安卓线程使用例子

   我也是刚刚接触程序开发，一个菜鸟。前面和几个同学准备做一个移动教务系统，网上看了很多资料都说了对运行一些费时。如数据库、网络的链接操作，需要新开一个thread对其进行处理。但是后面在对程序进行调试的过程中，刚开始的时候报了空指针错误。根据错误提示，进行修改。说实话，经过那个过程发现自己真的还很菜，排错的经验太少了。直到过了好久才想到报了空指针错误，是因为在线程里生成的对象，因为有时间延迟，对于线程后面的对象来说是空的，所以才导致了空指针错误。后面参考的解决方法是利用join()函数。当然也可用其他方法。

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   下面写的代码：

public class MyThread extends Thread {
    private InputStream is = null;
    private String url;
    private String method;
    private List params;
    public MyThread(String url, String method, List params) {
        this.method = method;
        this.url = url;
        this.params = params;
    }
    public void run() {
        try {
            // check for request method
            if (method.equals("POST")) {
                // request method is POST
                // defaultHttpClient
                BasicHttpParams httpParameters = new BasicHttpParams();
                // Set the default socket timeout (SO_TIMEOUT)
                HttpConnectionParams
                        .setConnectionTimeout(httpParameters, 30000);
                // in milliseconds which is the timeout for waiting for
                // data.
                HttpConnectionParams.setSoTimeout(httpParameters, 30000);
                DefaultHttpClient httpClient = new DefaultHttpClient();
                HttpPost httpPost = new HttpPost(url);
                httpPost.setEntity(new UrlEncodedFormEntity(params, HTTP.UTF_8));
                HttpResponse httpResponse = httpClient.execute(httpPost);
                HttpEntity httpEntity = httpResponse.getEntity();
                setIs(httpEntity.getContent());
            } else if (method.equals("GET")) {
                BasicHttpParams httpParameters = new BasicHttpParams();
                // Set the default socket timeout (SO_TIMEOUT)
                HttpConnectionParams
                        .setConnectionTimeout(httpParameters, 30000);
                // in milliseconds which is the timeout for waiting for
                // data.
                HttpConnectionParams.setSoTimeout(httpParameters, 30000);
                // request method is GET
                DefaultHttpClient httpClient = new DefaultHttpClient();
                String paramString = URLEncodedUtils.format(params, "utf-8");
                String temp_url = url + "?" + paramString;
                HttpGet httpGet = new HttpGet(temp_url);
                HttpResponse httpResponse = httpClient.execute(httpGet);
                HttpEntity httpEntity = httpResponse.getEntity();
                setIs(httpEntity.getContent());
            }
        } catch (UnsupportedEncodingException e) {
            e.printStackTrace();
        } catch (ClientProtocolException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
    public InputStream getIs() {
        return is;
    }
    public void setIs(InputStream is) {
        this.is = is;
    }
}

通过下面的语句对以上生成的对象（“setIs(httpEntity.getContent());“）进行调用

MyThread myThread = new MyThread(url, method, params);
myThread.start();
myThread.join();//同做join()函数对myThread进行处理，使其一般的对象那样使用即可
is = myThread.getIs();//获得is对象