java - 在android中创建菜单/子菜单

Question

我在开发 Android 应用程序方面几乎没有经验。我的 friend 要求我为他的应用程序创建一个小功能。我所坚持的是为选项创建一个子菜单，即我拥有它，这样当单击按钮时会弹出一个带有几个选项的菜单，并且当单击特定选项时我需要它打开第二个菜单。我将在下面发布我的代码(XML 和 Java)，希望有人能帮助我。目前我的菜单是通过 Java 代码而不是 XML 代码显示的。我不确定这是否是不好的做法，但我会让任何可以帮助我的人告诉我是否是。提前致谢。

XML 代码:

<?xml version="1.0" encoding="utf-8"?>
<android.support.constraint.ConstraintLayout
    xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    app:layout_behavior="@string/appbar_scrolling_view_behavior"
    tools:showIn="@layout/activity_main"
    tools:context="com.example.android.postvu.MainActivity">

<ImageView
    android:id="@+id/imageView2"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:contentDescription="@string/background"
    android:scaleType="centerCrop"
    android:src="@drawable/grid" />

<TextView
    android:id="@+id/textView"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_marginLeft="8dp"
    android:layout_marginRight="8dp"
    android:layout_marginTop="8dp"
    android:text="@string/image_text_editor"
    android:textColor="@android:color/black"
    android:textSize="28sp"
    android:textStyle="bold"
    app:layout_constraintLeft_toLeftOf="parent"
    app:layout_constraintRight_toRightOf="parent"
    app:layout_constraintTop_toTopOf="parent"
    tools:text="Image Text Editor" />


<Button
    android:layout_width="50dp"
    android:layout_height="50dp"
    android:layout_marginBottom="8dp"
    android:layout_marginLeft="8dp"
    android:layout_marginRight="8dp"
    android:layout_marginTop="8dp"
    android:background="@mipmap/ic_launcher"
    android:scaleType="centerCrop"
    android:onClick="myOnClickMethod"
    app:layout_constraintBottom_toBottomOf="parent"
    app:layout_constraintLeft_toLeftOf="parent"
    app:layout_constraintRight_toRightOf="parent"
    app:layout_constraintTop_toBottomOf="@+id/textView"
    app:layout_constraintVertical_bias="0.98" />

Java 代码(与单击按钮和显示菜单相关):

public void myOnClickMethod(View v) {
    registerForContextMenu(v);
    openContextMenu(v);
}

final int CONTEXT_MENU_VIEW = 1;
final int CONTEXT_MENU_EDIT = 2;
final int CONTEXT_MENU_ARCHIVE = 3;


@Override
public void onCreateContextMenu (ContextMenu menu, View v, ContextMenu.ContextMenuInfo menuInfo) {
    menu.setHeaderTitle("Options");
    menu.add(Menu.NONE, CONTEXT_MENU_VIEW, Menu.NONE, "Take Photo");
    menu.add(Menu.NONE, CONTEXT_MENU_EDIT, Menu.NONE, "Photo Album");
    menu.add(Menu.NONE, CONTEXT_MENU_ARCHIVE, Menu.NONE, "Plain Image");
}

@Override
public boolean onContextItemSelected (MenuItem item) {
    switch (item.getItemId()) {
        case CONTEXT_MENU_VIEW: {
        }
        break;
        case CONTEXT_MENU_EDIT: {
        }
        break;
        case CONTEXT_MENU_ARCHIVE: {
        }
        break;
    }

    return super.onContextItemSelected(item);
}

Answer 1

您可以通过以下方式显示子菜单。我修改了您的代码并使用了硬编码常量。我希望这会对您有所帮助。

public class MainActivity extends AppCompatActivity {
    private View menuAnchorView;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        menuAnchorView = findViewById(R.id.imageView2);
        menuAnchorView.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                myOnClickMethod(menuAnchorView);
            }
        });
    }

    public void myOnClickMethod(View v) {
        registerForContextMenu(v);
        openContextMenu(v);
    }

    final int CONTEXT_MENU_VIEW = 1;
    final int CONTEXT_MENU_EDIT = 2;
    final int CONTEXT_MENU_ARCHIVE = 3;


    @Override
    public void onCreateContextMenu (ContextMenu menu, View v, ContextMenu.ContextMenuInfo menuInfo) {
        if(v.getTag() == null || !v.getTag().equals("menu_item")) {
            menu.setHeaderTitle("Options");
            menu.add(Menu.NONE, CONTEXT_MENU_VIEW, Menu.NONE, "Take Photo");
            menu.add(Menu.NONE, CONTEXT_MENU_EDIT, Menu.NONE, "Photo Album");
            menu.add(Menu.NONE, CONTEXT_MENU_ARCHIVE, Menu.NONE, "Plain Image");
        }
        else {
            menu.setHeaderTitle("Sub menu");
            menu.add(Menu.NONE, 4, Menu.NONE, "Sub-view");
            menu.add(Menu.NONE, 5, Menu.NONE, "Sub-view-2");
        }
    }

    @Override
    public boolean onContextItemSelected (MenuItem item) {
        closeContextMenu();
        switch (item.getItemId()) {
            case CONTEXT_MENU_VIEW: {
                menuAnchorView.setTag("menu_item");
                openContextMenu(menuAnchorView);
            }
            break;
            case CONTEXT_MENU_EDIT: {
            }
            break;
            case CONTEXT_MENU_ARCHIVE: {
            }
            break;
            case 4:
            case 5: menuAnchorView.setTag(null);
                break;
        }

        return super.onContextItemSelected(item);
    }

}