在Android应用程序的屏幕/活动之间移动时保存UI状态

我正在做一个多屏幕测验应用程序。对于每个问题，我都有一个单独的活动/屏幕。在每个屏幕的底部都有下一个/上一个“按钮”，可导航到下一个/上一个屏幕。请参见带有问题的屏幕的UI示例：

不过我有个问题。假设用户选择问题2的答案，然后单击“上一步”，选择问题1中的答案并单击“下一步”

我想保存问题2的UI状态，这样，如果用户通过单击“上一步”或“下一步”返回某个问题，所选答案将保持不变。

我设法做到的一件事是，当用户单击“previous”时，UI将保持不变，我在清单文件中使用了以下代码：

android:launchMode="singleTask"

但是，当用户通过“下一步”来回答问题时，我无法将其保存。以下是我的问题2活动代码：

package com.example.justynagolawska.quizappiteration2;

import android.content.Intent;
import android.os.Bundle;
import android.support.v7.app.ActionBar;
import android.support.v7.app.AppCompatActivity;
import android.view.View;
import android.widget.CheckBox;
import android.widget.TextView;

public class Question2Activity extends AppCompatActivity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_question2);

        ActionBar actionbar = getSupportActionBar();

        // Applies the custom action bar style
        getSupportActionBar().setDisplayOptions(actionbar.DISPLAY_SHOW_CUSTOM);
        getSupportActionBar().setCustomView(R.layout.action_bar);

        // Changes the action bar title
        TextView title = (TextView) getSupportActionBar().getCustomView().findViewById(R.id.action_bar_title);
        title.setText(R.string.q2_name);

        //Getting the intent with score for question 1
        Intent question2Intent = getIntent();
        final int resultQ1 = question2Intent.getIntExtra("q1result", 0);

        // Find the View that shows the next TextView
        TextView nextQuestion = (TextView) findViewById(R.id.next);

        // Set a click listener on that View
        nextQuestion.setOnClickListener(new View.OnClickListener() {
            // The code in this method will be executed when next View is clicked on.
            @Override
            public void onClick(View view) {
                //Getting the answer to question 2 checkbox 1
                CheckBox checkBox1Q2 = (CheckBox) findViewById(R.id.checkbox1Q2);
                boolean isCheckBox1Q2 = checkBox1Q2.isChecked();

                //Getting the answer to question 2 checkbox 2
                CheckBox checkBox2Q2 = (CheckBox) findViewById(R.id.checkbox2Q2);
                boolean isCheckBox2Q2 = checkBox2Q2.isChecked();

                //Getting the answer to question 2 checkbox 3
                CheckBox checkBox3Q2 = (CheckBox) findViewById(R.id.checkbox3Q2);
                boolean isCheckBox3Q2 = checkBox3Q2.isChecked();

                //Calculate Question 2 score
                int resultQ2 = calculateResultQ2(isCheckBox1Q2, isCheckBox2Q2, isCheckBox3Q2);

                Intent question3Intent = new Intent(Question2Activity.this, Question3Activity.class);
                question3Intent.setFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP);

                question3Intent.putExtra ("q1result", resultQ1);
                question3Intent.putExtra ("q2result", resultQ2);
                startActivity(question3Intent);
            }
        });

        // Find the View that shows the next TextView
        TextView previousQuestion = (TextView) findViewById(R.id.previous);

        // Set a click listener on that View
        previousQuestion.setOnClickListener(new View.OnClickListener() {
            // The code in this method will be executed when next View is clicked on.
            @Override
            public void onClick(View view) {
                Intent question1Intent = new Intent(Question2Activity.this, Question1Activity.class);
                startActivity(question1Intent);
            }
        });
    }

    /**
     * Check which checkbox was selected in the question 2
     *
     * @param checkBox1 is whether or not the user checked the checkbox1
     * @param checkBox2 is whether or not the user checked the checkbox2
     * @param checkBox3 is whether or not the user checked the checkbox3
     * @return the score the user got for question 2
     */
    private int calculateResultQ2(boolean checkBox1, boolean checkBox2, boolean checkBox3) {
        int result = 0;
        if (checkBox1 && checkBox2 && checkBox3) {
            result = 1;
        }
        return result;
    }

如果有人能帮助我，我将不胜感激。谢谢大家!

编辑：下面是我使用SharedReferences的工作代码，@tahsinRupam提出的解决方案

package com.example.justynagolawska.quizappiteration2;

import android.content.Intent;
import android.content.SharedPreferences;
import android.os.Bundle;
import android.preference.PreferenceManager;
import android.support.v7.app.ActionBar;
import android.support.v7.app.AppCompatActivity;
import android.view.View;
import android.widget.CheckBox;
import android.widget.TextView;

public class Question2Activity extends AppCompatActivity {

SharedPreferences mypref;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_question2);

    final CheckBox checkBox1Q2 = (CheckBox) findViewById(R.id.checkbox1Q2);
    final CheckBox checkBox2Q2 = (CheckBox) findViewById(R.id.checkbox2Q2);
    final CheckBox checkBox3Q2 = (CheckBox) findViewById(R.id.checkbox3Q2);

    mypref = PreferenceManager.getDefaultSharedPreferences(this);

    ActionBar actionbar = getSupportActionBar();

    // Applies the custom action bar style
    getSupportActionBar().setDisplayOptions(actionbar.DISPLAY_SHOW_CUSTOM);
    getSupportActionBar().setCustomView(R.layout.action_bar);

    // Changes the action bar title
    TextView title = (TextView) getSupportActionBar().getCustomView().findViewById(R.id.action_bar_title);
    title.setText(R.string.q2_name);

    //Getting the intent with score for question 1
    Intent question2Intent = getIntent();


    final int resultQ1 = question2Intent.getIntExtra("q1result", 0);

    // Find the View that shows the next TextView
    TextView nextQuestion = (TextView) findViewById(R.id.next);

    // Set a click listener on that View
    nextQuestion.setOnClickListener(new View.OnClickListener() {
        // The code in this method will be executed when next View is clicked on.
        @Override
        public void onClick(View view) {


            //Getting the answer to question 2 checkbox 1
            boolean isCheckBox1Q2 = checkBox1Q2.isChecked();

            //Getting the answer to question 2 checkbox 2
            boolean isCheckBox2Q2 = checkBox2Q2.isChecked();

            //Getting the answer to question 2 checkbox 3
            boolean isCheckBox3Q2 = checkBox3Q2.isChecked();

            //Calculate Question 2 score
            int resultQ2 = calculateResultQ2(isCheckBox1Q2, isCheckBox2Q2, isCheckBox3Q2);

            Intent question3Intent = new Intent(Question2Activity.this, Question3Activity.class);
            question3Intent.putExtra ("q1result", resultQ1);
            question3Intent.putExtra ("q2result", resultQ2);
            startActivity(question3Intent);
        }
    });

    // Find the View that shows the next TextView
    TextView previousQuestion = (TextView) findViewById(R.id.previous);

    // Set a click listener on that View
    previousQuestion.setOnClickListener(new View.OnClickListener() {
        // The code in this method will be executed when next View is clicked on.
        @Override
        public void onClick(View view) {
            Intent question1Intent = new Intent(Question2Activity.this, Question1Activity.class);
            startActivity(question1Intent);
        }
    });
}

/**
 * Check which checkbox was selected in the question 2
 *
 * @param checkBox1 is whether or not the user checked the checkbox1
 * @param checkBox2 is whether or not the user checked the checkbox2
 * @param checkBox3 is whether or not the user checked the checkbox3
 * @return the score the user got for question 2
 */
private int calculateResultQ2(boolean checkBox1, boolean checkBox2, boolean checkBox3) {
    int result = 0;
    if (checkBox1 && checkBox2 && checkBox3) {
        result = 1;
    }
    return result;
}

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

    //Getting the answer to question 2 checkbox 1
    CheckBox checkBox1Q2 = (CheckBox) findViewById(R.id.checkbox1Q2);
    boolean isCheckBox1Q2 = checkBox1Q2.isChecked();

    //Getting the answer to question 2 checkbox 2
    CheckBox checkBox2Q2 = (CheckBox) findViewById(R.id.checkbox2Q2);
    boolean isCheckBox2Q2 = checkBox2Q2.isChecked();

    //Getting the answer to question 2 checkbox 3
    CheckBox checkBox3Q2 = (CheckBox) findViewById(R.id.checkbox3Q2);
    boolean isCheckBox3Q2 = checkBox3Q2.isChecked();

    if(isCheckBox1Q2 == true){
        mypref.edit().putBoolean("Iscb1Checked", true).apply();
    }
    else if(isCheckBox1Q2 == false){
        mypref.edit().putBoolean("Iscb1Checked", false).apply();
    }

    if(isCheckBox2Q2 == true){
        mypref.edit().putBoolean("Iscb2Checked", true).apply();
    }
    else if(isCheckBox2Q2 == false){
        mypref.edit().putBoolean("Iscb2Checked", false).apply();
    }

    if(isCheckBox3Q2 == true){
        mypref.edit().putBoolean("Iscb3Checked", true).apply();
    }
    else if(isCheckBox3Q2 == false){
        mypref.edit().putBoolean("Iscb3Checked", false).apply();
    }

}

@Override
protected void onResume() {
    super.onResume();

    //Getting the answer to question 2 checkbox 1
    CheckBox checkBox1Q2 = (CheckBox) findViewById(R.id.checkbox1Q2);

    //Getting the answer to question 2 checkbox 2
    CheckBox checkBox2Q2 = (CheckBox) findViewById(R.id.checkbox2Q2);

    //Getting the answer to question 2 checkbox 3
    CheckBox checkBox3Q2 = (CheckBox) findViewById(R.id.checkbox3Q2);

    if(mypref.contains("Iscb1Checked")){
        if(mypref.getBoolean("Iscb1Checked",false)){
            checkBox1Q2.setChecked(true);
        }
    }

    if(mypref.contains("Iscb2Checked")){
        if(mypref.getBoolean("Iscb2Checked",false)){
            checkBox2Q2.setChecked(true);
        }
    }

    if(mypref.contains("Iscb3Checked")){
        if(mypref.getBoolean("Iscb3Checked",false)){
            checkBox3Q2.setChecked(true);
        }
    }
}

}

请注意，我在onPause（）中替换了以下内容；方法，因为我正在获取null异常：

checkBox1Q2.isChecked()
!checkBox1Q2.isChecked()

与

---

您可以使用SharedReference来存储您的值

1） 公开声明复选框和SharedReference：

 CheckBox checkBox1Q2;
 CheckBox checkBox2Q2;
 CheckBox checkBox3Q2;
 SharedPreferences mypref;

2） 在onCreate（）中，初始化SharedReference：

 mypref = PreferenceManager.getDefaultSharedPreferences(this);

3） 保存onPause（）中的复选框状态（按下后退按钮时会调用cause onPause（）。您也可以在onStop（）或onDestroy（）中声明

4） 获取onResume（）方法中的复选框状态：

---

现在，您将在onClick中获得复选框视图。尽量避免这样。始终在onCreate的初始部分（在setContentView之后）获取视图（findViewById）。

为什么使用

android:launchMode=“singleTask”

？在用户单击“上一步”时保存UI状态。它完成了我需要完成的工作的一半，但当然不是我想要实现的。如果我找到上述问题的有效解决方案，我根本不需要使用它。我认为如果使用viewpager，这将解决您的问题，它将保存用户界面更改，直到销毁。您可以使用saveInstanceState或SharedReference来满足您的需求。Hi@tahsinRupam。谢谢你的建议。您能告诉我如何应用saveInstanceState的更多详细信息吗？我试着这样做，但我想这只是在我旋转屏幕时保存UI状态？嗨@tahsinRupam，不知为什么，它对我不起作用。我在onCreate（）之前应用了完全相同的代码；方法。你能告诉我有什么问题吗？我也看到了这篇文章：声称savedInstanceState仅适用于您在同一活动中的情况，例如屏幕旋转？也许分享经验会是一个更好的主意，你认为呢？是的，你是绝对正确的！我读了各种各样的意见后感到困惑。当系统出于资源目的或屏幕旋转而终止活动时，捆绑数据非常有用。但是，当某个活动由于应用程序行为（如按下后退按钮）而被终止时，该活动实例将永久消失。所以saveInstanceState在这里不起作用。在这件事上使用SharedReference是明智的。如果你愿意，我会编辑我的答案，用SharedReference解决这个问题。那太好了！非常感谢。Stackoverflow会因为这个广泛的评论块而杀了我；）但我想感谢你为这个问题付出的努力和时间！

 mypref = PreferenceManager.getDefaultSharedPreferences(this);

  @Override
protected void onPause() {
    super.onPause();
    if(checkBox1Q2.isChecked()){
        mypref.edit().putBoolean("Iscb1Checked", true).apply();
    }
    else if(!checkBox1Q2.isChecked()){
        mypref.edit().putBoolean("Iscb1Checked", false).apply();
    }

    if(checkBox2Q2.isChecked()){
        mypref.edit().putBoolean("Iscb2Checked", true).apply();
    }
    else if(!checkBox2Q2.isChecked()){
        mypref.edit().putBoolean("Iscb2Checked", false).apply();
    }

    if(checkBox3Q2.isChecked()){
        mypref.edit().putBoolean("Iscb3Checked", true).apply();
    }
    else if(!checkBox3Q2.isChecked()){
        mypref.edit().putBoolean("Iscb3Checked", false).apply();
    }


}

@Override
protected void onResume() {
    super.onResume();
        if(mypref.contains("Iscb1Checked")){
            if(mypref.getBoolean("Iscb1Checked",false)){
                checkBox1Q2.setChecked(true);
            }
        }

        if(mypref.contains("Iscb2Checked")){
            if(mypref.getBoolean("Iscb2Checked",false)){
                checkBox2Q2.setChecked(true);
            }
        }

        if(mypref.contains("Iscb3Checked")){
             if(mypref.getBoolean("Iscb3Checked",false)){
                checkBox3Q2.setChecked(true);
             }
         }
}