目前开发android应用,主要问题在内存的使用上,需要熟悉andorid虚拟机Dalvik的内存特性。以下是Nexusone Android 2.2(非官方的CM衍生版)做的实验。
使用系统自带的高级配置功能,不确定官方版本是否有这个选项,似乎是没有。
安装系统后默认的是32M,网上有人说设置12M小的应用启动更快。先设置成最小的12M。
为了测试方便,写了个小应用,就是循环增加内存,测试堆是否可到达12M。
这是运行的报错:
01-13 15:59:05.758: ERROR/dalvikvm-heap(2383): Out of memory on a 1466-byte allocation.
01-13 15:59:05.868: INFO/dalvikvm-heap(2383): Clamp target GC heap from 13.922MB to 12.000MB
01-13 15:59:28.929: ERROR/dalvikvm-heap(200): Heap Massage needed (36000-byte external allocation too big)
另外,监控在保存的时候ddms的heap界面监控到达11M多时一下子没有数据了,因为整个应用因为堆内存溢出而推出了。看来是设置有效的。
测试的代码很简单:
01private List list = new ArrayList();
02
03 /** Called when the activity is first created. */
04@Override
05public voidonCreate(Bundle savedInstanceState) {
06 super.onCreate(savedInstanceState);
07 setContentView(R.layout.main);
08 Button button = (Button) findViewById(R.id.Button01);
09 button.setOnClickListener(newOnClickListener() {
10 @Override
11 public voidonClick(View v) {
12 for(;;) {
13 byte[] data = newbyte[1024];
14 list.add(data);
15 try{
16 Thread.sleep(10);
17 } catch(InterruptedException e) {
18 // TODO Auto-generated catch block
19 e.printStackTrace();
20 }
21 }
22 }
23 });
再调整为16M。如果不重启Nexusone,还是在12M溢出。如果重启,确实是在16M的时候溢出。
01-13 16:04:19.808: INFO/dalvikvm-heap(796): Clamp target GC heap from 16.680MB to 16.000MB
01-13 16:04:32.428: INFO/dalvikvm-heap(796): Clamp target GC heap from 17.911MB to 16.000MB
01-13 16:04:32.459: INFO/dalvikvm-heap(796): Forcing collection of SoftReferences for 1040-byte allocation
01-13 16:04:32.508: INFO/dalvikvm-heap(796): Clamp target GC heap from 17.911MB to 16.000MB
01-13 16:04:32.538: ERROR/dalvikvm-heap(796): Out of memory on a 1040-byte allocation.
01-13 16:04:32.588: INFO/dalvikvm-heap(796): Clamp target GC heap from 17.916MB to 16.000MB
01-13 16:04:32.618: INFO/dalvikvm-heap(796): Forcing collection of SoftReferences for 1466-byte allocation
01-13 16:04:32.668: INFO/dalvikvm-heap(796): Clamp target GC heap from 17.916MB to 16.000MB
01-13 16:04:32.688: ERROR/dalvikvm-heap(796): Out of memory on a 1466-byte allocation.
01-13 16:04:32.748: INFO/dalvikvm-heap(796): Clamp target GC heap from 17.921MB to 16.000MB
01-13 16:04:32.778: INFO/dalvikvm-heap(796): Forcing collection of SoftReferences for 1126-byte allocation
01-13 16:04:32.818: INFO/dalvikvm-heap(796): Clamp target GC heap from 17.921MB to 16.000MB
01-13 16:04:32.849: ERROR/dalvikvm-heap(796): Out of memory on a 1126-byte allocation.
再测试了下第三方工具vm heap tool,在android market可免费下载。需要root权限,另外,需要安装busybox。以下是它的配置界面:
设置到48M重启机器。adb shell登到系统上看到/system/build.prop文件中:
dalvik.vm.heapsize=48m
但是不生效,用上述程序测试,还是在16M堆内存处溢出。可见在我的Nexusone环境下不论是通过vm heap tool还是手工修改build.prop文件配置都无效。