下面是一個(gè)沒(méi)問(wèn)題的Handler

public class DActivity extends AppCompatActivity {//    @Inject//    D d;        Handler mHandler = new Handler(new Handler.Callback() {        @Override        public boolean handleMessage(Message message) {            return false;        }    });    @Override    PRotected void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        setContentView(R.layout.activity_d);//        Diiii component = DaggerDiiii.builder().ddasfadfa(new Ddasfadfa()).build();//        component.injectD(this);            }}1,當(dāng)代碼改成下面的時(shí)候就會(huì)出現(xiàn)問(wèn)題
public class DActivity extends AppCompatActivity {//    @Inject//    D d;        Handler mHandler = new Handler(new Handler.Callback() {        @Override        public boolean handleMessage(Message message) {            return false;        }    });    @Override    protected void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        setContentView(R.layout.activity_d);//        Diiii component = DaggerDiiii.builder().ddasfadfa(new Ddasfadfa()).build();//        component.injectD(this);                mHandler.postDelayed(new Runnable() {            @Override            public void run() {                            }        },500*1000);    }}問(wèn)題的原因在于:
當(dāng)進(jìn)入到這個(gè)界面后,反復(fù)的旋轉(zhuǎn)屏幕,導(dǎo)致這個(gè)頁(yè)面不斷的重新繪制,同時(shí),如果持有很多的資源的話就會(huì)造成OOM;
分析原因:
一開(kāi)始進(jìn)入這個(gè)界面,初始化Handler,開(kāi)啟延時(shí)任務(wù),這時(shí),屏幕旋轉(zhuǎn),該activity需要被銷毀,卻發(fā)現(xiàn),自己有個(gè)孩子還在做延遲任務(wù),那么母親是肯定不能拋棄孩子的,所以,這個(gè)activity就銷毀不了了,當(dāng)不斷的旋轉(zhuǎn)屏幕時(shí),就會(huì)有很多個(gè)activity無(wú)法銷毀,如果持有很多的資源的話,那就更容易OOM了;
內(nèi)部類new Handler（）{}持有外部類Activity的引用
內(nèi)部類new Runable（）{}持有外部類Activity的引用
2,添加static(注意Handler和Runable都要加static)
public class DActivity extends AppCompatActivity {//    @Inject//    D d;        static Handler mHandler = new Handler(new Handler.Callback() {        @Override        public boolean handleMessage(Message message) {            return false;        }    });    static Runnable task = new Runnable() {        @Override        public void run() {                    }    };    @Override    protected void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        setContentView(R.layout.activity_d);//        Diiii component = DaggerDiiii.builder().ddasfadfa(new Ddasfadfa()).build();//        component.injectD(this);                mHandler.postDelayed(task,500*1000);    }}分析:
這時(shí)Handler就不再是activity的孩子了,是靜態(tài)成員變量(是屬于類的,不屬于這個(gè)實(shí)例了),這時(shí)activity就可以被銷毀了,同時(shí),Runable也用static修飾了；這樣就不會(huì)造成OOM了。
3,但是，如果在Handler或者在Runable中有引用外部類的成員，那也會(huì)OOM
public class DActivity extends AppCompatActivity {//    @Inject//    D d;
	ImageView iv；
	TextView tv；        static Handler mHandler = new Handler(new Handler.Callback() {        @Override        public boolean handleMessage(Message message) {
	    //tv.setText（“你好”）；
	    //iv.set。。。。。。            return false;        }    });    static Runnable task = new Runnable() {        @Override        public void run() {            tv.setText（“你好”）；
	    iv.set。。。。。。
	    finish；//引用了this        }    };    @Override    protected void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        setContentView(R.layout.activity_d);//        Diiii component = DaggerDiiii.builder().ddasfadfa(new Ddasfadfa()).build();//        component.injectD(this);                mHandler.postDelayed(task,500*1000);    }}如上，當(dāng)Runable中需要引用imageview和textview時(shí)，這時(shí)也會(huì)造成內(nèi)部類持有外部類的引用；如果Handler中有引用的話，也會(huì)造成內(nèi)部類持有外部類的引用，解決辦法是：將tv、iv用靜態(tài)static修飾，這樣就不會(huì)持有其引用了；但是如果，Runable里面有tv、iv、bt等等，很多個(gè)引用呢？代碼改起來(lái)就很麻煩了；這時(shí)想到，造成OOM的問(wèn)題在于Activity想銷毀時(shí)，這些成員變量tv、iv。。。卻還在被內(nèi)部類引用著；也就是說(shuō)，只要activity被銷毀了，就不讓他執(zhí)行那些邏輯；所以就有下面的代碼：
publicclassMainActivity extends AppCompatActivity {
private Activity mActivity;
privatestaticfinal String TAG="stay4it";
@Override
protectedvoidonCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
init();
}
privatevoidinit(){
mActivity=this;
BetterHandler betterHandler = new BetterHandler(mActivity);
Message message=Message.obtain();
message.what=9527;
betterHandler.sendMessage(message);
betterHandler.postDelayed(new BetterRunnable(), 1000 * 20);
}
privatestaticclassBetterRunnable implements Runnable {
@Override
publicvoidrun() {
Log.i(TAG,"Runnable run()");
}
}
privatestaticclassBetterHandler extends Handler {
private WeakReference<Activity> activityWeakReference;
publicBetterHandler(Activity activity) {
activityWeakReference = new WeakReference<>(activity);
}
@Override
publicvoidhandleMessage(Message msg) {
super.handleMessage(msg);
if (activityWeakReference.get() != null) {
Log.i(TAG,"handle message");
}
}
}
}
就Activity需要用軟引用WeakReference包一下，不然會(huì)造成activity回收不了；如上面的代碼，當(dāng)屏幕旋轉(zhuǎn)后，activity銷毀，activity為null，當(dāng)handler執(zhí)行任務(wù)時(shí)，activityWeakReference.get()為null，這樣就不會(huì)執(zhí)行里面的代碼。當(dāng)然這只是其中一種比較好的實(shí)現(xiàn)方式