Android - This Handler class should be static or leaks might occur.
今天学习了使用 HTTP协议,从Android客户端往Tomcat服务器端以GET发送请求,途中无意中发现自己写的Handler类被Android提示:This Handler class should be static or leaks might occur. 往google上type,发现很多网友都做了解释,也感触颇深,编译器的提示,有时真的要留意,这对自己学习也有很大的帮助.
虽然多了几行代码,但为了实用,我就上贴自己实际点的例子,Activity:
package spt.http.get.activity;
import java.lang.ref.WeakReference;
import spt.http.get.assist.SendDataToServer;
import android.app.Activity;
import android.os.Bundle;
import android.os.Handler;
import android.os.Message;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.Toast;
public class MainActivity extends Activity {
//view.
private EditText edt_name = null;
private EditText edt_pwd = null;
private Button btn_ok = null;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
initView();
initListener();
}
/**
* 初始化View.
*/
private void initView() {
edt_name = (EditText)findViewById(R.id.edt_name);
edt_pwd = (EditText)findViewById(R.id.edt_pwd);
btn_ok = (Button)findViewById(R.id.btn_ok);
//test:
edt_name.setText("你好");
edt_pwd.setText("abc");
}
/**使用静态内部类,解决'This Handler class should be static or leaks might occur',以免造成内存泄露.
* @author Administrator
*
*/
private static class StatusHandler extends Handler {
WeakReference<MainActivity> iMainActivity = null;
public StatusHandler(MainActivity mainActivity) {
iMainActivity = new WeakReference<MainActivity>(mainActivity);
}
@Override
public void handleMessage(Message msg) {
switch (msg.what) {
case SendDataToServer.SEND_SUCCESS:
//有iMainActivity.get()和iMainActivity.getClass().
Toast.makeText(iMainActivity.get(), "发送成功", Toast.LENGTH_SHORT).show();
break;
case SendDataToServer.SEND_FAIL:
Toast.makeText(iMainActivity.get(), "发送失败", Toast.LENGTH_SHORT).show();
break;
default:
throw new RuntimeException("未知的发送结果!");
}
}
}
/**
* 处理发送是否成功的状态的Handler.
*/
private final Handler handler = new StatusHandler(this);
/**
* 初始化监听器.
*/
private void initListener() {
btn_ok.setOnClickListener(new Button.OnClickListener() {
@Override
public void onClick(View v) {
String name = edt_name.getText().toString();
String pwd = edt_pwd.getText().toString();
if(name.isEmpty() || pwd.isEmpty()) {
Toast.makeText(MainActivity.this, "用户名和密码不能为空", Toast.LENGTH_SHORT).show();
return;
}
new SendDataToServer(handler).send(name, pwd);
}
});
}
}
将Handler声明为static,是为了解决可能出现'内存泄露'的问题,因为在一般情况下,通过Handler往消息队列中放入Message对象的时候,Message对象会持有对外部类的隐式引用,而是用static类,则不会对外部类有隐式引用.例如,Message对象引用主线程(UI)的视图等资源,如果不及时被处理,则他引用的对象将被一直占用,被引用的对象可能是很久以后才使用,这样一来,内存将很快被耗尽.
ref: http://www.jcodecraeer.com/a/anzhuokaifa/androidkaifa/2014/1106/1922.html