Drawable
以下这个是测试加载1000个Drawable对象的代码：
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("", "测试第" + (i+1) + "张图片"); array[i] = getResources().getDrawable(R.drawable.img); } } }
输出结果：
04-07 21:49:25.248: D/szipinf(7828): Initializing inflate state 04-07 21:49:25.398: E/(7828): 测试第1张图片 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): 测试第2张图片 04-07 21:49:25.748: E/(7828): 测试第3张图片 ……………… ……………… 04-07 21:49:26.089: E/(7828): 测试第998张图片 04-07 21:49:26.089: E/(7828): 测试第999张图片 04-07 21:49:26.089: E/(7828): 测试第1000张图片
程序没有报错，正常运行，加载1000个Drawable对象没问题。
Bitmap
下面再来看一下加载1000个Bitmap对象的代码：
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("", "测试第" + (i+1) + "张图片"); bitmap[i] = BitmapFactory.decodeResource(getResources(), R.drawable.img); } } }
输出结果：
04-07 22:06:05.344: D/szipinf(7937): Initializing inflate state 04-07 22:06:05.374: E/(7937): 测试第1张图片 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): 测试第2张图片 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): 测试第3张图片 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): 测试第4张图片 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): 测试第5张图片 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): 测试第6张图片 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): 测试第7张图片 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): 测试第8张图片 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$MethodAndArgsCaller.run(ZygoteInit.java:847) 04-07 22:06:06.885: E/AndroidRuntime(7937): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:605) 04-07 22:06:06.885: E/AndroidRuntime(7937): at dalvik.system.NativeStart.main(Native Method)
看看上面的输出，才加载到第8张图片，程序就报错了“java.lang.OutOfMemoryError: bitmap size exceeds VM budget”。通过上面的例子，可以看清楚地看出来，使用Drawable保存图片对象，占用更小的内存空间。而使用Biamtp对象，则会占用很大内存空间，很容易就出现OOM了！
下面我们再来看一个例子，这个也是加载Bitmap对象。只不过，之次不是使用BitmapFactory的decodeResource方法，而是使用decodeStream方法，看代码。
public class Main extends Activity { int number = 1000; Bitmap bitmap[]; @Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.main); bitmap = new Bitmap[number]; for (int i = 0; i < number; i++) { Log.e("", "测试第" + (i+1) + "张图片"); bitmap[i] =BitmapFactory.decodeStream(getResources().openRawResource(R.drawable.img));//这里换了方法 } } }
输出结果：
04-07 22:16:12.676: E/(8091): 测试第561张图片 04-07 22:16:12.756: E/(8091): 测试第562张图片 04-07 22:16:12.826: E/(8091): 测试第563张图片 04-07 22:16:12.906: E/(8091): 测试第564张图片 04-07 22:16:12.906: D/skia(8091): ---------- mmap failed for imageref_ashmem size=2744320 err=12 04-07 22:16:12.906: E/(8091): 测试第565张图片 04-07 22:16:12.906: D/skia(8091): ---------- mmap failed for imageref_ashmem size=2744320 err=12 04-07 22:16:12.906: E/(8091): 测试第566张图片 04-07 22:16:12.916: E/filemap(8091): mmap(0,416798) failed: Out of memory 04-07 22:16:12.916: D/filemap(8091): munmap(0x0, 0) failed 04-07 22:16:12.916: W/asset(8091): create map from entry failed 04-07 22:16:12.916: D/AndroidRuntime(8091): Shutting down VM 04-07 22:16:12.916: W/dalvikvm(8091): threadid=1: thread exiting with uncaught exception (group=0x40015560) 04-07 22:16:12.936: E/AndroidRuntime(8091): FATAL EXCEPTION: main 04-07 22:16:12.936: E/AndroidRuntime(8091): java.lang.RuntimeException: Unable to start activity ComponentInfo{bassy.test.drawable/bassy.test.drawable.Main}: android.content.res.Resources$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
从上面可以看出，程序在加载到第566张的时候，就出现了OOM错误。不过，跟第2个例子比起来，你会发现，程序可以加载更多的图片。这说明了使用BitmapFactory的decodeResource方法会占据大量内存，而使用使用decodeStream方法，则占据更小的内存。
我是天王盖地虎的分割线
从上面三个例子，可以看出，用第一种方法（即用Drawable加载图片）可以加载更加的图片，加载32张图片的时间约为0.01秒！我试着把Drawable的数量调至1000000，程序在运行时，停在了153761张图片里，手机提示，“应用程序无响应…”
个人猜测，Drawable应该不属于常驻内存的对象，不然的话，不可能不会出现OOM的～～
刚才又做了个测试，把第一个例子中的
array[i] = getResources().getDrawable(R.drawable.img);
方法换成了
array[i] = Drawable.createFromStream(getResources().openRawResource(R.drawable.img), null);
结果和第三个例子一样，在第566张图片中，出现了OOM错误！而且，加载的时间都是一样～～
我是天王盖地虎的分割线
- Bitmap转Drawable
Bitmap bm=xxx; //xxx根据你的情况获取 BitmapDrawable bd=BitmapDrawable(bm);
Android开发网提示因为BtimapDrawable是Drawable的子类，最终直接使用bd对象即可。
- Drawable转Bitmap
转成Bitmap对象后，可以将Drawable对象通过Android的SK库存成一个字节输出流，最终还可以保存成为jpg和png的文件。
Drawable d=xxx; //xxx根据自己的情况获取drawable BitmapDrawable bd = (BitmapDrawable) d; Bitmap bm = bd.getBitmap();
最终bm就是我们需要的Bitmap对象了。
参考：http://blog.csdn.net/ygc973797893/article/details/7620352