Android自带Samples(二)——ActionBarCompat

ActionBar实际上是用来替换导航菜单的一个选项，主要的作用是：

1. ActionBar是一个显示在屏幕顶部的控件，它包括了在左边显示的应用的logo图标和右边操作菜单的可见项。
2. 我们可以选择可见的操作菜单可见项，不可见项会以下拉列表的形式呈现出来。
3. ActionBar为Fragment之间提供标签导航
   

ok，接下来我们查看源码：

AndroidManifest.xml文件中我们看到设置了application的android:theme="@style/AppTheme"，我们去看看style.xml文件(为了快速简单的分析，我们仅针对Android 4.0以上版本的分析，所以这里检查的是values-v13)：

<resources>

    <style name="ActionBarTitle" parent="android:style/TextAppearance.Holo.Widget.ActionBar.Title">
        <!-- 颜色值在colors文件中有配置 -->
        <item name="android:textColor">@color/actionbar_title_color</item>
    </style>

</resources>

接下来我们看看MainActivity代码，总体上看Activity代码较为简单，主要处理了optionmenu：

public class MainActivity extends ActionBarActivity {
    private boolean mAlternateTitle = false;

    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);

        findViewById(R.id.toggle_title).setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
            	// 设置标题文字
                if (mAlternateTitle) {
                    setTitle(R.string.app_name);
                } else {
                    setTitle(R.string.alternate_title);
                }
                mAlternateTitle = !mAlternateTitle;
            }
        });
    }

    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        MenuInflater menuInflater = getMenuInflater();
        menuInflater.inflate(R.menu.main, menu);

        // Calling super after populating the menu is necessary here to ensure that the
        // action bar helpers have a chance to handle this event.
        return super.onCreateOptionsMenu(menu);
    }

    @Override
    public boolean onOptionsItemSelected(MenuItem item) {
    	// 响应按钮点击
        switch (item.getItemId()) {
//            case android.R.id.home:
//                Toast.makeText(this, "Tapped home", Toast.LENGTH_SHORT).show();
//                break;

            case R.id.menu_refresh:
                Toast.makeText(this, "Fake refreshing...", Toast.LENGTH_SHORT).show();
                getActionBarHelper().setRefreshActionItemState(true);
                getWindow().getDecorView().postDelayed(
                        new Runnable() {
                            @Override
                            public void run() {
                                getActionBarHelper().setRefreshActionItemState(false);
                            }
                        }, 1000);
                break;

            case R.id.menu_search:
                Toast.makeText(this, "Tapped search", Toast.LENGTH_SHORT).show();
                break;

//            case R.id.menu_share:
//                Toast.makeText(this, "Tapped share", Toast.LENGTH_SHORT).show();
//                break;
        }
        return super.onOptionsItemSelected(item);
    }
}

接着我们看MainActivity的父类ActionBarActivity：

public abstract class ActionBarActivity extends Activity {
    final ActionBarHelper mActionBarHelper = ActionBarHelper.createInstance(this);

    /**
     * Returns the {@link ActionBarHelper} for this activity.
     */
    protected ActionBarHelper getActionBarHelper() {
        return mActionBarHelper;
    }

    /**{@inheritDoc}*/
    @Override
    public MenuInflater getMenuInflater() {
        return mActionBarHelper.getMenuInflater(super.getMenuInflater());
    }

    /**{@inheritDoc}*/
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        mActionBarHelper.onCreate(savedInstanceState);
    }

    /**{@inheritDoc}*/
    @Override
    protected void onPostCreate(Bundle savedInstanceState) {
        super.onPostCreate(savedInstanceState);
        mActionBarHelper.onPostCreate(savedInstanceState);
    }

    /**
     * Base action bar-aware implementation for
     * {@link Activity#onCreateOptionsMenu(android.view.Menu)}.
     *
     * Note: marking menu items as invisible/visible is not currently supported.
     */
    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        boolean retValue = false;
        retValue |= mActionBarHelper.onCreateOptionsMenu(menu);
        retValue |= super.onCreateOptionsMenu(menu);
        return retValue;
    }

    /**{@inheritDoc}*/
    @Override
    protected void onTitleChanged(CharSequence title, int color) {
        mActionBarHelper.onTitleChanged(title, color);
        super.onTitleChanged(title, color);
    }
}

最重要的是ActionBarHelper，那么我们跟进去看：

public abstract class ActionBarHelper {
    protected Activity mActivity;

    /**
     * Factory method for creating {@link ActionBarHelper} objects for a
     * given activity. Depending on which device the app is running, either a basic helper or
     * Honeycomb-specific helper will be returned.
     */
    public static ActionBarHelper createInstance(Activity activity) {
        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.ICE_CREAM_SANDWICH) {
        	// 如果Build的SDK版本>=14，也就是我们正在分析的。
            return new ActionBarHelperICS(activity);
        } else if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.HONEYCOMB) {
        	// 如果Build的SDK版本在[11,14)之间
            return new ActionBarHelperHoneycomb(activity);
        } else {
        	// 其余SDK版本
            return new ActionBarHelperBase(activity);
        }
    }

    protected ActionBarHelper(Activity activity) {
        mActivity = activity;
    }

    /**
     * Action bar helper code to be run in {@link Activity#onCreate(android.os.Bundle)}.
     */
    public void onCreate(Bundle savedInstanceState) {
    }

    /**
     * Action bar helper code to be run in {@link Activity#onPostCreate(android.os.Bundle)}.
     */
    public void onPostCreate(Bundle savedInstanceState) {
    }

    /**
     * Action bar helper code to be run in {@link Activity#onCreateOptionsMenu(android.view.Menu)}.
     *
     * NOTE: Setting the visibility of menu items in <em>menu</em> is not currently supported.
     */
    public boolean onCreateOptionsMenu(Menu menu) {
        return true;
    }

    /**
     * Action bar helper code to be run in {@link Activity#onTitleChanged(CharSequence, int)}.
     */
    protected void onTitleChanged(CharSequence title, int color) {
    }

    /**
     * Sets the indeterminate loading state of the item with ID {@link R.id.menu_refresh}.
     * (where the item ID was menu_refresh).
     */
    public abstract void setRefreshActionItemState(boolean refreshing);

    /**
     * Returns a {@link MenuInflater} for use when inflating menus. The implementation of this
     * method in {@link ActionBarHelperBase} returns a wrapped menu inflater that can read
     * action bar metadata from a menu resource pre-Honeycomb.
     */
    public MenuInflater getMenuInflater(MenuInflater superMenuInflater) {
        return superMenuInflater;
    }
}

我们仅关心ActionBarHelperICS：

public class ActionBarHelperICS extends ActionBarHelperHoneycomb {
    protected ActionBarHelperICS(Activity activity) {
        super(activity);
    }

    @Override
    protected Context getActionBarThemedContext() {
        return mActivity.getActionBar().getThemedContext();
    }
}

发现父类是ActionBarHelperHoneycomb：

public class ActionBarHelperHoneycomb extends ActionBarHelper {
    private Menu mOptionsMenu;
    private View mRefreshIndeterminateProgressView = null;

    protected ActionBarHelperHoneycomb(Activity activity) {
        super(activity);
    }

    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        mOptionsMenu = menu;
        return super.onCreateOptionsMenu(menu);
    }

    @Override
    public void setRefreshActionItemState(boolean refreshing) {
        // On Honeycomb, we can set the state of the refresh button by giving it a custom
        // action view.
        if (mOptionsMenu == null) {
            return;
        }

        final MenuItem refreshItem = mOptionsMenu.findItem(R.id.menu_refresh);
        if (refreshItem != null) {
            if (refreshing) {
            	// 如果在刷新状态
                if (mRefreshIndeterminateProgressView == null) {
                    LayoutInflater inflater = (LayoutInflater)
                            getActionBarThemedContext().getSystemService(
                                    Context.LAYOUT_INFLATER_SERVICE);
                    mRefreshIndeterminateProgressView = inflater.inflate(
                            R.layout.actionbar_indeterminate_progress, null);
                }
                // 设置菜单上的显示
                refreshItem.setActionView(mRefreshIndeterminateProgressView);
            } else {
                refreshItem.setActionView(null);
            }
        }
    }

    /**
     * Returns a {@link Context} suitable for inflating layouts for the action bar. The
     * implementation for this method in {@link ActionBarHelperICS} asks the action bar for a
     * themed context.
     */
    protected Context getActionBarThemedContext() {
        return mActivity;
    }
}

另外还有两个辅助类SimpleMenu和SimpleMenuItem:

public class SimpleMenu implements Menu {

    private Context mContext;
    private Resources mResources;

    private ArrayList<SimpleMenuItem> mItems;

    public SimpleMenu(Context context) {
        mContext = context;
        mResources = context.getResources();
        mItems = new ArrayList<SimpleMenuItem>();
    }

    public Context getContext() {
        return mContext;
    }

    public Resources getResources() {
        return mResources;
    }

    public MenuItem add(CharSequence title) {
        return addInternal(0, 0, title);
    }

    public MenuItem add(int titleRes) {
        return addInternal(0, 0, mResources.getString(titleRes));
    }

    public MenuItem add(int groupId, int itemId, int order, CharSequence title) {
        return addInternal(itemId, order, title);
    }

    public MenuItem add(int groupId, int itemId, int order, int titleRes) {
        return addInternal(itemId, order, mResources.getString(titleRes));
    }

    /**
     * Adds an item to the menu.  The other add methods funnel to this.
     */
    private MenuItem addInternal(int itemId, int order, CharSequence title) {
        final SimpleMenuItem item = new SimpleMenuItem(this, itemId, order, title);
        mItems.add(findInsertIndex(mItems, order), item);
        return item;
    }

    private static int findInsertIndex(ArrayList<? extends MenuItem> items, int order) {
        for (int i = items.size() - 1; i >= 0; i--) {
            MenuItem item = items.get(i);
            if (item.getOrder() <= order) {
                return i + 1;
            }
        }

        return 0;
    }

    public int findItemIndex(int id) {
        final int size = size();

        for (int i = 0; i < size; i++) {
            SimpleMenuItem item = mItems.get(i);
            if (item.getItemId() == id) {
                return i;
            }
        }

        return -1;
    }

    public void removeItem(int itemId) {
        removeItemAtInt(findItemIndex(itemId));
    }

    private void removeItemAtInt(int index) {
        if ((index < 0) || (index >= mItems.size())) {
            return;
        }
        mItems.remove(index);
    }

    public void clear() {
        mItems.clear();
    }

    public MenuItem findItem(int id) {
        final int size = size();
        for (int i = 0; i < size; i++) {
            SimpleMenuItem item = mItems.get(i);
            if (item.getItemId() == id) {
                return item;
            }
        }

        return null;
    }

    public int size() {
        return mItems.size();
    }

    public MenuItem getItem(int index) {
        return mItems.get(index);
    }

    // Unsupported operations.

    public SubMenu addSubMenu(CharSequence charSequence) {
        throw new UnsupportedOperationException("This operation is not supported for SimpleMenu");
    }

    public SubMenu addSubMenu(int titleRes) {
        throw new UnsupportedOperationException("This operation is not supported for SimpleMenu");
    }

    public SubMenu addSubMenu(int groupId, int itemId, int order, CharSequence title) {
        throw new UnsupportedOperationException("This operation is not supported for SimpleMenu");
    }

    public SubMenu addSubMenu(int groupId, int itemId, int order, int titleRes) {
        throw new UnsupportedOperationException("This operation is not supported for SimpleMenu");
    }

    public int addIntentOptions(int i, int i1, int i2, ComponentName componentName,
            Intent[] intents, Intent intent, int i3, MenuItem[] menuItems) {
        throw new UnsupportedOperationException("This operation is not supported for SimpleMenu");
    }

    public void removeGroup(int i) {
        throw new UnsupportedOperationException("This operation is not supported for SimpleMenu");
    }

    public void setGroupCheckable(int i, boolean b, boolean b1) {
        throw new UnsupportedOperationException("This operation is not supported for SimpleMenu");
    }

    public void setGroupVisible(int i, boolean b) {
        throw new UnsupportedOperationException("This operation is not supported for SimpleMenu");
    }

    public void setGroupEnabled(int i, boolean b) {
        throw new UnsupportedOperationException("This operation is not supported for SimpleMenu");
    }

    public boolean hasVisibleItems() {
        throw new UnsupportedOperationException("This operation is not supported for SimpleMenu");
    }

    public void close() {
        throw new UnsupportedOperationException("This operation is not supported for SimpleMenu");
    }

    public boolean performShortcut(int i, KeyEvent keyEvent, int i1) {
        throw new UnsupportedOperationException("This operation is not supported for SimpleMenu");
    }

    public boolean isShortcutKey(int i, KeyEvent keyEvent) {
        throw new UnsupportedOperationException("This operation is not supported for SimpleMenu");
    }

    public boolean performIdentifierAction(int i, int i1) {
        throw new UnsupportedOperationException("This operation is not supported for SimpleMenu");
    }

    public void setQwertyMode(boolean b) {
        throw new UnsupportedOperationException("This operation is not supported for SimpleMenu");
    }
}

public class SimpleMenuItem implements MenuItem {

    private SimpleMenu mMenu;

    private final int mId;
    private final int mOrder;
    private CharSequence mTitle;
    private CharSequence mTitleCondensed;
    private Drawable mIconDrawable;
    private int mIconResId = 0;
    private boolean mEnabled = true;

    public SimpleMenuItem(SimpleMenu menu, int id, int order, CharSequence title) {
        mMenu = menu;
        mId = id;
        mOrder = order;
        mTitle = title;
    }

    public int getItemId() {
        return mId;
    }

    public int getOrder() {
        return mOrder;
    }

    public MenuItem setTitle(CharSequence title) {
        mTitle = title;
        return this;
    }

    public MenuItem setTitle(int titleRes) {
        return setTitle(mMenu.getContext().getString(titleRes));
    }

    public CharSequence getTitle() {
        return mTitle;
    }

    public MenuItem setTitleCondensed(CharSequence title) {
        mTitleCondensed = title;
        return this;
    }

    public CharSequence getTitleCondensed() {
        return mTitleCondensed != null ? mTitleCondensed : mTitle;
    }

    public MenuItem setIcon(Drawable icon) {
        mIconResId = 0;
        mIconDrawable = icon;
        return this;
    }

    public MenuItem setIcon(int iconResId) {
        mIconDrawable = null;
        mIconResId = iconResId;
        return this;
    }

    public Drawable getIcon() {
        if (mIconDrawable != null) {
            return mIconDrawable;
        }

        if (mIconResId != 0) {
            return mMenu.getResources().getDrawable(mIconResId);
        }

        return null;
    }

    public MenuItem setEnabled(boolean enabled) {
        mEnabled = enabled;
        return this;
    }

    public boolean isEnabled() {
        return mEnabled;
    }

    // No-op operations. We use no-ops to allow inflation from menu XML.

    public int getGroupId() {
        // Noop
        return 0;
    }

    public View getActionView() {
        // Noop
        return null;
    }

    public MenuItem setActionProvider(ActionProvider actionProvider) {
        // Noop
        return this;
    }

    public ActionProvider getActionProvider() {
        // Noop
        return null;
    }

    public boolean expandActionView() {
        // Noop
        return false;
    }

    public boolean collapseActionView() {
        // Noop
        return false;
    }

    public boolean isActionViewExpanded() {
        // Noop
        return false;
    }

    @Override
    public MenuItem setOnActionExpandListener(OnActionExpandListener onActionExpandListener) {
        // Noop
        return this;
    }

    public MenuItem setIntent(Intent intent) {
        // Noop
        return this;
    }

    public Intent getIntent() {
        // Noop
        return null;
    }

    public MenuItem setShortcut(char c, char c1) {
        // Noop
        return this;
    }

    public MenuItem setNumericShortcut(char c) {
        // Noop
        return this;
    }

    public char getNumericShortcut() {
        // Noop
        return 0;
    }

    public MenuItem setAlphabeticShortcut(char c) {
        // Noop
        return this;
    }

    public char getAlphabeticShortcut() {
        // Noop
        return 0;
    }

    public MenuItem setCheckable(boolean b) {
        // Noop
        return this;
    }

    public boolean isCheckable() {
        // Noop
        return false;
    }

    public MenuItem setChecked(boolean b) {
        // Noop
        return this;
    }

    public boolean isChecked() {
        // Noop
        return false;
    }

    public MenuItem setVisible(boolean b) {
        // Noop
        return this;
    }

    public boolean isVisible() {
        // Noop
        return true;
    }

    public boolean hasSubMenu() {
        // Noop
        return false;
    }

    public SubMenu getSubMenu() {
        // Noop
        return null;
    }

    public MenuItem setOnMenuItemClickListener(OnMenuItemClickListener onMenuItemClickListener) {
        // Noop
        return this;
    }

    public ContextMenu.ContextMenuInfo getMenuInfo() {
        // Noop
        return null;
    }

    public void setShowAsAction(int i) {
        // Noop
    }

    public MenuItem setShowAsActionFlags(int i) {
        // Noop
        return null;
    }

    public MenuItem setActionView(View view) {
        // Noop
        return this;
    }

    public MenuItem setActionView(int i) {
        // Noop
        return this;
    }
}

参考资料：http://blog.youkuaiyun.com/aomandeshangxiao/article/details/7674904