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POLarge memory chunk not garbage collected
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copied!<p>In a hunt for a memory-leak in my app I chased down a behaviour I can't understand. I allocate a large memory block, but it doesn't get garbage-collected resulting in a OOM, unless I explicit null the reference in onDestroy.</p> <p>In this example I have two almost identical activities that switch between each others. Both have a single button. On pressing the button MainActivity starts OOMActivity and OOMActivity returns by calling finish(). After pressing the buttons a few times, Android throws a OOMException.</p> <p>If i add the the onDestroy to OOMActivity and explicit null the reference to the memory chunk, I can see in the log that the memory is correctly freed. </p> <p>Why doesn't the memory get freed automatically without the nulling?</p> <p>MainActivity:</p> <pre><code>package com.example.oom; import android.app.Activity; import android.content.Intent; import android.os.Bundle; import android.view.View; import android.view.View.OnClickListener; import android.widget.Button; public class MainActivity extends Activity implements OnClickListener { private int buttonId; @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); System.gc(); Button OOMButton = new Button(this); OOMButton.setText("OOM"); buttonId = OOMButton.getId(); setContentView(OOMButton); OOMButton.setOnClickListener(this); } @Override public void onClick(View v) { if (v.getId() == buttonId) { Intent leakIntent = new Intent(this, OOMActivity.class); startActivity(leakIntent); } } } </code></pre> <p>OOMActivity:</p> <pre><code>public class OOMActivity extends Activity implements OnClickListener { private static final int WASTE_SIZE = 20000000; private byte[] waste; private int buttonId; protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); Button BackButton = new Button(this); BackButton.setText("Back"); buttonId = BackButton.getId(); setContentView(BackButton); BackButton.setOnClickListener(this); waste = new byte[WASTE_SIZE]; } public void onClick(View view) { if (view.getId() == buttonId) { finish(); } } } </code></pre>

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