE);
    tx_user.startAnimation(ani_ltr);

    tx_pass.setVisibility(View.VISIBLE);
    tx_pass.startAnimation(ani_ltr);

    btn_login.setVisibility(View.VISIBLE);
    btn_login.startAnimation(ani_fade);

    img_ghorme.startAnimation(ani_dtu);

}

@Override
protected void onPause() {
    super.onPause();
    finish();
    }
}

---

XML:

---

我希望当我为用户名和密码编写admin时，它会保存它，第二次打开应用程序时，它会跳过该登录页面，但它不工作，并再次显示登录页面

在使用它之前，您不会初始化SharedReference，也不会为每个密钥对定义两个SharedReference。更改您的代码如下

public class Login_page extends AppCompatActivity {

TextView tv_user, tv_pass;
EditText tx_user, tx_pass;
Button btn_login;
ImageView img_ghorme;

SharedPreferences save;

public void findall()
{
    tv_user = findViewById(R.id.tv_user);
    tv_pass = findViewById(R.id.tv_pass);
    tx_user = findViewById(R.id.tx_user);
    tx_pass = findViewById(R.id.tx_pass);
    btn_login = findViewById(R.id.btn_login);
    img_ghorme = findViewById(R.id.img_ghorme);
}



public String save_user = "";
public String save_pass = "";

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main2);

    findall();

    save = getSharedPreferences("userInfo", MODE_PRIVATE);
    save_user = save.getString("username", "");
    save_pass = save.getString("password", "");


    if(save_user.equals("admin") && save_pass.equals("admin"))
    {

        Intent skip = new Intent(Login_page.this, food_page.class);
        startActivity(skip);
    }


    btn_login.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v)
        {
            String user = tx_user.getText().toString();
            String pass = tx_pass.getText().toString();


            SharedPreferences.Editor e = save.edit();
            e.putString("username", user);
            e.putString("password", pass);
            e.apply();



            if(user.equals("admin") && pass.equals("admin"))
            {

                Intent food = new Intent(Login_page.this, food_page.class);
                startActivity(food);

            }

            if (!user.equals("admin") || !pass.equals("admin"))
            {

                e.putString("username", "");
                e.putString("password", "");
                e.apply();

                tx_user.setText("");
                tx_pass.setText("");
            }
        }
    });


    Typeface font_shabnam = Typeface.createFromAsset(getAssets(),"fonts/Shabnam.ttf");
    Typeface font_shabnam_light = Typeface.createFromAsset(getAssets(),"fonts/Shabnam_Light.ttf");
    Typeface font_shabnam_bold = Typeface.createFromAsset(getAssets(),"fonts/Shabnam.ttf");

    tv_user.setTypeface(font_shabnam_bold);
    tv_pass.setTypeface(font_shabnam_bold);
    tx_user.setTypeface(font_shabnam_light);
    tx_pass.setTypeface(font_shabnam_light);
    btn_login.setTypeface(font_shabnam_bold);


    Animation ani_rtl = AnimationUtils.loadAnimation(Login_page.this, R.anim.animation_ltr);
    Animation ani_ltr = AnimationUtils.loadAnimation(Login_page.this, R.anim.animation_rtl);
    Animation ani_fade = AnimationUtils.loadAnimation(Login_page.this, R.anim.fade);
    Animation ani_dtu = AnimationUtils.loadAnimation(Login_page.this, R.anim.animation_dtu);

    tv_user.setVisibility(View.VISIBLE);
    tv_user.startAnimation(ani_rtl);

    tv_pass.setVisibility(View.VISIBLE);
    tv_pass.startAnimation(ani_rtl);

    tx_user.setVisibility(View.VISIBLE);
    tx_user.startAnimation(ani_ltr);

    tx_pass.setVisibility(View.VISIBLE);
    tx_pass.startAnimation(ani_ltr);

    btn_login.setVisibility(View.VISIBLE);
    btn_login.startAnimation(ani_fade);

    img_ghorme.startAnimation(ani_dtu);

}

@Override
protected void onPause() {
    super.onPause();
    finish();
}

---

}

这是创建时的完整代码吗？如何初始化

save

并读取

save\u user

和

save\u pass

？将整个活动代码张贴在此处。@S-Sh这不是onCreate的漏洞。我用onCreate创建save并在onCreate上初始化它。请同时添加代码，看看如何初始化save@Kabir当我第二次打开应用程序时，当它想通过检查usrename和密码来更改活动时，我添加了我的代码，它强制stoped.yes其崩溃的java.lang.RuntimeException:无法启动活动ComponentInfo{com.home.seesion10/com.home.seesion10.Login_page}:java.lang.NullPointerException:尝试调用虚拟方法'boolean java.lang.String.equals（java.lang.Object）'在空对象引用上，然后设置公共字符串save_user=“”；公共字符串save_pass=“”；不堪一击。它不会崩溃，但不会第二次跳过登录页。我已经更新了答案。只有在您第一次输入用户名和密码时，才会跳过登录页面。

public class Login_page extends AppCompatActivity {

TextView tv_user, tv_pass;
EditText tx_user, tx_pass;
Button btn_login;
ImageView img_ghorme;

SharedPreferences save;

public void findall()
{
    tv_user = findViewById(R.id.tv_user);
    tv_pass = findViewById(R.id.tv_pass);
    tx_user = findViewById(R.id.tx_user);
    tx_pass = findViewById(R.id.tx_pass);
    btn_login = findViewById(R.id.btn_login);
    img_ghorme = findViewById(R.id.img_ghorme);
}



public String save_user = "";
public String save_pass = "";

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main2);

    findall();

    save = getSharedPreferences("userInfo", MODE_PRIVATE);
    save_user = save.getString("username", "");
    save_pass = save.getString("password", "");


    if(save_user.equals("admin") && save_pass.equals("admin"))
    {

        Intent skip = new Intent(Login_page.this, food_page.class);
        startActivity(skip);
    }


    btn_login.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v)
        {
            String user = tx_user.getText().toString();
            String pass = tx_pass.getText().toString();


            SharedPreferences.Editor e = save.edit();
            e.putString("username", user);
            e.putString("password", pass);
            e.apply();



            if(user.equals("admin") && pass.equals("admin"))
            {

                Intent food = new Intent(Login_page.this, food_page.class);
                startActivity(food);

            }

            if (!user.equals("admin") || !pass.equals("admin"))
            {

                e.putString("username", "");
                e.putString("password", "");
                e.apply();

                tx_user.setText("");
                tx_pass.setText("");
            }
        }
    });


    Typeface font_shabnam = Typeface.createFromAsset(getAssets(),"fonts/Shabnam.ttf");
    Typeface font_shabnam_light = Typeface.createFromAsset(getAssets(),"fonts/Shabnam_Light.ttf");
    Typeface font_shabnam_bold = Typeface.createFromAsset(getAssets(),"fonts/Shabnam.ttf");

    tv_user.setTypeface(font_shabnam_bold);
    tv_pass.setTypeface(font_shabnam_bold);
    tx_user.setTypeface(font_shabnam_light);
    tx_pass.setTypeface(font_shabnam_light);
    btn_login.setTypeface(font_shabnam_bold);


    Animation ani_rtl = AnimationUtils.loadAnimation(Login_page.this, R.anim.animation_ltr);
    Animation ani_ltr = AnimationUtils.loadAnimation(Login_page.this, R.anim.animation_rtl);
    Animation ani_fade = AnimationUtils.loadAnimation(Login_page.this, R.anim.fade);
    Animation ani_dtu = AnimationUtils.loadAnimation(Login_page.this, R.anim.animation_dtu);

    tv_user.setVisibility(View.VISIBLE);
    tv_user.startAnimation(ani_rtl);

    tv_pass.setVisibility(View.VISIBLE);
    tv_pass.startAnimation(ani_rtl);

    tx_user.setVisibility(View.VISIBLE);
    tx_user.startAnimation(ani_ltr);

    tx_pass.setVisibility(View.VISIBLE);
    tx_pass.startAnimation(ani_ltr);

    btn_login.setVisibility(View.VISIBLE);
    btn_login.startAnimation(ani_fade);

    img_ghorme.startAnimation(ani_dtu);

}

@Override
protected void onPause() {
    super.onPause();
    finish();
}