Android example source code file (Regions.java)

This example Android source code file (Regions.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, app, content, difference, graphicsactivity, intersect, os, override, paint, rect, region, regioniterator, regions, sampleview, string, ui, union, view, xor

The Regions.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.app.Activity;
import android.content.Context;
import android.graphics.*;
import android.os.Bundle;
import android.view.View;

public class Regions extends GraphicsActivity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(new SampleView(this));
    }
    
    private static class SampleView extends View {
        private final Paint mPaint = new Paint();
        private final Rect  mRect1 = new Rect();
        private final Rect  mRect2 = new Rect();

        public SampleView(Context context) {
            super(context);
            setFocusable(true);
            
            mPaint.setAntiAlias(true);
            mPaint.setTextSize(16);
            mPaint.setTextAlign(Paint.Align.CENTER);
            
            mRect1.set(10, 10, 100, 80);
            mRect2.set(50, 50, 130, 110);
        }

        private void drawOriginalRects(Canvas canvas, int alpha) {
            mPaint.setStyle(Paint.Style.STROKE);
            mPaint.setColor(Color.RED);
            mPaint.setAlpha(alpha);
            drawCentered(canvas, mRect1, mPaint);
            mPaint.setColor(Color.BLUE);
            mPaint.setAlpha(alpha);
            drawCentered(canvas, mRect2, mPaint);
            
            // restore style
            mPaint.setStyle(Paint.Style.FILL);
        }
        
        private void drawRgn(Canvas canvas, int color, String str, Region.Op op) {
            if (str != null) {
                mPaint.setColor(Color.BLACK);
                canvas.drawText(str, 80, 24, mPaint);
            }
            
            Region rgn = new Region();
            rgn.set(mRect1);
            rgn.op(mRect2, op);
            
            mPaint.setColor(color);
            RegionIterator iter = new RegionIterator(rgn);
            Rect r = new Rect();
            
            canvas.translate(0, 30);
            mPaint.setColor(color);
            while (iter.next(r)) {
                canvas.drawRect(r, mPaint);
            }
            drawOriginalRects(canvas, 0x80);
        }
        
        private static void drawCentered(Canvas c, Rect r, Paint p) {
            float inset = p.getStrokeWidth() * 0.5f;
            if (inset == 0) {   // catch hairlines
                inset = 0.5f;
            }
            c.drawRect(r.left + inset, r.top + inset,
                       r.right - inset, r.bottom - inset, p);
        }
        
        @Override protected void onDraw(Canvas canvas) {
            canvas.drawColor(Color.GRAY);            

            canvas.save();
            canvas.translate(80, 5);
            drawOriginalRects(canvas, 0xFF);
            canvas.restore();
            
            mPaint.setStyle(Paint.Style.FILL);
            
            canvas.save();
            canvas.translate(0, 140);
            drawRgn(canvas, Color.RED, "Union", Region.Op.UNION);
            canvas.restore();
            
            canvas.save();
            canvas.translate(0, 280);
            drawRgn(canvas, Color.BLUE, "Xor", Region.Op.XOR);
            canvas.restore();
            
            canvas.save();
            canvas.translate(160, 140);
            drawRgn(canvas, Color.GREEN, "Difference", Region.Op.DIFFERENCE);
            canvas.restore();
            
            canvas.save();
            canvas.translate(160, 280);
            drawRgn(canvas, Color.WHITE, "Intersect", Region.Op.INTERSECT);
            canvas.restore();
        }
    }
}