根据选定的选项卡在 ActionBar 中显示和隐藏项目

Question

我需要获取所选选项卡的数字位置，以便在 MainActivity 中显示/隐藏 ActionBar 项。比如我在Tab1，显示写新消息的项，进入Tab2，隐藏新消息项，显示添加用户到通讯录的项... 该应用程序的结构是：带有选项卡布局（4 个选项卡）的 MainActivity 和一个管理所有 Fragment 的 FragmentStatePagerAdapter。

MainActivity

public class MainActivity extends AppCompatActivity {

// Declaring Your View and Variables

Toolbar toolbar;
ViewPager pager;
ViewPagerAdapter adapter;
SlidingTabLayout tabs;
CharSequence Titles[]={"1","2","3","4"};
int Numboftabs =4;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    //getSupportActionBar().setElevation(0);
    setContentView(R.layout.activity_main);

    // Creating The Toolbar and setting it as the Toolbar for the activity

    toolbar = (Toolbar) findViewById(R.id.tool_bar);
    //setSupportActionBar(toolbar);

    // Creating The ViewPagerAdapter and Passing Fragment Manager, Titles fot the Tabs and Number Of Tabs.
    adapter =  new ViewPagerAdapter(getSupportFragmentManager(),Titles,Numboftabs);

    // Assigning ViewPager View and setting the adapter
    pager = (ViewPager) findViewById(R.id.pager);
    pager.setAdapter(adapter);

    // Assiging the Sliding Tab Layout View
    tabs = (SlidingTabLayout) findViewById(R.id.tabs);
    tabs.setDistributeEvenly(true); // To make the Tabs Fixed set this true, This makes the tabs Space Evenly in Available width

    // Setting Custom Color for the Scroll bar indicator of the Tab View
    tabs.setCustomTabColorizer(new SlidingTabLayout.TabColorizer() {
        @Override
        public int getIndicatorColor(int position) {
            return ContextCompat.getColor(getApplicationContext(), R.color.darkgreen);
        }
    });

    // Setting the ViewPager For the SlidingTabsLayout
    tabs.setViewPager(pager);

}

@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);
    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.
    int id = item.getItemId();

    switch (id) {
        case R.id.action_settings:
            Intent intentMSett = new Intent(this, MainSettings.class);
            startActivity(intentMSett);
            break;
        case R.id.action_add_user:
            Intent intent = new Intent(this, CreateUser.class);
            startActivityForResult(intent, 101);
            break;
        case R.id.action_search:
            Toast.makeText(getApplicationContext(),
                    "search", Toast.LENGTH_SHORT).show();
            break;
    }

    return super.onOptionsItemSelected(item);
}

}

ViewPagerAdapter

public class ViewPagerAdapter extends FragmentStatePagerAdapter {

CharSequence Titles[]; // This will Store the Titles of the Tabs which are Going to be passed when ViewPagerAdapter is created
int NumbOfTabs; // Store the number of tabs, this will also be passed when the ViewPagerAdapter is created
private Context context;

// Build a Constructor and assign the passed Values to appropriate values in the class
public ViewPagerAdapter(FragmentManager fm,CharSequence mTitles[], int mNumbOfTabsumb) {
    super(fm);

    this.Titles = mTitles;
    this.NumbOfTabs = mNumbOfTabsumb;

}

//This method return the fragment for the every position in the View Pager
@Override
public Fragment getItem(int position) {

    if(position == 0) // if the position is 0 we are returning the First tab
    {
        Tab1 tab1 = new Tab1();
        return tab1;
    } else if(position == 1){
        Tab2 tab2 = new Tab2();
        return tab2;
    } else if(position == 2) {
        Tab3 tab3 = new Tab3();
        return tab3;
    } else if(position == 3) {
        Tab4 tab4 = new Tab4();
        return tab4;
    } else {
        Tab1 tab1 = new Tab1();
        return tab1;
    }
}

// This method return the titles for the Tabs in the Tab Strip

@Override
public CharSequence getPageTitle(int position) {

    return Titles[position];
}

// This method return the Number of tabs for the tabs Strip

@Override
public int getCount() {
    return NumbOfTabs;
}
}

搜索解决方案我找到了 MainActivity 的这个方法：

 @Override
 public boolean onPrepareOptionsMenu(Menu menu) {
    // TODO Auto-generated method stub
    MenuInflater inflater = getMenuInflater();
    int currentTab = tabHost.getCurrentTab();
    Toast.makeText(getApplicationContext(), currentTab+"", Toast.LENGTH_SHORT);
    menu.clear();
    if (currentTab == 0) {
        inflater.inflate(R.menu.first, menu);  //  menu for photospec.
    } else {
        inflater.inflate(R.menu.second, menu);  // menu for songspec
    }
    return super.onPrepareOptionsMenu(menu);
}

SlidingTabLayout

public class SlidingTabLayout extends HorizontalScrollView {
/**
 * Allows complete control over the colors drawn in the tab layout. Set with
 * {@link #setCustomTabColorizer(TabColorizer)}.
 */
public interface TabColorizer {

    /**
     * @return return the color of the indicator used when {@code position} is selected.
     */
    int getIndicatorColor(int position);

}

private static final int TITLE_OFFSET_DIPS = 24;
private static final int TAB_VIEW_PADDING_DIPS = 16;
private static final int TAB_VIEW_TEXT_SIZE_SP = 12;

private int mTitleOffset;

private int mTabViewLayoutId;
private int mTabViewTextViewId;
private boolean mDistributeEvenly;

private ViewPager mViewPager;
private SparseArray<String> mContentDescriptions = new SparseArray<String>();
private ViewPager.OnPageChangeListener mViewPagerPageChangeListener;

private final SlidingTabStrip mTabStrip;

public SlidingTabLayout(Context context) {
    this(context, null);
}

public SlidingTabLayout(Context context, AttributeSet attrs) {
    this(context, attrs, 0);
}

public SlidingTabLayout(Context context, AttributeSet attrs, int defStyle) {
    super(context, attrs, defStyle);

    // Disable the Scroll Bar
    setHorizontalScrollBarEnabled(false);
    // Make sure that the Tab Strips fills this View
    setFillViewport(true);

    mTitleOffset = (int) (TITLE_OFFSET_DIPS * getResources().getDisplayMetrics().density);

    mTabStrip = new SlidingTabStrip(context);
    addView(mTabStrip, LayoutParams.MATCH_PARENT, LayoutParams.WRAP_CONTENT);
}

/**
 * Set the custom {@link TabColorizer} to be used.
 *
 * If you only require simple custmisation then you can use
 * {@link #setSelectedIndicatorColors(int...)} to achieve
 * similar effects.
 */
public void setCustomTabColorizer(TabColorizer tabColorizer) {
    mTabStrip.setCustomTabColorizer(tabColorizer);
}

public void setDistributeEvenly(boolean distributeEvenly) {
    mDistributeEvenly = distributeEvenly;
}

/**
 * Sets the colors to be used for indicating the selected tab. These colors are treated as a
 * circular array. Providing one color will mean that all tabs are indicated with the same color.
 */
public void setSelectedIndicatorColors(int... colors) {
    mTabStrip.setSelectedIndicatorColors(colors);
}

/**
 * Set the {@link ViewPager.OnPageChangeListener}. When using {@link SlidingTabLayout} you are
 * required to set any {@link ViewPager.OnPageChangeListener} through this method. This is so
 * that the layout can update it's scroll position correctly.
 *
 * @see ViewPager#setOnPageChangeListener(ViewPager.OnPageChangeListener)
 */
public void setOnPageChangeListener(ViewPager.OnPageChangeListener listener) {
    mViewPagerPageChangeListener = listener;
}

/**
 * Set the custom layout to be inflated for the tab views.
 *
 * @param layoutResId Layout id to be inflated
 * @param textViewId id of the {@link TextView} in the inflated view
 */
public void setCustomTabView(int layoutResId, int textViewId) {
    mTabViewLayoutId = layoutResId;
    mTabViewTextViewId = textViewId;
}

/**
 * Sets the associated view pager. Note that the assumption here is that the pager content
 * (number of tabs and tab titles) does not change after this call has been made.
 */
public void setViewPager(ViewPager viewPager) {
    mTabStrip.removeAllViews();

    mViewPager = viewPager;
    if (viewPager != null) {
        viewPager.setOnPageChangeListener(new InternalViewPagerListener());
        populateTabStrip();
    }
}

/**
 * Create a default view to be used for tabs. This is called if a custom tab view is not set via
 * {@link #setCustomTabView(int, int)}.
 */
protected TextView createDefaultTabView(Context context) {
    TextView textView = new TextView(context);
    textView.setGravity(Gravity.CENTER);
    textView.setTextSize(TypedValue.COMPLEX_UNIT_SP, TAB_VIEW_TEXT_SIZE_SP);
    textView.setTypeface(Typeface.DEFAULT_BOLD);
    textView.setLayoutParams(new LinearLayout.LayoutParams(
            ViewGroup.LayoutParams.WRAP_CONTENT, ViewGroup.LayoutParams.WRAP_CONTENT));

    TypedValue outValue = new TypedValue();
    getContext().getTheme().resolveAttribute(android.R.attr.selectableItemBackground,
            outValue, true);
    textView.setBackgroundResource(outValue.resourceId);
    textView.setAllCaps(true);

    int padding = (int) (TAB_VIEW_PADDING_DIPS * getResources().getDisplayMetrics().density);
    textView.setPadding(padding, padding, padding, padding);

    return textView;
}

private void populateTabStrip() {
    final PagerAdapter adapter = mViewPager.getAdapter();
    final View.OnClickListener tabClickListener = new TabClickListener();

    for (int i = 0; i < adapter.getCount(); i++) {
        View tabView = null;
        TextView tabTitleView = null;

        if (mTabViewLayoutId != 0) {
            // If there is a custom tab view layout id set, try and inflate it
            tabView = LayoutInflater.from(getContext()).inflate(mTabViewLayoutId, mTabStrip,
                    false);
            tabTitleView = (TextView) tabView.findViewById(mTabViewTextViewId);
        }

        if (tabView == null) {
            tabView = createDefaultTabView(getContext());
        }

        if (tabTitleView == null && TextView.class.isInstance(tabView)) {
            tabTitleView = (TextView) tabView;
        }

        if (mDistributeEvenly) {
            LinearLayout.LayoutParams lp = (LinearLayout.LayoutParams) tabView.getLayoutParams();
            lp.width = 0;
            lp.weight = 1;
        }

        tabTitleView.setText(adapter.getPageTitle(i));
        tabView.setOnClickListener(tabClickListener);
        String desc = mContentDescriptions.get(i, null);
        if (desc != null) {
            tabView.setContentDescription(desc);
        }

        mTabStrip.addView(tabView);
        if (i == mViewPager.getCurrentItem()) {
            tabView.setSelected(true);
        }
    }
}

private void addIconTab(final int position, int resId) {

    ImageButton tab = new ImageButton(getContext());
    tab.setImageResource(resId);

}

public void setContentDescription(int i, String desc) {
    mContentDescriptions.put(i, desc);
}

@Override
protected void onAttachedToWindow() {
    super.onAttachedToWindow();

    if (mViewPager != null) {
        scrollToTab(mViewPager.getCurrentItem(), 0);
    }
}

private void scrollToTab(int tabIndex, int positionOffset) {
    final int tabStripChildCount = mTabStrip.getChildCount();
    if (tabStripChildCount == 0 || tabIndex < 0 || tabIndex >= tabStripChildCount) {
        return;
    }

    View selectedChild = mTabStrip.getChildAt(tabIndex);
    if (selectedChild != null) {
        int targetScrollX = selectedChild.getLeft() + positionOffset;

        if (tabIndex > 0 || positionOffset > 0) {
            // If we're not at the first child and are mid-scroll, make sure we obey the offset
            targetScrollX -= mTitleOffset;
        }

        scrollTo(targetScrollX, 0);
    }
}

private class InternalViewPagerListener implements ViewPager.OnPageChangeListener {
    private int mScrollState;

    @Override
    public void onPageScrolled(int position, float positionOffset, int positionOffsetPixels) {
        int tabStripChildCount = mTabStrip.getChildCount();
        if ((tabStripChildCount == 0) || (position < 0) || (position >= tabStripChildCount)) {
            return;
        }

        mTabStrip.onViewPagerPageChanged(position, positionOffset);

        View selectedTitle = mTabStrip.getChildAt(position);
        int extraOffset = (selectedTitle != null)
                ? (int) (positionOffset * selectedTitle.getWidth())
                : 0;
        scrollToTab(position, extraOffset);

        if (mViewPagerPageChangeListener != null) {
            mViewPagerPageChangeListener.onPageScrolled(position, positionOffset,
                    positionOffsetPixels);
        }
    }

    @Override
    public void onPageScrollStateChanged(int state) {
        mScrollState = state;

        if (mViewPagerPageChangeListener != null) {
            mViewPagerPageChangeListener.onPageScrollStateChanged(state);
        }
    }

    @Override
    public void onPageSelected(int position) {
        if (mScrollState == ViewPager.SCROLL_STATE_IDLE) {
            mTabStrip.onViewPagerPageChanged(position, 0f);
            scrollToTab(position, 0);
        }
        for (int i = 0; i < mTabStrip.getChildCount(); i++) {
            mTabStrip.getChildAt(i).setSelected(position == i);
        }
        if (mViewPagerPageChangeListener != null) {
            mViewPagerPageChangeListener.onPageSelected(position);
        }
    }

}

private class TabClickListener implements View.OnClickListener {
    @Override
    public void onClick(View v) {
        for (int i = 0; i < mTabStrip.getChildCount(); i++) {
            if (v == mTabStrip.getChildAt(i)) {
                mViewPager.setCurrentItem(i);
                return;
            }
        }
    }
}

}

但我不知道如何设置 getCurrentTab() 以获取 Tab 位置，而是在 ViewPagerAdapter 中我有位置，但我不知道如何从 MainActivity 获取菜单。解决方案？

Answer 1

你可以用setHasOptionMenu(Boolean)来做；

然后在您的onCreateOptionsMenu() 中创建图标和标题，这是一个示例：

@Override
public void onCreateOptionsMenu(Menu menu, MenuInflater inflater) {
  super.onCreateOptionsMenu(menu, inflater);
  inflater.inflate(R.menu.your_fragment_menu, menu);
  //add the items here.
}

也看看这个example

编辑

在每个片段上，您可以扩展您的菜单，因为我说您已经创建了两个菜单，所以在onCreateOptionsMenu() 的一个片段中添加第一个，第二个添加第二个，依此类推。

Answer 2

步骤#1：创建一个包含所有操作栏项目的菜单资源。如有必要，请在资源中添加一个或多个 android:visible="false"。

步骤#2：在onPrepareOptionsMenu()中，调用findItem() on the Menu，在膨胀资源后，检索状态变化的MenuItem对象。在你的活动领域坚持这些。

步骤#3：将OnPageChangeListener 添加到您的ViewPager，并根据需要在MenuItem 对象上调用setVisibility()，以在用户选择不同选项卡时更改其状态。最有可能的是，这将需要更改您从哪里获得 SlidingTabLayout，因为它也可能设置一个 OnPageChangeListener，并且每个 ViewPager 只能有一个。

Answer 3

我已经解决了在 MainActivity 中添加一个带有 OnPageChangeListener 的方法，我发布了更新的代码：

MainActivity

public class MainActivity extends AppCompatActivity {

// Declaring Your View and Variables

Toolbar toolbar;
ViewPager pager;
ViewPagerAdapter adapter;
SlidingTabLayout tabs;
CharSequence Titles[]={"1","2","3","4"};
int Numboftabs =4;
Integer tabSelected = 1;

public static Integer MYACTIVITY_REQUEST_CODE = 101;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    //getSupportActionBar().setElevation(0);
    setContentView(R.layout.activity_main);

    //
    // Creating The Toolbar and setting it as the Toolbar for the activity

    toolbar = (Toolbar) findViewById(R.id.tool_bar);
    //setSupportActionBar(toolbar);

    // Creating The ViewPagerAdapter and Passing Fragment Manager, Titles fot the Tabs and Number Of Tabs.
    adapter =  new ViewPagerAdapter(getSupportFragmentManager(),Titles,Numboftabs);

    // Assigning ViewPager View and setting the adapter
    pager = (ViewPager) findViewById(R.id.pager);
    pager.setAdapter(adapter);

    // Assiging the Sliding Tab Layout View
    tabs = (SlidingTabLayout) findViewById(R.id.tabs);
    tabs.setDistributeEvenly(true); // To make the Tabs Fixed set this true, This makes the tabs Space Evenly in Available width

    // Setting Custom Color for the Scroll bar indicator of the Tab View
    tabs.setCustomTabColorizer(new SlidingTabLayout.TabColorizer() {
        @Override
        public int getIndicatorColor(int position) {
            return ContextCompat.getColor(getApplicationContext(), R.color.darkgreen);
        }
    });

    // Setting the ViewPager For the SlidingTabsLayout
    tabs.setViewPager(pager);

}


@Override
public boolean onPrepareOptionsMenu(Menu menu) {
    MenuInflater inflater = getMenuInflater();
    tabSelected = getCurrentTab();

    switch (tabSelected) {
        case 1:
            //other..
            break;
        case 2:
            //other..
            break;
        case 3:
            MenuItem addUser = menu.findItem(R.id.action_add_user);
            addUser.setVisible(true);
            break;
        case 4:
            MenuItem message = menu.findItem(R.id.action_message);
            message.setVisible(true);
            break;
    }
    return super.onPrepareOptionsMenu(menu);
}

@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);
    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.
    int id = item.getItemId();

    switch (id) {
        case R.id.action_settings:
            Intent intentMSett = new Intent(this, MainSettings.class);
            startActivity(intentMSett);
            break;
        case R.id.action_add_user:
            Intent intentCUser = new Intent(this, CreateUser.class);
            startActivityForResult(intentCUser, 101);
            break;
        case R.id.action_message:
            Intent intentMessage = new Intent(this, CreateMessage.class);
            startActivityForResult(intentMessage, 102);
            break;
    }

    return super.onOptionsItemSelected(item);
}


public Integer getCurrentTab(){
    pager.addOnPageChangeListener(new ViewPager.OnPageChangeListener() {
        @Override
        public void onPageScrolled(int position, float positionOffset, int positionOffsetPixels) {

        }

        @Override
        public void onPageSelected(int position) {
            switch (position) {
                case 0:
                    tabSelected = 1;
                    break;
                case 1:
                    tabSelected = 2;
                    break;
                case 2:
                    tabSelected = 3;
                    break;
                case 3:
                    tabSelected = 4;
                    break;
            }
        }

        @Override
        public void onPageScrollStateChanged(int state) {

        }
    });
    return tabSelected;
}

}