Android动态更新Menu菜单的实现过程

<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="com.example.menutest.MainActivity">
 
    <item
        android:id="@+id/sub_menu_grid"
        android:title="网格视图"
        android:icon="@drawable/ic_menu_view_grid"
        app:showAsAction="always"/>
    <item
        android:id="@+id/sub_menu_list"
        android:title="列表视图"
        android:icon="@drawable/ic_menu_view_list"
        app:showAsAction="always"/>
 
    <item
        android:id="@+id/action_settings"
        android:orderInCategory="100"
        android:title="设置"
        app:showAsAction="never" />
 
    <item
        android:id="@+id/action_about"
        android:orderInCategory="200"
        android:title="关于"
        app:showAsAction="never" />
 
    <item
        android:id="@+id/action_test"
        android:orderInCategory="300"
        android:title="测试"
        app:showAsAction="never" />
 
</menu>

public class MainActivity extends AppCompatActivity {
 
    //默认为网格模式
    private boolean isShowGridModeIcon = true;
 
    //网格菜单 和 列表菜单
    private MenuItem gridMenuItem;
    private MenuItem listMenuItem;
 
    //用字符串来表示当前的文件列表显示模式
    private TextView viewModeStatus;
 
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        Toolbar toolbar = findViewById(R.id.toolbar);
        setSupportActionBar(toolbar);
 
        viewModeStatus = findViewById(R.id.textview_refresh);
 
    }
 
 
    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        // Inflate the menu; this adds items to the action bar if it is present.
        getMenuInflater().inflate(R.menu.menu_main, menu);
        Log.e("test", "=====MenuTest onCreateOptionsMenu=====");
 
        gridMenuItem = menu.findItem(R.id.sub_menu_grid);
        listMenuItem = menu.findItem(R.id.sub_menu_list);
        return true;
    }
 
    @Override
    public boolean onPrepareOptionsMenu(Menu menu) {
        Log.e("test", "=====MenuTest onPrepareOptionsMenu=xxxx====");
        MenuItem aboutMenuItem = menu.findItem(R.id.action_about);
 
        // （3个点）【更多】菜单中把 关于 设置为不可点击
        aboutMenuItem.setEnabled(false);
 
        if (isShowGridModeIcon) {
            gridMenuItem.setVisible(true);
            listMenuItem.setVisible(false);
            viewModeStatus.setText("当前为网格模式");
        } else {
            gridMenuItem.setVisible(false);
            listMenuItem.setVisible(true);
            viewModeStatus.setText("当前为列表模式");
        }
        return super.onPrepareOptionsMenu(menu);
    }
 
    @Override
    public boolean onOptionsItemSelected(MenuItem item) {
        // Handle action bar item clicks here. The action bar will
        // automatically handle clicks on the Home/Up button, so long
        // as you specify a parent activity in AndroidManifest.xml.
        int id = item.getItemId();
        Log.e("test", "=====MenuTest onOptionsItemSelected= sssss ====");
        //noinspection SimplifiableIfStatement
        if (id == R.id.action_settings) {
            return true;
        } else if (id == R.id.sub_menu_grid) {
          /*1. 点击网格图标，界面中文件布局显示变成网格模式*/
          //伪代码：setViewMode(State.MODE_GRID);
            isShowGridModeIcon = false;
          /*2. 图标变成切换list图标*/
            invalidateOptionsMenu();
 
        } else if (id == R.id.sub_menu_list) {
            /*1.点击列表图标，界面中文件布局显示变成列表模式*/
            //伪代码：setViewMode(State.MODE_LIST);
            isShowGridModeIcon = true;
            /*2. 图标变成切换grid图标*/
            invalidateOptionsMenu();
        }
 
        return super.onOptionsItemSelected(item);
    }
}

21900 21900 E test    : =====MenuTest onCreateOptionsMenu=====
21900 21900 E test    : =====MenuTest onPrepareOptionsMenu=xxxx====

21900 21900 E test    : =====MenuTest onOptionsItemSelected= sssss ====
21900 21900 E test    : =====MenuTest onCreateOptionsMenu=====
21900 21900 E test    : =====MenuTest onPrepareOptionsMenu=xxxx====

21900 21900 E test    : =====MenuTest onPrepareOptionsMenu=xxxx====