调用方法一次

Question

我遇到了一个问题，当条件达到很多次时，如何调用一次方法！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 
    } 

} 

请与

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

你可以简单地设置一个标志帮助。如果你只需要它在Activity的每个实例中只发生一次，那么设置一个成员变量。

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; 
     } 
    } 

如果你想让它仅出现一次曾经在应用程序的生命然后设置变量为SharedPreference

Answer 3

设置一类广泛布尔

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

Answer 4

也许我不正确理解你的问题，但从你的问题定义我会建议使用类似的布尔变量。

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语句的代码被执行一次run将true并不会有任何后续调用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 
    } 

}