Android example source code file (FrameLayout.java)

This example Android source code file (FrameLayout.java) is included in the DevDaily.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Android by Example" ^TM.

Java - Android tags/keywords

android, attributeset, drawable, drawing, framelayout, gone, graphics, layoutparams, marginlayoutparams, override, paint, rect, remoteview, typedarray, ui, view, viewgroup

The FrameLayout.java Android example source code

/*
 * Copyright (C) 2006 The Android Open Source Project
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package android.widget;

import android.content.Context;
import android.content.res.TypedArray;
import android.graphics.Canvas;
import android.graphics.Rect;
import android.graphics.Region;
import android.graphics.drawable.Drawable;
import android.util.AttributeSet;
import android.view.View;
import android.view.ViewDebug;
import android.view.ViewGroup;
import android.view.Gravity;
import android.widget.RemoteViews.RemoteView;


/**
 * FrameLayout is designed to block out an area on the screen to display
 * a single item. You can add multiple children to a FrameLayout, but all
 * children are pegged to the top left of the screen.
 * Children are drawn in a stack, with the most recently added child on top.
 * The size of the frame layout is the size of its largest child (plus padding), visible
 * or not (if the FrameLayout's parent permits). Views that are GONE are used for sizing
 * only if {@link #setMeasureAllChildren(boolean) setConsiderGoneChildrenWhenMeasuring()}
 * is set to true.
 *
 * @attr ref android.R.styleable#FrameLayout_foreground
 * @attr ref android.R.styleable#FrameLayout_foregroundGravity
 * @attr ref android.R.styleable#FrameLayout_measureAllChildren
 */
@RemoteView
public class FrameLayout extends ViewGroup {
    @ViewDebug.ExportedProperty
    boolean mMeasureAllChildren = false;

    @ViewDebug.ExportedProperty
    private Drawable mForeground;
    @ViewDebug.ExportedProperty
    private int mForegroundPaddingLeft = 0;
    @ViewDebug.ExportedProperty
    private int mForegroundPaddingTop = 0;
    @ViewDebug.ExportedProperty
    private int mForegroundPaddingRight = 0;
    @ViewDebug.ExportedProperty
    private int mForegroundPaddingBottom = 0;

    private final Rect mSelfBounds = new Rect();
    private final Rect mOverlayBounds = new Rect();
    @ViewDebug.ExportedProperty
    private int mForegroundGravity = Gravity.FILL;

    /** {@hide} */
    @ViewDebug.ExportedProperty
    protected boolean mForegroundInPadding = true;

    boolean mForegroundBoundsChanged = false;
    
    public FrameLayout(Context context) {
        super(context);
    }
    
    public FrameLayout(Context context, AttributeSet attrs) {
        this(context, attrs, 0);
    }

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

        TypedArray a = context.obtainStyledAttributes(attrs, com.android.internal.R.styleable.FrameLayout,
                    defStyle, 0);

        mForegroundGravity = a.getInt(
                com.android.internal.R.styleable.FrameLayout_foregroundGravity, mForegroundGravity);

        final Drawable d = a.getDrawable(com.android.internal.R.styleable.FrameLayout_foreground);
        if (d != null) {
            setForeground(d);
        }
        
        if (a.getBoolean(com.android.internal.R.styleable.FrameLayout_measureAllChildren, false)) {
            setMeasureAllChildren(true);
        }

        mForegroundInPadding = a.getBoolean(
                com.android.internal.R.styleable.FrameLayout_foregroundInsidePadding, true);

        a.recycle();
    }

    /**
     * Describes how the foreground is positioned. Defaults to FILL.
     *
     * @param foregroundGravity See {@link android.view.Gravity}
     *
     * @attr ref android.R.styleable#FrameLayout_foregroundGravity
     */
    @android.view.RemotableViewMethod
    public void setForegroundGravity(int foregroundGravity) {
        if (mForegroundGravity != foregroundGravity) {
            if ((foregroundGravity & Gravity.HORIZONTAL_GRAVITY_MASK) == 0) {
                foregroundGravity |= Gravity.LEFT;
            }

            if ((foregroundGravity & Gravity.VERTICAL_GRAVITY_MASK) == 0) {
                foregroundGravity |= Gravity.TOP;
            }

            mForegroundGravity = foregroundGravity;


            if (mForegroundGravity == Gravity.FILL && mForeground != null) {
                Rect padding = new Rect();
                if (mForeground.getPadding(padding)) {
                    mForegroundPaddingLeft = padding.left;
                    mForegroundPaddingTop = padding.top;
                    mForegroundPaddingRight = padding.right;
                    mForegroundPaddingBottom = padding.bottom;
                }
            } else {
                mForegroundPaddingLeft = 0;
                mForegroundPaddingTop = 0;
                mForegroundPaddingRight = 0;
                mForegroundPaddingBottom = 0;
            }

            requestLayout();
        }
    }

    /**
     * {@inheritDoc}
     */
    @Override
    protected boolean verifyDrawable(Drawable who) {
        return super.verifyDrawable(who) || (who == mForeground);
    }

    /**
     * {@inheritDoc}
     */
    @Override
    protected void drawableStateChanged() {
        super.drawableStateChanged();
        if (mForeground != null && mForeground.isStateful()) {
            mForeground.setState(getDrawableState());
        }
    }

    /**
     * Returns a set of layout parameters with a width of
     * {@link android.view.ViewGroup.LayoutParams#MATCH_PARENT},
     * and a height of {@link android.view.ViewGroup.LayoutParams#MATCH_PARENT}.
     */
    @Override
    protected LayoutParams generateDefaultLayoutParams() {
        return new LayoutParams(LayoutParams.MATCH_PARENT, LayoutParams.MATCH_PARENT);
    }

    /**
     * Supply a Drawable that is to be rendered on top of all of the child
     * views in the frame layout.  Any padding in the Drawable will be taken
     * into account by ensuring that the children are inset to be placed
     * inside of the padding area.
     * 
     * @param drawable The Drawable to be drawn on top of the children.
     * 
     * @attr ref android.R.styleable#FrameLayout_foreground
     */
    public void setForeground(Drawable drawable) {
        if (mForeground != drawable) {
            if (mForeground != null) {
                mForeground.setCallback(null);
                unscheduleDrawable(mForeground);
            }

            mForeground = drawable;
            mForegroundPaddingLeft = 0;
            mForegroundPaddingTop = 0;
            mForegroundPaddingRight = 0;
            mForegroundPaddingBottom = 0;

            if (drawable != null) {
                setWillNotDraw(false);
                drawable.setCallback(this);
                if (drawable.isStateful()) {
                    drawable.setState(getDrawableState());
                }
                if (mForegroundGravity == Gravity.FILL) {
                    Rect padding = new Rect();
                    if (drawable.getPadding(padding)) {
                        mForegroundPaddingLeft = padding.left;
                        mForegroundPaddingTop = padding.top;
                        mForegroundPaddingRight = padding.right;
                        mForegroundPaddingBottom = padding.bottom;
                    }
                }
            }  else {
                setWillNotDraw(true);
            }
            requestLayout();
            invalidate();
        }
    }

    /**
     * Returns the drawable used as the foreground of this FrameLayout. The
     * foreground drawable, if non-null, is always drawn on top of the children.
     *
     * @return A Drawable or null if no foreground was set.
     */
    public Drawable getForeground() {
        return mForeground;
    }

    /**
     * {@inheritDoc}
     */
    @Override
    protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
        final int count = getChildCount();

        int maxHeight = 0;
        int maxWidth = 0;

        // Find rightmost and bottommost child
        for (int i = 0; i < count; i++) {
            final View child = getChildAt(i);
            if (mMeasureAllChildren || child.getVisibility() != GONE) {
                measureChildWithMargins(child, widthMeasureSpec, 0, heightMeasureSpec, 0);
                maxWidth = Math.max(maxWidth, child.getMeasuredWidth());
                maxHeight = Math.max(maxHeight, child.getMeasuredHeight());
            }
        }

        // Account for padding too
        maxWidth += mPaddingLeft + mPaddingRight + mForegroundPaddingLeft + mForegroundPaddingRight;
        maxHeight += mPaddingTop + mPaddingBottom + mForegroundPaddingTop + mForegroundPaddingBottom;

        // Check against our minimum height and width
        maxHeight = Math.max(maxHeight, getSuggestedMinimumHeight());
        maxWidth = Math.max(maxWidth, getSuggestedMinimumWidth());

        // Check against our foreground's minimum height and width
        final Drawable drawable = getForeground();
        if (drawable != null) {
            maxHeight = Math.max(maxHeight, drawable.getMinimumHeight());
            maxWidth = Math.max(maxWidth, drawable.getMinimumWidth());
        }

        setMeasuredDimension(resolveSize(maxWidth, widthMeasureSpec),
                resolveSize(maxHeight, heightMeasureSpec));
    }
 
    /**
     * {@inheritDoc}
     */
    @Override
    protected void onLayout(boolean changed, int left, int top, int right, int bottom) {
        final int count = getChildCount();

        final int parentLeft = mPaddingLeft + mForegroundPaddingLeft;
        final int parentRight = right - left - mPaddingRight - mForegroundPaddingRight;

        final int parentTop = mPaddingTop + mForegroundPaddingTop;
        final int parentBottom = bottom - top - mPaddingBottom - mForegroundPaddingBottom;

        mForegroundBoundsChanged = true;
        
        for (int i = 0; i < count; i++) {
            final View child = getChildAt(i);
            if (child.getVisibility() != GONE) {
                final LayoutParams lp = (LayoutParams) child.getLayoutParams();

                final int width = child.getMeasuredWidth();
                final int height = child.getMeasuredHeight();

                int childLeft = parentLeft;
                int childTop = parentTop;

                final int gravity = lp.gravity;

                if (gravity != -1) {
                    final int horizontalGravity = gravity & Gravity.HORIZONTAL_GRAVITY_MASK;
                    final int verticalGravity = gravity & Gravity.VERTICAL_GRAVITY_MASK;

                    switch (horizontalGravity) {
                        case Gravity.LEFT:
                            childLeft = parentLeft + lp.leftMargin;
                            break;
                        case Gravity.CENTER_HORIZONTAL:
                            childLeft = parentLeft + (parentRight - parentLeft - width) / 2 +
                                    lp.leftMargin - lp.rightMargin;
                            break;
                        case Gravity.RIGHT:
                            childLeft = parentRight - width - lp.rightMargin;
                            break;
                        default:
                            childLeft = parentLeft + lp.leftMargin;
                    }

                    switch (verticalGravity) {
                        case Gravity.TOP:
                            childTop = parentTop + lp.topMargin;
                            break;
                        case Gravity.CENTER_VERTICAL:
                            childTop = parentTop + (parentBottom - parentTop - height) / 2 +
                                    lp.topMargin - lp.bottomMargin;
                            break;
                        case Gravity.BOTTOM:
                            childTop = parentBottom - height - lp.bottomMargin;
                            break;
                        default:
                            childTop = parentTop + lp.topMargin;
                    }
                }

                child.layout(childLeft, childTop, childLeft + width, childTop + height);
            }
        }
    }

    /**
     * {@inheritDoc}
     */
    @Override
    protected void onSizeChanged(int w, int h, int oldw, int oldh) {
        super.onSizeChanged(w, h, oldw, oldh);
        mForegroundBoundsChanged = true;
    }

    /**
     * {@inheritDoc}
     */
    @Override
    public void draw(Canvas canvas) {
        super.draw(canvas);

        if (mForeground != null) {
            final Drawable foreground = mForeground;

            if (mForegroundBoundsChanged) {
                mForegroundBoundsChanged = false;
                final Rect selfBounds = mSelfBounds;
                final Rect overlayBounds = mOverlayBounds;

                final int w = mRight-mLeft;
                final int h = mBottom-mTop;

                if (mForegroundInPadding) {
                    selfBounds.set(0, 0, w, h);
                } else {
                    selfBounds.set(mPaddingLeft, mPaddingTop, w - mPaddingRight, h - mPaddingBottom);
                }

                Gravity.apply(mForegroundGravity, foreground.getIntrinsicWidth(),
                        foreground.getIntrinsicHeight(), selfBounds, overlayBounds);
                foreground.setBounds(overlayBounds);
            }
            
            foreground.draw(canvas);
        }
    }

    /**
     * {@inheritDoc}
     */
    @Override
    public boolean gatherTransparentRegion(Region region) {
        boolean opaque = super.gatherTransparentRegion(region);
        if (region != null && mForeground != null) {
            applyDrawableToTransparentRegion(mForeground, region);
        }
        return opaque;
    }

    /**
     * Determines whether to measure all children or just those in 
     * the VISIBLE or INVISIBLE state when measuring. Defaults to false.
     * @param measureAll true to consider children marked GONE, false otherwise.
     * Default value is false.
     * 
     * @attr ref android.R.styleable#FrameLayout_measureAllChildren
     */
    @android.view.RemotableViewMethod
    public void setMeasureAllChildren(boolean measureAll) {
        mMeasureAllChildren = measureAll;
    }
    
    /**
     * Determines whether to measure all children or just those in 
     * the VISIBLE or INVISIBLE state when measuring. 
     */
    public boolean getConsiderGoneChildrenWhenMeasuring() {
        return mMeasureAllChildren;
    }

    /**
     * {@inheritDoc}
     */
    @Override
    public LayoutParams generateLayoutParams(AttributeSet attrs) {
        return new FrameLayout.LayoutParams(getContext(), attrs);        
    }

    /**
     * {@inheritDoc}
     */
    @Override
    protected boolean checkLayoutParams(ViewGroup.LayoutParams p) {
        return p instanceof LayoutParams;
    }

    @Override
    protected ViewGroup.LayoutParams generateLayoutParams(ViewGroup.LayoutParams p) {
        return new LayoutParams(p);
    }

    /**
     * Per-child layout information for layouts that support margins.
     * See {@link android.R.styleable#FrameLayout_Layout FrameLayout Layout Attributes}
     * for a list of all child view attributes that this class supports.
     */
    public static class LayoutParams extends MarginLayoutParams {
        /**
         * The gravity to apply with the View to which these layout parameters
         * are associated.
         *
         * @see android.view.Gravity
         */
        public int gravity = -1;

        /**
         * {@inheritDoc}
         */
        public LayoutParams(Context c, AttributeSet attrs) {
            super(c, attrs);

            TypedArray a = c.obtainStyledAttributes(attrs, com.android.internal.R.styleable.FrameLayout_Layout);
            gravity = a.getInt(com.android.internal.R.styleable.FrameLayout_Layout_layout_gravity, -1);
            a.recycle();
        }

        /**
         * {@inheritDoc}
         */
        public LayoutParams(int width, int height) {
            super(width, height);
        }

        /**
         * Creates a new set of layout parameters with the specified width, height
         * and weight.
         *
         * @param width the width, either {@link #MATCH_PARENT},
         *        {@link #WRAP_CONTENT} or a fixed size in pixels
         * @param height the height, either {@link #MATCH_PARENT},
         *        {@link #WRAP_CONTENT} or a fixed size in pixels
         * @param gravity the gravity
         *
         * @see android.view.Gravity
         */
        public LayoutParams(int width, int height, int gravity) {
            super(width, height);
            this.gravity = gravity;
        }

        /**
         * {@inheritDoc}
         */
        public LayoutParams(ViewGroup.LayoutParams source) {
            super(source);
        }

        /**
         * {@inheritDoc}
         */
        public LayoutParams(ViewGroup.MarginLayoutParams source) {
            super(source);
        }
    }
}