android - 根据 ViewPager Android 显示菜单项

Question

我的 Android 应用程序中有一个带有 fragment 的 ViewPager。我想根据 ViewPager 的 fragment 显示操作栏菜单项。我已经阅读了一些关于此的问题，但我找不到正确的解决方案。我的 ViewPager 代码是这样的:

public class My_Activity extends ActionBarActivity {

    private ViewPager mViewPager;
    String idioma;

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

        ActionBar actionBar = getSupportActionBar(); // || getActionBar();
        actionBar.setIcon(getResources().getDrawable(R.drawable.navbar_logo));
        actionBar.setBackgroundDrawable(new ColorDrawable(Color.parseColor("#CC3333")));

        actionBar.setTitle("Hello");

        mViewPager = (ViewPager) findViewById(R.id.viewpager);
        PagerTabStrip pagerTabStrip = (PagerTabStrip) findViewById(R.id.pagerTabStrip);
        pagerTabStrip.setTabIndicatorColor(getResources().getColor(R.color.blanco));

        Title_Liga_Adapter titleAdapter = new Title_Liga_Adapter(getSupportFragmentManager());
        mViewPager.setAdapter(titleAdapter);

        mViewPager.setCurrentItem(0);

        getSupportActionBar().setIcon(R.drawable.navbar_logo);

        getSupportActionBar().setDisplayHomeAsUpEnabled(true);

    }

    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        if (mViewPager.getCurrentItem() == 4) {
            getMenuInflater().inflate(R.menu.menu_comunidad,
                                      menu);
        } else {

        }
        return true;
    }

    /* *
     * Called when invalidateOptionsMenu() is triggered
     */
    @Override
    public boolean onPrepareOptionsMenu(Menu menu) {

        menu.findItem(R.id.action_search)
            .setVisible(true);

        return super.onPrepareOptionsMenu(menu);
    }

    public boolean onOptionsItemSelected(MenuItem item) {
        switch (item.getItemId()) {
            // Respond to the action bar's Up/Home button
            case android.R.id.home:
                this.finish();
                return true;

            case R.id.action_search:

                return true;

            default:
                return super.onOptionsItemSelected(item);
        }
    }

}

我希望当 CurrentItem 为 4 时显示菜单项图标。

Answer 1

首先在onCreate方法中创建addOnPageChangeListener

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

    mViewPager.addOnPageChangeListener(new ViewPager.OnPageChangeListener() {
        @Override
        public void onPageScrolled(int position, float positionOffset, int positionOffsetPixels) {
            invalidateOptionsMenu();
        }

        @Override
        public void onPageSelected(int position) {

        }

        @Override
        public void onPageScrollStateChanged(int state) {

        }
    });
}

然后你覆盖 onCreateOptionMenu()

@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);
    if (mViewPager.getCurrentItem()==0){
        menu.findItem(R.id.action_search).setVisible(true);
    } else if(mViewPager.getCurrentItem()==1){
        menu.findItem(R.id.action_search).setVisible(false);
    } else if(mViewPager.getCurrentItem()==2){
        // configure
    } else if(mViewPager.getCurrentItem()==3){
        // configure
    }
    return super.onCreateOptionsMenu(menu);
}