[Android] Context應該怎麼寫？

如果想要彈出一個AlertDialog，要寫如下的代碼

AlertDialog.Builder alert =new AlertDialog.Builder(this);alert.setTitle("Warning");alert.setMessage("Wrong time!");alert.show();

 

這裡構造方法的原型是AlertDialog.Builder(Context arg) 需要一個Context類的對象作為參數，一般我們都在Activity裡寫，所以用this，表示在當前的會話中彈出AlertDialog。

 

在我的一個程式裡，我自訂了一個介面Public interface CustomPickerListener，在實現這個介面的方法時我需要彈出來一個AlertDialog，這裡，參數表裡填寫this的話會提示錯誤：The constructor AlertDialog.Builder(new CustomPickerListener(){}) is undefined.

其實這個地方寫this很明顯是錯誤的，但是要寫什麼才能達成目的呢？

官方文檔上對context的解釋是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.

於是我就試著寫上了我程式的 包.目標類.this ，如下

AlertDialog.Builder alert =new AlertDialog.Builder(com.android.alcoholtest.AlcoholTest.this);

然後就成功了