下面这段代码的意思 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(); //noinspection SimplifiableIfStatement if (id == R.id.action_add) { Intent intent = new Intent(this, AddActivity.class); startActivity(intent); //startActivity方法 return true; } else if (id == R.id.action_back) { Intent intent = new Intent(this, FragActivity.class); startActivity(intent); //startActivity方法 return true; } return super.onOptionsItemSelected(item); }

这段代码是在 Android 应用程序中处理菜单项的点击事件。在 onOptionsItemSelected() 方法中，首先通过 getItemId() 方法获得点击的菜单项的 ID，然后根据 ID 进行不同的操作。在这个例子中，如果点击了菜单中的 "action_add" 项，则会创建一个 Intent 对象，该对象用于启动 AddActivity 类，最后通过 startActivity() 方法启动该 Activity。同样，如果点击了菜单中的 "action_back" 项，则会创建一个 Intent 对象，该对象用于启动 FragActivity 类。最后，如果没有匹配的菜单项，调用 super.onOptionsItemSelected(item) 方法以让父类处理菜单项的点击事件。

相关问题

安卓drowlayout的使用案例代码

以下是一个简单的安卓drowlayout的使用案例代码：

XML布局文件：

<?xml version="1." encoding="utf-8"?>
<android.support.v4.widget.DrawerLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:id="@+id/drawer_layout"
    android:layout_width="match_parent"
    android:layout_height="match_parent">

    <!-- 主界面布局 -->
    <FrameLayout
        android:id="@+id/content_frame"
        android:layout_width="match_parent"
        android:layout_height="match_parent" />

    <!-- 侧滑菜单布局 -->
    <ListView
        android:id="@+id/left_drawer"
        android:layout_width="240dp"
        android:layout_height="match_parent"
        android:layout_gravity="start"
        android:background="#fff" />

</android.support.v4.widget.DrawerLayout>

Java代码：

public class MainActivity extends AppCompatActivity {

    private DrawerLayout mDrawerLayout;
    private ListView mDrawerList;
    private ActionBarDrawerToggle mDrawerToggle;

    private String[] mPlanetTitles;

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

        mPlanetTitles = getResources().getStringArray(R.array.planets_array);
        mDrawerLayout = (DrawerLayout) findViewById(R.id.drawer_layout);
        mDrawerList = (ListView) findViewById(R.id.left_drawer);

        // 设置侧滑菜单的列表项
        mDrawerList.setAdapter(new ArrayAdapter<String>(this,
                R.layout.drawer_list_item, mPlanetTitles));
        // 设置侧滑菜单的点击事件
        mDrawerList.setOnItemClickListener(new DrawerItemClickListener());

        // 设置ActionBarDrawerToggle，实现侧滑菜单的打开和关闭
        mDrawerToggle = new ActionBarDrawerToggle(
                this,                  /* host Activity */
                mDrawerLayout,         /* DrawerLayout object */
                R.string.drawer_open,  /* "open drawer" description */
                R.string.drawer_close  /* "close drawer" description */
        ) {

            /** Called when a drawer has settled in a completely closed state. */
            public void onDrawerClosed(View view) {
                super.onDrawerClosed(view);
                invalidateOptionsMenu(); // creates call to onPrepareOptionsMenu()
            }

            /** Called when a drawer has settled in a completely open state. */
            public void onDrawerOpened(View drawerView) {
                super.onDrawerOpened(drawerView);
                invalidateOptionsMenu(); // creates call to onPrepareOptionsMenu()
            }
        };

        // 设置ActionBarDrawerToggle为DrawerLayout的监听器
        mDrawerLayout.addDrawerListener(mDrawerToggle);

        // 设置ActionBar的Home按钮可点击，并且显示侧滑菜单图标
        getSupportActionBar().setDisplayHomeAsUpEnabled(true);
        getSupportActionBar().setHomeButtonEnabled(true);
    }

    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        // Inflate the menu; this adds items to the action bar if it is present.
        getMenuInflater().inflate(R.menu.main, menu);
        return true;
    }

    @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.
        if (mDrawerToggle.onOptionsItemSelected(item)) {
            return true;
        }
        return super.onOptionsItemSelected(item);
    }

    private class DrawerItemClickListener implements ListView.OnItemClickListener {
        @Override
        public void onItemClick(AdapterView<?> parent, View view, int position, long id) {
            // 处理侧滑菜单的点击事件
        }
    }
}