Android - This Handler class should be static or leaks might occur.

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　　今天學習了使用 HTTP協議,從Android用戶端往Tomcat伺服器端以GET發送請求,途中無意中發現自己寫的Handler類被Android提示:This Handler class should be static or leaks might occur. 往google上type,發現很多網友都做瞭解釋,也感觸頗深,編譯器的提示,有時真的要留意,這對自己學習也有很大的協助.

　　雖然多了幾行代碼,但為了實用,我就上貼自己實際點的例子,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");}/**使用靜態內部類,解決‘This Handler class should be static or leaks might occur‘,以免造成記憶體泄露. * @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(), "發送成功", Toast.LENGTH_SHORT).show();break;case SendDataToServer.SEND_FAIL:Toast.makeText(iMainActivity.get(), "發送失敗", Toast.LENGTH_SHORT).show();break;default:throw new RuntimeException("未知的發送結果!");}}}/** * 處理髮送是否成功的狀態的Handler. */private final  Handler handler = new StatusHandler(this);/** * 初始化監聽器. */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, "使用者名稱和密碼不可為空", Toast.LENGTH_SHORT).show();return;}new SendDataToServer(handler).send(name, pwd);}});}}

 將Handler聲明為static,是為瞭解決可能出現‘記憶體泄露‘的問題,因為在一般情況下,通過Handler往訊息佇列中放入Message對象的時候,Message對象會持有對外部類的隱式引用,而是用static類,則不會對外部類有隱式引用.例如,Message對象引用主線程(UI)的視圖等資源,如果不及時被處理,則他引用的對象將被一直佔用,被引用的對象可能是很久以後才使用,這樣一來,記憶體將很快被耗盡.

 ref: http://www.jcodecraeer.com/a/anzhuokaifa/androidkaifa/2014/1106/1922.html

Android - This Handler class should be static or leaks might occur.