如何从一个活动到另一个活动调用非静态方法 [英] How to call a non-static method from one Activity to another activity

问题描述

我有两项活动&我想从B调用明确的方法. 我这样尝试过，并且我得到了空指针异常.

I have two activities & i want to call a method clear from B. I tried like this and I am getting null pointer exceptions.

class A extends Activity {
    ...
    public void clear(){}

}

class B extends Activity{
    public void clearData() {
        A a=new A();
        a.clear();
    }        
}

推荐答案

class A extends Activity{
static A instance;
@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    instance = this;
}

public static A getInstance() {
    return instance;
}
....
public void clear(){}

}

以及B类:

class B extends Activity {
  public void  clearData(){
      A a = A.getInstance();
      a.clear();
    }
}

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