Android - This Handler class should be static or leaks might occur.
16lz
2021-01-23
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;@Overrideprotected 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);}@Overridepublic 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() {@Overridepublic 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
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