在线程中联网
为什么出现ANR?答案是联网动作阻塞在了主线程，长时间没有返回，这样OPhone弹出ANR错误。这个错误提示我们，如果否个任务可能需要长时间的运行才能返回，则必须把这个任务放置到单独线程中运行，避免阻塞UI线程。Java语言内置了对线程的支持，可以使用Thread类创建一个新线程，然后在run()方法中读取网页的内容，获得页面内容后调用TextView.setText()更新界面。修改后的connect() 方法如下所示：
private void connect() {
new Thread() {
public void run() {
try {
HttpClient client = new DefaultHttpClient();
// params[0]代表连接的url
HttpGet get = new HttpGet(url.getText().toString());
HttpResponse response = client.execute(get);
HttpEntity entity = response.getEntity();
long length = entity.getContentLength();
InputStream is = entity.getContent();
String s = null;
if (is != null) {
ByteArrayOutputStream baos = new ByteArrayOutputStream();
byte[] buf = new byte[128];
int ch = -1;
int count = 0;
while ((ch = is.read(buf)) != -1) {
baos.write(buf, 0, ch);
count += ch;
}
s = new String(baos.toByteArray());
message.setText(s);
}
} catch (Exception e) {
e.printStackTrace();
}
}
}.start();
}
new Thread() {
public void run() {
try {
HttpClient client = new DefaultHttpClient();
// params[0]代表连接的url
HttpGet get = new HttpGet(url.getText().toString());
HttpResponse response = client.execute(get);
HttpEntity entity = response.getEntity();
long length = entity.getContentLength();
InputStream is = entity.getContent();
String s = null;
if (is != null) {
ByteArrayOutputStream baos = new ByteArrayOutputStream();
byte[] buf = new byte[128];
int ch = -1;
int count = 0;
while ((ch = is.read(buf)) != -1) {
baos.write(buf, 0, ch);
count += ch;
}
s = new String(baos.toByteArray());
message.setText(s);
}
} catch (Exception e) {
e.printStackTrace();
}
}
}.start();
}
重新运行NetworkActivity，点击“连接”按钮。程序并没有像预期的那种获得网页的内容，并显示到TextView上。查看log可以看到在connect的执行过程中抛出了异常。接下来分析问题的所在。
