當我嘗試切換到 MainActivity 時應用程序停止

Question

在文件 AndroidManifest.xml 中，將開始屏幕更改為登錄，而不是 MainActivity。 當我單擊按鈕時，激活不會切換，應用程序會關閉。 請告訴我，這是什么錯誤？

PS一切工作到setSupportActionBar(toolbar)行；

登錄.java：

public class Login extends Activity {
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.login);

    Button next = (Button) findViewById(R.id.buttonLogin);
    next.setOnClickListener(new View.OnClickListener() {
        public void onClick(View view) {
            Intent myIntent = new Intent(view.getContext(), MainActivity.class);
            startActivityForResult(myIntent, 0);
        }
    });
}}

MainActivity.java：

public class MainActivity extends AppCompatActivity implements NavigationView.OnNavigationItemSelectedListener {
private DrawerLayout drawer;

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

    Toolbar toolbar = findViewById(R.id.toolbar);
    setSupportActionBar(toolbar);

    drawer = findViewById(R.id.drawer_layout);
    NavigationView navigationView = findViewById(R.id.nav_view);
    navigationView.setNavigationItemSelectedListener(this);

    ActionBarDrawerToggle toggle = new ActionBarDrawerToggle(this, drawer, toolbar,
            R.string.navigation_drawer_open, R.string.navigation_drawer_close);
    drawer.addDrawerListener(toggle);
    toggle.syncState();

    if (savedInstanceState == null) {
        getSupportFragmentManager().beginTransaction().replace(R.id.fragment_container,
                new MessageFragment()).commit();
        navigationView.setCheckedItem(R.id.nav_message);
    }

   ...
}

activity_main.xml：

<androidx.drawerlayout.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:context=".MainActivity"
tools:openDrawer="start">

<LinearLayout
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical">

    <androidx.appcompat.widget.Toolbar
        android:id="@+id/toolbar"
        android:layout_width="match_parent"
        android:layout_height="?attr/actionBarSize"
        android:background="#F5F5F5"
        android:elevation="4dp"
        android:theme="@style/ThemeOverlay.AppCompat.Dark.ActionBar"
        app:popupTheme="@style/ThemeOverlay.AppCompat.Light">
        <TextView
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:text="ВИЗИТКА"
            android:textColor="@color/black"
            android:textSize="20dp"
            android:paddingLeft="85dp"/>
    </androidx.appcompat.widget.Toolbar>

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

<com.google.android.material.navigation.NavigationView
    android:id="@+id/nav_view"
    android:layout_width="wrap_content"
    android:layout_height="match_parent"
    android:layout_gravity="start"
    app:headerLayout="@layout/nav_header"
    app:menu="@menu/drawer_menu"
    app:itemTextAppearance="@style/menu_text_style" />
</androidx.drawerlayout.widget.DrawerLayout>

崩潰日志：

E/AndroidRuntime: FATAL EXCEPTION: main
Process: com.example.alphabankproject, PID: 3917
java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.alphabankproject/com.example.alphabankproject.MainActivity}: java.lang.IllegalStateException: This Activity already has an action bar supplied by the window decor. Do not request Window.FEATURE_SUPPORT_ACTION_BAR and set windowActionBar to false in your theme to use a Toolbar instead.
    at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:3449)
    at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:3601)
    at android.app.servertransaction.LaunchActivityItem.execute(LaunchActivityItem.java:85)
    at android.app.servertransaction.TransactionExecutor.executeCallbacks(TransactionExecutor.java:135)
    at android.app.servertransaction.TransactionExecutor.execute(TransactionExecutor.java:95)
    at android.app.ActivityThread$H.handleMessage(ActivityThread.java:2066)
    at android.os.Handler.dispatchMessage(Handler.java:106)
    at android.os.Looper.loop(Looper.java:223)
    at android.app.ActivityThread.main(ActivityThread.java:7656)
    at java.lang.reflect.Method.invoke(Native Method)
    at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:592)
    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:947)
 Caused by: java.lang.IllegalStateException: This Activity already has an action bar supplied by the window decor. Do not request Window.FEATURE_SUPPORT_ACTION_BAR and set windowActionBar to false in your theme to use a Toolbar instead.
    at androidx.appcompat.app.AppCompatDelegateImpl.setSupportActionBar(AppCompatDelegateImpl.java:572)
    at androidx.appcompat.app.AppCompatActivity.setSupportActionBar(AppCompatActivity.java:159)
    at com.example.alphabankproject.MainActivity.onCreate(MainActivity.java:25)
    at android.app.Activity.performCreate(Activity.java:8000)
    at android.app.Activity.performCreate(Activity.java:7984)
    at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1309)
    at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:3422)
    at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:3601) 
    at android.app.servertransaction.LaunchActivityItem.execute(LaunchActivityItem.java:85) 
    at android.app.servertransaction.TransactionExecutor.executeCallbacks(TransactionExecutor.java:135) 
    at android.app.servertransaction.TransactionExecutor.execute(TransactionExecutor.java:95) 
    at android.app.ActivityThread$H.handleMessage(ActivityThread.java:2066) 
    at android.os.Handler.dispatchMessage(Handler.java:106) 
    at android.os.Looper.loop(Looper.java:223) 
    at android.app.ActivityThread.main(ActivityThread.java:7656) 
    at java.lang.reflect.Method.invoke(Native Method) 
    at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:592) 
    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:947) 

顯現：

<?xml version="1.0" encoding="utf-8"?>

<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/Theme.AlphaBankProject">
    <activity android:name=".Login"
        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=".MainActivity"></activity>
    <activity android:name=".ActivityForm"></activity>

    <meta-data
        android:name="preloaded_fonts"
        android:resource="@array/preloaded_fonts" />
</application>

styles.xml：

<resources>

<style name="AppTheme" parent="Theme.AppCompat.Light.DarkActionBar">
    <item name="colorPrimary">@color/purple_700</item>
    <item name="colorPrimaryDark">@color/purple_200</item>
    <item name="colorAccent">@color/black</item>

    <item name="drawerArrowStyle">@style/DrawerArrowStyle</item>
    <item name="windowActionBar">false</item>
    <item name="windowNoTitle">true</item>

</style>


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

<style name="DrawerArrowStyle" parent="Widget.AppCompat.DrawerArrowToggle">
    <item name="spinBars">true</item>
    <item name="color">@android:color/black</item>
</style>

<style name="menu_text_style" parent="@android:style/TextAppearance.DeviceDefault.Widget.ActionBar.Menu">
    <item name="android:textSize">18dp</item>
    <item name="android:textAllCaps">false</item>
</style>

Answer 1

在您的主題樣式中添加以下屬性：

<style name="MyTheme.Light" parent="Theme.AppCompat.Light">

<item name="colorPrimary">@color/colorPrimary_dark</item>
        <item name="colorPrimaryDark">@color/colorPrimaryDark_dark</item>
        <item name="colorAccent">@color/colorAccent_dark</item>
   <!-- add the following attrs -->
        <item name="windowActionBar">false</item> 
        <item name="windowNoTitle">true</item>
</style>

添加的屬性將刪除默認操作欄，因為您已在活動中定義了Toolbar 。

Answer 2

如果 SupportActionBar !=null 像這樣，你必須檢查

  if (getSupportActionBar()!=null){
     setSupportActionBar(toolbar);
    }

並將您的樣式更改為 styles 支持操作欄

Theme.AppCompat.Light.DarkActionBar