【Android】關於上下文的種種傳說

Context

1. 中文直譯爲「上下文」
2. SDK中對其說明以下

  Interface to global information about an application environment. This is an abstract class whose implementation

  is provided by the Android system. It allows access to application-specific resources and classes, as well as up-calls 

  for application-level operations such as launching activities, broadcasting and receiving intents, etc

 

 

 

看一段測試代碼

private Context mContext;
    public void method() { 
        mContext = this;
        mContext = MainActivity.this; 
        mContext = getApplicationContext(); 
        mContext = getBaseContext(); 
        Log.v("huangc","####  mContext="+ this );
        Log.v("huangc","####  MainActivity.this="+ MainActivity.this );
        Log.v("huangc","####  getApplicationContext()="+getApplicationContext() );
        Log.v("huangc","####  getBaseContext()="+ getBaseContext());
     }

看日誌輸出

####  mContext=com.example.test4intent.MainActivity@302ffdcb
####  MainActivity.this=com.example.test4intent.MainActivity@302ffdcb
####  getApplicationContext()=android.app.Application@39c519a8
####  getBaseContext()=android.app.ContextImpl@26ad4cc1

可見大多數狀況下

【1】 this == MainActivity.this

【2】this ！= getApplicationContext() ！= getBaseContext()

 

 

 

參考文檔

http://blog.csdn.net/qinjuning/article/details/7310620