When the system begins killing processes in the LRU cache, it primarily works bottom-up. The system also considers which processes consume more memory and thus provide the system more memory gain if killed. The less memory you consume while in the LRU list overall, the better your chances are to remain in the list and be able to quickly resume.
Here is a example code to implement the ComponentCallbacks2 interface and override onTrimMemory() callback method.
package com.blogspot.android_er.androidontrimmemory;
import android.content.ComponentCallbacks2;
import android.os.Bundle;
import android.support.v7.app.AppCompatActivity;
import android.util.Log;
/*
http://android-er.blogspot.com/
Example to use onTrimMemory()
*/
public class MainActivity extends AppCompatActivity
implements ComponentCallbacks2 {
private static final String TAG = "MyActivity";
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
Log.v(TAG, "onCreate() called");
}
public void onTrimMemory(int level){
Log.v(TAG, "onTrimMemory(" + level + ")");
switch(level){
case ComponentCallbacks2.TRIM_MEMORY_UI_HIDDEN:
Log.v(TAG, "TRIM_MEMORY_UI_HIDDEN");
break;
case ComponentCallbacks2.TRIM_MEMORY_RUNNING_MODERATE:
Log.v(TAG, "TRIM_MEMORY_RUNNING_MODERATE");
break;
case ComponentCallbacks2.TRIM_MEMORY_RUNNING_LOW:
Log.v(TAG, "TRIM_MEMORY_RUNNING_LOW");
break;
case ComponentCallbacks2.TRIM_MEMORY_RUNNING_CRITICAL:
Log.v(TAG, "TRIM_MEMORY_RUNNING_CRITICA");
break;
case ComponentCallbacks2.TRIM_MEMORY_BACKGROUND:
Log.v(TAG, "TRIM_MEMORY_BACKGROUND");
break;
case ComponentCallbacks2.TRIM_MEMORY_MODERATE:
Log.v(TAG, "TRIM_MEMORY_MODERATE");
break;
case ComponentCallbacks2.TRIM_MEMORY_COMPLETE:
Log.v(TAG, "TRIM_MEMORY_COMPLETE");
break;
default:
Log.v(TAG, "default");
}
}
}
To simulate the memory low condition, you can use the adb command:
adb shell am send-trim-memory
Example for my case, it's:
adb shell am send-trim-memory com.blogspot.android_er.androidontrimmemory MODERATE
Notice that you cannot set background level if your app is in foreground. Otherwise the following exception will be thrown, as shown in the video.
java.lang.IllegalArgumentException: Unable to set a background trim level on a foreground process
reference:
Overview of memory management
Manage your app's memory
