Android 主菜单未在应用程序中显示

大家好，我的问题是菜单甚至没有显示出来，我尝试了以下方法：

app:showAsAction=“always”

但没有帮助，然后我尝试更改

tools:context=“.Main”

以下是我的完整代码：

main_menu.xml

<menu 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"
tools:context=".Main">



<item
    android:id="@+id/changeCityID"
    android:title="@string/changeCity"
    android:icon="@drawable/search"
    android:orderInCategory="1"
    app:showAsAction="always"/>

</menu>

---

验证是否实现了在主活动中选择的方法OnCreateOptions菜单和OnOptions项

@Override
public boolean onCreateOptionsMenu(Menu menu)
{
    MenuInflater inflater = getMenuInflater();

    inflater.inflate(R.menu.main_menu, menu);
    return super.onCreateOptionsMenu(menu);
}

@Override
public boolean onOptionsItemSelected(MenuItem item)
{
    switch (item.getItemId())
    {
      case R.id.changeCityID:
        //doSomething
        break;
    }

    return true;
}

---

您没有显示主活动代码。您的活动应该调用main_menu.xml文件。确保main_menu.xml位于菜单文件夹下。然后在您希望此菜单进入的活动（或您的应用程序屏幕）中，确保实现了类似的功能

@Override
public boolean onCreateOptionsMenu(Menu menu)
{
    MenuInflater inflater = getMenuInflater();
    inflater.inflate(R.menu.main_menu, menu);
    return super.onCreateOptionsMenu(menu);
}

@Override
public boolean onOptionsItemSelected(MenuItem item)
{
    switch (item.getItemId())
    {
      case R.id.changeCityID:
        // Enter what you would like to do when user clicks on menu item
        break;
    }

---

将此行放在onCreate（..）上

调用Android菜单，实现菜单方法

public boolean onCreateOptionsMenu(Menu menu)
{
    MenuInflater inflater = getMenuInflater();
    inflater.inflate(R.menu.main_menu, menu);
    return super.onCreateOptionsMenu(menu);
}

---

请阅读“开发>API指南>用户界面>菜单”注意，OnCreateOptions菜单和OnOptions ItemSelected函数上方缺少“@Override”关键字。改变它，让我知道。如果它解决了你的问题，接受这个答案。

@Override
public boolean onCreateOptionsMenu(Menu menu)
{
    MenuInflater inflater = getMenuInflater();

    inflater.inflate(R.menu.main_menu, menu);
    return super.onCreateOptionsMenu(menu);
}

@Override
public boolean onOptionsItemSelected(MenuItem item)
{
    switch (item.getItemId())
    {
      case R.id.changeCityID:
        //doSomething
        break;
    }

    return true;
}

@Override
public boolean onCreateOptionsMenu(Menu menu)
{
    MenuInflater inflater = getMenuInflater();
    inflater.inflate(R.menu.main_menu, menu);
    return super.onCreateOptionsMenu(menu);
}

@Override
public boolean onOptionsItemSelected(MenuItem item)
{
    switch (item.getItemId())
    {
      case R.id.changeCityID:
        // Enter what you would like to do when user clicks on menu item
        break;
    }

invalidateOptionsMenu();

public boolean onCreateOptionsMenu(Menu menu)
{
    MenuInflater inflater = getMenuInflater();
    inflater.inflate(R.menu.main_menu, menu);
    return super.onCreateOptionsMenu(menu);
}