1 /* 2 * Copyright (C) 2013 The Android Open Source Project 3 * 4 * Licensed under the Apache License, Version 2.0 (the "License"); 5 * you may not use this file except in compliance with the License. 6 * You may obtain a copy of the License at 7 * 8 * http://www.apache.org/licenses/LICENSE-2.0 9 * 10 * Unless required by applicable law or agreed to in writing, software 11 * distributed under the License is distributed on an "AS IS" BASIS, 12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 13 * See the License for the specific language governing permissions and 14 * limitations under the License. 15 */ 16 17 package com.example.android.bitmapallocation; 18 19 import android.app.Activity; 20 import android.graphics.Bitmap; 21 import android.graphics.BitmapFactory; 22 import android.os.Bundle; 23 import android.view.View; 24 import android.widget.CheckBox; 25 import android.widget.ImageView; 26 import android.widget.TextView; 27 28 /** 29 * This example shows how to speed up bitmap loading and reduce garbage collection 30 * by reusing existing bitmaps. 31 * 32 * Watch the associated video for this demo on the DevBytes channel of developer.android.com, 33 * or on YouTube at https://www.youtube.com/watch?v=rsQet4nBVi8. 34 */ 35 public class BitmapAllocation extends Activity { 36 37 // There are some assumptions in this demo app that don't carry over well to the real world: 38 // it assumes that all bitmaps are the same size and that loading all bitmaps as the activity 39 // starts is good enough. A real application would be take a more flexible and robust 40 // approach. But these assumptions are good enough for the purposes of this tutorial, 41 // which is about reusing existing bitmaps of the same size. 42 43 int mCurrentIndex = 0; 44 Bitmap mCurrentBitmap = null; 45 BitmapFactory.Options mBitmapOptions; 46 47 @Override 48 public void onCreate(Bundle savedInstanceState) { 49 super.onCreate(savedInstanceState); 50 setContentView(R.layout.activity_bitmap_allocation); 51 52 final int[] imageIDs = {R.drawable.a, R.drawable.b, R.drawable.c, R.drawable.d, 53 R.drawable.e, R.drawable.f}; 54 55 final CheckBox checkbox = (CheckBox) findViewById(R.id.checkbox); 56 final TextView durationTextview = (TextView) findViewById(R.id.loadDuration); 57 final ImageView imageview = (ImageView) findViewById(R.id.imageview); 58 59 // Create bitmap to be re-used, based on the size of one of the bitmaps 60 mBitmapOptions = new BitmapFactory.Options(); 61 mBitmapOptions.inJustDecodeBounds = true; 62 BitmapFactory.decodeResource(getResources(), R.drawable.a, mBitmapOptions); 63 mCurrentBitmap = Bitmap.createBitmap(mBitmapOptions.outWidth, 64 mBitmapOptions.outHeight, Bitmap.Config.ARGB_8888); 65 mBitmapOptions.inJustDecodeBounds = false; 66 mBitmapOptions.inBitmap = mCurrentBitmap; 67 mBitmapOptions.inSampleSize = 1; 68 BitmapFactory.decodeResource(getResources(), R.drawable.a, mBitmapOptions); 69 imageview.setImageBitmap(mCurrentBitmap); 70 71 // When the user clicks on the image, load the next one in the list 72 imageview.setOnClickListener(new View.OnClickListener() { 73 74 @Override 75 public void onClick(View v) { 76 mCurrentIndex = (mCurrentIndex + 1) % imageIDs.length; 77 BitmapFactory.Options bitmapOptions = null; 78 if (checkbox.isChecked()) { 79 // Re-use the bitmap by using BitmapOptions.inBitmap 80 bitmapOptions = mBitmapOptions; 81 bitmapOptions.inBitmap = mCurrentBitmap; 82 } 83 long startTime = System.currentTimeMillis(); 84 mCurrentBitmap = BitmapFactory.decodeResource(getResources(), 85 imageIDs[mCurrentIndex], bitmapOptions); 86 imageview.setImageBitmap(mCurrentBitmap); 87 88 // One way you can see the difference between reusing and not is through the 89 // timing reported here. But you can also see a huge impact in the garbage 90 // collector if you look at logcat with and without reuse. Avoiding garbage 91 // collection when possible, especially for large items like bitmaps, 92 // is always a good idea. 93 durationTextview.setText("Load took " + 94 (System.currentTimeMillis() - startTime)); 95 } 96 }); 97 } 98 99 } 100
