组合模式实现与研究 - bei1999/work GitHub Wiki

@UiThread
public class View implements Drawable.Callback, KeyEvent.Callback,
        AccessibilityEventSource {
  ...
    /**
     * Ignore any optimizations using the measure cache.
     */
    private static boolean sIgnoreMeasureCache = false;

    /**
     * This view does not want keystrokes. Use with TAKES_FOCUS_MASK when
     * calling setFlags.
     */
    private static final int NOT_FOCUSABLE = 0x00000000;

    /**
     * This view wants keystrokes. Use with TAKES_FOCUS_MASK when calling
     * setFlags.
     */
    private static final int FOCUSABLE = 0x00000001;

    /**
     * Mask for use with setFlags indicating bits used for focus.
     */
    private static final int FOCUSABLE_MASK = 0x00000001;

    /**
     * This view will adjust its padding to fit sytem windows (e.g. status bar)
     */
    private static final int FITS_SYSTEM_WINDOWS = 0x00000002;

    /** @hide */
    @IntDef({VISIBLE, INVISIBLE, GONE})
    @Retention(RetentionPolicy.SOURCE)
    public @interface Visibility {}
}

@UiThread
public abstract class ViewGroup extends View implements ViewParent, ViewManager {
    private static final String TAG = "ViewGroup";

    private static final boolean DBG = false;
    /** @hide */
    public static boolean DEBUG_DRAW = false;

    /**
     * Views which have been hidden or removed which need to be animated on
     * their way out.
     * This field should be made private, so it is hidden from the SDK.
     * {@hide}
     */
    protected ArrayList<View> mDisappearingChildren;

...

   public void addView(View child) {
        addView(child, -1);
    }

    /**
     * Adds a child view. If no layout parameters are already set on the child, the
     * default parameters for this ViewGroup are set on the child.
     * 
     * <p><strong>Note:</strong> do not invoke this method from
     * {@link #draw(android.graphics.Canvas)}, {@link #onDraw(android.graphics.Canvas)},
     * {@link #dispatchDraw(android.graphics.Canvas)} or any related method.</p>
     *
     * @param child the child view to add
     * @param index the position at which to add the child
     *
     * @see #generateDefaultLayoutParams()
     */
    public void addView(View child, int index) {
        if (child == null) {
            throw new IllegalArgumentException("Cannot add a null child view to a ViewGroup");
        }
        LayoutParams params = child.getLayoutParams();
        if (params == null) {
            params = generateDefaultLayoutParams();
            if (params == null) {
                throw new IllegalArgumentException("generateDefaultLayoutParams() cannot return null");
            }
        }
        addView(child, index, params);
    }

    /**
     * Adds a child view with this ViewGroup's default layout parameters and the
     * specified width and height.
     *
     * <p><strong>Note:</strong> do not invoke this method from
     * {@link #draw(android.graphics.Canvas)}, {@link #onDraw(android.graphics.Canvas)},
     * {@link #dispatchDraw(android.graphics.Canvas)} or any related method.</p>
     *
     * @param child the child view to add
     */
    public void addView(View child, int width, int height) {
        final LayoutParams params = generateDefaultLayoutParams();
        params.width = width;
        params.height = height;
        addView(child, -1, params);
    }

   /**
     * {@inheritDoc}
     * 
     * <p><strong>Note:</strong> do not invoke this method from
     * {@link #draw(android.graphics.Canvas)}, {@link #onDraw(android.graphics.Canvas)},
     * {@link #dispatchDraw(android.graphics.Canvas)} or any related method.</p>
     */
    public void removeView(View view) {
        if (removeViewInternal(view)) {
            requestLayout();
            invalidate(true);
        }
    }

 /**
     * Returns the view at the specified position in the group.
     *
     * @param index the position at which to get the view from
     * @return the view at the specified position or null if the position
     *         does not exist within the group
     */
    public View getChildAt(int index) {
        if (index < 0 || index >= mChildrenCount) {
            return null;
        }
        return mChildren[index];
    }
...
}

@RemoteView
public class RelativeLayout extends ViewGroup {
    public static final int TRUE = -1;

    /**
     * Rule that aligns a child's right edge with another child's left edge.
     */
    public static final int LEFT_OF                  = 0;
    /**
     * Rule that aligns a child's left edge with another child's right edge.
     */
    public static final int RIGHT_OF                 = 1;
    /**
     * Rule that aligns a child's bottom edge with another child's top edge.
     */
    public static final int ABOVE                    = 2;
...
}

@RemoteView
public class Button extends TextView {
    public Button(Context context) {
        this(context, null);
    }

    public Button(Context context, AttributeSet attrs) {
        this(context, attrs, com.android.internal.R.attr.buttonStyle);
    }

    public Button(Context context, AttributeSet attrs, int defStyleAttr) {
        this(context, attrs, defStyleAttr, 0);
    }

    public Button(Context context, AttributeSet attrs, int defStyleAttr, int defStyleRes) {
        super(context, attrs, defStyleAttr, defStyleRes);
    }

    @Override
    public CharSequence getAccessibilityClassName() {
        return Button.class.getName();
    }
}