Android activity onNewIntent调用时机

╰+哭是因爲堅強的太久メ 2022-08-30 04:25 150阅读 0赞

#### 一、官方文档描述 ####

[Android Activity官网][Android Activity]

> void onNewIntent (Intent intent)  
> This is called for activities that set launchMode to “singleTop” in their package, or if a client used the FLAG\_ACTIVITY\_SINGLE\_TOP flag when calling startActivity(Intent).  
> In either case, when the activity is re-launched while at the top of the activity stack instead of a new instance of the activity being started, onNewIntent() will be called on the existing instance with the Intent that was used to re-launch it.  
> An activity will always be paused before receiving a new intent, so you can count on onResume() being called after this method.  
> Note that getIntent() still returns the original Intent. You can use setIntent(Intent) to update it to this new Intent.

#### 二、个人理解 ####

当通过intent启动activiy时，它处于栈顶，并且已有一个实例存在，这时就不会调用onCreate->onStart->onResume, 而是调用 onNewIntent->onRestart->onStart->onResume  
activity有4种启动模式，当activity的launchMode为默认standard时，重新启动会生成新的实例。所以不会调用onNewIntent, 但其他三种模式都会调用onNewIntent： singleTop是本身已处于栈顶， 重新启动会调用；singleTask是重新启动会销毁上层所有activity，之后会处于栈顶，也会被调用；singleInstance类似。  
官方提示，在 onNewIntent 中应调用 setIntent()来更新intent，否则后面的 getIntent会得到旧的 intent  
所以正确的代码编写是：

public void onCreate(Bundle savedInstanceState) { 
       super.onCreate(savedInstanceState);
       setContentView(R.layout.main);
       initViewWithData();
     }
    
     protected void onNewIntent(Intent intent) { 
       super.onNewIntent(intent);
       // Note that getIntent() still returns the original Intent. You can use setIntent(Intent) to update it to this new Intent.
       setIntent(intent);
       initViewWithData();
     }
    
     private void processExtraData(){ 
       Intent intent = getIntent();
       // ...
     }

[Android Activity]: https://developer.android.com/reference/android/app/Activity.html