背靠背上的Android按下多个子活动不工作

Question

我在按后退按钮时遇到了问题，我有三个包含列表view.The的活动--首先，单击HomeActivity中的Listview项目，在subListAntivity中打开另一个Listview2，然后单击第二个Listview，它将在SubList2Activity中打开Listview3，然后单击Listview3，它将打开QuizActivity。

视图层次结构类似于

HomeActivity ==> subListAntivity ==> SubList2Activity ==>QuizActivity

我重写了onBackPressed方法，它适用于上述两个层次结构。当从SubList2Activity返回到subListAntivity时，它显示的是空列表。

我将一个视图中的附加内容传递到另一个视图中，根据选定的项目，我将显示第二个活动。

@Override
public void onBackPressed()
{
    // code here to show dialog
    super.onBackPressed();  // optional depending on your needs
}

Activity_home.xml：

<?xml version="1.0" encoding="utf-8"?>
<android.support.v4.widget.DrawerLayout 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:id="@+id/drawer_layout"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:fitsSystemWindows="true"
    tools:openDrawer="start">



    <include
        layout="@layout/app_bar_home"
        android:layout_width="match_parent"
        android:layout_height="match_parent" />

    <android.support.design.widget.NavigationView
        android:id="@+id/nav_view"
        android:layout_width="wrap_content"
        android:layout_height="match_parent"
        android:layout_gravity="start"
        android:fitsSystemWindows="true"
        app:headerLayout="@layout/nav_header_home"
        app:menu="@menu/activity_home_drawer" />

</android.support.v4.widget.DrawerLayout>

HomeActivity.java

public class HomeActivity extends AppCompatActivity
        implements NavigationView.OnNavigationItemSelectedListener {
    private FirebaseAuth mAuth;
    // [END declare_auth]

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_home);
        Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
        setSupportActionBar(toolbar);
     ;
        mAuth = FirebaseAuth.getInstance();
        FloatingActionButton fab = (FloatingActionButton) findViewById(R.id.fab);
        fab.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                Snackbar.make(view, "Replace with your own action", Snackbar.LENGTH_LONG)
                        .setAction("Action", null).show();
            }
        });

        DrawerLayout drawer = (DrawerLayout) findViewById(R.id.drawer_layout);
        ActionBarDrawerToggle toggle = new ActionBarDrawerToggle(
                this, drawer, toolbar, R.string.navigation_drawer_open, R.string.navigation_drawer_close);
        drawer.addDrawerListener(toggle);
        toggle.syncState();
        FirebaseUser currentUser = mAuth.getCurrentUser();
        NavigationView navigationView = (NavigationView) findViewById(R.id.nav_view);
        navigationView.setNavigationItemSelectedListener(this);
        String[] dataArray = {"Online Test","Test Series","+1 & +2 Math Formula","+1 & +2 Physics Formula","+1 & +2 Chemistry Formula",
                "+1 & +2 Statistics Formula","+1 & +2 Biology Quiz","Computer Science","English",
                "Privious Year Question Paper With Answer","Leaderboard","GK","Current affairs","Aptitude","Reasoning","Exam Tips","Exam Notification","Trends"};
        ArrayAdapter adapter = new ArrayAdapter<String>(this,
                R.layout.activity_listitem, dataArray);

        ListView listView = (ListView) findViewById(R.id.data_list);
        listView.setAdapter(adapter);

        // Set an item click listener for ListView
        listView.setOnItemClickListener(new AdapterView.OnItemClickListener() {
            @Override
            public void onItemClick(AdapterView<?> parent, View view, int position, long id) {
                // Get the selected item text from ListView
                String selectedItem = (String) parent.getItemAtPosition(position);

                Intent intent = new Intent(HomeActivity.this,SubListActivity.class);
                // intent.putExtra("hm",hm);

                intent.putExtra("listItem",selectedItem);


                intent.addFlags(Intent.FLAG_ACTIVITY_NO_ANIMATION);
                startActivity(intent);
            }
        });
    }

    @Override
    public void onBackPressed() {
        this.finish();

    }

    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        // Inflate the menu; this adds items to the action bar if it is present.
        getMenuInflater().inflate(R.menu.home, menu);
        return true;
    }

    @Override
    public boolean onOptionsItemSelected(MenuItem item) {
        // Handle action bar item clicks here. The action bar will
        // automatically handle clicks on the Home/Up button, so long
        // as you specify a parent activity in AndroidManifest.xml.
        int id = item.getItemId();

        //noinspection SimplifiableIfStatement
        if (id == R.id.action_settings) {
            return true;
        }

        return super.onOptionsItemSelected(item);
    }

    @SuppressWarnings("StatementWithEmptyBody")
    @Override
    public boolean onNavigationItemSelected(MenuItem item) {
        // Handle navigation view item clicks here.
        int id = item.getItemId();

        if (id == R.id.nav_dashboard) {
        } else if (id == R.id.nav_quiz) {
            Intent intent = new Intent(HomeActivity.this, SubListActivity.class);
            String selectedItem ="Online Test";
            intent.putExtra("listItem",selectedItem);
            intent.addFlags(Intent.FLAG_ACTIVITY_NO_ANIMATION);
            startActivity(intent);

        } else if (id == R.id.nav_math) {
            Intent intent = new Intent(HomeActivity.this, SubListActivity.class);
            String selectedItem ="+1 & +2 Math Formula";
            intent.putExtra("listItem",selectedItem);
            intent.addFlags(Intent.FLAG_ACTIVITY_NO_ANIMATION);
            startActivity(intent);
        } else if (id == R.id.nav_physics) {
            Intent intent = new Intent(HomeActivity.this, SubListActivity.class);
            String selectedItem ="+1 & +2 Physics Formula";
            intent.putExtra("listItem",selectedItem);
            intent.addFlags(Intent.FLAG_ACTIVITY_NO_ANIMATION);
            startActivity(intent);
        } else if (id == R.id.nav_chemistry) {
            Intent intent = new Intent(HomeActivity.this, SubListActivity.class);
            String selectedItem ="1 & +2 Chemistry Formula";
            intent.putExtra("listItem",selectedItem);
            intent.addFlags(Intent.FLAG_ACTIVITY_NO_ANIMATION);
            startActivity(intent);
        } else if (id == R.id.nav_about) {
            Intent viewIntent =
                    new Intent("android.intent.action.VIEW",
                            Uri.parse("http://swainsoft.blogspot.in/"));
            startActivity(viewIntent);
        } else if (id == R.id.nav_feedback) {
            Intent viewIntent =
                    new Intent("android.intent.action.VIEW",
                            Uri.parse("https://docs.google.com/forms/d/e/1FAIpQLScklsZ-ymN4WfYAWuPuWU4Ez6tlp5-De8MZaT06jmbZXixqgg/viewform?usp=sf_link"));
            startActivity(viewIntent);

        } else if (id == R.id.nav_rating) {
            Intent viewIntent =
                    new Intent("android.intent.action.VIEW",
                            Uri.parse("https://docs.google.com/forms/d/e/1FAIpQLScklsZ-ymN4WfYAWuPuWU4Ez6tlp5-De8MZaT06jmbZXixqgg/viewform?usp=sf_link"));
            startActivity(viewIntent);
        } else if (id == R.id.nav_share) {
            String message = "Share Science formula";
            Intent share = new Intent(Intent.ACTION_SEND);
            share.setType("text/plain");
            share.putExtra(Intent.EXTRA_TEXT, message);

            startActivity(Intent.createChooser(share, "Share"));

        } else if (id == R.id.nav_signout) {
            FirebaseAuth.getInstance().signOut();
            Intent iinent = new Intent(HomeActivity.this, MainActivity.class);
            startActivity(iinent);
        }

        DrawerLayout drawer = (DrawerLayout) findViewById(R.id.drawer_layout);
        drawer.closeDrawer(GravityCompat.START);
        return true;
    }
}

Activity_sub_list.xml：

<?xml version="1.0" encoding="utf-8"?>
<android.support.constraint.ConstraintLayout 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="com.sitansu.coder.swainsoft.javaquiz.SubListActivity">
    <ListView
    android:id="@+id/sub_data_list"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:background="@color/colorPrimaryDark"
    android:backgroundTint="@color/colorPrimaryDark"
    tools:background="@color/colorPrimaryDark"
    tools:layout_editor_absoluteX="1117dp"
    tools:layout_editor_absoluteY="0dp"></ListView>
</android.support.constraint.ConstraintLayout>

SublistActivity.java

public class SubListActivity extends AppCompatActivity {

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

        new InitListData().invoke();
    }

    @Override
    public void onBackPressed()
    {
        // code here to show dialog
        super.onBackPressed();  // optional depending on your needs
    }




    public class InitListData {
        public void invoke() {
            Bundle extras = getIntent().getExtras();
            if(extras == null)
                return;
            String list_item = extras.getString("listItem");
            String[] dataArray = null;
            if ("Online Test".equalsIgnoreCase(list_item)) {
                dataArray = new String[]{"+1 Physics Test", "+2 Physics Test", "+1 Chemistry Test", "+2 Chemistry Test", "+1 Math Test", "+2 Math Test", "Biology Test", "Statistics Test", "Computer Science Test", "English Test",
                        "+2 Privious Year Question Paper Test", "GK Test", "Current affairs Test", "Aptitude test", "Reasoning test"};

            } else if ("Test Series".equalsIgnoreCase(list_item)) {
                dataArray = new String[]{"+2 Physics Test Series for CBSE", "+2 Physics Test Series for ICSE", "+2 Physics Test Series for State Boards", "+2 Physics Test Series for IB", "+2 Chemistry Test Series for CBSE", "+2 Chemistry Test Series for ICSE", "+2 Chemistry Test Series for State Boards", "+2 Chemistry Test Series for IB",
                        "+2 Math Test Series for CBSE", "+2 Math Test Series for ICSE", "+2 Math Test Series for State Boards", "+2 Math Test Series for IB",
                        "+2 Biology Test Series for CBSE", "+2 Biology Test Series for ICSE", "+2 Biology Series for State Boards", "+2 Biology Test Series for IB"};
            } else if ("+1 & +2 Math Formula".equalsIgnoreCase(list_item)) {
                dataArray = new String[]{"Relations & Functions", "Set Theory", "Probability", "Derivative", "Differentiation", "Integration", "Definite Integral", "Differential Equations", "Complex Numbers", "De Moivre's Theorem", "Quadratic Equations",
                        "Progression", "Logarithmic,Exponential & Maclaurian Series", "Permutation & Combination", "Bionomial Theorem",
                        "Statistics", "Matrices", "Determinant", "Trigonometric Equations", "Triangles", "Inverse Trigonometric", "Functions & Graphs", "Limit & Continuity",
                        "Coordinate Geometry", "Straight Lines", "Pair of Straight Line", "Circle", "Parabola", "Ellipse", "Hyperbola", "3 Dimensional Geometry", "Straight Line in Space",
                        "The Plane", "Vector", "Dot & Cross Product Of Vector", "Triple Product of Vector", "Logarithm"};
            } else if ("+1 & +2 Physics Formula".equalsIgnoreCase(list_item)) {
                dataArray = new String[]{"Electric Field & Potential", "Gauss's Law", "Capacitor", "Current Electricity", "Magnetism & Magnetic Dipole", "Magnetic Field", "Permannent Magnet",
                        "Magnetic Properties", "Electromagnetic Induction", "Alternating Current(AC)",
                        "Electromagnetic Wave", "Bohr Model of Atom", "Photoelectric Effect,Xrays,Radioactivity", "Semiconductor Devices",
                        "Logic Gates", "Communication System", "Important Math Forumal", "Error Mesurement & Dimentional Anslysis", "Vectors", "Kinematics", "Projectile Motion", "Newtons Law of Motion & friction",
                        "Circular Motion", "Work Energy & Power", "Center Of Mass", "Rotational Motion", "Combined Translation & Rotation", "Gravitation", "Simple Harmonic Motion",
                        "SHM & Pendulam", "Fluid Mechanics",
                        "Elasticity & Surface Tension", "Kinetics Theory of Gases", "Calorimetry & Tharmal Expansion", "Thermodynamics,Isothermal,Adiabatic Process", "Heat Conduction",
                        "Wave Motion", "Sound Wave", "Stationary Wave", "Interference & Yong's Principle", "Beats & Doppler's Effect", "Reflection Of Light", "Lens",
                        "Snell's Law & Prism", "Dispersion,Microscope & Telescope"};
            } else if ("1 & +2 Chemistry Formula".equalsIgnoreCase(list_item)) {
                dataArray = new String[]{"Mole Concept", "Atomic Structure", "Radio Activity", "Chemical Bonding", "Electro-Chemistry", "Gas Laws", "Kinetic Theory of Gases",
                        "Theory of Dilute Solution", "Chemical Kinetics", "Solubility Product",
                        "Titration", "Chemical Equilibrium", "Thermo-Chemistry", "Equivalent Atomic & Molecular Weight",
                        "EudiomertrybOr Gass Analysis", "Periodic Table", "Qualitative Analysis", "Alloy-Composition & Uses", "Important Minerals", "Important Ores", "Important Coumpounds & Formula", "Records of Chemistry-1",
                        "Records Of Chemistry-2", "General Formula Of Organic Compounds", "IUPAC Name", "Aliphatic Series Conversion-1", "Aliphatic Series Conversion-2", "Synthesis From Alkyl Hallides", "Name & Formula Of Some Aromatic Compounds",
                        "Aromatic Series Conversion-1", "Aromatic Series Conversion-2",
                        "Organic Chemistry Important Points", "Properties Of Functional Groups", "Important Name Reactions", "Qualitative Analysis-Oraganic"};
            } else if ("+1 & +2 Statistics Formula".equalsIgnoreCase(list_item)) {
                dataArray = new String[]{"MEAN MEDIAN MODE", "Population Mean", "Mean Deviation", "Standard Deviation", "Quartile", "Correlation Coefficient", "Variance",
                        "Coefficient Of Determination", "Margin Of Error", "Relative Frequency",
                        "Linear Regrassion", "T Test", "F Test", "Gaussian Distribution",
                        "Chi Square", "Confidence Interval", "Sample Size", "Degrees of Freedom", "Estimation", "Linear Transformations", "Discrete Probability Distributions", "Standard Error",
                        "Sampling Distributions", "Random Variables", "Probability", "Counting", "Simple Linear Regression", "Correlation", "Statistics",
                        "Parameters"};
            } else if ("+1 & +2 Biology Quiz".equalsIgnoreCase(list_item)) {
                dataArray = new String[]{"Reproduction In Oraganisms", "Sexual Reproduction in Flowering Plants", "Human Reproduction", "Reproductive Health", "Principles Of Inheritance & Variation", "Molecular Basis Of Inheritance", "Evolution",
                        "Human Health & Disease", "Strategies For Enhancement in Food Production", "Microbes in Human Walfare",
                        "Biotechnology & Its Applications", "Organisms & Populations", "Ecosystem", "Biodiversity & Conservation",
                        "Environmental Issues"};
            } else if ("Computer Science".equalsIgnoreCase(list_item)) {
                dataArray = new String[]{"Object Oriented Programming With Python", "Advance Programming with Python", "Database Management System & SQL", "Boolean Algebra", "Communication Technologies"};
            } else if ("English".equalsIgnoreCase(list_item)) {
                dataArray = new String[]{"Tenses", "Modals", "Use of Passive Voice", "Subject-Verb Concord", "Reporting", "Clauses", "Determiners", "Prepositions"};
            } else if ("Privious Year Question Paper With Answer".equalsIgnoreCase(list_item)) {
                dataArray = new String[]{"2017", "2016", "2015", "2014", "2013", "2012", "2011", "2010"};
            }

            if (dataArray != null) {
                ArrayAdapter adapter1 = new ArrayAdapter<String>(SubListActivity.this, R.layout.activity_listitem, dataArray);

                ListView listView1 = (ListView) findViewById(R.id.sub_data_list);
                listView1.setAdapter(adapter1);
                getSupportActionBar().setDisplayHomeAsUpEnabled(true);

                // Set an item click listener for ListView
                listView1.setOnItemClickListener(new AdapterView.OnItemClickListener() {
                    @Override
                    public void onItemClick(AdapterView<?> parent, View view, int position, long id) {
                        // Get the selected item text from ListView
                        String selectedItem = (String) parent.getItemAtPosition(position);

                        Intent intent = new Intent(SubListActivity.this,SubList2Activity.class);
                        // intent.putExtra("hm",hm);

                        intent.putExtra("list2Item",selectedItem);


                        intent.addFlags(Intent.FLAG_ACTIVITY_NO_ANIMATION);
                        startActivity(intent);
                    }
                });
            }
        }
    }
}

activity_sub_list2.xml

<?xml version="1.0" encoding="utf-8"?>
<android.support.constraint.ConstraintLayout 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="com.sitansu.coder.swainsoft.javaquiz.SubList2Activity">
    <ListView
        android:id="@+id/sub_data_list2"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:background="@color/colorPrimaryDark"
        android:backgroundTint="@color/colorPrimaryDark"
        tools:background="@color/colorPrimaryDark"
        tools:layout_editor_absoluteX="1117dp"
        tools:layout_editor_absoluteY="0dp"></ListView>
</android.support.constraint.ConstraintLayout>

SubList2Activity.java

public class SubList2Activity extends AppCompatActivity {

    private String tempExtras;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_sub_list2);

        new SubList2Activity.InitListData2().invoke();
    }

    @Override
    public void onBackPressed()
    {
        // code here to show dialog
        super.onBackPressed();  // optional depending on your needs
    }



    private class InitListData2 {
        public void invoke() {
            Bundle   extras = getIntent().getExtras();
            if(extras == null)
                return;
            String list_item = extras.getString("list2Item");
            tempExtras=list_item;
            String[] dataArray = null;
            if ("+1 Physics Test".equalsIgnoreCase(list_item)) {
                dataArray = new String[]{"+1 Physics Set 1", "+1 Physics Set 2", "+1 Physics Set 3", "+1 Physics Set 4", "+1 Physics Set 5"};
            } else if ("+2 Physics Test".equalsIgnoreCase(list_item)) {
                dataArray = new String[]{"+2 Physics Set 1", "+2 Physics Set 2", "+2 Physics Set 3", "+2 Physics Set 4", "+2 Physics Set 5"};
            } else if ("+1 Chemistry Test".equalsIgnoreCase(list_item)) {
                dataArray = new String[]{"+1 Chemistry Set 1", "+1 Chemistry Set 2", "+1 Chemistry Set 3", "+1 Chemistry Set 4", "+1 Chemistry Set 5"};
            } else if ("+2 Chemistry Test".equalsIgnoreCase(list_item)) {
                dataArray = new String[]{"+2 Chemistry Set 1", "+2 Chemistry Set 2", "+2 Chemistry Set 3", "+2 Chemistry Set 4", "+2 Chemistry Set 5"};
            } else if ("+1 Math Test".equalsIgnoreCase(list_item)) {
                dataArray = new String[]{"+1 Math Set 1", "+1 Math Set 2", "+1 Math Set 3", "+1 Math Set 4", "+1 Math Set 5"};
            } else if ("+2 Math Test".equalsIgnoreCase(list_item)) {
                dataArray = new String[]{"+2 Math Set 1", "+2 Math Set 2", "+2 Math Set 3", "+2 Math Set 4", "+2 Math Set 5"};
            } else if ("Biology Test".equalsIgnoreCase(list_item)) {
                dataArray = new String[]{"Biology Set 1", "Biology Set 2", "Biology Set 3", "Biology Set 4", "Biology Set 5"};
            } else if ("Statistics Test".equalsIgnoreCase(list_item)) {
                dataArray = new String[]{"Statistics Set 1", "Statistics Set 2", "Statistics Set 3", "Statistics Set 4", "Statistics Set 5"};
            } else if ("Computer Science Test".equalsIgnoreCase(list_item)) {
                dataArray = new String[]{"Computer Science Set 1", "Computer Science Set 2", "Computer Science Set 3", "Computer Science Set 4", "Computer Science Set 5"};
            } else if ("+2 Privious Year Question Paper Test".equalsIgnoreCase(list_item)) {
                dataArray = new String[]{"2017 Test", "2016 Test", "2015 Test", "2014 Test", "2013 Test", "2012 Test", "2011 Test", "2010 Test"};
            }else if ("English Test".equalsIgnoreCase(list_item)) {
                dataArray = new String[]{"English Set 1", "English Set 2", "English Set 3", "English Set 4", "English Set 5"};
            }else if ("GK Test".equalsIgnoreCase(list_item)) {
                dataArray = new String[]{"GK Set 1", "GK Set 2", "GK Set 3", "GK Set 4", "GK Set 5"};
            }else if ("Current affairs Test".equalsIgnoreCase(list_item)) {
                dataArray = new String[]{"Current affairs Set 1", "Current affairs Set 2", "Current affairs Set 3", "Current affairs Set 4", "Current affairs Set 5"};
            }else if ("Aptitude test".equalsIgnoreCase(list_item)) {
                dataArray = new String[]{"Aptitude Set 1", "Aptitude Set 2", "Aptitude Set 3", "Aptitude Set 4", "Aptitude Set 5"};
            }else if ("Reasoning test".equalsIgnoreCase(list_item)) {
                dataArray = new String[]{"Reasoning Set 1", "Reasoning Set 2", "Reasoning Set 3", "Reasoning Set 4", "Reasoning Set 5"};
            }

            if (dataArray != null) {
                ArrayAdapter adapter1 = new ArrayAdapter<String>(SubList2Activity.this, R.layout.activity_listitem, dataArray);

                ListView listView1 = (ListView) findViewById(R.id.sub_data_list2);
                listView1.setAdapter(adapter1);
                getSupportActionBar().setDisplayHomeAsUpEnabled(true);

                // Set an item click listener for ListView
                listView1.setOnItemClickListener(new AdapterView.OnItemClickListener() {
                    @Override
                    public void onItemClick(AdapterView<?> parent, View view, int position, long id) {
                        // Get the selected item text from ListView
                        String selectedItem = (String) parent.getItemAtPosition(position);
                        Intent intent = new Intent(SubList2Activity.this,QuizActivity.class);
                        // intent.putExtra("hm",hm);
                        intent.putExtra("list3Item",selectedItem);
                        intent.addFlags(Intent.FLAG_ACTIVITY_NO_ANIMATION);
                        startActivity(intent);
                    }
                });
            }
        }
    }


}

AndroidMainfest.xml

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="com.sitansu.coder.swainsoft.javaquiz">

    <uses-permission android:name="android.permission.INTERNET" />
    <uses-permission android:name="android.permission.ACCESS_NETWORK_STATE" />

    <application
        android:allowBackup="true"
        android:icon="@mipmap/ic_launcher"
        android:label="@string/app_name"
        android:roundIcon="@mipmap/ic_launcher_round"
        android:supportsRtl="true"
        android:theme="@style/AppTheme">
        <activity android:name=".MainActivity" />
        <activity
            android:name=".HomeActivity"
            android:label="@string/title_activity_home"
            android:theme="@style/AppTheme.NoActionBar">
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />

                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>
        <activity
            android:name=".onlinetest.ResultActivity"
            android:icon="@mipmap/ic_launcher"
            android:label="Result!"
            android:parentActivityName=".HomeActivity" />
        <activity
            android:name=".onlinetest.QuizActivity"
            android:icon="@mipmap/ic_launcher"
            android:label="@string/app_name"
            android:parentActivityName=".SubList2Activity" />
        <activity
            android:name=".SubListActivity"
            android:parentActivityName=".HomeActivity" />
        <activity
            android:name=".SubList2Activity"
            android:parentActivityName=".SubListActivity" />
        <activity android:name=".SubList3Activity" android:parentActivityName=".SubList2Activity" />
        <activity android:name=".DetailActivity"></activity>
    </application>

</manifest>

如何解决这个问题，请任何人帮助我，我是新的Android，我已经尝试了很多代码从这样。无法实施。

谢斯坦

Answer 1

看起来，您没有在onSaveInstanceState方法中保存包数据。

查看本文的“保存和还原活动状态”部分：

https://developer.android.com/guide/components/activities/activity-lifecycle.html

在您的onCreate方法中，您必须在下面放置一个if：

    if (savedInstanceState != null) {
        //Get bundle values from savedInstanceState bundle
    } else {
        //Get bundle values from getIntent.getExtras() the first time
    }

Answer 2

首先，硬编码将要显示的数据并不是一个好做法。这样，每次您想要添加、删除或更新数据时，您都必须重新构建应用程序。您可以做的一件事是将数据放在res/value/array.xml文件中的字符串数组中，甚至更好，因为您正在使用Firebase，您可以创建一个实时数据库，并使您的应用程序从其中读取内容。

第二，自从几年前发布ListView以来，不再推荐使用RecyclerView，因为RecyclerView比ListView具有更高的内存效率。

在回答您的问题时，当您“向前”(如A -> B -> C等等)等“前进”时，将额外的附加信息从一个活动传递到另一个活动很好，但是如果您“向后移动”，比如C -> B -> A，您将不会有这些额外的东西，因为它们不会保存在任何地方，除非您按下回放时将这些数据作为附加数据再次传递，就像下面的示例一样：

@Override
public void onBackPressed() {
    Intent intent = new Intent(CurrentActivity.this, PreviousActivity.class);
    intent.putExtra("your_extra_key", extraYouWantToPass);
    startActivity(intent);
    finish(); // Finish this activity so you don't have too many activities running in your stack
}

另一个选项是使用onSaveInstanceState和onRestoreInstanceState方法在活动实例中保存数据：

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    // Do your stuff
    if (savedInstanceState == null) {
        yourData = getIntent().getStringExtra("your_key");
    } else {
        yourData = savedInstanceState.getString("your_key"); // This is an example using String data
    }
}

@Override
public void onSaveInstanceState(Bundle outState) {
    super.onSaveInstanceState(outState);
    outState.putString("your_key", yourData); // This is an example using String data
}

@Override
public void onRestoreInstanceState(Bundle savedInstanceState) {
    super.onRestoreInstanceState(savedInstanceState);
    yourData = savedInstanceState.getString("your_key"); // Again, this is just an example retrieving String data
}

通过正确地这样做，您不必担心在活动之间切换或更改设备的方向(即:旋转屏幕)时会丢失数据。

Answer 3

刷新onResume中的适配器。

@Override
public void onResume() {
    // fetch updated data
    adapter.notifyDataSetChanged();
}