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POWhy does heap memory increase when re-launching an activity?
 

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  1. POWhy does heap memory increase when re-launching an activity?
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    <p>This question concerns memory in Android.</p> <p><strong>My method:</strong></p> <p>I have two activites, A and B. From A, I launch B like this:</p> <pre><code>Intent i = new Intent(A.this, B.class); startActivity(i); </code></pre> <p>On button click in B, I do this:</p> <pre><code>B.this.finish(); </code></pre> <ul> <li>In B, I override the onDestroy method and set all references to null. </li> <li>I do not allocate new memory in the onResume method of A. </li> <li>I am not leaking a context. </li> <li>I am not using multiple threads. </li> <li>I am not using services.</li> <li>All variables in B are private class variables, and all of them are set to null in the onDestroy of B. </li> <li>Also, ImageViews in B have their background set null in the onDestroy of B. </li> <li>I am certain that B gets destroyed.</li> </ul> <p><strong>The result:</strong></p> <p>When I am in Activity A, heap memory is at 7.44 MB. Then when I start B and call finish on B(and thus returning to A), heap is increased by 0.16 MB. Repeating this process again, heap is increased by 0.08 MB every time.</p> <ul> <li>I'm not looking at the heap limit, I'm looking at the allocated heap.</li> <li>I'm calling System.gc() at the end of the onDestroy method of B.</li> </ul> <p><strong>Additional info:</strong></p> <p>-I have used MAT to analyse memory allocations and try to find this leak. Something strange is that Activity B seems to have 5 instances. As it so happens, I was repeating the startActivity/finish process 5 times. The bottom entry is the Activity, the others are listeners in the activity:</p> <p><img src="https://i.stack.imgur.com/rQVzF.png" alt="enter image description here"></p> <p>And this is screenshot of the dominator tree. I can't find anything unusual or suspect.</p> <p><img src="https://i.stack.imgur.com/27eCf.png" alt="Dominator Tree"></p> <p>-I have watched both google IO videos on memory usage(and leaks).</p> <p><strong>Question:</strong></p> <p>Is it possible that this 0.08 MB of heap will always be allocated(and not collectable by the GC) no matter what I do? If not, any idea of what might be causing this?</p> <p><strong>Update:</strong></p> <ol> <li><p>I tried to launch activity B without setting a content view in B. This means that B is a completely empty activity. The result was that the heap memory did NOT increase when I'm relaunching the activity several times. Note, however, that this is no solution. I must be able to set a content view.</p></li> <li><p>scorpiodawg: I tried running my app on an emulator, and the heap still grows. Good try though.</p></li> <li><p>ntc: I changed all occurences of "this" to "getApplicationContext()" where it was possible. I could not call setContentView(getApplicationContext()); because setContentView wants a reference to a layout file, not a context. What I did instead was to create an empty layout file and call setContentView(emptylayout); in the onDestroy method of Activity B. That did not help.</p></li> <li><p>I tried to remove all the code so that only setContentView(mylayout) gets called. Problem persisted. Then I removed all the gui elements in the layout XML file. Problem persisted. The only thing that was left was the container views, a couple of nested linear, relative and scrolllayouts. I tried to remove setting the "android:scrollbarDefaultDelayBeforeFade" attribute in the scrollbar. The result was great, the memory leak had vanished. Then I put back all the code I previously removed but didn't set the "android:scrollbarDefaultDelayBeforeFade" attribute and the memory leak was back. How strange is that?</p></li> </ol>
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    1. COBut if you repeat the process again and again, will you get OutOfMemory exception?
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    2. COYes, eventually I would.
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    3. COHow have you defined and set your listeners? and what kind of listeners are they?
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