讀取圖片 最佳化android記憶體

public  class Main extends Activity { int number = 1000; Drawable[] array;  @Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.main);    array = new BitmapDrawable[number];      for(int i = 0; i <</SPAN> number; i++)   {   Log.e("", "測試第" + (i+1) + "張圖片");   array[i] = getResources().getDrawable(R.drawable.img);   } } }   輸出結果： 04-07 21:49:25.248: D/szipinf(7828): Initializing inflate state 04-07 21:49:25.398: E/(7828): 測試第1張圖片 04-07 21:49:25.658: D/dalvikvm(7828): GC_EXTERNAL_ALLOC freed 48K, 50% free 2692K/5379K, external 0K/0K, paused 24ms 04-07 21:49:25.748: E/(7828): 測試第2張圖片 04-07 21:49:25.748: E/(7828): 測試第3張圖片 ……………… ……………… 04-07 21:49:26.089: E/(7828): 測試第998張圖片 04-07 21:49:26.089: E/(7828): 測試第999張圖片 04-07 21:49:26.089: E/(7828): 測試第1000張圖片  程式沒有報錯，正常運行，載入1000個Drawable對象沒問題。  下面再來看一下載入1000個Bitmap對象的代碼，同樣的，代碼很簡單的，我就不解釋了！ public  class Main extends Activity { int number = 1000; Bitmap bitmap[];  @Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.main);  bitmap = new Bitmap[number];  for (int i = 0; i <</SPAN> number; i++) { Log.e("", "測試第" + (i+1) + "張圖片"); bitmap[i] = BitmapFactory.decodeResource(getResources(), R.drawable.img); } } }  輸出結果： 04-07 22:06:05.344: D/szipinf(7937): Initializing inflate state 04-07 22:06:05.374: E/(7937): 測試第1張圖片 04-07 22:06:05.544: D/dalvikvm(7937): GC_EXTERNAL_ALLOC freed 51K, 50% free 2692K/5379K, external 0K/0K, paused 40ms 04-07 22:06:05.664: E/(7937): 測試第2張圖片 04-07 22:06:05.774: D/dalvikvm(7937): GC_EXTERNAL_ALLOC freed 1K, 50% free 2691K/5379K, external 6026K/7525K, paused 31ms 04-07 22:06:05.834: E/(7937): 測試第3張圖片 04-07 22:06:05.934: D/dalvikvm(7937): GC_EXTERNAL_ALLOC freed <1K, 50% free 2691K/5379K, external 12052K/14100K, paused 24ms 04-07 22:06:06.004: E/(7937): 測試第4張圖片 04-07 22:06:06.124: D/dalvikvm(7937): GC_EXTERNAL_ALLOC freed <1K, 50% free 2691K/5379K, external 18078K/20126K, paused 27ms 04-07 22:06:06.204: E/(7937): 測試第5張圖片 04-07 22:06:06.315: D/dalvikvm(7937): GC_EXTERNAL_ALLOC freed <1K, 50% free 2691K/5379K, external 24104K/26152K, paused 26ms 04-07 22:06:06.395: E/(7937): 測試第6張圖片 04-07 22:06:06.495: D/dalvikvm(7937): GC_EXTERNAL_ALLOC freed <1K, 50% free 2691K/5379K, external 30130K/32178K, paused 22ms 04-07 22:06:06.565: E/(7937): 測試第7張圖片 04-07 22:06:06.665: D/dalvikvm(7937): GC_EXTERNAL_ALLOC freed <1K, 50% free 2691K/5379K, external 36156K/38204K, paused 22ms 04-07 22:06:06.745: E/(7937): 測試第8張圖片 04-07 22:06:06.845: D/dalvikvm(7937): GC_EXTERNAL_ALLOC freed 2K, 51% free 2689K/5379K, external 42182K/44230K, paused 23ms 04-07 22:06:06.845: E/dalvikvm-heap(7937): 6170724-byte external allocation too large for this process. 04-07 22:06:06.885: I/dalvikvm-heap(7937): Clamp target GC heap from 48.239MB to 48.000MB 04-07 22:06:06.885: E/GraphicsJNI(7937): VM won't let us allocate 6170724 bytes 04-07 22:06:06.885: D/dalvikvm(7937): GC_FOR_MALLOC freed <1K, 51% free 2689K/5379K, external 42182K/44230K, paused 25ms 04-07 22:06:06.885: D/AndroidRuntime(7937): Shutting down VM 04-07 22:06:06.885: W/dalvikvm(7937): threadid=1: thread exiting with uncaught exception (group=0x40015560) 04-07 22:06:06.885: E/AndroidRuntime(7937): FATAL EXCEPTION: main 04-07 22:06:06.885: E/AndroidRuntime(7937): java.lang.OutOfMemoryError: bitmap size exceeds VM budget 04-07 22:06:06.885: E/AndroidRuntime(7937): at android.graphics.Bitmap.nativeCreate(Native Method) 04-07 22:06:06.885: E/AndroidRuntime(7937): at android.graphics.Bitmap.createBitmap(Bitmap.java:477) 04-07 22:06:06.885: E/AndroidRuntime(7937): at android.graphics.Bitmap.createBitmap(Bitmap.java:444) 04-07 22:06:06.885: E/AndroidRuntime(7937): at android.graphics.Bitmap.createScaledBitmap(Bitmap.java:349) 04-07 22:06:06.885: E/AndroidRuntime(7937): at android.graphics.BitmapFactory.finishDecode(BitmapFactory.java:498) 04-07 22:06:06.885: E/AndroidRuntime(7937): at android.graphics.BitmapFactory.decodeStream(BitmapFactory.java:473) 04-07 22:06:06.885: E/AndroidRuntime(7937): at android.graphics.BitmapFactory.decodeResourceStream(BitmapFactory.java:336) 04-07 22:06:06.885: E/AndroidRuntime(7937): at android.graphics.BitmapFactory.decodeResource(BitmapFactory.java:359) 04-07 22:06:06.885: E/AndroidRuntime(7937): at android.graphics.BitmapFactory.decodeResource(BitmapFactory.java:385) 04-07 22:06:06.885: E/AndroidRuntime(7937): at bassy.test.drawable.Main.onCreate(Main.java:37) 04-07 22:06:06.885: E/AndroidRuntime(7937): at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1047) 04-07 22:06:06.885: E/AndroidRuntime(7937): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1722) 04-07 22:06:06.885: E/AndroidRuntime(7937): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:1784) 04-07 22:06:06.885: E/AndroidRuntime(7937): at android.app.ActivityThread.access$1500(ActivityThread.java:123) 04-07 22:06:06.885: E/AndroidRuntime(7937): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:939) 04-07 22:06:06.885: E/AndroidRuntime(7937): at android.os.Handler.dispatchMessage(Handler.java:99) 04-07 22:06:06.885: E/AndroidRuntime(7937): at android.os.Looper.loop(Looper.java:130) 04-07 22:06:06.885: E/AndroidRuntime(7937): at android.app.ActivityThread.main(ActivityThread.java:3835) 04-07 22:06:06.885: E/AndroidRuntime(7937): at java.lang.reflect.Method.invokeNative(Native Method) 04-07 22:06:06.885: E/AndroidRuntime(7937): at java.lang.reflect.Method.invoke(Method.java:507) 04-07 22:06:06.885: E/AndroidRuntime(7937): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:847) 04-07 22:06:06.885: E/AndroidRuntime(7937): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:605) 04-07 22:06:06.885: E/AndroidRuntime(7937): at dalvik.system.NativeStart.main(Native Method) 看看上面的輸出，才載入到第8張圖片，程式就報錯了“java.lang.OutOfMemoryError: bitmap size exceeds VM budget”。  通過上面的例子，可以看清楚地看出來，使用Drawable儲存圖片對象，佔用更小的記憶體空間。 而使用Biamtp對象，則會佔用很大記憶體空間，很容易就出現OOM了！  下面我們再來看一個例子，這個也是載入Bitmap對象。 只不過，之次不是使用BitmapFactory的decodeResource方法， 而是使用decodeStream方法，看代碼。 public class Main extends Activity { int number = 1000; Bitmap bitmap[];  @Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.main);  bitmap = new Bitmap[number];  for (int i = 0; i <</SPAN> number; i++) { Log.e("", "測試第" + (i+1) + "張圖片"); bitmap[i] = BitmapFactory.decodeStream(getResources().openRawResource(R.drawable.img));//這裡換了方法 } } } 輸出結果： 04-07 22:16:12.676: E/(8091): 測試第561張圖片 04-07 22:16:12.756: E/(8091): 測試第562張圖片 04-07 22:16:12.826: E/(8091): 測試第563張圖片 04-07 22:16:12.906: E/(8091): 測試第564張圖片 04-07 22:16:12.906: D/skia(8091): ---------- mmap failed for imageref_ashmem size=2744320 err=12 04-07 22:16:12.906: E/(8091): 測試第565張圖片 04-07 22:16:12.906: D/skia(8091): ---------- mmap failed for imageref_ashmem size=2744320 err=12 04-07 22:16:12.906: E/(8091): 測試第566張圖片 04-07 22:16:12.916: E/filemap(8091): mmap(0,416798) failed: Out of memory 04-07 22:16:12.916: D/filemap(8091): munmap(0x0, 0) failed 04-07 22:16:12.916: W/asset(8091): create map from entry failed 04-07 22:16:12.916: D/AndroidRuntime(8091): Shutting down VM 04-07 22:16:12.916: W/dalvikvm(8091): threadid=1: thread exiting with uncaught exception (group=0x40015560) 04-07 22:16:12.936: E/AndroidRuntime(8091): FATAL EXCEPTION: main 04-07 22:16:12.936: E/AndroidRuntime(8091): java.lang.RuntimeException: Unable to start activity ComponentInfo{bassy.test.drawable/bassy.test.drawable.Main}: android.content.res.Resources$NotFoundException: File res/drawable-mdpi/img.png from drawable resource ID #0x7f020001 04-07 22:16:12.936: E/AndroidRuntime(8091): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1768) 04-07 22:16:12.936: E/AndroidRuntime(8091): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:1784) 04-07 22:16:12.936: E/AndroidRuntime(8091): at android.app.ActivityThread.access$1500(ActivityThread.java:123) 04-07 22:16:12.936: E/AndroidRuntime(8091): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:939) 04-07 22:16:12.936: E/AndroidRuntime(8091): at android.os.Handler.dispatchMessage(Handler.java:99) 04-07 22:16:12.936: E/AndroidRuntime(8091): at android.os.Looper.loop(Looper.java:130) 04-07 22:16:12.936: E/AndroidRuntime(8091): at android.app.ActivityThread.main(ActivityThread.java:3835) 04-07 22:16:12.936: E/AndroidRuntime(8091): at java.lang.reflect.Method.invokeNative(Native Method) 04-07 22:16:12.936: E/AndroidRuntime(8091): at java.lang.reflect.Method.invoke(Method.java:507) 04-07 22:16:12.936: E/AndroidRuntime(8091): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:847) 04-07 22:16:12.936: E/AndroidRuntime(8091): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:605) 04-07 22:16:12.936: E/AndroidRuntime(8091): at dalvik.system.NativeStart.main(Native Method) 04-07 22:16:12.936: E/AndroidRuntime(8091): Caused by: android.content.res.Resources$NotFoundException: File res/drawable-mdpi/img.png from drawable resource ID #0x7f020001 04-07 22:16:12.936: E/AndroidRuntime(8091): at android.content.res.Resources.openRawResource(Resources.java:860) 04-07 22:16:12.936: E/AndroidRuntime(8091): at android.content.res.Resources.openRawResource(Resources.java:836) 04-07 22:16:12.936: E/AndroidRuntime(8091): at bassy.test.drawable.Main.onCreate(Main.java:43) 04-07 22:16:12.936: E/AndroidRuntime(8091): at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1047) 04-07 22:16:12.936: E/AndroidRuntime(8091): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1722) 04-07 22:16:12.936: E/AndroidRuntime(8091): ... 11 more 04-07 22:16:12.936: E/AndroidRuntime(8091): Caused by: java.io.FileNotFoundException: res/drawable-mdpi/img.png 04-07 22:16:12.936: E/AndroidRuntime(8091): at android.content.res.AssetManager.openNonAssetNative(Native Method) 04-07 22:16:12.936: E/AndroidRuntime(8091): at android.content.res.AssetManager.openNonAsset(AssetManager.java:429) 04-07 22:16:12.936: E/AndroidRuntime(8091): at android.content.res.Resources.openRawResource(Resources.java:857) 04-07 22:16:12.936: E/AndroidRuntime(8091): ... 15 more  從上面可以看出，程式在載入到第566張的時候，就出現了OOM錯誤。 不過，跟第2個例子比起來，你會發現，程式可以載入更多的圖片。 這說明了使用BitmapFactory的decodeResource方法會佔據大量記憶體， 而使用使用decodeStream方法，則佔據更小的記憶體。  從時間上來說，看看日誌輸出，大概估算了一下載入一張圖片所需要的時間，發現， decodeResource載入圖片需要約0.17秒的時間， 而使用decodeStream方法，只需要約0.08秒的時間！ 這說明了，decodeStream無論是時間上還是空間上，都比decodeResource方法更優秀！！   從上面三個例子，可以看出，用第一種方法（即用Drawable載入圖片）可以載入更加的圖片，載入32張圖片的時間約為0.01秒！ 我試著把Drawable的數量調至1000000，程式在運行時，停在了153761張圖片裡，手機提示，“應用程式無響應…” 個人猜測，Drawable應該不屬於常駐記憶體的對象，不然的話，不可能不會出現OOM的～～  網上關於Drawable與Bitmap的資料太少，不能深入學習，真是遺憾～   剛才又做了個測試，把第一個例子中的 array[i] = getResources().getDrawable(R.drawable.img); 方法換成了 array[i] = Drawable.createFromStream(getResources().openRawResource(R.drawable.img), null); 結果和第三個例子一樣，在第566張圖片中，出現了OOM錯誤！