調用方法一次

Question

我遇到了一個問題，當條件達到很多次時，如何調用一次方法！例如：

public void onLocaitonChanged(Location location){ 

    // this if statement may achieve the condition many times 
    if(somethingHappened){ 

     callAMethodOnce();// this method is called once even if the condition achieved again 
    } 

} 

請與

Answer 1

public void onLocaitonChanged(Location location){ 

    // this if statement may achieve the condition many times 
    if(somethingHappened){ 

     if (!isAlreadyCalled){ 
      callAMethodOnce();// this method is called once even if the condition achieved again 
      isAlreadyCalled = true; 
     } 
    } 

} 

Answer 2

你可以簡單地設置一個標誌幫助。如果你只需要它在Activity的每個實例中只發生一次，那麼設置一個成員變量。

public class MyActivity extends Activity 
{ 
    boolean itHappened = false; 

    ... 

    public void onLocaitonChanged(Location location) 
    { 

     // this if statement may achieve the condition many times 
     if(somethingHappened && !itHappened) 
     { 
      callAMethodOnce();// this method is called once even if the condition  achieved again 
      itHappened = true; 
     } 
    } 

如果你想讓它僅出現一次曾經在應用程序的生命然後設置變量爲SharedPreference

Answer 3

設置一類廣泛布爾

if(!hasRun){ 
    callAMethodOnce(); 
    hasRun = true; 
} 

Answer 4

也許我不正確理解你的問題，但從你的問題定義我會建議使用類似的布爾變量。

boolean run = false; 
public void onLocaitonChanged(Location location){ 

    // this if statement may achieve the condition many times 
    if(somethingHappened && run == false){ 
     run = true; 
     callAMethodOnce();// this method is called once even if the condition achieved again 
    } 

} 

一旦下if語句的代碼被執行一次run將true並不會有任何後續調用callAMethodOnce()

Answer 5

boolean isHappendBefore = false; 

public void onLocaitonChanged(Location location){ 

    // this if statement may achieve the condition many times 

    if(somethingHappened && (! isHappendBefore)){ 
     isHappendBefore = true; 
     callAMethodOnce();// this method is called once even if the condition achieved again 
    } 

}