Android example source code file (AlphaBitmap.java)

This example Android source code file (AlphaBitmap.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

alpha, alphabitmap, android, bitmap, canvas, content, graphicsactivity, inputstream, io, lineargradient, os, override, paint, sampleview, shader, ui, view

The AlphaBitmap.java Android example source code

/*
 * Copyright (C) 2007 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 com.example.android.apis.R;

import android.app.Activity;
import android.content.Context;
import android.graphics.*;
import android.os.Bundle;
import android.view.KeyEvent;
import android.view.*;

import java.io.InputStream;
import java.io.ByteArrayOutputStream;

public class AlphaBitmap extends GraphicsActivity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(new SampleView(this));
    }
    
    private static class SampleView extends View {
        private Bitmap mBitmap;
        private Bitmap mBitmap2;
        private Bitmap mBitmap3;
        private Shader mShader;
        
        private static void drawIntoBitmap(Bitmap bm) {
            float x = bm.getWidth();
            float y = bm.getHeight();
            Canvas c = new Canvas(bm);
            Paint p = new Paint();
            p.setAntiAlias(true);
            
            p.setAlpha(0x80);
            c.drawCircle(x/2, y/2, x/2, p);
            
            p.setAlpha(0x30);
            p.setXfermode(new PorterDuffXfermode(PorterDuff.Mode.SRC));
            p.setTextSize(60);
            p.setTextAlign(Paint.Align.CENTER);
            Paint.FontMetrics fm = p.getFontMetrics();
            c.drawText("Alpha", x/2, (y-fm.ascent)/2, p);
        }
        
        public SampleView(Context context) {
            super(context);
            setFocusable(true);
            
            InputStream is = context.getResources().openRawResource(R.drawable.app_sample_code);
            mBitmap = BitmapFactory.decodeStream(is);
            mBitmap2 = mBitmap.extractAlpha();
            mBitmap3 = Bitmap.createBitmap(200, 200, Bitmap.Config.ALPHA_8);
            drawIntoBitmap(mBitmap3);
            
            mShader = new LinearGradient(0, 0, 100, 70, new int[] {
                                         Color.RED, Color.GREEN, Color.BLUE },
                                         null, Shader.TileMode.MIRROR);
        }
        
        @Override protected void onDraw(Canvas canvas) {
            canvas.drawColor(Color.WHITE);

            Paint p = new Paint();
            float y = 10;
            
            p.setColor(Color.RED);
            canvas.drawBitmap(mBitmap, 10, y, p);
            y += mBitmap.getHeight() + 10;
            canvas.drawBitmap(mBitmap2, 10, y, p);
            y += mBitmap2.getHeight() + 10;
            p.setShader(mShader);
            canvas.drawBitmap(mBitmap3, 10, y, p);
        }
    }
}