java - 应用范围菜单中 onOptionsItemSelected 的上下文

Question

这个应用程序只有两个活动。MainActivity 已重命名为 SpecialsActivity。另一个活动是 PizzaActivity。使用 BottomNavigationView，我想在两个活动之间导航。到目前为止，该应用程序在 SpecialsActivity 中打开，并且披萨按钮确实打开了 PizzaActivity。但随后它不会切换回 SpecialsActivity。我认为这个问题与上下文有关。请帮忙。

SpecialsActivity.java

public class SpecialsActivity extends AppCompatActivity {
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_specials);
        Toolbar myToolbar = findViewById(R.id.my_toolbar);
        setSupportActionBar(myToolbar);
    }

        @Override
        public boolean onOptionsItemSelected(MenuItem item) {
            switch (item.getItemId()) {
                case R.id.action_specials:
                    Intent specials_intent = new Intent(this, SpecialsActivity.class);
                    startActivity(specials_intent);
                    return true;
                case R.id.action_pizza:
                    Intent pizza_intent = new Intent(getApplicationContext(), PizzaActivity.class);
                    startActivity(pizza_intent);
                    return true;
                default:
                    // Do nothing
            }
            return super.onOptionsItemSelected(item);
        }
    }

activity_specials.xml

<android.support.design.widget.BottomNavigationView
            android:layout_width="0dp"
            android:layout_height="49dp"
            app:itemBackground="@color/colorPrimaryDark"
            app:layout_constraintBottom_toBottomOf="parent"
            app:layout_constraintEnd_toEndOf="parent"
            app:layout_constraintStart_toStartOf="parent"
            app:menu="@menu/bottom_menu" />

AndroidManifest.xml

<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.AppCompat.Light.NoActionBar">
        <activity android:name=".SpecialsActivity">
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />
                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>
        <activity android:name=".PizzaActivity"></activity>
    </application>

bottom_menu.xml

<menu xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto">
    <item
        android:id="@+id/action_specials"
        android:icon="@drawable/ic_home_black_24dp"
        android:title="Specials"
        app:showAsAction="always"
        android:onClick="onOptionsItemSelected" />

    <item
        android:id="@+id/action_pizza"
        android:enabled="true"
        android:icon="@drawable/ic_local_pizza_black_24dp"
        android:title="Pizza"
        app:showAsAction="always"
        android:onClick="onOptionsItemSelected"/>
</menu>

标签： javaandroidandroid-studio

Answer 1

尝试改变

Intent pizza_intent = new Intent(getApplicationContext(), PizzaActivity.class);

进入这个

Intent pizza_intent = new Intent(this, PizzaActivity.class);