public class CallBackTools {

    //接口
    public interface OnListener {
        void execute();
    }
    
    //声明接口
    OnListener callBack;

    //被调用，执行接口实现
    public void callListen() {
        callBack.execute();
    }

    //外部进行接口实现
    public void setCallBackListener(OnListener listener) {
        this.callBack = listener;
    }

}

@Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        final CallBackTools callBackTools = new CallBackTools();
        callBackTools.setCallBackListener(new CallBackTools.OnListener() {
            @Override
            public void execute() {
                // do waht you want when this callback be called
                Log.e("callback","success");
            }
        });

        findViewById(R.id.button).setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                callBackTools.callListen();
            }
        });
    }

Android -- 回调函数的使用