安卓下 按钮监听重复开启线程

public void onClick(View arg0) {
if(isRun)handler.removeCallbacks(thread);
else{
thread = new Thread(new Runnable() {

@Override
public void run() {

String json = UrlHtmlUtil.getHtmlJsonByUrl(uri);

Message m = handler.obtainMessage();
Bundle bundle = new Bundle();
bundle.putString("jsondata", json);
m.setData(bundle);
m.what = 0x11;
handler.sendMessage(m);

}

});
cityName = et.getText().toString();
thread.start();
//bt.setEnabled(false);
}

<span style="font-size:24px;">定义一个Boolean变量isRun来判断线程是否已经开启。如开启则抛出线程。</span>