App startet nicht - Wie, die Ursache finden?

Hallo allerseits,

wenn ich in einer komplexen App eine bestimmte Funktionalität nicht umsetzen/einbinden kann,
erstelle ich meist eine neue kleine App, um mich nur auf diesen 1 Punkt zu konzentrieren.
(Ist auch für die anderen dann einfacher und schneller lesbar, da kaum Code vorhanden ist.)

Jedenfalls habe ich in letzter Zeit immer wieder das Problem, dass selbst diese Mini-Test-Apps nicht starten.
Obwohl ich keinen Fehler in den Layouts oder den java-Codes sehe, hab ich keine Chance, die App zum Laufen zu bekommen.

Diese App besteht aus 1 Activity und 2 Fragmenten.
Ich habe sogar extra noch zusätzlich Codezeilen entfernt.

MainActivity.java

Code:

import android.os.Bundle;
import android.support.annotation.Nullable;
import android.support.v4.app.Fragment;
import android.support.v4.app.FragmentManager;
import android.support.v4.app.FragmentPagerAdapter;
import android.support.v4.view.ViewPager;
import android.support.v7.app.AppCompatActivity;
import java.util.ArrayList;
import java.util.List;

public class MainActivity extends AppCompatActivity
{
    ViewPager vp;
    private static final String TAG = "MainActivity";

    @Override
    protected void onCreate(Bundle savedInstanceState)
    {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        ViewPager vp = findViewById(R.id.vp);
        SetUpViewPager(vp);
    }
    public void SetUpViewPager(ViewPager viewpage)
    {
        MyViewPagerAdapter Adapter = new MyViewPagerAdapter(getSupportFragmentManager());
        Adapter.AddPageFragment(new Fragment1(), "Fragment1"); // Load pages inside of ViewPager
        Adapter.AddPageFragment(new Fragment2(), "Fragment2");
        viewpage.setAdapter(Adapter);
    }
    public class MyViewPagerAdapter extends FragmentPagerAdapter
    {
        private List<Fragment> MyFragment = new ArrayList<>();
        private List<String> MyPageTitle = new ArrayList<>();

        public MyViewPagerAdapter(FragmentManager manager)
        {
            super(manager);
        }
        public void AddPageFragment(Fragment Frag, String Title)
        {
            MyFragment.add(Frag);
            MyPageTitle.add(Title);
        }
        @Override
        public Fragment getItem(int i)
        {
            return MyFragment.get(i);
        }
        @Nullable
        @Override
        public CharSequence getPageTitle(int position)
        {
            return MyPageTitle.get(position);
        }
        @Override
        public int getCount()
        {
            return 2; // 2 pages total
        }
    }
}

Fragment1.java:

Code:

import android.os.Bundle;
import android.support.annotation.NonNull;
import android.support.annotation.Nullable;
import android.support.v4.app.Fragment;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;

public class Fragment1 extends Fragment
{
    @Nullable
    @Override
    public View onCreateView(@NonNull LayoutInflater inflater, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState)
    {
        View fragmentOne = inflater.inflate(R.layout.fragment1, container, false); // Link view and layout
        return fragmentOne;
    }
}

Fragment2.java:

Code:

import android.os.Bundle;
import android.support.annotation.NonNull;
import android.support.annotation.Nullable;
import android.support.v4.app.Fragment;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;

    @Nullable
    @Override
    public View onCreateView(@NonNull LayoutInflater inflater, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState)
    {
        View fragmentTwo = inflater.inflate(R.layout.fragment2, container, false); // Link view and layout
        return fragmentTwo;
    }
}

activity_main.xml

Code:

<?xml version="1.0" encoding="utf-8"?>
<android.support.design.widget.CoordinatorLayout 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=".MainActivity">

    <android.support.design.widget.AppBarLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:theme="@style/AppTheme.AppBarOverlay">

        <android.support.v7.widget.Toolbar
            android:id="@+id/toolbar"
            android:layout_width="match_parent"
            android:layout_height="?attr/actionBarSize"
            android:background="?attr/colorPrimary"
            app:popupTheme="@style/AppTheme.PopupOverlay" />

    </android.support.design.widget.AppBarLayout>

    <include layout="@layout/content_main" />

    <FrameLayout
        android:id="@+id/frame_layout"
        android:layout_width="match_parent"
        android:layout_height="match_parent">

    </FrameLayout>

</android.support.design.widget.CoordinatorLayout>

fragment1.xml

Code:

<?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">

    <Button
        android:id="@+id/button_1"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginEnd="8dp"
        android:layout_marginStart="8dp"
        android:layout_marginTop="64dp"
        android:text="Write 1"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent" />

    <Button
        android:id="@+id/button_2"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginEnd="8dp"
        android:layout_marginStart="8dp"
        android:layout_marginTop="48dp"
        android:text="Write 2"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toBottomOf="@+id/button_1" />
</android.support.constraint.ConstraintLayout>

fragment2.xml

Code:

<?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">

    <TextView
        android:id="@+id/text_view"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginBottom="8dp"
        android:layout_marginEnd="8dp"
        android:layout_marginStart="8dp"
        android:layout_marginTop="8dp"
        android:textSize="30sp"
        android:text="TextView"
        android:background="@color/colorPrimaryDark"
        android:textColor="@color/white"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent" />
</android.support.constraint.ConstraintLayout>

content_main.xml

Code:

<?xml version="1.0" encoding="utf-8"?>
<android.support.v4.view.ViewPager 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/vp"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".MainActivity"
    tools:showIn="@layout/activity_main"/>

strings.xml

Code:

<resources>
    <string name="app_name">RefreshFragment</string>
</resources>

styles.xml

Code:

<resources>

    <!-- Base application theme. -->
    <style name="AppTheme" parent="Theme.AppCompat.Light.DarkActionBar">
        <!-- Customize your theme here. -->
        <item name="colorPrimary">@color/colorPrimary</item>
        <item name="colorPrimaryDark">@color/colorPrimaryDark</item>
        <item name="colorAccent">@color/colorAccent</item>
    </style>

    <style name="AppTheme.NoActionBar">
        <item name="windowActionBar">false</item>
        <item name="windowNoTitle">true</item>
    </style>

    <style name="AppTheme.AppBarOverlay" parent="ThemeOverlay.AppCompat.Dark.ActionBar" />

    <style name="AppTheme.PopupOverlay" parent="ThemeOverlay.AppCompat.Light" />

</resources>

AndroidManifest.xml

Code:

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="com.example.USER.refreshfragment">

    <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">
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />

                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>
    </application>

</manifest>

build.gradle

Code:

apply plugin: 'com.android.application'

android {
    compileSdkVersion 27
    defaultConfig {
        applicationId "com.example.USER.refreshfragment"
        minSdkVersion 23
        targetSdkVersion 27
        versionCode 1
        versionName "1.0"
        testInstrumentationRunner "android.support.test.runner.AndroidJUnitRunner"
    }
    buildTypes {
        release {
            minifyEnabled false
            proguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.pro'
        }
    }
}

dependencies {
    implementation fileTree(dir: 'libs', include: ['*.jar'])
    implementation 'com.android.support:appcompat-v7:27.0.2'
    implementation 'com.android.support.constraint:constraint-layout:1.0.2'
    testImplementation 'junit:junit:4.12'
    androidTestImplementation 'com.android.support.test:runner:1.0.1'
    androidTestImplementation 'com.android.support.test.espresso:espresso-core:3.0.1'
}

"Build completed successfully" heißt es.
Allerdings erscheint beim Starten der App immer die Meldung: "RefreshFragment has stopped."

Was kann ich als "normaler User" denn tun, um den Fehler ausfindig zu machen?
Kann der Debugger in diesem Fall helfen?
Oder ist das einfach nur ein weiterer typischer Anfängerfehler?

P.S. Wie gesagt, auch mit den Buttons und TextViews im Code tut sich nichts.

Danke für jede Hilfe!

 

@deek:
Das mit dem Logcat schaue ich mir nochmal genauer an.
Logcat ist bei mir an, aber bisher hab ich nur "Bahnhof" verstanden.
Ich gucke das nochmal genau an.

@jogimuc:
Du hast Recht, aber der Code, den ich hier gepostet hab, ist auch der tatsächliche.
Es wird also nichts refreshed.
Der Fehler muss irgendwo in der Basis liegen.

Und ja, ich erinnere mich an deinen Beitrag

 

Ich danke euch beiden für eure Hilfe!

Gut, nachdem ich die build.gradle (Module: app) bearbeitet habe, funktioniert es.
Ist es sinnvoll, diesen gesamten Code-Block zu archivieren und ihn dann in neuen Apps einzufügen,
damit nicht wieder der gleiche Fehler auftritt?

Ich habe mal absichtlich die implementation 'com.android.support:design:27.1.1 auskommentiert.
Das Programm stürzt wieder ab (logisch), aber mittels LogCat denke ich, dass ich den Fehler hätte lokalisieren können.
Habe sowohl die Option "Show only selected application" als auch "Error" ausgewählt und vor App-Start den Log geleert.

Sind weniger als 80 Zeilen, aber interessant sind diese hier:

Code:

java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.USER.refreshfragment/com.example.USER.refreshfragment.MainActivity}: android.view.InflateException: Binary XML file line #9: Binary XML file line #9: Error inflating class android.support.design.widget.AppBarLayout

Caused by: android.view.InflateException: Binary XML file line #9: Binary XML file line #9: Error inflating class android.support.design.widget.AppBarLayout
     Caused by: android.view.InflateException: Binary XML file line #9: Error inflating class android.support.design.widget.AppBarLayout
     Caused by: java.lang.ClassNotFoundException: Didn't find class "android.support.design.widget.AppBarLayout" on path: DexPathList[[zip file "/data/app/com.example.USER.refreshfragment-raHUyGsGH2X4_siF1AGy_g==/base.apk", zip file "/data/app/com.example.USER.refreshfragment-raHUyGsGH2X4_siF1AGy_g==/split_lib_dependencies_apk.apk", zip file "/data/app/com.example.USER.refreshfragment-raHUyGsGH2X4_siF1AGy_g==/split_lib_resources_apk.apk", zip file "/data/app/com.example.USER.refreshfragment-raHUyGsGH2X4_siF1AGy_g==/split_lib_slice_0_apk.apk", zip file "/data/app/com.example.USER.refreshfragment-raHUyGsGH2X4_siF1AGy_g==/split_lib_slice_1_apk.apk", zip file "/data/app/com.example.USER.refreshfragment-raHUyGsGH2X4_siF1AGy_g==/split_lib_slice_2_apk.apk", zip file "/data/app/com.example.USER.refreshfragment-raHUyGsGH2X4_siF1AGy_g==/split_lib_slice_3_apk.apk", zip file "/data/app/com.example.USER.refreshfragment-raHUyGsGH2X4_siF1AGy_g==/split_lib_slice_4_apk.apk", zip file "/data/app/com.example.USER.refreshfragment-raHUyGsGH2X4_siF1AGy_g==/split_lib_slice_5_apk.apk", zip file "/data/app/com.example.USER.refreshfragment-raHUyGsGH2X4_siF1AGy_g==/split_lib_slice_6_apk.apk", zip file "/data/app/com.example.USER.refreshfragment-raHUyGsGH2X4_siF1AGy_g==/split_lib_slice_7_apk.apk", zip file "/data/app/com.example.USER.refreshfragment-raHUyGsGH2X4_siF1AGy_g==/split_lib_slice_8_apk.apk", zip file "/data/app/com.example.USER.refreshfragment-raHUyGsGH2X4_siF1AGy_g==/split_lib_slice_9_apk.apk"],nativeLibraryDirectories=[/data/app/com.example.USER.refreshfragment-raHUyGsGH2X4_siF1AGy_g==/lib/x86, /system/lib, /vendor/lib]]

Kurz gefasst schlussfolgere ich:
Wenn ich mir zu 99% sicher bin, dass es kein funktionales Problem ist und die App nicht mal startet,
ist irgendwas mit dem Design verkehrt.

Danke nochmals!

 

Zum Thema Fragment refreshen:
Habe es hinbekommen (natürlich mit Hilfe)!
Falls es euch interessiert:

Fragment1:

Code:

import android.content.Context;
import android.content.SharedPreferences;
import android.os.Bundle;
import android.support.annotation.NonNull;
import android.support.annotation.Nullable;
import android.support.v4.app.Fragment;
import android.util.Log;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.Button;
import android.widget.TextView;
public class Fragment1 extends Fragment
{
    String text; // Text of textViewValue
    int bColor; // Background color of constraintLayout
    SharedPreferences prefs; // Variable for SharedPreferences
    @Nullable
    @Override
    public View onCreateView(@NonNull LayoutInflater inflater, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState)
    {
        View fragmentOne = inflater.inflate(R.layout.fragment1, container, false); // Link view and layout
        // Link variables to IDs:
        Button button1 = fragmentOne.findViewById(R.id.button_1); // Link variable to ID
        Button button2 = fragmentOne.findViewById(R.id.button_2); // Link variable to ID
        Button buttonColorRed = fragmentOne.findViewById(R.id.button_color_red); // Link variable to ID
        Button buttonColorBlue = fragmentOne.findViewById(R.id.button_color_blue); // Link variable to ID
        //-----------------------
        loadPreferences(); // Load SharedPreferences
        button1.setOnClickListener(new View.OnClickListener()
        {
            @Override
            public void onClick(View v)
            {
                text = "1";
                savePreferences();
            }
        });
        button2.setOnClickListener(new View.OnClickListener()
        {
            @Override
            public void onClick(View v)
            {
                text = "2";
                savePreferences();
            }
        });
        buttonColorRed.setOnClickListener(new View.OnClickListener()
        {
            @Override
            public void onClick(View v)
            {
                bColor = getResources().getColor(R.color.red);
                savePreferences();
            }
        });
        buttonColorBlue.setOnClickListener(new View.OnClickListener()
        {
            @Override
            public void onClick(View v)
            {
                bColor = getResources().getColor(R.color.blue);
                savePreferences();
            }
        });
        return fragmentOne;
    }
    public void savePreferences()
    {
        SharedPreferences prefs = getActivity().getSharedPreferences("MY_SHARED_PREF", Context.MODE_PRIVATE); // Create new SharedPreferences instance
        SharedPreferences.Editor editor = prefs.edit(); // Create variable for SharedPreferences
        editor.putString("text", text); // Write text coming from button inside of editor
        editor.putInt("bcolor", bColor); // Write background color coming from button inside of editor
        editor.apply(); // Apply and close SharedPreferences instance
        Log.wtf("Text is: ", text); // Check if text is correct - yes, it's correct
    }
    public void loadPreferences()
    {
        prefs = getActivity().getSharedPreferences("MY_SHARED_PREF", Context.MODE_PRIVATE); // Load SharedPreferences
        bColor = prefs.getInt("bcolor", 0); // Retrieve bColor from SharedPreferences
        text = prefs.getString("text", "0"); // Retrieve text from SharedPreferences
    }
}

Fragment2:

Code:

import android.content.Context;
import android.content.SharedPreferences;
import android.os.Bundle;
import android.support.annotation.NonNull;
import android.support.annotation.Nullable;
import android.support.constraint.ConstraintLayout;
import android.support.v4.app.Fragment;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.TextView;

public class Fragment2 extends Fragment
{
    String text; // Text of textViewValue
    int bColor; // Background color of constraintLayout
    SharedPreferences prefs; // Variable for SharedPreferences
    private SharedPreferences.OnSharedPreferenceChangeListener preferenceChangeListener; // Variable for SharedPreferencesChangeListener
    @Nullable
    @Override
    public View onCreateView(@NonNull LayoutInflater inflater, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState)
    {
        View fragmentTwo = inflater.inflate(R.layout.fragment2, container, false); // Link view and layout
        final TextView textViewValue = fragmentTwo.findViewById(R.id.text_view); // Link variable to ID
        final ConstraintLayout constraintLayout = fragmentTwo.findViewById(R.id.constraint_layout); // Link variable to ID
        loadPreferences(); // Load SharedPreferences
        textViewValue.setText(text); // Update text in textViewValue
        constraintLayout.setBackgroundColor(bColor); // Update background color of constraintLayout
        preferenceChangeListener = new SharedPreferences.OnSharedPreferenceChangeListener() // Check if SharedPreferences have been changed recently
        {
            @Override
            public void onSharedPreferenceChanged(SharedPreferences sharedPreferences, String key)
            {
                switch (key) // Check, which key has been changed
                {
                    case "text":
                        text = sharedPreferences.getString("text", "0"); // Load value of text from SharedPreferences
                        textViewValue.setText(text); // Update text in textViewValue
                    case "bcolor":
                        bColor = sharedPreferences.getInt("bcolor", getResources().getColor(R.color.white)); // Load value of bColor from SharedPreferences
                        constraintLayout.setBackgroundColor(bColor); // Update background color of constraintLayout
                    break;
                }
            }
        };
        prefs.registerOnSharedPreferenceChangeListener(preferenceChangeListener); // Apply changes
        return fragmentTwo;
    };
    @Override
    public void onDestroy()
    {
        super.onDestroy();
        if (preferenceChangeListener != null)
        {
            prefs.unregisterOnSharedPreferenceChangeListener(preferenceChangeListener);
        }
    }
    public void loadPreferences()
    {
        prefs = getActivity().getSharedPreferences("MY_SHARED_PREF", Context.MODE_PRIVATE); // Load SharedPreferences
        text = prefs.getString("text", "0"); // Retrieve text from SharedPreferences
        bColor = prefs.getInt("bcolor", 0); // Retrieve bColor from SharedPreferences
    }
}

Beim Klick auf einen oder mehrere Buttons in Fragment1 wird sofort das 2. Fragment aktualisiert.
Auch nach Drehen des Bildschirms und Neustarten der App ist noch alles da.

Hättet ihr allgemein Verbesserungsvorschläge in den Codes?
Habe übrigens absichtlich globale Variablen verwendet, da ich sonst in Fragment1 2 Methoden gebraucht hätte.
Methode 1 erwartet den bColor-Wert, Methode 2 den Text-Wert.
Bei globalen Variablen kann ich mir die Übergabe der Werte (direkt an die Methode) sparen.

Grüße