Drawable與Bitmap佔用記憶體大小與比較decodeResource與decodeStream方法的效率

阿新 • • 發佈：2019-01-01

今天做了個記憶體優化的小測試，包括兩點
1，比較Drawable與Bitmap佔用記憶體大小
2，比較BitmapFactory類的decodeResource方法與decodeStream方法的效率

好吧，先來看第1個測試！
以下這個是測試載入1000個Drawable物件的程式碼，很簡單的，我就不解釋了！

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 < 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，正常執行，載入1000個Drawable物件沒問題。

下面再來看一下載入1000個Bitmap物件的程式碼，同樣的，程式碼很簡單的，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 < 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儲存圖片物件，佔用更小的記憶體空間。
而使用Biamtp物件，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物件。
只不過，之次不是使用BitmapFactory的decodeResource方法，
而是使用decodeStream方法，看程式碼。
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 < 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，程式在執行時，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物件，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！
而且，載入的時間都是一樣～～

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