Android example source code file (PictureLayout.java)

This example Android source code file (PictureLayout.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, gone, graphics, illegalstateexception, layoutparams, override, paint, picturelayout, rect, ui, view, viewgroup, viewparent

The PictureLayout.java Android example source code

/*
 * Copyright (C) 2008 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 com.example.android.apis.graphics;

import android.content.Context;
import android.graphics.Canvas;
import android.graphics.Picture;
import android.graphics.Rect;
import android.graphics.drawable.Drawable;
import android.util.AttributeSet;
import android.view.View;
import android.view.ViewGroup;
import android.view.ViewParent;


public class PictureLayout extends ViewGroup {
    private final Picture mPicture = new Picture();

    public PictureLayout(Context context) {
        super(context);
    }

    public PictureLayout(Context context, AttributeSet attrs) {
        super(context, attrs);
    }    

    @Override
    public void addView(View child) {
        if (getChildCount() > 1) {
            throw new IllegalStateException("PictureLayout can host only one direct child");
        }

        super.addView(child);
    }

    @Override
    public void addView(View child, int index) {
        if (getChildCount() > 1) {
            throw new IllegalStateException("PictureLayout can host only one direct child");
        }

        super.addView(child, index);
    }

    @Override
    public void addView(View child, LayoutParams params) {
        if (getChildCount() > 1) {
            throw new IllegalStateException("PictureLayout can host only one direct child");
        }

        super.addView(child, params);
    }

    @Override
    public void addView(View child, int index, LayoutParams params) {
        if (getChildCount() > 1) {
            throw new IllegalStateException("PictureLayout can host only one direct child");
        }

        super.addView(child, index, params);
    }

    @Override
    protected LayoutParams generateDefaultLayoutParams() {
        return new LayoutParams(LayoutParams.MATCH_PARENT, LayoutParams.MATCH_PARENT);
    }

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

        int maxHeight = 0;
        int maxWidth = 0;

        for (int i = 0; i < count; i++) {
            final View child = getChildAt(i);
            if (child.getVisibility() != GONE) {
                measureChild(child, widthMeasureSpec, heightMeasureSpec);
            }
        }

        maxWidth += getPaddingLeft() + getPaddingRight();
        maxHeight += getPaddingTop() + getPaddingBottom();

        Drawable drawable = getBackground();
        if (drawable != null) {
            maxHeight = Math.max(maxHeight, drawable.getMinimumHeight());
            maxWidth = Math.max(maxWidth, drawable.getMinimumWidth());
        }

        setMeasuredDimension(resolveSize(maxWidth, widthMeasureSpec),
                resolveSize(maxHeight, heightMeasureSpec));
    }
    
    private void drawPict(Canvas canvas, int x, int y, int w, int h,
                          float sx, float sy) {
        canvas.save();
        canvas.translate(x, y);
        canvas.clipRect(0, 0, w, h);
        canvas.scale(0.5f, 0.5f);
        canvas.scale(sx, sy, w, h);
        canvas.drawPicture(mPicture);
        canvas.restore();
    }

    @Override
    protected void dispatchDraw(Canvas canvas) {
        super.dispatchDraw(mPicture.beginRecording(getWidth(), getHeight()));
        mPicture.endRecording();
        
        int x = getWidth()/2;
        int y = getHeight()/2;
        
        if (false) {
            canvas.drawPicture(mPicture);
        } else {
            drawPict(canvas, 0, 0, x, y,  1,  1);
            drawPict(canvas, x, 0, x, y, -1,  1);
            drawPict(canvas, 0, y, x, y,  1, -1);
            drawPict(canvas, x, y, x, y, -1, -1);
        }
    }

    @Override
    public ViewParent invalidateChildInParent(int[] location, Rect dirty) {
        location[0] = getLeft();
        location[1] = getTop();
        dirty.set(0, 0, getWidth(), getHeight());
        return getParent();
    }

    @Override
    protected void onLayout(boolean changed, int l, int t, int r, int b) {
        final int count = super.getChildCount();

        for (int i = 0; i < count; i++) {
            final View child = getChildAt(i);
            if (child.getVisibility() != GONE) {
                final int childLeft = getPaddingLeft();
                final int childTop = getPaddingTop();
                child.layout(childLeft, childTop,
                        childLeft + child.getMeasuredWidth(),
                        childTop + child.getMeasuredHeight());

            }
        }
    }
}