Android查找dalvikvm疯狂调用GC原因

将原生书demo做完后，合入到移动学习中。发现翻页时疯狂调用GC，GC代码如下：

11-17 00:56:35.659 4674-4674/com.handsome.hxm D/dalvikvm: GC_FOR_ALLOC freed 8097K, 23% free 68244K/87592K, paused 62ms, total 62ms
11-17 00:56:35.719 4674-4674/com.handsome.hxm D/dalvikvm: GC_FOR_ALLOC freed 8049K, 23% free 68298K/87592K, paused 49ms, total 49ms
11-17 00:56:35.779 4674-4674/com.handsome.hxm D/dalvikvm: GC_FOR_ALLOC freed 8164K, 23% free 68302K/87592K, paused 47ms, total 47ms
11-17 00:56:35.839 4674-4674/com.handsome.hxm D/dalvikvm: GC_FOR_ALLOC freed 8055K, 22% free 68350K/87592K, paused 48ms, total 48ms
11-17 00:56:35.909 4674-4674/com.handsome.hxm D/dalvikvm: GC_FOR_ALLOC freed 8101K, 22% free 68354K/87592K, paused 53ms, total 53ms
11-17 00:56:35.969 4674-4674/com.handsome.hxm D/dalvikvm: GC_FOR_ALLOC freed 8149K, 23% free 68311K/87592K, paused 49ms, total 49ms
11-17 00:56:36.029 4674-4674/com.handsome.hxm D/dalvikvm: GC_FOR_ALLOC freed 8140K, 22% free 68362K/87592K, paused 48ms, total 48ms
11-17 00:56:36.079 4674-4674/com.handsome.hxm D/dalvikvm: GC_FOR_ALLOC freed 8172K, 22% free 68366K/87592K, paused 47ms, total 47ms
11-17 00:56:36.139 4674-4674/com.handsome.hxm D/dalvikvm: GC_FOR_ALLOC freed 8200K, 23% free 68320K/87592K, paused 47ms, total 47ms
11-17 00:56:36.199 4674-4674/com.handsome.hxm D/dalvikvm: GC_FOR_ALLOC freed 8067K, 22% free 68323K/87592K, paused 47ms, total 47ms
11-17 00:56:36.259 4674-4674/com.handsome.hxm D/dalvikvm: GC_FOR_ALLOC freed 8186K, 22% free 68326K/87592K, paused 47ms, total 47ms
11-17 00:56:36.319 4674-4674/com.handsome.hxm D/dalvikvm: GC_FOR_ALLOC freed 8042K, 22% free 68380K/87592K, paused 50ms, total 50ms
11-17 00:56:36.379 4674-4674/com.handsome.hxm D/dalvikvm: GC_FOR_ALLOC freed 8171K, 22% free 68360K/87592K, paused 48ms, total 48ms
11-17 00:56:36.439 4674-4674/com.handsome.hxm D/dalvikvm: GC_FOR_ALLOC freed 8044K, 22% free 68364K/87592K, paused 49ms, total 49ms
11-17 00:56:36.509 4674-4674/com.handsome.hxm D/dalvikvm: GC_FOR_ALLOC freed 8129K, 22% free 68366K/87592K, paused 54ms, total 54ms
11-17 00:56:36.579 4674-4674/com.handsome.hxm D/dalvikvm: GC_FOR_ALLOC freed 8216K, 23% free 68245K/87592K, paused 55ms, total 55ms
11-17 00:56:36.639 4674-4674/com.handsome.hxm D/dalvikvm: GC_FOR_ALLOC freed 7919K, 22% free 68377K/87592K, paused 52ms, total 52ms
11-17 00:56:36.699 4674-4674/com.handsome.hxm D/dalvikvm: GC_FOR_ALLOC freed 8108K, 22% free 68379K/87592K, paused 48ms, total 48ms
11-17 00:56:36.759 4674-4674/com.handsome.hxm D/dalvikvm: GC_FOR_ALLOC freed 8181K, 22% free 68382K/87592K, paused 47ms, total 47ms

...........

一共调用了大概300次GC

找问题吧，以为是解析书时出现问题，便在adapter的getview()方法中，解析书的方法前后加上Log打印：

Log.i("","position " + position + "; 解析开始时间：" + new SimpleDateFormat("yyyy-MM-dd HH:mm:ss").format(new Date()));
positionPageNode = parser.parseTargetPageHtml(path, hpm.getHtmlPageNodeNumber());
Log.i("","position " + position + "; 解析结束时间：" + new SimpleDateFormat("yyyy-MM-dd HH:mm:ss").format(new Date()));		

实际运行过程中却发现，只打印结束时间，不打印开始时间，简直牛逼死了。查看日志发现GC确实是在这个函数中打印的。

贴出parseTargetHtml方法：

public PageNode parseTargetPageHtml(String fileName, int position) throws Exception {
		String szContent = openFile(fileName);

		parser = Parser.createParser(szContent, "UTF-8");

		// 1 load pageNodes
		NodeFilter filter = new HasAttributeFilter("class", "page ui-droppable");

		String[] fileNames = fileName.split("/");
		String htmlName = fileNames[fileNames.length-1];

		NodeList nodes;
		Node[] nodesList = null;
		if(!common.allNodeList.containsKey(htmlName)){
			Log.i("","allNodeList中不包含该key");
			nodes = parser.extractAllNodesThatMatch(filter);
			if(nodes != null){
				common.allNodeList.put(htmlName, nodes);
				nodesList = nodes.toNodeArray();
			}
		}else{
			Log.i("","allNodeList中包含该key,直接取出");
			nodes = common.allNodeList.get(htmlName);
			if(nodes != null)
				nodesList = nodes.toNodeArray();
		}


		if(nodesList != null && nodesList.length > position){
			Node pageNode1 = nodesList[position];

			PageNode page = new PageNode();
			common.threadList.clear();
			List elementNodes = new ArrayList();
			for (Node eleNode : pageNode1.getChildren().toNodeArray()) {
				elementNodes.addAll(loadTagNode(eleNode));
			}
			for (Thread thread : common.threadList) {
				thread.join();
			}
			page.setElementNodes(elementNodes);

			return page;
		}else{
			return null;
		}

	}

debug这个函数，发现是走到openFile()这个函数时，疯狂调用GC，进去一看，大开眼界：

private String openFile(String fileName) {
		try {
			BufferedReader bis = new BufferedReader(new InputStreamReader(new FileInputStream(new File(fileName)), "UTF-8"));
			String szContent = "";
			String szTemp;

			while ((szTemp = bis.readLine()) != null) {
				szContent += szTemp + "\n";
			}
			bis.close();
			return szContent;
		} catch (Exception e) {
			e.printStackTrace();
			return "";
		}
	}

while当中竟然用String+=.....

去找当事人，他说当时着急，随便这么一写。。。。。

换成StringBuilder和.append()就好了

String += 数据量大时真是害死人啊