메모리 누수 방지 Handler 사용법

Handler는 잘 사용하지 않는데, Handler를 이용한 코딩이 필요하여 다시 Handler 개념 살펴보면서 적어둔다.

public class HandlerActivity extends AppCompatActivity {     Handler mainThreadHandler;     @Override     protected void onCreate(Bundle savedInstanceState) {         super.onCreate(savedInstanceState);         setContentView(R.layout.activity_thread);         mainThreadHandler = new Handler(){             @Override             public void handleMessage(Message msg) {                 super.handleMessage(msg);                 if(msg.what == 1){                 }             }         };     } }

public class HandlerActivity extends AppCompatActivity {     CHandler mainThreadHandler;     @Override     protected void onCreate(Bundle savedInstanceState) {         super.onCreate(savedInstanceState);         setContentView(R.layout.activity_thread);         mainThreadHandler = new Handler();     }     private class CHandler extends Handler {         @Override         public void handleMessage(Message msg) {             super.handleMessage(msg);             if(msg.what == 1){                 //handle message             }         }     } }

보통의 경우 위와 같이 Handler 클래스를 생성하는 방법으로 사용한다. 하지만 이런 방식의 경우 "The handler class should be static or leak might occur." 라는 메모리 누수 경고 문구가 발생할 수 있다.

Activity가 종료되더라도 Garbage collect 가 실행되지 않게 되고 결국 Message가 Message Queue에 상당 시간동안 남아있게 되어 Memory Leak 의 원인이 된다.

이를 해결할 방법은 static inner class 로 Handler를 정의해주고 WeakReference 를 이용하여 Activity 메소드를 호출하는 코드를 구현한다.

import android.os.Bundle; import android.os.Handler; import android.os.Message; import android.support.v7.app.AppCompatActivity; import android.view.View; import android.widget.Button; import android.widget.TextView; import java.lang.ref.WeakReference; public class HandlerActivity extends AppCompatActivity {     Button handlerStartButton;     Button handlerStopButton;     Handler mainThreadHandler;     static TextView handlerExampleTextView;     static int workValue = 0;     boolean running = true;     @Override     protected void onCreate(Bundle savedInstanceState) {         super.onCreate(savedInstanceState);         setContentView(R.layout.activity_handler);         handlerStartButton = findViewById(R.id.btn_start);         handlerStopButton = findViewById(R.id.btn_stop);         handlerExampleTextView = findViewById(R.id.tv);         mainThreadHandler = new MyHandler(this);         handlerStartButton.setOnClickListener(new View.OnClickListener() {             @Override             public void onClick(View v) {                 running = true;                 startCount();             }         });         handlerStopButton.setOnClickListener(new View.OnClickListener() {             @Override             public void onClick(View v) {                 running = false;                 workValue = 0;             }         });     }     private void startCount(){         // Start a child thread when button is clicked.         WorkerThread thread = new WorkerThread();         thread.start();     }     private static class MyHandler extends Handler{         private final WeakReference<HandlerActivity> mActivity;         private MyHandler(HandlerActivity activity) {             mActivity = new WeakReference<HandlerActivity>(activity);         }         @Override         public void handleMessage(Message msg) {             HandlerActivity activity = mActivity.get();             if(activity != null){                 if(msg.what == 1){                     handlerExampleTextView.setText("BackValue:" + workValue);                 }             }         }     }     private class WorkerThread extends Thread{         @Override         public void run() {             super.run();             while(running){                 workValue++;  // 작업스레드 값 증가                 try {                     java.lang.Thread.sleep(1000); // 1000ms(1초)이므로 1초 단위로 실행                     System.out.println(java.lang.Thread.currentThread().getName());                 } catch (InterruptedException e) {                     e.printStackTrace();                 }                 // Create a message in child thread.                 Message childThreadMessage = new Message();                 childThreadMessage.what = 1;                 childThreadMessage.arg1 = workValue;                 // Put the message in main thread message queue.                 mainThreadHandler.sendMessage(childThreadMessage);             }         }     } }

<?xml version="1.0" encoding="utf-8"?> <LinearLayout     xmlns:android="http://schemas.android.com/apk/res/android"     xmlns:tools="http://schemas.android.com/tools"     android:layout_width="match_parent"     android:layout_height="match_parent"     android:orientation="vertical">     <LinearLayout         android:layout_width="wrap_content"         android:layout_height="wrap_content"         android:orientation="horizontal">         <Button             android:id="@+id/btn_start"             android:layout_width="match_parent"             android:layout_height="match_parent"             android:layout_gravity="center"             android:text="시작"/>         <Button             android:id="@+id/btn_stop"             android:layout_width="wrap_content"             android:layout_height="wrap_content"             android:layout_gravity="center"             android:text="중지"/>     </LinearLayout>     <TextView         android:id="@+id/tv"         android:layout_width="match_parent"         android:layout_height="wrap_content"         android:layout_marginTop="20dp"         android:layout_gravity="center"         android:gravity="center"         android:text="결과"         android:textSize="20dp"/> </LinearLayout>

참조 : https://blog.naver.com/zoomen1004/220053616676