參考:
Android 如何有效的解決內存泄漏的問題
Java-內部類的相關知識
Android-LeakCanary檢測內存泄漏
非靜態內部類: 成員內部類, 局部內部類、 匿名內部類。 會有對外部類的引用。這樣內部類中耗時操作在用戶頻繁退出重啓APP相關Activity時很容易導致內存泄漏。
一、匿名內部類:Runnable
1、泄漏版
new Thread(new Runnable() {
@Override
public void run() {
try {
//模擬耗時操作
Thread.sleep(15000);
} catch (InterruptedException e) {
e.printStackTrace();
}
}
}).start();
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連續多次退出重啓後發現:
2、優化版:
將 非靜態內部類 改爲 靜態非匿名內部類
new Thread(new MyRunnable()).start();
private static class MyRunnable implements Runnable {
@Override
public void run() {
try {
Thread.sleep(15000);
} catch (InterruptedException e) {
e.printStackTrace();
}
}
}
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二、成員內部類:Handler
1、泄漏版:
private final static int MESSAGECODE = 1;
private Handler handler = new Handler() {
@Override
public void handleMessage(Message msg) {
super.handleMessage(msg);
Log.d("mmmmmmmm", "handler " + msg.what);
}
};
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
new Thread(new Runnable() {
@Override
public void run() {
handler.sendEmptyMessage(MESSAGECODE);
try {
Thread.sleep(8000);
} catch (InterruptedException e) {
e.printStackTrace();
}
handler.sendEmptyMessage(MESSAGECODE);
}
}).start();
}
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連續多次退出重啓後發現:
2、優化版:
2.1、使用靜態內部類
2.2、使用弱引用
2.3、在onDestroy() 裏面取消異步任務。(注意:單純的取消還是會內存泄漏)
private final static int MESSAGECODE = 1;
private static Handler handler;//靜態
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
//創建Handler
handler = new MyHandler(this);
//創建線程並且啓動線程
new Thread(new MyRunnable()).start();
}
//1、避免Handler引用activity造成的內存泄漏:使用靜態內部類+ 使用弱引用
private static class MyHandler extends Handler {
WeakReference<HandlerActivity> weakReference;
public MyHandler(HandlerActivity activity) {
weakReference = new WeakReference<HandlerActivity>(activity);
}
@Override
public void handleMessage(Message msg) {
super.handleMessage(msg);
if (weakReference.get() != null) {
// update android ui
Log.d("mmmmmmmm", "handler " + msg.what);
}
}
}
//2、避免非靜態Runnable內部類引用activity造成的內存泄漏
private static class MyRunnable implements Runnable {
@Override
public void run() {
handler.sendEmptyMessage(MESSAGECODE);
try {
Thread.sleep(8000);
} catch (InterruptedException e) {
e.printStackTrace();
}
handler.sendEmptyMessage(MESSAGECODE);
}
}
@Override
protected void onDestroy() {
super.onDestroy();
//3、如果參數爲null的話,會將所有的Callbacks和Messages全部清除掉。
handler.removeCallbacksAndMessages(null);
}
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三、匿名內部類:TimerTask
1、泄漏版:
new Timer().schedule(new TimerTask() {
@Override
public void run() {
while (true) ;
}
}, 1000); // 1秒後啓動一個任務
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連續多次退出重啓後發現:
2、優化版:
1、在適當的時機進行Cancel。
2、TimerTask用靜態內部類
private TimerTask timerTask ;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
timerTask = new MyTimerTask() ;
new Timer().schedule( timerTask ,1000 ); // 1秒後啓動一個任務
}
private static class MyTimerTask extends TimerTask {
@Override
public void run() {
while(true){
Log.d( "ttttttttt" , "timerTask" ) ;
}
}
}
@Override
protected void onDestroy() {
super.onDestroy();
//取消定時任務
if ( timerTask != null ){
timerTask.cancel() ;
}
}
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四、匿名內部類:AsyncTask
1、泄露版:
new AsyncTask<String,Integer,String>(){
@Override
protected String doInBackground(String... params) {
try {
Thread.sleep( 6000 );
} catch (InterruptedException e) {
}
return "ssss";
}
@Override
protected void onPostExecute(String s) {
super.onPostExecute(s);
Log.d( "mmmmmm activity2 " , "" + s ) ;
}
}.execute();
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2、優化版
1、自定義靜態AsyncTask類
2、AsyncTask的週期和Activity週期應該保持一致。也就是在Activity生命週期結束時要將AsyncTask cancel掉。
private static MyTask myTask;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
myTask = new MyTask();
myTask.execute();
}
//1、創建靜態內部類
private static class MyTask extends AsyncTask {
@Override
protected Object doInBackground(Object[] params) {
try {
//模擬耗時操作
Thread.sleep(15000);
} catch (InterruptedException e) {
e.printStackTrace();
}
return "";
}
}
@Override
protected void onDestroy() {
super.onDestroy();
//2、取消異步任務
if (myTask != null) {
myTask.cancel(true);
}
}
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作者:Mars-xq
來源:CSDN
原文:https://blog.csdn.net/sinat_31057219/article/details/74533647
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