Android更新UI的两种方法（一）
在Android开发中，通常将联网、i/o、复杂的算法、查询数据库（大量数据）等耗时操作放在子线程中进行，这样可以避免ANR常（application not responing）。在子线程的操作过程中常常需要更新UI，而更新UI操作主要有两种方法。一种是直接在子线程中覆盖runOnUiThread()方法，另一种则是使用Android的消息机制。
本文先介绍第一种方法：
界面如图所示：
public class MainActivity extends AppCompatActivity implements View.OnClickListener {
private Button button;
private TextView textView;
@Override
protected void onCreate(@Nullable Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
button = (Button) findViewById(R.id.bt_button);
textView = (TextView) findViewById(R.id.tv_message);
button.setOnClickListener(this);
}
@Override
public void onClick(View v) {
switch (v.getId()) {
case R.id.bt_button:
new workThread().start();
break;
default:
break;
}
}
private class workThread extends Thread{
//servlet地址
final String serverPath="http://xxx.xxx.xxx.xxx:8080/ServletTest/MainMessage";
@Override
public void run() {
super.run();
try {
URL url=new URL(serverPath);
HttpURLConnection httpURLConnection=(HttpURLConnection) url.openConnection();
httpURLConnection.setConnectTimeout(5000);
httpURLConnection.setRequestMethod("GET");
httpURLConnection.setRequestProperty("contentType","utf-8");
final int responseCode=httpURLConnection.getResponseCode();
if (responseCode==200){//200==OK
InputStream inputStream=httpURLConnection.getInputStream();
BufferedReader bufferedReader=new BufferedReader(new InputStreamReader(inputStream,"GB2312"));//设置编码格式
final String responseMsg=bufferedReader.readLine();
runOnUiThread(new Runnable() {//使用runOnUIThread()方法更新主线程
@Override
public void run() {
textView.setText(responseMsg);
}
});
bufferedReader.close();
httpURLConnection.disconnect();
}else {
Toast.makeText(MainActivity.this,"responseCode="+responseCode,Toast.LENGTH_SHORT).show();
}
} catch (Exception e) {
e.printStackTrace();
}
}
}
}